WIRING A 12 V SWITCH AND LED TO A 5 V CIRCUIT In the on position, it uses about: (12 V power source - 0.6 V base drop) ÷ 10000 Ω = 0.00114 A = 1.14 mA. + 5 V ÷ 22000 Ω = 0.00023 A = 0.23 mA. = 1.37 mA. The downsides to this circuit are: The switch state is inverted such that “on” outputs 0 V and “off” outputs 5 V. But, that’s an ordinary arrangement for most pushbutton and 14-SEGMENT ALPHANUMERIC LED DISPLAY Multifunction Display and Alphanumeric LED Font. All Electronics has a fascinating multifunction LED display that includes seven 14-segment alphanumeric digits, four 7-segment numeric digits, and four LED icons. The Lite-On part number is LTM-Y2K19JF-03. It costs only $1 from All Electronics (CAT# DSY-1). MATERIALS AND INSTRUCTIONS FOR ELECTROLYSIS A plastic container big enough for the object to be restored. Measuring cup and spoons. Rubber gloves. Distilled water (to avoid minerals or chemicals in tap water that could deposit or interfere). Available at most supermarkets. Pure washing soda (also called soda

ash or

PCB LAYOUT TIPS AND TRICKS PCB Design Patterns. I’ve been laying out custom printed circuit boards for over ten years. There are a few tricks and tips that I use repeatedly from prototype to production PCBs to provide flexibility on parts, easier assembly, and faster circuit testing. BIG TRAK SALES AND REVISIONS H-BRIDGE DC MOTOR SCHEMATIC A schematic and wiring diagram photograph of an example fully-implemented H-Bridge. An H-Bridge circuit allows logic chips (even microcontrollers) to provide power to a DC motor (standard or gearhead). Motors can be driven forward or reverse with simple TTL or CMOS logic signals or with pulse-width modulation (PWM). SPOTTING BAD CAPACITORS Quiz time -- spot the bad capacitors. Spot the bad capacitors. If you said “all three of them”, then you’re right! The tops are slightly domed and two of them are obviously lifted off the board. The adhesive seems to be somewhat holding them down, but one of the capacitors is clearly tilted underneath. PROGRAMMING AN ATMEL AVR ATTINY MICROCONTROLLER WITH AN Programming an ATtiny Microcontroller with AVR Studio and Atmel STK500. This is a tutorial for programming an Atmel AVR ATtiny12, ATtiny13, ATtiny22, ATtiny25, ATtiny45, or ATtiny85 8-pin microcontroller chip using the Atmel STK500 tool. COLOR SENSOR FROM A REVERSED LED AND OP AMP, PAGE 4 Electrical emissions from a computer monitor, fluorescent lamp, or electrical motor normally consist of much less electrical power than the output of a chip or transistor. So, the signal from a digital chip easily overrides the environmental electrical noise. But, the photodiode (in this case a reversed LED) doesn’t put out much power. WRITING THE FUSES AND CODE TO AN AVR ATTINY Setting Fuse Bits and Writing a HEX File to an ATtiny Microcontroller. We have successfully verified that AVR Studio is communicating with the STK500 programming tool. We’re ready to write to the microcontroller chip itself. WIRING A 12 V SWITCH AND LED TO A 5 V CIRCUIT In the on position, it uses about: (12 V power source - 0.6 V base drop) ÷ 10000 Ω = 0.00114 A = 1.14 mA. + 5 V ÷ 22000 Ω = 0.00023 A = 0.23 mA. = 1.37 mA. The downsides to this circuit are: The switch state is inverted such that “on” outputs 0 V and “off” outputs 5 V. But, that’s an ordinary arrangement for most pushbutton and 14-SEGMENT ALPHANUMERIC LED DISPLAY Multifunction Display and Alphanumeric LED Font. All Electronics has a fascinating multifunction LED display that includes seven 14-segment alphanumeric digits, four 7-segment numeric digits, and four LED icons. The Lite-On part number is LTM-Y2K19JF-03. It costs only $1 from All Electronics (CAT# DSY-1). MATERIALS AND INSTRUCTIONS FOR ELECTROLYSIS A plastic container big enough for the object to be restored. Measuring cup and spoons. Rubber gloves. Distilled water (to avoid minerals or chemicals in tap water that could deposit or interfere). Available at most supermarkets. Pure washing soda (also called soda

ash or

PCB LAYOUT TIPS AND TRICKS PCB Design Patterns. I’ve been laying out custom printed circuit boards for over ten years. There are a few tricks and tips that I use repeatedly from prototype to production PCBs to provide flexibility on parts, easier assembly, and faster circuit testing. BIG TRAK SALES AND REVISIONS H-BRIDGE DC MOTOR SCHEMATIC A schematic and wiring diagram photograph of an example fully-implemented H-Bridge. An H-Bridge circuit allows logic chips (even microcontrollers) to provide power to a DC motor (standard or gearhead). Motors can be driven forward or reverse with simple TTL or CMOS logic signals or with pulse-width modulation (PWM). SPOTTING BAD CAPACITORS Quiz time -- spot the bad capacitors. Spot the bad capacitors. If you said “all three of them”, then you’re right! The tops are slightly domed and two of them are obviously lifted off the board. The adhesive seems to be somewhat holding them down, but one of the capacitors is clearly tilted underneath. PROGRAMMING AN ATMEL AVR ATTINY MICROCONTROLLER WITH AN Programming an ATtiny Microcontroller with AVR Studio and Atmel STK500. This is a tutorial for programming an Atmel AVR ATtiny12, ATtiny13, ATtiny22, ATtiny25, ATtiny45, or ATtiny85 8-pin microcontroller chip using the Atmel STK500 tool. COLOR SENSOR FROM A REVERSED LED AND OP AMP, PAGE 4 Electrical emissions from a computer monitor, fluorescent lamp, or electrical motor normally consist of much less electrical power than the output of a chip or transistor. So, the signal from a digital chip easily overrides the environmental electrical noise. But, the photodiode (in this case a reversed LED) doesn’t put out much power. WRITING THE FUSES AND CODE TO AN AVR ATTINY Setting Fuse Bits and Writing a HEX File to an ATtiny Microcontroller. We have successfully verified that AVR Studio is communicating with the STK500 programming tool. We’re ready to write to the microcontroller chip itself. ELECTRONIC ANALOG AND DIGITAL COUNTER For digital sensors, the counter device accepts a square wave signal with a low between -0.5 V to 1.5 V and a high between 3.5 V and 5.5 V. For analog sensors, the user can set the low and high trip points for any value between 0 V and 5 V in steps of about 0.02 V. Although analog is more adjustable, the device can read much faster digital INFRARED (IR) OBJECT TESTING USING A REMOTE CONTROL The dark cover is a good example of a material that is mostly opaque to visible light but mostly transparent to infrared. Steps to test an object for IR transparency with an infrared remote control: 1. Make sure the remote works. 2. Make sure a solid object can block the remote from working. 3. PCB LAYOUT TIPS AND TRICKS PCB Design Patterns. I’ve been laying out custom printed circuit boards for over ten years. There are a few tricks and tips that I use repeatedly from prototype to production PCBs to provide flexibility on parts, easier assembly, and faster circuit testing. DOUBLE-SIDED PRINTED CIRCUIT BOARDS Double-sided CAD image. Design the board using a CAD (computer-aided drafting) program and print to iron-on film just as you would for single-sided boards. The obvious difference is that the films aren’t two separate boards, but two layers of the same circuit. Design the two sides to interact with each other, passing signals and voltage

from

H-BRIDGE DC MOTOR SCHEMATIC A schematic and wiring diagram photograph of an example fully-implemented H-Bridge. An H-Bridge circuit allows logic chips (even microcontrollers) to provide power to a DC motor (standard or gearhead). Motors can be driven forward or reverse with simple TTL or CMOS logic signals or with pulse-width modulation (PWM). BIPOLAR TRANSISTOR HBRIDGE MOTOR DRIVER The classic beginner’s DC motor driver circuit that appears in every electronics textbook is the bipolar transistor H-bridge. An H-bridge is an arrangement of transistors that allows a circuit full control over a standard electric DC motor. That is, an H-bridge allows a microcontroller, logic chip, or remote control to electronically

command

ALPHANUMERIC TEXT LCD MODULE PINOUTS On the previous page, we learned how to find the connector holes that match chip pins . Here is the resulting pinout for the Nanox NDM082 module: Pinouts for standard 14 pin LCD display (thanks to correction by Spud). Good news! This matches the industry-standard pinout on most alphanumeric LCD text displays. GND Ground. Vdd +4.5 VDC to +5.5 VDC. SELF-DISCHARGE OF ULTRACAPACITORS The newer class of ultracapacitors has an ESR less than 1 ohm and a maximum voltage of 2.7 V or less. They charge and discharge rapidly. They are available in much larger capacities, such as over 10 farad. They are commonly used to supply massive surge current to get a large electric motor started or for regenerative braking in electric cars. REPLACING A BATTERY PACK WITH CONSUMER AAA RECHARGEABLE The official AT&T battery pack costs $19.95 (plus shipping) for three AAA cells. Knock-off battery packs are as low as $6 each, plus shipping. Rayovac AAA platinum rechargeable NiMH. The advantages of using off-the-shelf consumer batteries are: The newer formulations of NiMH batteries are superior in their ability to retain a charge and in

the

WRITING THE FUSES AND CODE TO AN AVR ATTINY Setting Fuse Bits and Writing a HEX File to an ATtiny Microcontroller. We have successfully verified that AVR Studio is communicating with the STK500 programming tool. We’re ready to write to the microcontroller chip itself. WIRING A 12 V SWITCH AND LED TO A 5 V CIRCUIT In the on position, it uses about: (12 V power source - 0.6 V base drop) ÷ 10000 Ω = 0.00114 A = 1.14 mA. + 5 V ÷ 22000 Ω = 0.00023 A = 0.23 mA. = 1.37 mA. The downsides to this circuit are: The switch state is inverted such that “on” outputs 0 V and “off” outputs 5 V. But, that’s an ordinary arrangement for most pushbutton and DOUBLE-SIDED PRINTED CIRCUIT BOARDS Double-sided CAD image. Design the board using a CAD (computer-aided drafting) program and print to iron-on film just as you would for single-sided boards. The obvious difference is that the films aren’t two separate boards, but two layers of the same circuit. Design the two sides to interact with each other, passing signals and voltage

from

14-SEGMENT ALPHANUMERIC LED DISPLAY Multifunction Display and Alphanumeric LED Font. All Electronics has a fascinating multifunction LED display that includes seven 14-segment alphanumeric digits, four 7-segment numeric digits, and four LED icons. The Lite-On part number is LTM-Y2K19JF-03. It costs only $1 from All Electronics (CAT# DSY-1). MATERIALS AND INSTRUCTIONS FOR ELECTROLYSIS A plastic container big enough for the object to be restored. Measuring cup and spoons. Rubber gloves. Distilled water (to avoid minerals or chemicals in tap water that could deposit or interfere). Available at most supermarkets. Pure washing soda (also called soda

ash or

EASIEST WAY TO REVERSE ELECTRIC MOTOR DIRECTIONS Solder the yellow and blue motor wires to the DPDT switch. 3. Connect the yellow and blue wires from the motor to the center terminals of the DPDT switch as shown above. 4. Connect the yellow and blue wires to the motor terminals. 5. Make sure the switch is in the center (off) position, before connecting the BIG TRAK SALES AND REVISIONS CUSTOM MODEL ROCKET LAUNCH CONTROLLER SPOTTING BAD CAPACITORS Quiz time -- spot the bad capacitors. Spot the bad capacitors. If you said “all three of them”, then you’re right! The tops are slightly domed and two of them are obviously lifted off the board. The adhesive seems to be somewhat holding them down, but one of the capacitors is clearly tilted underneath. PROGRAMMING AN ATMEL AVR ATTINY MICROCONTROLLER WITH AN Programming an ATtiny Microcontroller with AVR Studio and Atmel STK500. This is a tutorial for programming an Atmel AVR ATtiny12, ATtiny13, ATtiny22, ATtiny25, ATtiny45, or ATtiny85 8-pin microcontroller chip using the Atmel STK500 tool. WRITING THE FUSES AND CODE TO AN AVR ATTINY Setting Fuse Bits and Writing a HEX File to an ATtiny Microcontroller. We have successfully verified that AVR Studio is communicating with the STK500 programming tool. We’re ready to write to the microcontroller chip itself. WIRING A 12 V SWITCH AND LED TO A 5 V CIRCUIT In the on position, it uses about: (12 V power source - 0.6 V base drop) ÷ 10000 Ω = 0.00114 A = 1.14 mA. + 5 V ÷ 22000 Ω = 0.00023 A = 0.23 mA. = 1.37 mA. The downsides to this circuit are: The switch state is inverted such that “on” outputs 0 V and “off” outputs 5 V. But, that’s an ordinary arrangement for most pushbutton and DOUBLE-SIDED PRINTED CIRCUIT BOARDS Double-sided CAD image. Design the board using a CAD (computer-aided drafting) program and print to iron-on film just as you would for single-sided boards. The obvious difference is that the films aren’t two separate boards, but two layers of the same circuit. Design the two sides to interact with each other, passing signals and voltage

from

14-SEGMENT ALPHANUMERIC LED DISPLAY Multifunction Display and Alphanumeric LED Font. All Electronics has a fascinating multifunction LED display that includes seven 14-segment alphanumeric digits, four 7-segment numeric digits, and four LED icons. The Lite-On part number is LTM-Y2K19JF-03. It costs only $1 from All Electronics (CAT# DSY-1). MATERIALS AND INSTRUCTIONS FOR ELECTROLYSIS A plastic container big enough for the object to be restored. Measuring cup and spoons. Rubber gloves. Distilled water (to avoid minerals or chemicals in tap water that could deposit or interfere). Available at most supermarkets. Pure washing soda (also called soda

ash or

EASIEST WAY TO REVERSE ELECTRIC MOTOR DIRECTIONS Solder the yellow and blue motor wires to the DPDT switch. 3. Connect the yellow and blue wires from the motor to the center terminals of the DPDT switch as shown above. 4. Connect the yellow and blue wires to the motor terminals. 5. Make sure the switch is in the center (off) position, before connecting the BIG TRAK SALES AND REVISIONS CUSTOM MODEL ROCKET LAUNCH CONTROLLER SPOTTING BAD CAPACITORS Quiz time -- spot the bad capacitors. Spot the bad capacitors. If you said “all three of them”, then you’re right! The tops are slightly domed and two of them are obviously lifted off the board. The adhesive seems to be somewhat holding them down, but one of the capacitors is clearly tilted underneath. PROGRAMMING AN ATMEL AVR ATTINY MICROCONTROLLER WITH AN Programming an ATtiny Microcontroller with AVR Studio and Atmel STK500. This is a tutorial for programming an Atmel AVR ATtiny12, ATtiny13, ATtiny22, ATtiny25, ATtiny45, or ATtiny85 8-pin microcontroller chip using the Atmel STK500 tool. WRITING THE FUSES AND CODE TO AN AVR ATTINY Setting Fuse Bits and Writing a HEX File to an ATtiny Microcontroller. We have successfully verified that AVR Studio is communicating with the STK500 programming tool. We’re ready to write to the microcontroller chip itself. DAVID COOK'S ROBOT ROOM: ROBOTICS, CIRCUITS, AND MACHINING Robot schematics, books, and circuits for mini-sumo, line-following, BEAM, and electronic projects. DIY instructions on making robots at home. Basic help and tips on how to build robotic sensors. Homemade autonomous bots for a hobby! By David Cook. BIPOLAR TRANSISTOR HBRIDGE MOTOR DRIVER The classic beginner’s DC motor driver circuit that appears in every electronics textbook is the bipolar transistor H-bridge. An H-bridge is an arrangement of transistors that allows a circuit full control over a standard electric DC motor. That is, an H-bridge allows a microcontroller, logic chip, or remote control to electronically

command

CUSTOM MODEL ROCKET LAUNCH CONTROLLER The custom launch controller must be operated in a very specific way, or else it aborts the launch until the key is returned to the safe position. Launch control sequence. Power on (the switch illuminates) Insert the key in the Lockout switch in the safe position and turn

until the

WRITING THE FUSES AND CODE TO AN AVR ATTINY Setting Fuse Bits and Writing a HEX File to an ATtiny Microcontroller. We have successfully verified that AVR Studio is communicating with the STK500 programming tool. We’re ready to write to the microcontroller chip itself. INFRARED EMITTER FROM CMOS 555 A schematic and pictures of how to use a CMOS 555 multivibrator chip in astable mode to generate a 36 kHz, 38 kHz, or 40 kHz infrared wave. The IR emission can be used for robotic object detection, remote control, or even communication. MEASURING CAPACITOR LEAKAGE capacitance in farads = 0.001 A / (0.5 V / 600 s) capacitance in farads = 0.001 A / 0.00083333333333333 V/s. capacitance in farads = 1.2 F. Wow. A farad is a pretty big capacitor value. Most of us are accustomed to values in the microfarad range (0.000001 F). If you need a value in the farad range, that’s a job for an ultracapacitor. APPLE IPAD PRO DESK MOUNT SWING ARM Huzzah! Here is the LapWorks full motion desk mount tablet arm holding an Apple iPad Pro 12.9 tablet . Desk mount tablet arm for YouTube videos. This makes it easy to adjust the position of the camera while recording, while simultaneously being able to see if the subject is properly framed. Because the arm takes up little space, it doesn’t DIELECTRIC ABSORPTION IN CAPACITORS Voltage Rebound in Capacitors. (Continued from previous page that discussed ultracapacitors ) Many capacitors have an usual characteristic known as dielectric absorption, soakage, or memory effect. If you charge a capacitor for a while, then discharge it quickly to 0 V, and then leave it disconnected, the capacitor’s voltage magically increases. CIRCUIT BOARD DRILL HOLE SIZE TOLERANCE Many PCB manufacturers specify a hole tolerance of ±0.004. So, 0.022 resistor lead + 0.003 resistor lead tolerance + 0.004 PCB hole tolerance = 0.029 inches. The 0.007 inch rule of thumb is adequate for hobbyists and prototyping most of the time. Of course, it is better to check out the datasheets and online specifications for the part and

PCB

CLEANING UP AFTER RUST REMOVAL USING ELECTROLYSIS The corrosion removed by electrolysis appears as ugly gunk at the top and bottom of the tank. The no-longer rusted hardware needs a little bit of scrubbing, drying, and oiling to finish the job. WIRING A 12 V SWITCH AND LED TO A 5 V CIRCUIT In the on position, it uses about: (12 V power source - 0.6 V base drop) ÷ 10000 Ω = 0.00114 A = 1.14 mA. + 5 V ÷ 22000 Ω = 0.00023 A = 0.23 mA. = 1.37 mA. The downsides to this circuit are: The switch state is inverted such that “on” outputs 0 V and “off” outputs 5 V. But, that’s an ordinary arrangement for most pushbutton and DOUBLE-SIDED PRINTED CIRCUIT BOARDS Double-sided CAD image. Design the board using a CAD (computer-aided drafting) program and print to iron-on film just as you would for single-sided boards. The obvious difference is that the films aren’t two separate boards, but two layers of the same circuit. Design the two sides to interact with each other, passing signals and voltage

from

14-SEGMENT ALPHANUMERIC LED DISPLAY Multifunction Display and Alphanumeric LED Font. All Electronics has a fascinating multifunction LED display that includes seven 14-segment alphanumeric digits, four 7-segment numeric digits, and four LED icons. The Lite-On part number is LTM-Y2K19JF-03. It costs only $1 from All Electronics (CAT# DSY-1). MATERIALS AND INSTRUCTIONS FOR ELECTROLYSIS A plastic container big enough for the object to be restored. Measuring cup and spoons. Rubber gloves. Distilled water (to avoid minerals or chemicals in tap water that could deposit or interfere). Available at most supermarkets. Pure washing soda (also called soda

ash or

EASIEST WAY TO REVERSE ELECTRIC MOTOR DIRECTIONS Solder the yellow and blue motor wires to the DPDT switch. 3. Connect the yellow and blue wires from the motor to the center terminals of the DPDT switch as shown above. 4. Connect the yellow and blue wires to the motor terminals. 5. Make sure the switch is in the center (off) position, before connecting the BIG TRAK SALES AND REVISIONS CUSTOM MODEL ROCKET LAUNCH CONTROLLER SPOTTING BAD CAPACITORS Quiz time -- spot the bad capacitors. Spot the bad capacitors. If you said “all three of them”, then you’re right! The tops are slightly domed and two of them are obviously lifted off the board. The adhesive seems to be somewhat holding them down, but one of the capacitors is clearly tilted underneath. PROGRAMMING AN ATMEL AVR ATTINY MICROCONTROLLER WITH AN Programming an ATtiny Microcontroller with AVR Studio and Atmel STK500. This is a tutorial for programming an Atmel AVR ATtiny12, ATtiny13, ATtiny22, ATtiny25, ATtiny45, or ATtiny85 8-pin microcontroller chip using the Atmel STK500 tool. WRITING THE FUSES AND CODE TO AN AVR ATTINY Setting Fuse Bits and Writing a HEX File to an ATtiny Microcontroller. We have successfully verified that AVR Studio is communicating with the STK500 programming tool. We’re ready to write to the microcontroller chip itself. WIRING A 12 V SWITCH AND LED TO A 5 V CIRCUIT In the on position, it uses about: (12 V power source - 0.6 V base drop) ÷ 10000 Ω = 0.00114 A = 1.14 mA. + 5 V ÷ 22000 Ω = 0.00023 A = 0.23 mA. = 1.37 mA. The downsides to this circuit are: The switch state is inverted such that “on” outputs 0 V and “off” outputs 5 V. But, that’s an ordinary arrangement for most pushbutton and DOUBLE-SIDED PRINTED CIRCUIT BOARDS Double-sided CAD image. Design the board using a CAD (computer-aided drafting) program and print to iron-on film just as you would for single-sided boards. The obvious difference is that the films aren’t two separate boards, but two layers of the same circuit. Design the two sides to interact with each other, passing signals and voltage

from

14-SEGMENT ALPHANUMERIC LED DISPLAY Multifunction Display and Alphanumeric LED Font. All Electronics has a fascinating multifunction LED display that includes seven 14-segment alphanumeric digits, four 7-segment numeric digits, and four LED icons. The Lite-On part number is LTM-Y2K19JF-03. It costs only $1 from All Electronics (CAT# DSY-1). MATERIALS AND INSTRUCTIONS FOR ELECTROLYSIS A plastic container big enough for the object to be restored. Measuring cup and spoons. Rubber gloves. Distilled water (to avoid minerals or chemicals in tap water that could deposit or interfere). Available at most supermarkets. Pure washing soda (also called soda

ash or

EASIEST WAY TO REVERSE ELECTRIC MOTOR DIRECTIONS Solder the yellow and blue motor wires to the DPDT switch. 3. Connect the yellow and blue wires from the motor to the center terminals of the DPDT switch as shown above. 4. Connect the yellow and blue wires to the motor terminals. 5. Make sure the switch is in the center (off) position, before connecting the BIG TRAK SALES AND REVISIONS CUSTOM MODEL ROCKET LAUNCH CONTROLLER SPOTTING BAD CAPACITORS Quiz time -- spot the bad capacitors. Spot the bad capacitors. If you said “all three of them”, then you’re right! The tops are slightly domed and two of them are obviously lifted off the board. The adhesive seems to be somewhat holding them down, but one of the capacitors is clearly tilted underneath. PROGRAMMING AN ATMEL AVR ATTINY MICROCONTROLLER WITH AN Programming an ATtiny Microcontroller with AVR Studio and Atmel STK500. This is a tutorial for programming an Atmel AVR ATtiny12, ATtiny13, ATtiny22, ATtiny25, ATtiny45, or ATtiny85 8-pin microcontroller chip using the Atmel STK500 tool. WRITING THE FUSES AND CODE TO AN AVR ATTINY Setting Fuse Bits and Writing a HEX File to an ATtiny Microcontroller. We have successfully verified that AVR Studio is communicating with the STK500 programming tool. We’re ready to write to the microcontroller chip itself. DAVID COOK'S ROBOT ROOM: ROBOTICS, CIRCUITS, AND MACHINING Robot schematics, books, and circuits for mini-sumo, line-following, BEAM, and electronic projects. DIY instructions on making robots at home. Basic help and tips on how to build robotic sensors. Homemade autonomous bots for a hobby! By David Cook. BIPOLAR TRANSISTOR HBRIDGE MOTOR DRIVER The classic beginner’s DC motor driver circuit that appears in every electronics textbook is the bipolar transistor H-bridge. An H-bridge is an arrangement of transistors that allows a circuit full control over a standard electric DC motor. That is, an H-bridge allows a microcontroller, logic chip, or remote control to electronically

command

CUSTOM MODEL ROCKET LAUNCH CONTROLLER The custom launch controller must be operated in a very specific way, or else it aborts the launch until the key is returned to the safe position. Launch control sequence. Power on (the switch illuminates) Insert the key in the Lockout switch in the safe position and turn

until the

WRITING THE FUSES AND CODE TO AN AVR ATTINY Setting Fuse Bits and Writing a HEX File to an ATtiny Microcontroller. We have successfully verified that AVR Studio is communicating with the STK500 programming tool. We’re ready to write to the microcontroller chip itself. INFRARED EMITTER FROM CMOS 555 A schematic and pictures of how to use a CMOS 555 multivibrator chip in astable mode to generate a 36 kHz, 38 kHz, or 40 kHz infrared wave. The IR emission can be used for robotic object detection, remote control, or even communication. MEASURING CAPACITOR LEAKAGE capacitance in farads = 0.001 A / (0.5 V / 600 s) capacitance in farads = 0.001 A / 0.00083333333333333 V/s. capacitance in farads = 1.2 F. Wow. A farad is a pretty big capacitor value. Most of us are accustomed to values in the microfarad range (0.000001 F). If you need a value in the farad range, that’s a job for an ultracapacitor. APPLE IPAD PRO DESK MOUNT SWING ARM Huzzah! Here is the LapWorks full motion desk mount tablet arm holding an Apple iPad Pro 12.9 tablet . Desk mount tablet arm for YouTube videos. This makes it easy to adjust the position of the camera while recording, while simultaneously being able to see if the subject is properly framed. Because the arm takes up little space, it doesn’t DIELECTRIC ABSORPTION IN CAPACITORS Voltage Rebound in Capacitors. (Continued from previous page that discussed ultracapacitors ) Many capacitors have an usual characteristic known as dielectric absorption, soakage, or memory effect. If you charge a capacitor for a while, then discharge it quickly to 0 V, and then leave it disconnected, the capacitor’s voltage magically increases. CIRCUIT BOARD DRILL HOLE SIZE TOLERANCE Many PCB manufacturers specify a hole tolerance of ±0.004. So, 0.022 resistor lead + 0.003 resistor lead tolerance + 0.004 PCB hole tolerance = 0.029 inches. The 0.007 inch rule of thumb is adequate for hobbyists and prototyping most of the time. Of course, it is better to check out the datasheets and online specifications for the part and

PCB

CLEANING UP AFTER RUST REMOVAL USING ELECTROLYSIS The corrosion removed by electrolysis appears as ugly gunk at the top and bottom of the tank. The no-longer rusted hardware needs a little bit of scrubbing, drying, and oiling to finish the job. WIRING A 12 V SWITCH AND LED TO A 5 V CIRCUIT In the on position, it uses about: (12 V power source - 0.6 V base drop) ÷ 10000 Ω = 0.00114 A = 1.14 mA. + 5 V ÷ 22000 Ω = 0.00023 A = 0.23 mA. = 1.37 mA. The downsides to this circuit are: The switch state is inverted such that “on” outputs 0 V and “off” outputs 5 V. But, that’s an ordinary arrangement for most pushbutton and MATERIALS AND INSTRUCTIONS FOR ELECTROLYSIS A plastic container big enough for the object to be restored. Measuring cup and spoons. Rubber gloves. Distilled water (to avoid minerals or chemicals in tap water that could deposit or interfere). Available at most supermarkets. Pure washing soda (also called soda

ash or

14-SEGMENT ALPHANUMERIC LED DISPLAY Multifunction Display and Alphanumeric LED Font. All Electronics has a fascinating multifunction LED display that includes seven 14-segment alphanumeric digits, four 7-segment numeric digits, and four LED icons. The Lite-On part number is LTM-Y2K19JF-03. It costs only $1 from All Electronics (CAT# DSY-1). BIG TRAK SALES AND REVISIONS PCB LAYOUT TIPS AND TRICKS PCB Design Patterns. I’ve been laying out custom printed circuit boards for over ten years. There are a few tricks and tips that I use repeatedly from prototype to production PCBs to provide flexibility on parts, easier assembly, and faster circuit testing. PENCIL ERASER FOR PCB TARNISH AND OXIDES ON PADS, HOLES Removing Tarnish from PCB Pads, Holes, Contacts, and Connectors. Tarnishing is a chemical change on the surface of a metal due to compounds in the air. Tarnish can form on a printed circuit board, on the contacts of a switch, on the pins of a part, or on connectors. Tarnish makes soldering more difficult and reduces electrical

conductance.

SPOTTING BAD CAPACITORS Quiz time -- spot the bad capacitors. Spot the bad capacitors. If you said “all three of them”, then you’re right! The tops are slightly domed and two of them are obviously lifted off the board. The adhesive seems to be somewhat holding them down, but one of the capacitors is clearly tilted underneath. PROGRAMMING AN ATMEL AVR ATTINY MICROCONTROLLER WITH AN Programming an ATtiny Microcontroller with AVR Studio and Atmel STK500. This is a tutorial for programming an Atmel AVR ATtiny12, ATtiny13, ATtiny22, ATtiny25, ATtiny45, or ATtiny85 8-pin microcontroller chip using the Atmel STK500 tool. COLOR SENSOR FROM A REVERSED LED AND OP AMP, PAGE 4 Electrical emissions from a computer monitor, fluorescent lamp, or electrical motor normally consist of much less electrical power than the output of a chip or transistor. So, the signal from a digital chip easily overrides the environmental electrical noise. But, the photodiode (in this case a reversed LED) doesn’t put out much power. WRITING THE FUSES AND CODE TO AN AVR ATTINY Setting Fuse Bits and Writing a HEX File to an ATtiny Microcontroller. We have successfully verified that AVR Studio is communicating with the STK500 programming tool. We’re ready to write to the microcontroller chip itself. WIRING A 12 V SWITCH AND LED TO A 5 V CIRCUIT In the on position, it uses about: (12 V power source - 0.6 V base drop) ÷ 10000 Ω = 0.00114 A = 1.14 mA. + 5 V ÷ 22000 Ω = 0.00023 A = 0.23 mA. = 1.37 mA. The downsides to this circuit are: The switch state is inverted such that “on” outputs 0 V and “off” outputs 5 V. But, that’s an ordinary arrangement for most pushbutton and MATERIALS AND INSTRUCTIONS FOR ELECTROLYSIS A plastic container big enough for the object to be restored. Measuring cup and spoons. Rubber gloves. Distilled water (to avoid minerals or chemicals in tap water that could deposit or interfere). Available at most supermarkets. Pure washing soda (also called soda

ash or

14-SEGMENT ALPHANUMERIC LED DISPLAY Multifunction Display and Alphanumeric LED Font. All Electronics has a fascinating multifunction LED display that includes seven 14-segment alphanumeric digits, four 7-segment numeric digits, and four LED icons. The Lite-On part number is LTM-Y2K19JF-03. It costs only $1 from All Electronics (CAT# DSY-1). BIG TRAK SALES AND REVISIONS PCB LAYOUT TIPS AND TRICKS PCB Design Patterns. I’ve been laying out custom printed circuit boards for over ten years. There are a few tricks and tips that I use repeatedly from prototype to production PCBs to provide flexibility on parts, easier assembly, and faster circuit testing. PENCIL ERASER FOR PCB TARNISH AND OXIDES ON PADS, HOLES Removing Tarnish from PCB Pads, Holes, Contacts, and Connectors. Tarnishing is a chemical change on the surface of a metal due to compounds in the air. Tarnish can form on a printed circuit board, on the contacts of a switch, on the pins of a part, or on connectors. Tarnish makes soldering more difficult and reduces electrical

conductance.

SPOTTING BAD CAPACITORS Quiz time -- spot the bad capacitors. Spot the bad capacitors. If you said “all three of them”, then you’re right! The tops are slightly domed and two of them are obviously lifted off the board. The adhesive seems to be somewhat holding them down, but one of the capacitors is clearly tilted underneath. PROGRAMMING AN ATMEL AVR ATTINY MICROCONTROLLER WITH AN Programming an ATtiny Microcontroller with AVR Studio and Atmel STK500. This is a tutorial for programming an Atmel AVR ATtiny12, ATtiny13, ATtiny22, ATtiny25, ATtiny45, or ATtiny85 8-pin microcontroller chip using the Atmel STK500 tool. COLOR SENSOR FROM A REVERSED LED AND OP AMP, PAGE 4 Electrical emissions from a computer monitor, fluorescent lamp, or electrical motor normally consist of much less electrical power than the output of a chip or transistor. So, the signal from a digital chip easily overrides the environmental electrical noise. But, the photodiode (in this case a reversed LED) doesn’t put out much power. WRITING THE FUSES AND CODE TO AN AVR ATTINY Setting Fuse Bits and Writing a HEX File to an ATtiny Microcontroller. We have successfully verified that AVR Studio is communicating with the STK500 programming tool. We’re ready to write to the microcontroller chip itself. ELECTRONIC ANALOG AND DIGITAL COUNTER For digital sensors, the counter device accepts a square wave signal with a low between -0.5 V to 1.5 V and a high between 3.5 V and 5.5 V. For analog sensors, the user can set the low and high trip points for any value between 0 V and 5 V in steps of about 0.02 V. Although analog is more adjustable, the device can read much faster digital PCB LAYOUT TIPS AND TRICKS PCB Design Patterns. I’ve been laying out custom printed circuit boards for over ten years. There are a few tricks and tips that I use repeatedly from prototype to production PCBs to provide flexibility on parts, easier assembly, and faster circuit testing. INFRARED (IR) OBJECT TESTING USING A REMOTE CONTROL The dark cover is a good example of a material that is mostly opaque to visible light but mostly transparent to infrared. Steps to test an object for IR transparency with an infrared remote control: 1. Make sure the remote works. 2. Make sure a solid object can block the remote from working. 3. DOUBLE-SIDED PRINTED CIRCUIT BOARDS Double-sided CAD image. Design the board using a CAD (computer-aided drafting) program and print to iron-on film just as you would for single-sided boards. The obvious difference is that the films aren’t two separate boards, but two layers of the same circuit. Design the two sides to interact with each other, passing signals and voltage

from

H-BRIDGE DC MOTOR SCHEMATIC A schematic and wiring diagram photograph of an example fully-implemented H-Bridge. An H-Bridge circuit allows logic chips (even microcontrollers) to provide power to a DC motor (standard or gearhead). Motors can be driven forward or reverse with simple TTL or CMOS logic signals or with pulse-width modulation (PWM). PROGRAMMING AN ATMEL AVR ATTINY MICROCONTROLLER WITH AN Programming an ATtiny Microcontroller with AVR Studio and Atmel STK500. This is a tutorial for programming an Atmel AVR ATtiny12, ATtiny13, ATtiny22, ATtiny25, ATtiny45, or ATtiny85 8-pin microcontroller chip using the Atmel STK500 tool. EASIEST WAY TO REVERSE ELECTRIC MOTOR DIRECTIONS Solder the yellow and blue motor wires to the DPDT switch. 3. Connect the yellow and blue wires from the motor to the center terminals of the DPDT switch as shown above. 4. Connect the yellow and blue wires to the motor terminals. 5. Make sure the switch is in the center (off) position, before connecting the SELF-DISCHARGE OF ULTRACAPACITORS The newer class of ultracapacitors has an ESR less than 1 ohm and a maximum voltage of 2.7 V or less. They charge and discharge rapidly. They are available in much larger capacities, such as over 10 farad. They are commonly used to supply massive surge current to get a large electric motor started or for regenerative braking in electric cars. WRITING THE FUSES AND CODE TO AN AVR ATTINY Setting Fuse Bits and Writing a HEX File to an ATtiny Microcontroller. We have successfully verified that AVR Studio is communicating with the STK500 programming tool. We’re ready to write to the microcontroller chip itself. REPLACING A BATTERY PACK WITH CONSUMER AAA RECHARGEABLE The official AT&T battery pack costs $19.95 (plus shipping) for three AAA cells. Knock-off battery packs are as low as $6 each, plus shipping. Rayovac AAA platinum rechargeable NiMH. The advantages of using off-the-shelf consumer batteries are: The newer formulations of NiMH batteries are superior in their ability to retain a charge and in

the

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Robot

Building for Beginners A beginner’s book on how to build a robot, from the author of Robot Room. Contains tricks, tips, and advice on getting started creating your own robots from scratch. THIRD EDITION! Intermediate Robot Building Learn how to make a robot power supply, compare motor driver circuits, create an infrared obstacle / wall / opponent sensor, play music, and much more. SECOND EDITION! WHAT’S NEW? (FOLLOW @ROBOTROOM ON

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New Articles on Patreon There are at least 30 new Robot Room articles available for patrons. Click here to check them out: Goodbye Google Adsense! I've removed Google Ads from Robot Room. Why?

5V Regulator Cap

for 9V Battery

For quick portable projects and temporary hacks, it is often faster to reuse a simple 5V regulator circuit than to integrate a power supply into the device design. My toolbox has an LED tester and magnifier light, so why not add a convenient 5V regulator cap to the collection? There are nicer ones on the market that have surface mount components, but half the fun of an electronics hobby is creating something basic in your own style. This double-decker board with flashing LED power indicator allowed me to experiment with flush battery snaps and board

interconnects.

Mercury Battery Replacement Regulator Several decades ago, mercuric oxide button cells were common consumer power sources. Mercury was phased out due to environmental concerns, leaving behind vintage photographic equipment and watches that were incompatible with alkaline's wide voltage change or silver-oxide's slightly higher nominal voltage. Tinkerers have come up with a variety of solutions for many devices. Perhaps modern technology can address a few more with an itty-bitty 1.35V low-dropout linear regulator. 3D Printed Spool and Wire

Soldering Holder

Buying new wire begs the question of what type of insulation to choose. PTFE is selected since it doesn't tend to melt back as common PVC wire insulation does. The new wire arrives without a spool, which necessitates printing a spool on a three-dimensional printer. The spool is easy enough to model but consumes the day with a six-hour print time. Soldering the newly acquired wire to another wire is frustrating with the classic misaligned 'helping' hands tool. Thus, old-fashioned wooden clothes pin attached to a base become the project being worked on rather than whatever I needed that wire for in the

first place.

Generating Waveforms with Paper Discs In a pinch, you can generate square, sawtooth, sinusoidal, triangular, and noisy/static waveforms by playing a patterned disc on a record player or spare motor using a light sensor. An LED illuminates the paper disc, which reflects varying amounts of light into the light sensor as the disc rotates on the turntable (see the video for a demonstration.) The circuitry is fairly simple and uses commonly found parts. Can you guess the waveform generated by the thumbnail image? Resistor Forming Tool Who hasn't looked at a classic red resistor lead forming tool and exclaimed "I could 3D print this!" I took a shot at designing and printing a few variations. The end result is a functional tool with a couple of improvements, but not as crisp, due to the limitations of home fused-filament resolutions. Upgrading Magnifying Desk Lamp to LEDs Circular T9 LED bulbs are available to replace fluorescent bulbs in desk lamps. LEDs provide a broader spectrum of light, which is particularly important if you are shooting macro photographs, but is also easier on your eyes if you're soldering or inspecting boards. Unfortunately, the commercial LED bulb I received was defective and had a flickering power supply. Hacking in six additional smoothing capacitors and replacing a missing LED solved the problem. Identifying Bad Capacitors If your consumer electronic device is failing, it is often caused by old, overheated, or defective capacitors. If you open up the case and inspect the capacitors, you may find some that are bulging, crusty, or are lifting off the PCB. Here are some photographs of damaged CapXon brand aluminum-electrolytic capacitors found inside failing Samsung LCD monitors. Also included is a photo of a good capacitor that has beneficial goop surrounding it. How *Not* to Cast and Machine Bismuth Bismuth is a high-density non-toxic metal that forms beautiful crystals. Well, supposedly it forms beautiful crystals, just not for me. See examples of clay casting failures and chipped surfaces as I muddle my way through trying to make anything out of bismuth. Sun Tracker Failed Project Sometimes you gotta know when to walk away -- which was eight years ago. I dug up this robot that was supposed to emulate a sunflower tracking the sun. Due to a design flaw in an overly complicated analog sensor bus, and general ugliness, this project got literally shelved. Now it sees the light of day, if only to be a lesson to others.

Mounting an iPad

for Desk-Based YouTube Videos For many hobbies, an overhead shot of your desk or workbench is the ideal view for your videos. This is unwieldy for tripods, but suitable for a desk swing arm. Similar to a desk-mounted magnifier light, the camera can be quickly positioned at various distances, and can be swung away when not in use. The single arm does not tend to block room lighting. Take a look at my tablet-mount setup, and see how the arms were extended to fit a larger form factor. Macro Photo vs Microscope Fifteen years ago, I proudly photographed a PCB using an Intel QX3 toy microscope. How well does that old microscope compete against a modern 16 megapixel camera with macro lens, extension tubes, tripod, linear table, linear slide, remote shutter, 28 LED ring light, and stacked photography software? Can such a photo setup match the microscope's 200x magnification? In fact, exactly small of details can we clearly see with a modern rig? Would you believe 10 µm? 3D Printed Trimpot Thumb Dial Create your own colorful finger-friendly dials for common trimmer potentiometers. With a little slot that press-fits into the screwdriver slot, and a dab of emblem adhesive, these home printed dials will make your projects much easier to adjust. LED Tester with Display Throw away your multimeter and spreadsheets, here is a self-contained current-limited LED tester that displays LED voltage drop, current, and recommended resistor. With about $10 in parts and a 9V battery, this indispensible tool is tailored for the everyday tasks of the electronics enthusiast.

The TGIMBOEJ Curse

Remember that thing you were going to get to? Well, it took me seven years to ship a package. No kidding. What's inside? Are there more like that? (Yes, 144) Come closer to hear the tale of The Great Internet Migratory Box Of Electronics Junk. Replacing Broken Tip of IC Hook Probe Arg! The multimeter measurements are wrong because the probe detached from the circuit because the IC hook tip broke, again! I go through far too many broken IC hooks to keep throwing them away. Is it possible to 3D print a replacement tip? Is this an opportunity to improve the tip to be more robust? Leveling A 3D Printer How to accurately set the extruder nozzle height above the print bed when leveling a 3D printer. Use a thickness gauge, magnet, and a multimeter in continuity mode to beep when the print head makes contact. Includes a trick to clean the tip of the nozzle by scraping it with the zinc interior of a penny. Printed Circuit Board Survey What features do hobbyists, students, and small shops look for in a PCB manufacturer? Do people care about lead free? What about board shape and internal cutouts? Is board color important enough to offer as an option? Find out the results of the PCB survey...

PCB Motor Mount

If you don't have a home machine shop or 3D printer, you can make a motor mounting bracket from a PCB. Printed circuit boards are strong, lightweight, precise, and are easily manufactured. The PCB bracket can then be attached to your project using screws, straight solder, right-angle headers, or dual-row headers. The video in the article shows you the process step-by-step, including how to make the board non-rectangular and how to place screw holes at angles. Better Etching of Homemade PCBs You consistently create homemade PCBs with traces as fine as 6 mil traces, using common household objects, such as sandpaper, cleanser, aluminum foil, and a clothes iron. I test various chemicals, temperatures, and pressures to determine how to make circuits with minimal voids, distortion, and fills.

PCB Hole Sizing

How big of a hole do you need drilled in a printed circuit board to fit a part? Don't just measure the part with calipers and use that for the hole size! You must make the hole larger to account for the tolerances of the part and the circuit board manufacturer. Of course, that brings up the question of how much can you trust the size of the holes the manufacturer is drilling. Let's see what pin gages say about some of the boards laying around the robot room.

Hamming ECC

Error correcting code (ECC) is superior to ordinary checksums, in that is can both detect and correct errors in data storage and transmission. Learn how Hamming codes work. Fully working C library

included.

Thermal Imaging

Infrared pictures and images can reveal energy waste, health issues, security codes, animal behavior, and circuit board flaws. It is also a great way to cheat at hide-and-go-seek. Take look at a gallery of fascinating thermal images taken with the Flir E4 infrared camera. Additionally, there is a video of a power-supply heating up, as well as desoldering wires. Rocket Ignition System The problem with most model rocket launch controllers is that the battery is located with the operator, far away from the launch pad. This requires thick cables and wastes significant energy. By locating the battery near the rocket engine and using a remotely-controlled relay, the improved launch system is more efficient but can still be built at home. Includes complete schematics, the pcb layout, and

source/object code.

Back And Forth Mark II The single motor drive train on the original Back And Forth robot was unique but a failure. To overcompensate, the next generation is four wheel drive and six switches just to move forward and move back, repeatedly. There are some nice mating parts that may be useful in your next project. And, you'll be surprised to see what's inside the half-height batteries. Maximum Sampling in Software When sampling at the maximum software rate, the signal itself may affect the software, resulting in inaccurate readings. Here is an example of how I debugged an issue and doubled the rate. Yummy Candy Tin Robot Yummy is a line-following robot made from an m&m's candy tin, in homage of Sweet . Yummy features a light sensor for detecting when the candy tin has been closed, to delay starting the motors as long as necessary. The rear tail lights use 10 mm red LEDs with Fresnel lenses. Cleaning a Mouse Scroll Wheel The scroll wheel on the Microsoft Wireless Mouse 5000 can stop working over time. As you'll see, the scroll wheel is a classic interrupter encoder wheel that can be fixed by cleaning. The difficult part was figuring out how to open this mouse, which ended up being held together with four T6 torx screws hiding underneath the glide strips. Removing Solder from PCB Holes Excess solder can clog circuit board holes due to overzealous soldering or when desoldering to remove a part. It can be annoying to try to get the solder out of the hole, but these methods and tools can help. Article also describes how to make your own Teflon desoldering

tips.

Sturdy Attachment of a Lego Wheel to

a Gearmotor

Nothing is more pathetic than a robot that has lost a wheel. Couplings based on the standard mating cross axle have a habit of sliding off. But, the peg holes present in larger wheels provide opportunities to securely attach the hub with screws. Using a lathe, milling machine, digital readout, magnets, PVC plastic, and a carefully-drafted layout can produce a rugged Lego coupler. Ah, an article on math and machining; what could be more universally appealing? Replacement Battery Pack from AAA

Cells

When a consumer device stops working because of a proprietary battery pack, you may be able to repair it by replacing the batteries with off-the-shelf rechargeables. If necessary, it is possible to solder together your own battery pack so long as you wear safety equipment, have a solder gun, and clean the terminals. Of course, this assumes you can find cells that match in size, voltage, and chemistry. Afterthought Cake Robot A pleasant robot that doesn’t do much consists of a collection of interesting parts assembled together because they didn’t fit any other robots. The robot is a successful experiment in making couplers shorter, employing escap rectangular motors, detecting distance moved with an interrupter infrared encoder, and a cube of multiple smaller PCBs. Powered by a single 180 mAh lithium polymer cell without a voltage regulator. Motors driven using low-voltage high-current Zetex bipolar transistors. Includes lots of big pictures and a descriptive demonstration movie. Replacement for PNA4602M The Panasonic PNA4602M 38-kHz infrared detector was a very popular electronic part for obstacle and wall detection. Unfortunately, the PNA4602M is discontinued and similar modules can’t handle continuous signals. Good news! The new Vishay TSOP4038 is an excellent substitute. Tests compare detection distance, false pulses, and detection time. Also included is the relevant source code to variable-frequency duty-cycle measurement. Serial Communication A very popular method of sending and receiving data between devices and computers is good old asynchronous serial communication. See traces of characters being transmitted. Learn how far timing can be off before introducing errors. Includes a table of popular crystal frequencies and baud rates, as well as machining information and a source code snippet for an automatic bps detection tool.

Digital Indicator

Reuse is a good thing. In this case, a unique surplus item that appears to be a digital caliper is actually a digital indicator based on the caliper body and circuitry. The data port pinouts, mounting screw sizes, and example output analysis are posted, along with a cheap way of powering the tool from a 'AA' cell.

Repairing

a Model Rocket

A rocket found in a tree had loose and missing fins, a broken parachute, and a lifeless shock cord. Replacement fins can be made from balsa wood, using a pen and a hobby knife. After sanding, they can be reattached with two kinds of glue. Simple repairs and replacements make the rocket flight capable again. After all that work, an overzealous choice of a rocket motor sealed the rocket’s fate. Where do you think the rocket (and “Lego Major Tom”) ended

up?

Machining Magnesium for Elemental Density Comparison To demonstrate the massive difference in densities of naturally-occurring elemental metals, a large magnesium ingot is machined down to a precise cylinder using a hacksaw, milling machine,

and lathe.

Long Exposure Photography LEDs create beautiful and informative light trails when a robot is photographed in a dark place with the shutter open. This approach captures the exact movements and behavior in a single photo, as opposed to replaying a movie over and over. Use a tripod, remote control, and experiment with lighting conditions for best results.

Capacitor Leakage

When power is disconnected from a circuit, the capacitors on the board are discharged by the electronic components until no voltage remains. That’s fine. But, did you know that if you charge a capacitor on its own, it will slowly discharge through itself? More surprisingly, some capacitors become leakier with time, but can be healed through usage. I was shocked to discover how difficult self-discharge is to measure. Industry-Standard LCD

Modules

A blowout price on a 2x8 LCD module without specs leads to a bargain on industry-standard 14-pin alphanumeric LCDs. Demonstrates simple techniques for determining connector pins. Ultimately, the datasheet is found, and the contrast and backlighting pins are covered as well. Includes an example of writing custom bitmap characters. Color Printed Circuit Boards Green is so boring! Finally, your electronic devices can have beautiful red, black, and blue color circuit boards. The example shows an exposed-PCB Sandwich robot that starts with colored copper clad boards. The PCBs are etched at home with a peristaltic pump, after including an image of my dog and dealing with government-coded dots. The project is rounded out with a clear DIP socket and a shrouded

battery cap.

Trimpots

A visual guide to breadboard-friendly trimpots (small variable resistors) that appear in nearly every hobbyist electronic project. The article features comparison pictures and part numbers of 3/8-inch and 1/4-inch square single-turn and multi-turn trimmers. Even more interesting is the cutaway close-up photographs of the inside gears and brushes of these tiny potentiometers. Back-And-Forth Robot A robot that drives forward to a wall and returns is a popular contest and student project. Surprisingly, this robot can be made with an off-the-shelf 8-pin motor chip, a couple of resistors, and a couple of chips. The article provides a complete walkthrough of the schematics, along with an animation of the changing states and a video. Minifigure Multimeter Have you ever had a pile of assorted resistors that you wish to quickly organize? Place each resistor in the hands of the electrified Lego minifigure to see and hear the nearest standard resistance. This practical meter includes both an ohmmeter for resistance measurement as well as a voltmeter for battery measurement. Weatherproof Project Box Modifying a Pelican micro-case for a dustproof, waterproof, and bugproof outdoor electronics container. Tips on punching a rubber liner and connecting external wires through a PVC pipe, or hacking a seal with poster tack.

Safe Sync for

External Flash

Digital cameras have a relatively low voltage limit on their sync hot shoe, compared to mechanical cameras. This makes modern cameras susceptible to damage from higher-voltage external flash units, which consumers and hobbyists may attempt to reuse from previous generations. The circuit described in this article is a classic solid-state level-shifter often used to interface DC circuits to AC

appliances.

Electrolysis Rust Removal There’s nothing more depressing than to see corrosion on your precision tools or antique hardware, particularly if the rust is in a hard to reach area. Fortunately, there’s an electrical technique to reverse oxidation without harming steel or iron the way abrasives or harsh chemicals can. Includes results of testing a graphite electrode

for the anode.

How to Measure Low

Resistances

Occasionally you'll run across electronics such as relays, cables, igniters, switches, or current-sense resistors that have resistances less than one ohm. Few multimeters accurately measure less than 1 Ω, but most have a millivolt mode that can be combined with a 5 V source, a fixed resistor, and some simple math to determine milliohm

resistances.

PCB Layout Tricks and Tips A few extra holes, wider pads, and copper fills can greatly increase the versatility, solderability, and ease of testing of the printed circuit boards you design.

Solar Recharging

A small solar panel or series of solar cells can power an electronic device during the day, as well as recharge NiMH batteries to power the device at night. This simple recharger uses diodes for reverse-power protection and so that the project can measure the power source voltages. Includes schematics and graphs.

Multimeter Reviews

A digital meter is an essential tool for all robot builders and electronic hobbyists. If you’re just starting out, can you buy the least expensive model and still get accurate results? How much do you need to spend to get a decent mid-range model? A dozen multimeters are tested and compared. _Previous articles are moved into the categories below._ To be automatically alerted to new articles when they are posted, subscribe to the Robot Room

RSS feed .

ALL ARTICLES

Robots

All robots

Line-Following Robots Including maze solving

Mini-Sumo Robots

Plus ring making and rules

Solar Robots

BEAM and microcontroller

Motors

Mounts, couplers, H-bridge, PWM

Machining

Milling, drilling, and lathe PCBs and Breadboards Solderless and printed circuits

Tachometers

Also counters and encoders

Electronic Projects

And various electronic parts

Sensors

Infrared, photo, and distance

Inside Toys

Reverse-engineering

Calculators

Ohm’s law and resistor bands

Miscellaneous

Multimeters and more

Obsolete

Scrapyard of old articles

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