http://www.robotroom.com Recent articles about robots, electronics, machining, and software en-us Copyright 2000-2013 David Cook http://blogs.law.harvard.edu/tech/rss http://www.robotroom.com/David-Cook-Robot-Room.png http://www.robotroom.com David Cook thinking about robots 100 100 Manual. By hand. Which is sort of odd for a guy who builds automated things. Sat, 30 Mar 2013 00:10:30 -0500 Sat, 30 Mar 2013 00:10:30 -0500 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. 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.]]> http://www.robotroom.com/Sampling-Rate-1.html http://www.robotroom.com/Sampling-Rate-1.html Software Electronics Measurement Sat, 30 Mar 2013 00:10:30 -0500 Easy-to-use free PCB software from Robot Room. Hobbyist and student friendly, but with powerful features. All of the standard drawing tools, plus continuity tester, board flip, dynamic fills, notes, and even images. Create your own robot and electronic-project circuit boards in no time! And with the Export to Gerber upgrade, you can order professionally-manufactured boards from the vender of your choice. Easy-to-use free PCB software from Robot Room. Hobbyist and student friendly, but with powerful features. All of the standard drawing tools, plus continuity tester, board flip, dynamic fills, notes, and even images. Create your own robot and electronic-project circuit boards in no time! And with the Export to Gerber upgrade, you can order professionally-manufactured boards from the vender of your choice.]]> http://www.robotroom.com/CopperConnection/index.html http://www.robotroom.com/CopperConnection/index.html PCBs Software Robots Electronics Fri, 01 Feb 2013 01:26:14 -0600 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. 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.]]> http://www.robotroom.com/Yummy-Robot-1.html http://www.robotroom.com/Yummy-Robot-1.html Robots Machining Motors Thu, 24 May 2012 21:11:42 -0500 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. 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.]]> http://www.robotroom.com/Cleaning-Mouse-Scroll-Wheel.html http://www.robotroom.com/Cleaning-Mouse-Scroll-Wheel.html Inside Salvage Sat, 28 Jan 2012 21:09:46 -0600 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. 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.]]> http://www.robotroom.com/Desoldering-Holes-1.html http://www.robotroom.com/Desoldering-Holes-1.html PCBs Machining Sat, 28 Jan 2012 15:04:07 -0600 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? 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?]]> http://www.robotroom.com/Sturdy-Lego-Coupler-1.html http://www.robotroom.com/Sturdy-Lego-Coupler-1.html Motors Machining Robots Thu, 12 Jan 2012 22:06:21 -0600 When a consumer appliance stops working because of a built-in battery or 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. When a consumer appliance stops working because of a built-in battery or 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.]]> http://www.robotroom.com/Soldering-Batteries-1.html http://www.robotroom.com/Soldering-Batteries-1.html Inside Salvage Tue, 10 Jan 2012 20:54:31 -0600 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. 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.]]> http://www.robotroom.com/Afterthought-Cake-Robot-1.html http://www.robotroom.com/Afterthought-Cake-Robot-1.html Robots Mon, 02 Jan 2012 23:02:16 -0600 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. 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.]]> http://www.robotroom.com/PNA4602M-Replacement-1.html http://www.robotroom.com/PNA4602M-Replacement-1.html Robots Measurement Electronics Parts Mon, 26 Dec 2011 00:18:47 -0600 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. 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.]]> http://www.robotroom.com/Asynchronous-Serial-Communication-1.html http://www.robotroom.com/Asynchronous-Serial-Communication-1.html Measurement Electronics Machining Sat, 17 Dec 2011 10:44:38 -0600 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. 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.]]> http://www.robotroom.com/Digital-Indicator-1.html http://www.robotroom.com/Digital-Indicator-1.html Machining Measurement Salvage Electronics Sun, 27 Nov 2011 19:33:55 -0600 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? 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?]]> http://www.robotroom.com/Rocket-Repairs.html http://www.robotroom.com/Rocket-Repairs.html Model Rocketry Thu, 17 Nov 2011 21:30:02 -0600 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. 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.]]> http://www.robotroom.com/Elemental-Cylinders-1.html http://www.robotroom.com/Elemental-Cylinders-1.html Machining Sun, 13 Nov 2011 12:16:20 -0600 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. 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.]]> http://www.robotroom.com/Long-Exposure-1.html http://www.robotroom.com/Long-Exposure-1.html Robots Sandwich Photography Sun, 11 Sep 2011 23:36:09 -0500 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. 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.]]> http://www.robotroom.com/Capacitor-Self-Discharge-1.html http://www.robotroom.com/Capacitor-Self-Discharge-1.html Electronics Measurement Sat, 09 Jul 2011 16:40:28 -0500 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. 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.]]> http://www.robotroom.com/LCD-Nanox-Sanyo.html http://www.robotroom.com/LCD-Nanox-Sanyo.html Electronics Displays Salvage Sun, 22 May 2011 16:23:54 -0500 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. 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.]]> http://www.robotroom.com/Color-PCBs.html http://www.robotroom.com/Color-PCBs.html PCBs Sandwich Robots Tue, 17 May 2011 23:59:09 -0500 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. 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.]]> http://www.robotroom.com/Trimpots.html http://www.robotroom.com/Trimpots.html Electronics Parts Inside Sat, 30 Apr 2011 19:04:01 -0500 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. 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.]]> http://www.robotroom.com/Back-And-Forth.html http://www.robotroom.com/Back-And-Forth.html Robots Motors Machining Breadboards Schematics Mon, 14 Mar 2011 19:06:49 -0500 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. 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.]]> http://www.robotroom.com/Minifigure-Multimeter.html http://www.robotroom.com/Minifigure-Multimeter.html Lego Multimeters Electronics Sun, 06 Mar 2011 19:07:28 -0500 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. 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.]]> http://www.robotroom.com/Weatherproof-Project-Box.html http://www.robotroom.com/Weatherproof-Project-Box.html Electronics Enclosures Weather Mon, 03 Jan 2011 19:07:45 -0500