Spark Fun Electronics has made a name for themselves recently by selling interesting parts like this $20 color LCD. Hack-A-Day reader [Refik Hadzialic] decided to buy one and see how easy it was to use. It is a 128×128 display and should be a clone of the one you would fine in a Nokia 6100. He wired it up to an ATMega32L-PI8 microcontroller. He grabbed source code from a couple different places and eventually got something to work. In the end, the actual control commands seem pretty simple. Refik has been posting a lot of quick projects and info on his site, e-dsp. Have a look.

Continue reading “Controlling A Cheap Color LCD” →

Risto K?’s PC to R/C interface let’s you connect to your Futaba radio transmitter. You can use this device to do direct control of your R/C project: prewritten trajectories, user called macros, or direct PC joystick control. He’s built two versions. The original one used multiple D-latches. The second version was an attempt to reduce the number of components. It uses interrupts in the microcontroller software instead of the latches. This would normally cause a lot of jitter, but Risto implemented the interrupts in assembly. The controller can handle up to 16 channels. The LCD displays the last pulse-width and channel.

[thanks Will]

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Reader [alberto ricci bitti]’s DVD thermometer is a temperature sensing infrared remote that controls a DVD showing the temperature. Since the box doesn’t get any feedback from the DVD player, it stops and starts the disc to make sure it is at a known state. The brain of the device is a Motorola MC68HC908QT4, an 8-pin microcontroller. Communication with the Maxim DS1621 temperature sensor I2C bus is done in software. Even if you don’t want to build a gaudy thermometer the article features a lot of interesting information. It covers reverse engineering the remote, emulating an I2C bus, and creating a programmable pulse generator instead of bitbanging.

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LEDs are extremely common in electronic devices. They are used as light emitters, but can also be used as light detectors since they are photodiodes. By quickly switching between light emitting and detecting, you can use the LEDs to determine the ambient lighting and even do bidirectional communication. MERL has a good paper covering the basics of how this system works and how they used it as a “last-centimeter” communication device. The system can be implemented using one LED, a resistor, and two I/O pins. So, it could be used cheaply in almost any device. The microprocessor quickly switches the LED between emitting light, detecting light (LED acts as a charging capacitor), and measuring the discharge rate of the LED to determine light level. Jeff Han has a neat video demo of how this system can be used as a proximity sensor.

UPDATE: [hawkeyeaz1] pointed to a blog covering one person’s investigations into LED sensors.

[thanks branen]

So, if you were wondering what [Kenn Sebesta] was working on that needed yesterday’s hack, this is it. The plate can maintain the cue ball in its current position or make it travel an arbitrary path like a circle or figure-eight. It can also avoid obstacles placed on the plate. Kenn has documented his project thoroughly and covers many of the problems he faced along the way, like how to find the ball in the webcam image. Like most quality thesis projects, it’s constructed out of LEGO.

UPDATE: Now with video!

Continue reading “Ball And Plate Doohickey” →

While working on his masters degree in controls and robotics, Hack-A-Day reader [Kenn Sebesta] developed a cheap method for digitally reading analog gauges. This method was necessitated by needing to take over 3000 measurements using a dial indicator during his thesis work. The system is implemented in Matlab and uses a webcam to take a picture of the gauge. Once picture is taken it goes through several steps: First, it is reduced to a single color. Then, edge extraction is used to find the lines. Next, the lines are thickened. Finally, the Hough transform is applied to find the longest line: the needle. All that is left to do is measure the arc back to the zero point and match it to your scale. Using this method Kenn’s laptop can take 4 measurements per second.

Continue reading “Digitally Reading Analog Gauges” →

The RepRap project hopes to build a universal constructor; a machine that can replicate itself and make a number of useful products. The machine is open source and uses fused deposition modeling (FDM) to layer melted material into parts. One of the key technologies in self-replication is the ability to lay conductive circuit paths. The RepRap machine is able to lay down conductive material and an insulator. For a conductor they are using Wood’s metal, a fusible alloy that has a melting point of 158degF. To demonstrate this conductor laying ability they built the FDM head pictured in a commercial FDM machine. The project makes some reasonable compromises; it doesn’t attempt to make common items like brass bushings, microcontrollers, stepper motors, self-tapping screws, and power supplies.