[Doug Jackson] makes word clocks, and he must be doing quite a bit of business. We say that because he put together a programming and test bed for the clock circuit boards.
This is a great example to follow if you’re doing any kind of volume assembly. The jig lets the populated PCB snap into place, making all the necessary electrical connections. This was made possible by a package of goods he picked up on eBay which included rubber spacers to separate the board from the acrylic mounting plate, pogo pins to make the electrical connections, and a spring-loaded board clamp seen to the left in this image.
The switch in the lower right connects power to the board and pulls a Raspberry Pi GPIO pin high. The Python script running on the RPi polls that pin, executing a bash script which programs the ATmega169 microcontroller using the GPIO version of AVRdude. We looked through his Python script and didn’t see code for testing the boards. But the image above shows a “Passed” message on the screen that isn’t in his script. We would wager he has another version that takes the hardware through a self test routine.
We first saw one of [Doug’s] word clocks back in 2009 and then again a few months later. The look of the clock is fantastic and it’s nice to see the project is still going strong.
For a power hungry project the supply is sometimes a pretty big unknown. Whether stapling together a few different power supplies to meet a current requirement, or designing a system from the ground up: a big power supply can be quite a dangerous thing. It helps to have some kind of a dummy load to really shake down the electronics and get an idea of how hot things get or test stability before trusting the supply to run your stuff. [Paulo Oliveira] has constructed just such a thing, a slick looking adjustable constant current load.
Following the popular LM324 circuit from [David Jones] at EEVblog [Paulo] decided to make use of the two spare op-amps to provide both a thermal overload and a cooling fan circuit. We have seen other tweaks to [David]’s circuit in the past but through some resistors and MOSFETs [Paulo] can now load up to 7A (limited by resistor wattage). We would have used a really crazy server
vacuum fan to make it genuinely frightening to push heavier loads. Thanks [Paulo]!
Inspired by a design he saw on the EEVblog, [George Graves] put together this constant current dummy load. You might need on of these if you’re testing power supplies or batteries. They pull a constant current regardless of the voltage of the supply. [George’s] version extends the range of the original a little bit by running the op-amp at 8 volts. He says that everything runs fine at 1 amp. He tried 2 amps but things got hot pretty quickly. What we really like though, is he took fantastic pictures. Sometimes even simple things can catch our attention with the right pictures!
If you ever watched MacGyver as a kid, you know that given any number of random objects, he could craft the exact tool he would need to get out of a sticky situation. If he ever made his way into the medical research field, you could be sure that this test for Acute Pancreatitis would be among his list of accomplishments.
Designed by University of Texas grad student [Brian Zaccheo], the Acute Pancreatitis test seen in the image above looks as unassuming as it is effective. Crafted out of little more than foil, jello, and milk, the test takes under an hour to diagnose patients while costing less than a dollar.
The test works by checking the patient’s blood for trypsin, an enzyme present in high concentrations if they are suffering from pancreatitis. Once a few drops of the patient’s blood is placed on the gelatin layer of the test, it is left to sit for a bit, after which sodium hydroxide is added. If elevated trypsin levels are present, it will have eaten through the gelatin and milk protein, creating a pathway for the sodium hydroxide to reach the foil layer. If the foil is dissolved within an hour, a circuit is formed and a small LED lights up, indicating that the patient has acute pancreatitis.
The test really is ingenious when you think about it, and will be a huge help to doctors practicing in developing countries, under less than ideal working conditions.
[via PopSci via Gizmodo]
Needing to test the display interface for a multitude of different sensors [Fileark] built himself this analog and digital input/output simulator. Along the bottom is a double row of trimpots that adjust analog voltages. Each voltage is measured by the Arduino inside and its value is displayed on the graphic LCD screen to confirm that the hardware you’re testing is making correct measurements. There’s also digital I/O in two different forms. To the upper left are momentary push buttons but the DIP switch bank below that allows the same connections to be toggled on and off. It’s not an automated test bed, but if you’ve got a lot of I/O, or a lot of hardware to test this will save you some real time.
Don’t miss the demonstration video after the break.
Continue reading “Mixed I/O testing module”
[Alex Papadimoulis] wrote about ingenuity and hacking in high school. Immediately after the teacher’s installed a new electronic note taking and test giving software, the students began hacking. They managed to find several ways to ace their tests, none of which involved studying hard the night before. Ultimately, the teachers went back to the old system to prevent such shenanigans.