You might want to store information from a multimeter to be graphed over time. This comes with pretty much all of the high-end professional models. But if you buy a super cheap meter you can bet this isn’t an option. [Jazzzzzz] has found a way to pull the data from a $4 meter via RS232. It’s not impossible, but we definitely think he’s doing it the hard way. That’s because he’s not just tapping into a dormant feature. He’s actually adding a microcontroller to sample the data and push it via the RS232 protocol.

On the bright side, this is easier than building a multimeter from scratch. The sampling circuits are still being used, with a PIC 16F688 intercepting the signals as they enter the stock microcontroller. The signal he was after comes into the chip on just one pin, but to get the readings right on the PIC he had to use an OpAmp. That’s only part of the puzzle as he also needed a way to tell what the selector switch was set at. In the end, adding a potentiometer and reading its value let him calculate the position.

[Thanks Karl]

[funnypolynomial] saw this Pong clock years ago and had been planning on building his own version. With a move looming he decided it was finally time to finish up his Pong clock since completed projects take far less room than incomplete ones. The core of the system is a ThinkPad. He separated the hinge and bolted the keyboard to the back of the screen. The display ribbon was long enough, but he had to extend the wires for the backlight. The power button was also extended and the battery removed. The software is a Windows screen saver that uses the two mouse buttons for navigation similar to how you set a two button watch. Every minute the the left player misses the ball and the right player’s score increases. You can see a video of the clock below. In the past, he also turned a digital multimeter into a clock. Read the rest of this entry »