FPGA Rescues Scope From The Dumpster

I’m always on the lookout for a quality addition to my lab that would respect my strict budget. Recently, I’ve found myself pushing the Hertz barrier with every other project I do and hence desperately wanted a high bandwidth scope. Unfortunately, only recently have 70 MHz to 100 MHz become really affordable, whilst a new quad channel oscilloscope in the 500 MHz to 1 GHz range still costs a fortune to acquire. My only option was to find an absolute miracle in the form of an old high bandwidth scope.

It seemed the Gods of Hand Me Down electronics were smiling upon me when I found this dumpster destined HP 54542C. It appeared to be in fairy good shape and was the Top Dog in its day. But something had to be broken right? Sure enough, the screen was clearly faulty and illegible. Want to know how I fixed it? Four letters: FPGA.

Continue reading “FPGA Rescues Scope From The Dumpster”

Simulating VR Obstacles with Wheelchair Brakes

[Joey Campbell] is studying for his PhD at the Bristol Interaction and Graphics Lab, focusing on the interplay between real and virtual objects within the realm of exergaming–“gamercising” where physical motion and effort drives the game. The goal is to make the physical effort seem to correspond with what’s seen on the headset.

[Joey] set up a test rig where an exercise bike’s gears were adjusted based on the terrain encountered, seeking to find out if that realism inspired a greater feeling of immersion. He also provided some test subjects a HUD with their heart rate and other stats, to see if that encouraged gamers to exercise more.

In his current project, [Joey] has equipped a wheelchair with a pair of Arduino-controlled servos that squeeze the brakes to simulate an obstacle. In the VR realm, a player pushes the wheelchair toward a virtual block and the brakes engage, requiring the player push harder to bypass the obstacle.

One imagines the possibilities of games designed for specifically for wheelchairs. The Eyedrivomatic wheelchair that won the 2015 Hackaday Prize sounds perfect for the job!

Continue reading “Simulating VR Obstacles with Wheelchair Brakes”

Current Sink Keeps The Smoke In

One of the most versatile tools on anyone’s work bench, at least as far as electrical projects are concerned, is a power supply. Often we build our own, but after we’ve cobbled together some banana jacks with a computer’s PSU or dead-bug soldered a LM317 voltage regulator to a wall wart, how will that power supply perform? Since it’s not desirable to use a power supply that’ll let the smoke out of everything it powers (or itself, for that matter) a constant current sink, or load, can help determine the operating limits of the power supply.

[electrobob] built this particular current sink from parts he had lying around. The theory of a constant current sink is relatively straightforward so it’s easily possible to build one from parts out of the junk drawer, provided you can find a few transistors, fuses, an op amp, and some heat sinks. The full set of schematics that [electrobob] designed can be found on his main project page. He’s also gone a step further with this build as well, since he shorted out his first prototype and destroyed some of the transistors. But, using a few extra transistors in his design also improves the safety and performance of the load, so it’s a win-win.

This constant current load also has the added feature of being able to interface with a waveform generator (an Analog Discovery, specifically) and as a result can connect and disconnect the load quickly. If you aren’t in need of an industrial-grade constant current sink and you have some spare parts lying around, this would be a great one to have around the work bench.