This power supply is built with a variable voltage regulator from Radio Shack. After playing with the resistors I had a stable voltage for the VEX controller
im woundering what resistors you had used in this project, my team is wanting to do the same thing, Thanks!
Whoa, way to revive an old thread!
The key part is a variable voltage regulator (probably an LM317T), so take a look at the datasheet to find out exactly what resistors you need. The Vex controller needs between 7.2 and 9V. You could also use a straight 9V voltage regulator, although you would probably have to order these instead of getting them from Radio Shack.
Plug it into your Digital Sidecar, that’s all we did.
There were no Digital Sidecars in 2006.
the vextrollers do work at 12v. just have to be careful with the amp draw at the higher voltage.
The LM317T also really prefers a heat sink for anything more than about 1/2 Amp, and a large capacitor (~10 uF) at the output will help it as well. Again the datasheet is your friend.
I made one of these based on the information in this thread and a data sheet from I believe it was TI. I’ve drawn up a rough sketch of what the circuit looks like and figured I’d share it. Works great for us and outputs 7.2 Volts, just about what the Vex computer would love to have.
Here’s the rough schematic I made:
http://s7.postimage.org/8v269gm4p/20120504_181754.jpg
http://www.vexrobotics.com/products/accessories/logic/276-2170.html
At least on the old computer it says that with motors and servos the computer should draw about 62 mA. I have a heatsink on the LM317 on the converter I made but after testing it and reading this bit of information, i think it may be unnecessary.