Wednesday, March 24, 2010

Acer Aspire One RAM mod

I'm using an Acer Aspire One to control my robot. I'm coding using Eclipse, but the 512 MB RAM in the Aspire is too small, and it swaps. Swapping on the flash drive is very slow, so I finally took the courage to upgrade it to 1.5 GB, following this nice guide: .

It worked!

Sunday, March 14, 2010

Inside the circuit box

The circuit box is getting quite crowded with all these wires.

6 servos and a gate sensor

While I had my circuit board disconnected to fix the tachometers I also added support for an extra servo motor, so the board can now control 6 servos. I've also added a gate sensor since I first blogged about the robot. The gate sensor is nothing more than a switch on a stick.

I need to shorten that USB wire from the camera...

Tachometer blues

So my tachometers suddenly started acting weird. When on the edge between black and white, the tachometers counted up like crazy. I figured the Schmitt triggers on the input pens on the Atmega must be a little too sensitive. They have a hysteresis of only 0.25 volts @ a supply voltage of 5V, thats a bit in the low end. So I added a 4093 quad nand schmitt trigger IC (hysteresis 0.9V), and after a little confusion (forgot one single connection on the circuit board - that gave really odd results), the tachometers now run flawlessly.