Jon's Place

Sunday, March 29, 2009

New Chest

In order to fit the RX-64 shoulders into BrainBot, we needed to design a new chest. Given the cost of printing the chest in one piece like we were doing before, we decided to make this new chest modular, with six sides (like a cube), and have everything screw together.

The new chest looks neat - we have a different 3D printer now, and it prints semi-transparent material. The tolerances are actually better than what the ABS printers do, although the material is not nearly as nice to machine or to tap. All in all, I'm pretty happy with how it turned out.

We also printed a gripper with this new printer. The structural parts of the gripper (specifically, the shaft and offset crank arm) are machined from aluminum and Delrin respectively. We use the foot pressure sensor board to provide feedback from four sensors on the grip.

Wednesday, March 25, 2009

BrainBot - Getting Bigger

So, I've been working full time on BrainBot for six weeks now. Things have changed somewhat - the researcher who wants us to build a bunch of these wanted a Core 2 Duo class onboard cpu, so we had to redesign to allow for a mini-itx. As it happens, we can now put a Core 2 Quad onboard, since the board is the same size...

In order to handle that, we needed to add more batteries, so the chassis has gotten quite a bit wider - we can now fit four 12 volt 4.2 amp-hour NiMh battery packs inside the chassis, two on each side of the motherboard.

We upgraded the chassis panels to be 1/4" Delrin, and the standoffs between them are 49mm long, in aluminum.

The motors are 12 volt 200 RPM gearmotors, with 100-tick encoders, which feed into a pair of LSI LS7366R 32-bit SPI quadrature encoder counter chips.

Its pretty funny when your robot has more onboard processing power than your development laptop...