Nov 112013

So frequent readers of my blog (Hi Mom!) will remember my sumo robot competition coming up. The competition came and went and this is what happened. Last post I commented that if I had it to redo my sumo board again I would choose another motor driver IC. I spoke too loudly and Murphy heard me. After one failed repair job and one failed protoboard bot I finally got something working using the Teensy 2 and the TB6612FNG.

Where did I mess up on the custom board?
I’m not entirely sure. I had a few board level problems and a few IC troubles. First is the board it’s self, when you look at the schematics be sure to note that on the L298 I have the motor voltage and logic voltage mixed up. I pulled the pins out and soldered wires connecting to the correct spots like so.

Whats odd is before I did this one motor only worked in reverse and one worked well. After this nothing worked. I measured the current draw from the IC when the motors should be moving and got nothing out of it at all. The deadline was moving closer and I still had to finish the program logic so I decided to just build one on protoboard. So now I have two nice $50 coasters and one “art”. At least until I fix it.

It was also my first go at a big board like this and ended up getting some components way too close to each other. 3D view might have helped in this case.

Plan: F

I named my robot Plan F because if this last ditch resort didn’t work, I’d get an F.  Here it is with the chips and with out.

The board is really just a mother board or signal card. I wanted to reuse the Teensy or the motor control IC later so I stuck them on some headers. 

I have no idea what the rating for the motors is I just used a 9volt and made my base from 1/8th inch aluminum with a plexiglass top plate to set the brains on.  I did fairly well with my little sumo. First place in the smart robot portion and third over all. I even went up against some of the heavy weight bots and did fairly well. I didn’t win simply because they have so much more weight than me.

Files and etc.

Schematics, and board layout can be found there. Posted as is, errors and all. Use at own risk.  You can also find the sourcecode on Github

robotbattle from Digitalundernet . on Vimeo.

Jun 062012

You see them all the time from fresh faced EE students looking to power their new arduinos and LED’s. The simple computer power supply hacked and forged into a fixed output power supply for a range of very common voltages. Which is exactly why I did the same thing. I like my design, rather than trying to cram it all into the PSU case I attached a piece of bent Lexan to the underside of the case and brought all the wires out. I’ve got all the common voltages, and this supply has two different 12v outputs. Later on I may open it back up and throw an LM317 on that second rail for a variable voltage.

I didn’t take any pictures of the bending process but its stupidly simple. Find where you want the bend and add about 1/4 inch (6.4 mm for my metric friends). Then place the sheet in a vice and use a heat gun to heat the joint up. Keep the heat even or the plastic will bubble and ruin. Eventually the weight of the Lexan will cause it to bend at the vice. Just hold it in place for a minute until it cools.