October 2004

Monday 18thOctober 2004

After a long break from robot- building due to holidays and other commitments I finally made a start on building a couple of current limiters for the motor drive circuits. There was no free space within the motor controller box itself to mount the limiter, but I found a void right next to the box just under the mounting bracket.

I was hoping to mount the current limiting MOSFETs on an aluminium "brick" similar in construction to the existing MOSFET final power stage. I was going to squeeze both left and right motor current limiters onto one brick and at the same time position the MOSFETs as close together as possible on the heatsink base. Both the heatsink and the bus bars were going to be made out of 6mm alluminium which I happen to have an abundance of.

Current limiter plates and bus bars
Current limiting mouting
plates and bus bars

MOFETs mounted on current limiter plate
Each row of MOSFETs provide 245 amps
of current limiting for each motor drive

The fully assembled current limiting brick
Fully assembled current limiting brick

Current limiter mounted on underside of motor controller
The current limiter mounted on the left
next to the motor power stage MOSFET bricks

Here are a few pictures of the current limiter in various stages of construction. It's a little hard to see clearly in the last photo, but the limiter fits quite nicely on the motor controller mounting brackets close to the power stage MOSFET bricks which simplified the wiring routing considerably.

Go to top top

Saturday 30thOctober 2004

I tackled the problem of the hog's twisted flipper during the last week. During my last battle against Spawn Again, I was hurled into the air and landed on the front corner of the flipper. Most of the impact was absorbed by the aluminium flipper tip whose edge bent up. It was a simple case of unscrewing the tip and then wealding a club hammer at it to restore it near enough to its previous shape. The rest of the flipper was a different matter because of the triangulation nature of the struts. All of these had stretched slightly in the impact so it was virtually impossible to twist the flipper back to its original shape. In the end I hacksawed through several strutts and then ligned them all up again before welding them back together.

Go to top top
Go to top top

Back to Hassocks Hog home pageBack to July 2004Forward to November 2004

Last updated 8th November