July 2002

Saturday 20th July 2002

The first battle was now over, so it was time to review what to do. The question was whether to repair the Hog and restore it to its former glory, or to review the lessons learnt and make some changes. The areas where I wanted to make some improvements were:

  • Clad the complete robot to reduce the damage sustained from the flame pit.
  • Increase the power and efficiency of the motors by upgrading the motor controller from 12v to 24v (or higher).
  • Improve the power of the flipper.
  • Reduce the overall size of the robot.
  • Remove the need for a self-righter, or combine it with other features/weapons.
  • Allow control of the robot without the need of a radio transmitter.

I'm still a bit undecided about which way to go, but am erring on the "new robot" side of the fence at the moment rather that the rebuild side.

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Saturday 27th July 2002

I thought I would have nothing to loose by trying out my Winch motors on a 24v supply to see if I could get some more power out of them. I had always been a bit apprehensive about increasing the supply to the winch motors because they were not particularly efficient and drew a lot of current.

I first connected 24 volts directly to the motors using a set of jump leads. The motors span considerably faster than on 12volts, but there were an awful lot of sparks as I made the connection to the batteries. I dreaded to think what current was being drawn, but leaving that aside I ran the motors for about 30 seconds at full speed and found that they didn't seem to suffer too much. There was no smell of burning wires, and there was no smoke either.

Now came the moment of truth, I gingerly used one MOSFET block to supply the -ve feed to the motors and then turned on the motor controller. I wound the speed up slowly and the motor increased speed nicely. The MOSFETs were doing well so far, so I increased the speed until it was driving the motor at full speed. Things seemed to be going well until all of a sudden there was a bang and two MOSFETs blew holes in themselves.

I quickly turned everything off and felt the MOSFET heatsink gingerly with a wet finger. I could have fried eggs on them they were so hot! Obviously the MOSFETs had been able to carry the load for a while, but they were working well outside their temperature range.

This convinced me that if I wanted more power, I would have to look at using more efficient motors. Either Litton motors that the Wheely big Cheese sells for a reasonable price, or what is now the robot standard Bosch motors as sold by Technobots. The Bosch motors are a bit more expensive, but there are more variants to choose from (12v and 24v versions).

I will mull over which ones I will go for over the next few weeks. This experience was now making me err even more on the "new robot" front than the "rebuild" front, so I decided to think about renewing contact with my sponsors!.



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Last updated 1st August 2002