I decided to make some last minute changes to Mini Me before going to Chicago Tardis 2013, and as the convention Reversed Polarity was going to happen a few weeks beforehand it seemed like the perfect place to test out these upgrades

Upgrade 1) To make him have 3 wheels instead of 4, driving the 2 back wheels and having the 3rd like a shopping trolley style wheel.

Upgrade 2) To add a blue glow to go with this new mobility.

Upgrade Number 1

Was a matter of taking the Vex chassis out, removing the 2 front wheels, and replacing them with 1 wheel. Because of the arrangement of how the Vex is attached, this takes a long time and is hard on the arms (you have to hold the skirt from the inside and from the bottom while screwing and unscrewing).

Upgrade number 2

I added 10 AA batteries giving a total of approx 15 volts. I bought 2 x 50cm strips of blue LEDs and wired them in parallel. The strips need 12 volts. I tested them and found that they worked down to around 9 volts and were still reasonably bright. In the past I always used a 78xx type power supply but I had purchased some cheap (buck) switching power supply boards from offshore. I set it to 10.5 volts. This was great as there was very little heat and as far as I could tell very little current draw above the 200mA for the LEDs.

When I got to the convention we had mechanical difficulties and one motor was not working. He would drive about 2 feet and then not move. But at least the glow from his skirt looked good.

I was only there Friday night and Saturday and so I tried to do a quick (unsuccessful) repair to the motor late on Friday, only to pull a wire off my blue light power supply. So on Saturday he did not move and his base did not glow.