Installing the guts

Tim had me build some heat sinks for the fets we were going to use to turn the motors on and off. I started with an aluminum angle and with the use of a table saw equipped with a negative 2 degree rake on the blade, I was able to make quick work of the aluminum.

The fins were created by making several passed on the table saw using a sliding miter box. Once the heat sink was cut to length the positioning of the fets were considered and installed on the board.

you might notice that the heat sink changes color, it looks anodized but its just some translucent red paint.

At this point we are all excited that things are coming together despite massive amperage draws on the batteries. We were able to get the motors to pulse in response to the ultrasonic sensors, except for one of the banks that was drawing an excessive amount of amps. Bil, Paul and I fixed the bank that was drawing excessive amps due to the motors grounding out on the tubes. Once the last bank of motors was installed it all went to hell. Tim felt that the fets were not working as planed and came up with some alternative fets but in the end I don't think it was our best option. I am also unhappy with the the way the machine respondes to the viewer.

this image of complications is the last thing I wanted to happen just before the opening. Our piece probably had the most amount of man hours and still fell short of the finish line.

One of the major problems was that the motors were manufactured with a brass electrical contact protrude beyond the body of the motors. Despite the fact that the motors were covered with heat shrink, the brass contact cut through the plastic and caused most of the motors to grounding out or were on the verge of grounding out.

I went ahead and pulled all the motors and striped all the heat shrink in order to trim back the brass plate that has reeked such havoc. I used pneumatic die grinder and an abrasive wheel to trim of the brass protrusion on all 80 motors and then re heat shrink the motors. One other problem was that several of the motors got some flux around the shaft of the motor and caused it to freeze up. I used a bit of lacquer thinner to clean of the flux.

Once all the motor banks were put in working order and had consistent amperage draw, Tim rounded up some more fets and got it working again. We did have one of the sensors go out and one is on order to replace the third sensor.

The last thing I have done so far is to put a cover plate on the back side of the machine. I provided a place for a on/off switch, serial port and battery recharging jack.

The ultrasonic sensors were purchased from a company called Acroname. The cost is about 25$ per sensor per unit. We used 3 units, I would have proferred a few more but money isn't growing on trees these days.

I found some info about the sensor at this link