As part of the 2003 Project season John Felcyn designed and built a complete charging and metering system for Thumper assembled entirely from parts that we had in stock. He build the complete system by himself from concept to working prototype in under 2 weeks.

Up to that point Thumper's control systems consisted of the CB-1 power cabinet (used mainly for Gemini), a loose diode/heatsink assembly that we had been using since the very early testing, and some various bits of wire. All metering was done by hand probing with a DMM.

John's work brought us out of the dark ages and into the middle ages with a old-school relay logic based design that was very rugged and worked well under the hard conditions that Thumper is prone to creating.

The charging system is composed of two main areas, the control cabinet and the high-voltage charging supply.


Here's the main interior of the control cabinet. As you can see it's based on a set of 4 TDRs (Time Delay Relays) and 2 regular "Ice Cube" relays. Everything in the control system is rugged old-school analog with no delicate digital systems that could more easily fail in this application. The 4 TDRs change the tap points into a 0-50-70-100-120VAC autotransformer and this allows us to charge the system as fast as possible while maintaining current limiting in balance. Thumper can charge to 1,600VAC in about a minute and a half from a 20A 120VAC power feed.


Here are the controls from the back side of the door. The top is the voltage meter, below that is a 5VDC "wall wart" style power supply (from an old Zip drive actually). John needed a quick&dirty solution for powering the meter and this was handy. By simply putting a couple Panduit crimp connectors onto the standard wall plug tips it was pressed into service for an application that Iomega never imagined.


Here you can see the control cabinet from the front (and Moose's right leg...we spared no expense on hiring a professional photographer and graphic designer). Moose also did the very high tech custom graphics for the control labeling.

For the curious, the controls are as follows. The top is the voltage readout of the capacitor bank. The row of 4 consists of the pair of Push To Fire buttons (one on each end), the Charge Complete light (Orange), and the System Hot light (Green). The covered switch (which is MilSpec no less) is the main power switch. The bottom row is the Push To Charge button, the Charge-Dump-Fire selector switch, and the Warning Horn button.

Also of note is that if you look closely on the bottom of the cabinet you can see a thick robbed cable coming out. That tells us that this picture is relatively recent because that cable is not John's work. That cable feeds the large outboard red firing button that triggers the pneumatic gap. The button (and gap) were installed years later by Chris Boden as part of the Mk-6 Prototype upgrade.

The High Voltage Charging Supply is located on the bottom shelf of the cabinet and consists of five main components, the MOT, the HV contactor, the Diode Bank, the main contactor, and the limiting resistor.




Here you can see the layout of the bottom shelf.


The MOT (Microwave Oven Transformer) has a promary side of 120VAC and a secondary side at about 2000VAC. Power is fed from here into the full-wave bridge rectifier.


Here is the board on the slide out shelf. The shelves were donated by Hoffman Inc.


In the event of a misfire or operational failure this is the high voltage contactor that will trip and dump the entire array into the safety system where all of the stored energy is dissipated as heat.


This is the backside of the cabinet at the bottom shelf. You can see the voltage metering pickup board hanging in between the rails.


Here's a closeup of the metering range adjustment.