WHEN: Most Friday evenings. TIME:

16 July 2009

Costa's bread board controller - part 3 MRRC addendum

Trotted Costa's new Parma Turbo down to club, only to be greeted with "Ja, but wot about the MRRC". Having motivated the MRRC up front, I was obliged to cobble together the one I had pre-ordered way back. Decided to this as a complete breadboard approach to minimise connection lengths and cable change - the only existing main cable change being to disconnect the red cable to facilitate brake adjustment, with one only cut to the controller case to let the bread board poke through. Note how the bread board is wasted to minimise the case cut.

Both pot terminals poke through to the board front so that connecting up is a breeze and the TIP36c was reverted to in this case to minimise weight and complexity.

It is vital that all cut adjustments are made to the breadboard and nix to the controller case - the internal pimples and bits are for holding the existing board!

The exercise to cut and drill the bread board took one episode of Desperate Housewives and was simply eyeballed, it is really not a tricky exercise. The existing board has four holes perfectly located to hold the home brew bread board. The wiper board is spaced and bolted to the bread board in the space previously used for the resistor.

There are excellent features in the MRRC, like two trigger options, adjustable spring tension, sprung wiper arm and adjustable full throttle stop.

The stock 12 band wiper board had the bottom third trimmed off for clearance of the spring mechanism on the wiper arm. The jury still out on the neat sprung arm as I think the wiper button may be of overly hard material [proved fine] and require a mod, time will tell.

The sensitivity pot is the same 20 ohm volume control pot we have been sourcing for the brake adjustment, through the net from Yebo Electronics in Cape Town. Two 20 ohm pots at forty bucks a pop and a cheapie Tip36c plus heatsink and one can have an adequate transistor conversion of the MRRC unit......

The lightweight heatsink for the Tip36c is widely available and more than adequate cooliing, ignore the mini fan unit in the picture.

The MRRC unit is easily the simplest and quickest way for Ecurie folk to home brew a change to the transistor approach.

The new unit proved a success for all of one and half laps, which is why the picture of the main cable is shown here. It would be crazy to change the magic cable but the colour sequence is white / black / red against our normal white / red / black jack plugs - no problem, simply swapped the red and black cables across but under tension it pulled the red and black jack plug terminals together and instant brakes, no go! Took a while to find and not a big deal, just be careful when fitting a jack plug - the club will be converting to three pin 5 amp plug, which will obviate this issue.