WHEN: Most Friday evenings. TIME:

10 March 2014

BYO multi board thirty band controller for 1/32 racing

This one is for those tight on local Rands and willing to do a relatively simple bit of handiwork to give themselves the versatility similar to the 1/32 Difalco 30 band controller, especially if contemplating something like non magnet plastic racing in addition to magnet racing, where alternative resistance boards are a must.

One way is to source a Parma turbo controller and bolt on:
1.   1/24 difalco conversion module economy rheostat slot dd253-hd30
2.   for that "feel" Difalco ball bearing upgrade kit w/trigger pin
3.   If you really want to go the whole hog (not necessary) - Difalco diy genesis frame kit w/trig pin

Using the conversion module instructions and this useful little pictorial which shows how to modify the Parma Turbo frame and fit the board - the board is different but the assembly and hook up precisely the same:

Or one can go the cheapie approach I used for Craig's controller, using the Euro style pnp transistor and simply bolting (with bolt insulation) the pnp transistor to the Parma Turbo frame and following the simple hook up. I recommend using the 1/24 upgrade board with 148 ohm for magnet racing and purchasing a spare 290 ohm board only if you intend non magnet racing.

For this approach source a Parma Turbo controller and bolt on:
3.   R12     From Mantech or many electronic shops, the Tip36c Transistor
4.   £7        Brake pot Wirewound 4W Power Potentiometer 25-Ohms (50 ohms ok as well)
5.   £7        Sens pot Wirewound 4W Power Potentiometer 50 Ohms (25 ohms ok as well)

Just follow the hook up guide in this picture using colored wire, cut completely though the board rail shown between H and C so there is no continuity and you good to go. No cutting of the existing wiring other than splicing in to the existing white and black cable and chopping and extending the red cables to hook to the 25 ohm brake pot, which is bolted on along with the 50 ohm sensitivity pot, which is soldered on where shown. That's it you done.

This the assembly sequence for the Craig pnp controller:

Bolt on upgrade board and transistor and cut frame heat sink

Note screw insulator for transistor and home made "L" brackets to hold board to frame

See it fits and chop case to suit

Chopped Case

Wiring and wiper arm added

Hook up to back of upgrade board.
That is pretty much it. If you prefer to go with the original US npn transistor approach then you don't have to cut through the track between H and C but you do have to insulate the wiper arm from the wiper base using tape on similar, as per the detail hook picture below:

On my version I used a Difalco replacement power transistor 1/32 for $7 or you can local and cheap with the Tip35c npn transistor for about R14.

Once complete, if you wish one can add a 30 amp or more automotive relay. One has to disconnect the white cable from the full power stop and connect in a new "skinny wire" from the relay to the full power stop. The rest is hooked up as per Jim Difalco: The brake wire is on #86, the skinny control wire that turns on relay is terminal #85. Then the two main black and white controller wires go to terminals #30 and #87 (does not matter which goes where).

Changing the Wiper arm button to floating is also recommended, guide as per Jim Difalco:

A floating button is pretty simple. About 1/4" below the wiper button hole bend the arm down, towards the circuit board, at about a 30 degree angle. Next at the centre of the wiper button hole bend the arm up at a 30 degree angle. Make sure you make both bends parallel to the top of the trigger. This setup with all the wiper pressure on the centre of the button lets the button pivot top to bottom. This is needed so when you pull the trigger the top or bottom button edges do not lose contact because of the play in trigger bearings.

Next file the face of the wiper button flat. File the face of the stud and tin it with solder. Now install the trigger in controller. If you have an electronic type controller solder the skinny wire to the wiper button stud. If it is a resistor type controller solder a short 1" piece of leadwire from the stud to the wiper contact that is over the wiper arm to ensure connection. Leave a little slack here, do not run the wire straight from button to trigger contact. The button needs slack to pivot. 

Tips: if you are trying this on a resistor controller the wiper button edges should be rounded off. If you are trying this on a Parma resistor that resistor should be sanded flat or you will be causing the button to catch the edge of any high band.

Adjust the wiper arm tension by gently pulling it away from the wiper board. Check that the wiper button does not lose contact as you pull the trigger across the contacts. Also check that the button contacts the first band at the front edge of the button. If it does not, you can twist the front edge of the wiper arm down until this happens. 

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