The parking brake driver powers up a solenoid (to release an electromagnetically operated brake) when the controller starts to drive the motor. Power is released a fraction of a second after the controller stops the motor, to re-apply the brake.

The option is fitted as standard on the NCC-70 controller but is not fitted as standard on NCC-35, NCC-50 or NCC-60, where it is a factory option.

There are few components to the driver option and (if you are safe with a soldering iron) this page details how to fit the option. However please read the caveat (about the guarantee) at the end.

Components required.

PNP power transistor, TO220 case. TIP32A or TIP42A.
• NPN small signal transistor.
  We use BC546 which has centre base and leads identified in the diagram. This is a popular transistor outside America - but American transistors (e.g. 2N 3905) tend to have their leads reversed (c-b-e instead of e-b-c)
• Diode, 1N4148 - or any similar diode.
• Diode, type 1N4002 or similar.
• 100K resistor, 250mW CR25 size (or smaller).
• 1µ0 capacitor, Plug-in, wire ended. 10v working or more. Note that, in the diagram, the white mark on the capacitor indicates the negative.
• 3 pin connector, 0.1¨ pitch.

The components are identified in the diagram. The copper area under the case (collector) of the PNP power transistor is battery negative, circuit ground. Negative lead of the capacitor connects to it, as does the emitter of the BC546 transistor. This copper area also acts as a heatsink for the power transistor.

The diagram shows the NCC-60/70 - the NCC 35 and 50 are the same in this area.

Warning:

Other relevant pages

• Service Manuals - Index
• NCC circuit diagram, Issue 24

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