1QD Speed Controller


The 1QD is an obsolete controller: this page is for reference only.

As a replacement, we would advise the Porter range of controllers.

4QD’s 1QD series are motor speed controllers for 12v or 24v battery operation. They are state-of-the-art MOSFET chopper drivers giving fully variable fine speed control. Two versions are available, 1QD-70 and 1QD-35, in 12v or 24v options – 36v and 48v versions are available to special order.

The controller is designed primarily for mobile uses such as heavy golf caddies (or golf trolleys), miniature railways, model cars but may be used for other applications as well. The controllers has special circuitry to reduce heat dissipation making them far more powerful than the industry standard golf caddy controllers.

The controller has been ‘value engineered’ for high volume users but we have taken great pains to ensure that the 1QD is technically as good as possible. It is a circuit board suitable for mounting inside a diecast aluminium box. It is highly efficient, minimising losses, maximising battery life and giving excellent fine speed control. It are fully protected against overload and a thermal cutout is available as an option (on quantity orders) making the unit virtually indestructible.

1QD layout diagram
1QD motor speed controller layout


Supply voltage 12v or 24v. 36v and 48v versions are available.
Supply current 20mA at zero speed
Output voltage 0 to 100% full speed
Output current (typical) 100 amps cold (70amp version)
70 amps hot 70amp version
20 amps hot, cutout operated.
Voltage drop 140mV at 20 amps typical 70amp version
Switching frequency 20kHz approximately
Input 10k pot (can be supplied for 1k to 100k)
Input volts for full speed 3v approx at pot slider
Overvoltage (pot fault detect) 6v approx
Size 93mm x 55mm x 35mm
Weight 100g

Construction: the controller consists of a circuit board with an aluminium heatsink mounted vertically at one end. The heatsink forms the main mounting so that the mounting or box gives additional heat dissipation.

The control range from the speed pot can be factory set either full scale to use the full 270° rotation of a standard pot, or it can be 1/3 full scale, using only 90° of the pot, making it suitable for twist-grip type speed controls.

Will fit in to an industry standard diecast aluminium box


You can download the instruction manual, in PDF format, via our manuals and catalogues page.