4QD - DC Motor Control

2QD series
2 Quadrant 25A to 100A 12v & 24v to 48v Motor controllers

The 2QD is an 'old' product: it was about our simplest 2 quadrant controller, but for general use we would recommend out Porter 5 or Porter 10.

Because of its age, we regret we can no longer offer technical support on the 2QD series.

4QD's 2QD is a simple motor speed controllers for 12v, 24v, 36v and 48v battery operation. They are 'Two Quadrant', i.e. they control acceleration and braking. The controllers are state-of-the-art MOSFET chopper drivers giving fully variable fine speed control of all motors at up to 100A intermittent.

The controllers are primarily for mobile uses such as miniature railways, model cars, golf buggies and golf caddies but may be used for other applications as well. The controller is ideal for industrial purposes and is ideally suited for use as a building block where control is from a computer of similar system. Being an open circuit board with easy accessibility, they are also ideally suited to prototype and experimental work and to small quantity applications.

And as one customer said:

they're also good for custom-designed homebrew ebike experimentation by those knowledgeable enough in controllers to wish to access theirs for repairs or modifications. (since cheap off-the-shelf ones for bikes are sometimes potted as solid bricks, making them difficult or impossible to repair or modify, and none of the OTS units I've ever seen has schematics etc. available for it, unlike the 2QD, much less pages of material explaining it's entire operation!).


Supply voltage10v to 47v12/24/36v version
10v to 56v12/24/36/48v version
Supply current20mAat zero speed
Output voltage0 to 100% full speed
Output current (typical)coldhotmV drop at 20 amps
          2QD-3550A (40A braking)37A280mV
 2QD-70100A (80A braking)75A140mV
Switching frequency 15kHzapproximately
Size: (board only)122mm x 55mm x 30mm
Size: (with heatsink)180mm x 55mm x 35mm
Input 10k to 100k pot.
Input voltage 0v to full speed
Full speed inputadjustable 3v to 20v

Reversing can be done by using two controllers back-to-back to give a full four quadrant drive. Alternately use a switch or relay to change over the armature connections. For best results, 4QD also manufacture reversing controllers (4QD, Pro and NCC series).


The diagram above shows the features of the controllers, which are un-cased circuit boards. They are assembled, fully tested and guaranteed. The diagram below is a side view, showing the mounting arrangement.


Input is suitable for a standard potentiometer. There is an on-board adjustment to alter sensitivity to suit different operating mechanisms. A connector is supplied. Various speed controls can be supplied as extras, including a spring-return-to-zero speed pot arrangement suitable for hand operation.

Ordering information and prices.

The 2QD is not now being manufactured.


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

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© 1996-2016 4QD/4QD Ltd.
Page's Author: Richard Torrens
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Last modified: 2015