We’ve written this guide to help customers diagnose and fix problems that may occur with the Pro-150. We don’t release complete circuit diagrams for current models but we hope this guide will shed some light Read More

It doesn’t happen often but when the mosfets in a 4QD series controller do blow they can take a number of other components with them. If you are attempting a DIY repair this photo shows Read More

When using the DMR-203 to control a 4QD series controller, the yellow connection to pin A of the 6 way connector[s] must not be used. This is because the 4QD series uses pin A is Read More

This problem deserves a place in the knowledgebase if only because we posted a lot of equipment backwards and forwards before we found the solution. The system; 2 x DNO-10, DMR-203, Ex 2.4 GHz radio Read More

The DNO PCB number is 30-2D-01. The following is a list of modifications listed by serial number. The DNO was originally designed to block transition from ahead to reverse without reducing the throttle to zero. Read More

Although the DNO is very similar to the VTX, one feature that it does not have is the provision for disabling regen braking via on-board links. A number of people have asked if it is Read More

This optional battery contactor arrangement can be fitted as part of the 4QD-200/300 installation to provide reverse polarity protection and also an emergency power disconnection. The relay should be chosen so that it is capable Read More

What exactly is  Pulse Width Modulation? how does PWM motor control work, and what does a PWM circuit look like? On this page we’ll go into a bit  of detail to explain the theory and Read More

If a Pro-150 gives the Pt [pot top] fault code, or just gives a continuous rapid beeps, this indicates a pot or wiring fault or blown F1 fuse track such that the voltage on the Read More

Unless specifically requested for 48V, we usually configure the 4QD series for 24V operation. When operating at 48V the acceleration ramp control may need to be adjusted as well as the gain control in order Read More

Pro-150 mechanical information Dimensions Board only: 145mm x 102mm x 38mm With base and cover: 181mm x 121mm x 46mm Weight Board only: 320 gm Complete: 630gm Power connectors 9.5mm push-on for battery, combined with Read More

This dmr-203 drop-out fault was one of the strangest ones I’ve seen for a while, as it took so long to solve it deserves a place in the knowledgebase. The system; VTX-75-24, DMR-203, Spektrum DX Read More

Fraser golf buggies (A La Carts), e.g. the Firefly and Dragonfly originally used 4QD’s Pro-120-48. When the Pro-150 was released, we stopped making the 48v Pro-120 as the Pro-150 is just as simple and does Read More

We get a lot of of enquiries from Robot Wars contestants who don’t know where to start building their robot. I sometimes get the impression that they are starting with the robot control system – Read More

Towing an electric vehicle with a permanent magnet motor can cause major problems. If any E.V. is to be towed, you must disconnect the motors or else jack the machine so that the drive wheels Read More

Torque is not really a controller function, but it is directly related to the current flowing in the motor. The mechanical torque is proportional to the motor current and the relationship is defined by the Read More

Many people try to use a tooted belt as a reduction gear from a motor to a drive wheel. This is fine – as long as you do not expect to get regenerative braking through Read More

If a motor is connected straight to a battery with no controller, it will draw a very large surge current.This surge current will generate a large torque pulse from the motor, we have seen relay Read More

A motor which is heavily loaded will always run slower than an unloaded motor. This statement seems so obvious that it is hardly worth saying – yet there are motors (stepper motors and synchronous motors) Read More

We are often asked to recommend motor manufacturers, so here is a list of motor manufactures that we know about [in alphabetical order]. Ametek Ampflow AMT Crystalyte motors Electrocraft EV drives Fracmo [closed in summer Read More

When you apply a battery direct to a motor, without a controller, there is a large surge as the motor gets up to speed and the vehicle is subject to rapid acceleration. When a motor Read More

Motor examples. Certain motors are very popular and we keep getting asked about them, this section gives our findings on a few of them. We are not the manufacturers and our opinions are just that Read More

There are several electric motor types that use brushes for d.c. operation. Permanent magnet motors These have two wires. Reversing th polarity of the applied voltage reverses the rotation. Shunt wound motors These have 4 Read More

Mobility scooters generally operate at 24v and have a legal top speed of 4 mph on the pavement, road vehicles can have a top speed of 8 mph. 4QD controllers can be wired with a Read More

Electrical heating occurs in any component or wire that carries an electrical current. How hot the component or wire gets depends on the rate that heat is generated and on how quickly heat can get Read More

4QD have supplied motor speed controllers to the Greenpower battery powered electric car competition for many years, and our controllers are highly efficient. The event has been won more than once using our controllers. This Read More

One of 4QD’s principal markets is ride-on golf carts or buggies. Now there is a different market for buggies in UK as opposed to the USA. Most American machines use petrol engines and the buggies Read More

The battery current and motor current in a PWM controller can be very different.  Many people do not realise is that a PWM controller operates rather like a transformer (using the motor’s inductance) to deliver Read More

MOSFET is an acronym – I’ll give you the whole phrase, so you know why they’re always called MOSFETs.. Metal Oxide Silicon Field Effect Transistor. MOSFETs are very near to perfect semiconductor switches, capable of Read More

Our controllers use either a full bridge or a half bridge PWM circuit to to control the speed of an electric motor. In the half bridge configuration two sets of MOSFETS are connected across the Read More

All 4QDs controllers have a switching frequency of (around) 20 thousand times per second – 20kHz. This is high enough to give no whistle or whine from the motor but, more importantly, it means that Read More

Regenerative braking is a way of diverting the kinetic energy of a moving motor / vehicle back into the battery so that it re-charges the battery and provides a braking effect. Most of 4QDs controllers Read More

Current limit – drive Protection is fitted to all controllers so that the initial starting surge (or the current that would flow if the armature were locked) cannot exceed that which the MOSFETs can handle. Read More

Thermal shutdown and current trip On some controllers a thermal sensor is fitted (or can be fitted as an option) to detect the MOSFET temperature and reduce the available current if the heatsink overheats. At Read More

All electrical items carrying current get hot. The amount of heat is actually proportional to the square of the current, so doubling the current causes four times the heat. A high current motor and controller Read More

When the controller is not in use it needs to be deactivated. The ignition circuitry (fitted to all controllers) does this, so the controller draws no current and the throttle input will have no effect. Read More

When the controller is powered down (ignition turned off) but with the battery still connected, different controllers behave in different ways. There are, essentially, 3 possibilities: Open circuit Short circuit Diode Open circuit All semiconductor Read More

Acceleration Ramp Even if the throttle is applied sharply, the controller must accelerate the motor smoothly, without a jerk, so an ‘acceleration ramp’ is built into all controllers. This may be a an adjustable ramp Read More

A permanent magnet motor is reversed simply by interchanging its two armature wires. This can of course be done with any controller by using a suitable, high current, double pole changeover switch. However reversing should Read More

  If a vehicle is fitted with a hand or foot brake, it can be useful to disable the controller. This can be done with an interlock to ignition circuit on any controller. The problem Read More

Some controllers can be used with either a 3 position toggle or rocker to give forward/off/reverse or with two push buttons to give ‘go forward’ and ‘go reverse’ control. The DNO and Pro series need Read More

If a controller includes regenerative braking, then there is a potential problem if a battery connection fails during braking. This can happen on a golf buggy if the batteries are not properly secured. If it Read More

Undervoltage cutback – or Battery Discharge Protection When a battery is discharged its voltage falls. It is a widely known fact that discharging a battery too far can damage it, especially if it is left Read More

All 4QD’s controllers work on an input voltage, which is usually derived from a potentiometer. Gain adjustment This enables the top speed to be reduced, e.g. in a child’s car where the child is too Read More

A joystick (know in USA as a Wig-Wag control) is a lever operated speed and direction control. Move the lever forward to go forward, and pull it back to go backwards. The speed is controlled Read More

Parking Brake Driver Regenerative braking relies on the voltage generated by the rotating armature to cause braking so it is speed dependent. If the speed is slow enough there is no effective braking, so the Read More

On some controller we can fit, at the factory, a ‘braking’ light driver. This braking light option replaces the standard parking brake driver. On road vehicles a brake light may be required. If the vehicle Read More

If a wire to the pot breaks various things can happen. If the full speed wire breaks, then the pot cannot select full speed so this is generally safe. If the output (wiper|) from the Read More

If the controller’s ignition is turned on while the throttle pot is not at zero the vehicle could accelerate to speed. High pot lockout [HPLO] prevents this by disabling the vehicle until the throttle returned Read More

If you inadvertently connect the battery up the wrong way round , then depending on which model you have, the controller may be destroyed in quite a spectacular manner! Only you can decide if this Read More

If you have read the page entitled Half-Bridge you will remember that the battery current is being switched on and off 20,000 times per second. Now electricity in wires has the equivalent of ‘mass’ – Read More

Most controllers are situated close to the user, e.g. in a ride-on golf buggy, so are controlled by a speed control pot wired directly to the controller. However some markets, such as Robots and some Read More

A tacho generator generates a feedback signal proportional to the speed of rotation, which can be used to provide closed loop control of a motors speed. Varying loads If such a ‘tacho’ is used and Read More

All controllers made by 4QD work with a voltage input, normally derived from a potentiometer. However it’s the voltage input that determines the speed. The controller cannot tell whether that voltage is coming from a Read More

Double heading is a term used by loco builders, it is where you have an engine on each end of the locomotive, so each end is a ‘head’, hence double heading. For double heading, you Read More

When choosing a controller, both it and the motor should be matched to the mechanical task that is to be done. So – you first of all need to understand the mechanics: What mass do Read More