Old Controllers

Uni: Disabling Regen

Disabling Regen braking. From Issue 7, two scratch-through links are present on the circuit board. If both of these are broken, regenerative braking will be disabled. However this modification is not recommended: our experience shows Read More

PCB numbers

Our controllers last so long that sometimes the only marking left on them is the part number etched onto the PCB. If this is the case for you, we’ve put together this table of PCB Read More

Waveforms and Fault Finding

  Although this page refers specifically to NCC series controllers, the principles apply to several other controllers of our manufacture as most employ very similar circuitry. The principal exception is the 4QD series. Warning If Read More

Ramp Timings (NCC)

NCC series controllers. Ramps – acceleration and deceleration. Details of the equivalent modification to the Pro-120 are on another page. Introduction The ramps on the NCC are adjustable from around 300mS to around 7 second, Read More

Internal Power Supply and Protection Circuitry

The Pro-120 and Scoota series controllers have some sophisticated internal power supply circuitry which includes reverse polarity protection, pot fault detection and high pedal lockout. This is a description of the features and of some Read More

UNI: Use with PWM Input

Introduction The Uni controllers sense the voltage on the pot input (after the gain preset) to give pot fault protection. If the voltage on the pot wiper is ever greater than about 5.3v the pot Read More

Uni: POT Track Fused

The ‘pot min’ connection on the Uni controller is directly connected on the component side of the circuit board to the battery -ve. In the event of a wiring fault that causes excess current to Read More

Pro-120 Mk1 History

This page refers to the very early Mark 1 Pro-120 which is now too old for factory repair. Warning: this listing was originally generated for 4QD internal use only, so is not as fully detailed Read More

Pro-120 Key Components

The Pro-120 series are card controllers, open to the elements – and users. They are similar to the VTX and older NCC series – but have several more sophisticated protection mechanisms built in. This page Read More

Earth Fuses: Why Do They Blow?

This page deals specifically with the Pro-120, but other controllers have a fuse in the earth, or can blow a pot earth connection. This page explains how. Wiring faults can cause the fuse in the Read More

Modifying the Pro-120 for other voltages

All controllers made by 4QD are generally wide voltage operating range: limits are the operating voltages on the MOSFETs and the relays, and the power dissipation in the current source transistor used for the internal Read More

PRO-120 Ramp Reduction

The Pro-120 series acceleration and deceleration ramps are adjustable down to as fast as about 330mS. It is possible to reduce this timing but any modifications should be done with extreme caution. The ramps are Read More

Fitting Expansion Connector

Pro-120, VTX and NCC series controllers. Retro-fitting expansion connector Contents, this page Introduction Mark 1 / Mark 2 mixes VTX Pro-120 NCC Double Heading Tacho feedback board Solder Side All Controllers Additional controllers Older issues Read More

Pro-120 Robot Wars Version

The Pro is available in two versions, the standard version and the -RW version. This page explains the differences. Input decoupling There is, on the input to the standard controller, a noise decoupling circuit – Read More

Pro-120 Ignition Options

The Power relay drive circuit on the Pro-120 can be factory configured in three different ways. This page explains them. The power relay is switched on and off by a transistor that detects the internal Read More

Positional Servo Control [DNO / VTX]

Notes on how to create a positional servo control. There are two types of servo system: speed and position. These are explained in our Answers to FAQs on Battery Motors & Controllers. There is also Read More

Battery Discharge Protection: PRO-120

The Pro-120 is fitted with under voltage cutback a.k.a. battery discharge protection which turns the controller off if the battery voltage falls too low. This operates at around 20v measured inside the controller. This means Read More

Uni: Alternative Voltage Usage

Warning: Information on this page is given in good faith but you should be aware that any modification to a controller is done entirely at your own risk and will invalidate any guarantee. 4QD will Read More

Wiring for Push Button Use

This diagram shows how to connect a Pro or DNO (or earlier NTX and NCC) series controller for push button use, or with a centre-off switch. Note that the diode shown between the buttons must Read More

VTX Modification History

The VTX has changed relatively little in its life since first introduced on 2004. The best indicator of a controller’s age is the date code hand-written on the board, of the form 06e (or maybe Read More

VTX Speed Controller

The VTX was one of our most popular 24v motor controllers which was also made in 12v, 36v, and 48v variants. It has now evolved into the DNO range which is electrically interchangeable with the Read More

UNI Speed Controller

The Uni has been replaced by the Porter 5 and Porter 10 controllers.  Two current ratings are available, the Uni-8 with a current limit of over 100 amps and the Uni-4 with current limit of over Read More

Scoota Speed Controller

This page is for reference only: the Scoota is no longer manufactured We ceased production at the end of 2005. The Scoota is, in essence, a non-reversing version of our popular Pro controller. It is the Read More

Pro 120 Mark 1 Speed Controller

Professional 120 Mark 1 4 Quadrant 12v, 24v, 36v & 48v Vehicle Controller This page is for reference only. This page describes the early Pro-120. It was upgraded in 2003 to become the Mark 2 Pro-120. Read More

Porter 40: Use with PWM Input

The Porter 40 controller sense the current through the pot input to switch the controller on and to give pot fault protection. If the voltage across the pot is greater than about 7v, the pot Read More

Porter 40 Speed Controller

The Porter 40 has been replaced by the Porter 5 and 10. The Porter 40 is a simple, economical, general purpose analogue controller for power handling machinery including golf caddies and wheelbarrows. It will also Read More

NCC Speed Controller

NCC series Mark 2 4 Quadrant 12v, 24v, 36v & 48v Vehicle controllers This page is for reference only. The NCC is no longer available. The latest equivalent is the DNO range. NCC Mark 2 Read More

VTX and NCC Operating Voltages

  These notes refer to the last issue of VTX controllers. So if you controller is older, the notes may be sequentially less ‘correct’. All controllers made by 4QD are generally wide voltage operating range: limits Read More

NCC Circuit Description

This description refers to the Issue 18 and later NCC Mk1 series controllers. Circuit Diagram The NCC Mk 2 and the VTX are similar: main additions on these are an adjustable Reverse Acceleration Threshold (a Read More

VTX / NCC Fault Finding

Introduction Common faults on the NCC & VTX  series are – not common.  But there are a few faults which occur, mainly because the ‘bare board’ style of the controller makes it vulnerable to damage. You will Read More

NCC Mark 2 Issue Number History

The NCC Mark 2 was issued in 2003 as an update to the earlier highly successful NCC controller. It is very similar – the main noticeable difference being that there is a reduced deadband at Read More

NCC Mark 1 Issue Number History

These Mark 1 controllers are now too old for factory service. Warning: this listing was originally generated for 4QD internal use only, so is not as fully detailed as it should be if it were Read More

NCC Key Components

This page identifies some of the components on the NCC series controller. It shows a Mk 1, issue 24 controller. Mk 2 is similar, but uses sub-miniature resistors. Mk 1 boards issue 18 and later Read More

NCC Zener Diode Failure

Symptom If the main power line zener has been damaged, the voltage on the pot will be lower than 8.5v. However, this voltage being low can also indicated that the pot fault transistor has been Read More

UNI / Egret Wiring Options

The Uni and Egret both have a 4 pin input connector, but only require 3 wires for input. This is done to allow different options to be selected by varying the input wiring. Standard 10K Read More

Egret Speed Controller

This page is for reference only: the Eagle is no longer manufactured. Suggested replacement is the Porter. The Egret is essentially the circuit board used in the Eagle series. It has all the features of Read More

Eagle Speed Controller

This page is for reference only: the Eagle is no longer manufactured (manufacture ceased September 2005). Suggested replacement is the Porter. 4QD’s Eagle series is a motor speed controller for 12v, 24v, 36v battery operation. Read More

2QD Speed Controller

The 2QD is an ‘old’ product: it was about our simplest 2 quadrant controller, but for general use we would recommend our Porter 5 or Porter 10. This page is now for reference only. The 2QD Read More

1QD Speed Controller

Introduction 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. Read More