Current models

Ampflow motor

We recently encountered a strange issue with a 4QD-300 driving an Ampflow A28-400-F24 motor. Forward operation worked as expected but in reverse a very slight pulsing or oscillation of the motor speed could be detected Read More

Pro-150 Fault Finding Guide

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

Damage From Blown Mosfets

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

DNO Version history

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

Disabling regen braking [DNO]

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

Double Heading Wiring Diagram [DNO]

This diagram shows how to connect two DNOs in different model locomotives together using the expansion port.     You can download a PDF version here. For the slave cable we recommend using a bulgin Read More

Battery Contactor

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

Porter Current Limit Adjustment

It is possible to adjust the Porter current limit setting by fitting either a fixed resistor or a potentiometer across the pads circled in red below Fitting a 100k potentiometer gives an upper limit of Read More

Driving the DNO by Raspberry Pi

Our DNO range is ideally suited for use as an interface between a Raspberry Pi, Arduino  etc, and a motor. The Pi can provide a PWM output via its GPIO pins and this can be Read More

Pro-150 Pt Fault Code

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

Adjustment for 48V

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

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

Pro-150 Basic Wiring Diagram

This diagram shows a basic wiring scheme for the Pro-150 running on 24V with ignition and reversing switches. For clarity we haven’t shown the optional display / programmer which connects via 2 cables to its Read More

Overheating in Boats

If you are using the 4QD series in a boat then you should pay particular attention to airflow and cooling to prevent the controller from overheating. It’s not kind to shut your controller away in 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

4QD Series: Use with Series Wound Motors

The 4QD series controllers are designed for Permanent Magnet motors. This application note is based on theory and feedback from customers who have used series wound motors. As such it is an application which 4QD Read More

Pro-120 Mk2 History

In early 2003 we released a redesigned Pro-120 controller. However – in general it’s such a popular and good controller that not a huge redesign was possible. The main change is that it uses sub-miniature 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 Fault Finding Tips

Faults on the Pro-120 series are not common, but there are a few which occur, mainly because the ‘bare board’ style of the controller makes it susceptible to certain abuses. These fault finding tips may Read More

PRO-120: Multiple Slaves

This applicaton note applies to Mark 2 Pro-120 controllers only. The Pro-120 has an expansion connector that may be used to connect a master controller to a single slave. Connecting to more than one slave 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

Converting Parking Brake to Brake Light

The 4QD series has a Parking Brake solenoid driver. Optionally controllers can be supplied from the factory with this converted to a ‘Braking’ Light driver. This page describes the modification. Warning. The parts that need Read More

Inhibit Ramp Modification [4QD series]

The inhibit input on the 4QD controllers is designed to be used in conjunction with a microswitch sensing the foot brake on an electrical vehicle. Our features area explains this operation of the Foot-Brake inhibit. Read More

Deadband values and removal

This page specifically refers to modifying pre issue 15 boards. From issue 15 onwards there is an on-board jumper to alter the deadband. With issue 17 boards, the half-speed reverse feature was changed to make Read More

How to dismantle the 4QD series

Hopefully you’ll never have to do this, but if the need arises then here is how to do it. Top board removal. Remove the top board by loosening the four corner screws. Disconnect the 14 Read More

Fault finding on the 4QD series

4QDs policy on all controllers is one of continuous modification. If we find a mechanism whereby a user can blow a controller, we modify the controller, if possible, to prevent it happening. This means that Read More

Testing the 4QD Base Board and MOSFETs

Bridge testing Method All testing of faulty controllers should be done on a current-limited bench power supply: testing a faulty controller from a battery will almost certainly exacerbate the fault, causing yet more damage. The Read More

Current limit resistors

Notes on the current limit resistors for the 4QD series. The control board current limit resistors have changed frequently, as MOSFET improve the Rds generaly decreases. This increases the current, but it has to be Read More

Use with Tacho Feedback Board

The circuit of the standard tacho-generator feedback board is described on the 4QDTEC.com site and a drawing with other information is available. Mechanically, this board is designed to plug into the NCC and Pro series Read More

Control Board Modification [Pre June 2010]

Control board modification This page details two modifications The first part should be done to all controllers with serial numbers below 4028. After that, the modification was included in production. Modification is to the top Read More

Reverse Speed Modification [pre issue 17]

How to adjust the maximum reverse speed on earlier 4QD control boards. This information applies to earlier 4QD series only. With issue 17 control boards the method of incorporating half speed reverse changed. It is Read More

Mixing 4QD 150 / 200 / 300 series boards

With several ‘caveats’, the control boards and base boards of the 4QD series are interchangeable and may be mixed and matched. However – it is important that you understand the potential problems. 4QD 300: This Read More

4QD version history

This page lists the different versions of the 4QD series circuit boards, and their date of introduction. This listing was originally generated for 4QD internal use only so the descriptions may not be as full Read More

DMR-203: Use with PRO-150 Controllers

The DMR-203 may be used with Pro-150 controllers. There are two ways of doing this. One involves a slight modification if the DMR but has simpler wiring. The second does not involve modifying the DMR, Read More

Pro-150 Capacitor Modification

This modification should be applied to all Pro-150 controllers with serial numbers 0198 or higher and lower than 0550. On 0550 and later controllers the capacitor is not fitted. On serial numbers 0198 and lower Read More

PRO-150 Current Limit

The circuit of the Pro-150 is available as a pdf. Current limit amplifier is in the bottom right corner. Current is monitored by sensing the voltage drop across the lowside MOSFETs when they are conducting. Read More

PRO-150 Issue History

These notes are by serial number, rather than by date. The list is mainly for 4QD internal reference so is somewhat technical. 0000 to 0105 Are Mark 1. In these, there was no 12v connection 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

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

PRO-150 Joystick Programming

This page describes how to use the “pot learn” feature of the Pro-150 to set up joystick programming, [or wig-wag operation]. Before starting this sequence the Pro-150 should have power connected to B+ and B-, Read More

Inhibit

These notes apply to the inhibit function of the 4QD series controllers. If a vehicle is fitted with a hand or foot brake, it can be useful to disable the controller. This can be done Read More

Multiple Controllers [Double Heading]

This page describes wiring that allows multiple Pro-150s and 4QD series controllers to be controlled from a single speed potentiometer. This is useful when double heading model locomotives. As the Pro-150 is a programmable controller, Read More