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Circuits Archive


4QD-TEC: Electronics Circuits Reference Archive
Modular Relay System

This is simple transistorised relay into which can be plugged 'personality modules' to turn the base unit into a timer (pulse, delay on energise or delay on de-energise) or a latching relay or whatever is required. This is therefore a universal relay system. It was designed to simplify industrial machinery control.

4QD would be delighted to manufacture a system based on this design and the ideas in this page so if you require any quantity, however small, please contact 4QD.

The circuit was designed to work off a nominal 12v supply - but could readily be used for other voltages.

Transistorised relay driver

The drawing shows the circuit board of a typical implementation. This one uses a common 3 pole changeover, 10 amp relay such as IMO type 6043. The circuit board shown measures about 47 x 75 mm. It has all 9 relay contacts (3 pole, changeover) brought out to 6.3mm push-on connectors at the edge of the circuit board. This type of connector is very versatile in an industrial control panel environment.

Inputs, at thee other end of the panel, are also 6.3mm push-on. These are the same connectors 4QD use in their NC-35 controller and the particular one uses will accept either a single 6.3mm push on or two 2.8mm push-on terminals. However, the input connector can be easily changed: the circuit shows a 6 way connector in use.


The circuit and principle

The circuit is very simple: it uses two transistors with overall feedback to give a high input impedance (470K) and a fast 'snap action' drive to the relay. The circuit also includes a few extra bits which are not used in the standard version but enable changes in its operating parameters to be easily made. Full circuit description and values are given, with the circuit board copper layout and more detail in the 'members only' area.



The board also includes a 6 way connector in the centre, with an associated 3 way pin strip. Into the connector plugs a 'personality module' - maybe a delay on energise time, or some 2 input logic gate.

The use of a personality module like this makes the system extremely versatile as a single type of relay can be quickly tailored to whatever is required.

Other relevant pages

Part two, in member's area (needs a password)

Personality Modules described on this site.

Page Information

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Page's Author: Richard Torrens