A circuit for two simple push-button operated relays.

COMMENTS SUGGESTIONS	Toggle Switch No.3 - Testing Your Circuit	MORE SWITCHING CIRCUITS

Toggle Switch No.3 Schematic	The Rest of Ron's Circuits	Write To Ron	More Free-to-Use Circuits	Circuit Exchange International

Toggle Switch No.3 - Support Material

Important

Do not use the "on-board" relays to switch mains voltage. The board's layout does not offer sufficient isolation between the relay contacts and the low-voltage components. If you want to switch mains voltage - mount suitably rated relays somewhere safe - Away From The Board.

Introduction

The prototype of this circuit was built using only the Stripboard Layout as a guide. So - if you have faithfully reproduced that layout - you should have a working circuit.

Once you're satisfied that your layout is correct - and you have made a careful and thorough check of the underside of the board - it's time to power-up the circuit and test its operation. This is always an anxious moment. If you construct a lot of circuits - you might consider building the Current Limiting Power Supply - or alternatively - you could add the Simple Current Limiter to your existing PSU. Both will let you set an upper limit on the amount of current supplied to your circuit - and so protect it from any serious damage.

Setup

Click Here For A Photograph Of The Prototype

Details of How to Prepare The
Toggle Switch No.3 - For Testing

Two resistor and four LEDs are all that's needed to demonstrate that the relays are working properly. 

Connect a 2k7 resistor from the Pole of each relay - to the Negative terminal. 

And connect four LEDs - from the Positive terminal - to each of the N/O and N/C terminals 

I used different coloured LED in the diagram - so that I can distinguish between them.

But you can use whatever colour LEDs you have available. 

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Next - connect two small push-to-make switches to the input terminals.

I used a couple of PCB mounting push switches - that I salvaged from the front panel of an old VCR.

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Finally - connect the 12-volts DC to the input terminals. 

Pay particular attention to the polarity of the supply. 

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When you switch on the power - both relays should remain de-energized. 

Both of the green LEDs should be off.

The blue and the orange LEDs should be lighting.

And the yellow and the white LEDs should be off.

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Press Sw1.

The top relay should energize.

The top green LED should light.

The blue LED should turn off.

And the yellow LED should light.

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Press Sw1 again.

The top relay should de-energize.

The top green LED should turn off.

The blue LED should light.

And the yellow LED should turn off.

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Press Sw1 a few more times - until you're satisfied that Ry1 is toggling on and off reliably.

Then switch it off - and test Sw2.

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When you press Sw2 - the bottom relay should energize.

The bottom green LED should light.

The orange LED should turn off.

And the white LED should light.

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Press Sw2 again.

The bottom relay should de-energize.

The bottom green LED should turn off.

The orange LED should light.

And the white LED should turn off.

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Press Sw2 a few more times - until you're satisfied that Ry2 is toggling on and off reliably.

Then leave Ry2 energized - and press Sw1.

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When you press Sw1 once - Ry2 should de-energize.

And when you press Sw1 a second time - Ry1 should energize.

Sw2 should work in a similar way.

When you press Sw2 once - Ry1 should de-energize.

And when you press Sw2 a second time - Ry2 should energize.

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Continue to energize and de-energize the relays - until you're satisfied that your circuit is working reliably.

When a relay is energized - it's green LEDs should be lighting.

And when it's de-energized - the green LED should be off.

Each button should be able to toggle its own relay on and off.

And each button should be able to de-energize the opposing relay - with the first push.

Before energizing its own relay - with the second push.


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If You Find a Problem

If - in the course of the test - you find that something is not working properly - then a careful inspection of the relevant area of the circuit board should turn up the cause of the problem. Where you've cut the board to size - look for small loose strands of copper left behind by the saw. Check the board for short-circuits caused by component leads touching each other. If an LED is not lighting - check that it's connected the right way round. It can also happen that the stripboard itself is faulty. I have seen cases where the copper tracks have not been completely severed from one another during manufacture.

If you've built your circuit using the specified components - and you've followed the step-by-step construction guide described on the Toggle Switch No.3 - Support Page - then the chances are that any bug will be caused by something minor - a component connected the wrong way round - a missing or unwanted solder bridge - an incomplete cut in the track etc.

If you can't see anything obvious then adopt a systematic approach to faultfinding. Begin by double-checking that all of the cuts in the tracks have been made, that they are all - In The Right Place - and that they sever the track completely. Use a magnifying glass. It only takes the smallest strand of copper to cause a problem. If you backlight the board during the examination - it makes them easier to spot.

When you're satisfied that the tracks have been severed in all the right places, check that you have made - and correctly placed - all of the solder bridges. Mark each bridge with a felt-tip pen - or something similar - so that it can be easily identified later.

Next - carefully examine the full length of each track. Look for unwanted solder bridges. Your felt-tip markings will tell you which ones should be there - and help you identify any that shouldn't be there. Again, if you backlight the board during the examination - it makes potential problem areas easier to spot.

If all else fails and you still haven't found the cause of the problem - work your way through the assembly instructions on the Support Page. Check each individual component and link - to make sure that it's present and correctly positioned.

Print out the drawings and mark off the components as you go. Pay particular attention to the orientation of the diodes, the LEDs and the transistors. Take your time and examine each individual component carefully.

Toggle Switch No.3 - Support Material

Toggle Switch No.3 Schematic	The Rest of Ron's Circuits	Write To Ron	More Free-to-Use Circuits	Circuit Exchange International

Toggle Switch No.3 - Testing Your Circuit

Introduction

Setup

If You Find a Problem