LeeH68

Hi, another novice in need of help. I have bought some 24V Bulgin illuminated momentary switches MPI002 - see attachment and need them to illuminate when i press the button and turn off when I press the button again. I am not switching anything, just need the button to light up when I want. (I actually have 3 switches in a line, red, amber, green and ideally only one switch led can be illuminated at any one time, but this isnt too important, a like to have but not a necessity). Bulgin have told me what resisters to install, I just need a method of switching the led bit of the switch on and off.

I found this link to a PCB wiring diagram that seems to do the job but its 12V so no good to me.
http://www.cpemma.co.uk/flipflop.html

Is there a bi-stable latching relay that operates using an single supply impulse that is 24V?, if not can I make the above circuit into 24V easily?.

I need something relatively cheap as I have 50 switches to do, around £12 and available off the shelf if at all possible.

Any help appreciated

Attached Files

Illuminated Switches.pdf (61.4 KB, 21 views)

Hero999

You can easilly power the CD4013 from a 12V regulator like the LM7812 and it'll work from a 24V power supply.

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LeeH68

Hero999, thanks for the prompt reply.

So if I just change the Q1 and Q2 as shown on the board to the LM7812 it will work?.

KMoffett

Though a bit klunky (electromechanical), here is a push-on/push-off switching circuit I found some time back. Credit:
http://radiomagonline.com/notebook/r...hoff_switch_2/
He doesn't spell it out, but the relay coil voltage (12V) is 1/2 the supply voltage(24V), and R1, R2, and the coil resistances are all equal. I've used this with a 5V relay on a 12v supply.

Ken

Attached Images

PushOnPushOffRelay.gif (7.4 KB, 30 views)

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Pommie

That's clever.

Mike.

LeeH68

That looks great, I think. Would anybody be kind enough to draw this onto a cricuit board with a parts list for me as I have no idea what the components are and how they go together (like the link on my original post as this was easy to follow).

Also, does anyone know approximatly how much it would be to buy all the bits. I have 50 switches.

Thanks for the fantastic quick responses, your all stars.

Lee

LeeH68

Also, is this arrangment okay for leaving the led on one button illuminated for long periods i.e. days at a time?.

Lee

KMoffett

LeeH68,

If you are going to impliment 50 of these, you should look at some version of Hero999's solid state toggle switch. 50 relays are not going to be cheap and is going to draw a lot of current...besides that drawn by the LEDs. For one, or maybe a couple, this is slick, but for a large array logic level flip-flops and transistor drivers would be much better.

Ken

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"To invent, you need a good imagination and a pile of junk."
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Hero999

It's got nothing to do with Q1 and Q2.

The LM7812 is a linear regulator, use it to supply the circuit.

The CD4013 contains two flip-flops on the IC therefore you only need 25 IC for 20 switches.

I've made a couple of modifications to the circuit.

The CD4013 can light an LED - no transistor is required.

You might need to put a capacitor across the switch to help eliviate bounce.

You need a 100nF capacitor across the supply of the IC.

1F is also needed before the regulator.

Attached Images

Flip-flop.GIF (5.1 KB, 17 views)

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KMoffett

Or, he could go to a 40174 quad-D FFs and get by with even less. The 4013 and 40174 can only source or sink about 2mA@12v per output, so he still might need to add drive transistor arrays and resistor SIPs. But, that's still a lot better than 50 of my relay circuits.

Ken

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Hero999

That's if you're bothered about connecting other gates to the output as the voltage loss would stop them from working.

I can't remember off the top of my head but I think a CMOS IC can supply something like 6mA if you don't care about the voltage loss.

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LeeH68

I have no idea what you both are talking about, but if its any help my PSU is 24V DC output and is 3Amp.

If using the items you are talking about means when I push one of the three buttons that button illuminates and the other buttons are inhibited and similarly if you then press one of the other buttons that button illuminates and the other goes out?. this would be the ideal situation (if its easy enough).

It has been suggested to me to use a repol unit, see attachment. What do you think?.

Lee

Attached Files

NEED.pdf (727.4 KB, 11 views)

Hero999

That looks like a miniture a PLC (Programmable Logic Controller), it looks a bit overkill but will do whatever you want.

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KMoffett

LeeH68,

We were discussing the minutia of the one-button/one-LED toggle circuit.

I'm confused. What is it that you really want? 50 P-buttons/LEDs in groups of 3 or 50 groups of 3 P-buttons/LEDs, that only one of 3 will light...and do nothing else? The devil's in the details, and different solutions lend themselves to different spec's.

I'm not sure how the commercial programmable controlled fits into your request.

Ken

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Roff

Most (all?) brands of CD4013's don't have Schmitt trigger clock inputs. Philips makes HEF4013, which does. The ones that don't, have maximum clock rise and fall times measured in microseconds. You need a Schmitt trigger in the clock line, or use an HEF4013.

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