# A single switch to control two circuits

#### tcmtech

Joined Nov 4, 2013
2,867
This seems workable with my limited knowledge of assembling circuits. Would of like to avoid any batteries / extra power supplies though - seems like the relay would need its own power source though.
Well if you have a 5 volt power source to make the pad work you obviously already have a 5 volt power source to run a tiny 5 volt relay as well.

Joined Jan 18, 2017
6
A single touch pad ON/OFF toggle switch, you could choose two sets of relay contacts. (6 pins)

Only needs a small touch pad and no need the push switch, or connects the input pin to +V with a push switch.

You can reduce R4 to match the current of your relay needed.

The circuit is a gif file, having Chinese/Japanese(I can not read), please give it in English. Also I am requesting to put number of Q1. Thanks.

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#### tcmtech

Joined Nov 4, 2013
2,867
Low-power relays with a 9V rated coil are rare,
How do you figure? Mini and micro relays come with coils in every voltage you could ask for if you are willing to spend a minute on any electronics supply sites search system.

#### AnalogKid

Joined Aug 1, 2013
8,492
Three things.

The 1-transistor circuit is based on the (reasonable, of course) assumption that the control input is a logic gate with a pull-up resistor. If it is something else, such as a transistor with a pull-up resistor on its base, then the open circuit voltage will not be high enough to power the FET.

For that reason, the relay circuit probably is more reliable in that it will work no matter what the input circuit is. But it needs a battery. To extend battery life, you can exploit a fact about DC relay coils - they need more power to pull in initially than to stay pulled in. You can put a parallel resistor and capacitor in series with the relay coil. This applies full voltage to the coil to make sure it pulls in, then reduces the current through the coil while it it on. If people are standing on the mat for a long time, this can double the battery life.

If you are worried about battery life, a dirt cheap 5V cell phone charger wall wart is fine for this circuit if you use a relay with a 5V coil. Actually, any old wall wart from a calculator or whatever will work. Just make sure the output is DC and the relay coil is rated for the voltage.

ak

#### tcmtech

Joined Nov 4, 2013
2,867
For that reason, the relay circuit probably is more reliable in that it will work no matter what the input circuit is. But it needs a battery.
I don't see why being the unit already has a 5 volt external power supply it's plugged into that can easily be tapped into for the necessary power for the relay operation.

Just pull the + and - off the power supply cord and run it through the pad and relay coil in series to activate the relay to do the video source switching. Simple two wire remote operation of the input selection feature with no additional external battery needed and the video units input select stays isolated from the pad circuits as well.

#### AnalogKid

Joined Aug 1, 2013
8,492
How do you figure? Mini and micro relays come with coils in every voltage you could ask for if you are willing to spend a minute on any electronics supply sites search system.
True, but a) I don't know the location of the TS or what kinds of components he has access to, and 12 V relays are much more common and available with a much larger range of coil currents; and b) (all other things being equal) a 12 V relay with an 8.4V min pull in voltage rating will draw considerably less current than the same relay with a 9V coil.

ak

#### ScottWang

Joined Aug 23, 2012
6,913
The circuit is a gif file, having Chinese/Japanese(I can not read), please give it in English. Also I am requesting to put number of Q1. Thanks.
You can use Q1 as 2N3904, 2SC1815, 2SC945, etc,...
You can choose the input as Touch pad, C1, R1, or Sw1, C4, R5(I haven't try the values, if you have problem then point out.)

#### tcmtech

Joined Nov 4, 2013
2,867
I don't know the location of the TS or what kinds of components he has access to, and 12 V relays are much more common and available with a much larger range of coil currents;
5 volt relays are only as common as any other relay. Just because you haven't seen them around much doesn't make them uncommon or hard to find.

http://www.ebay.com/sch/i.html?_sacat=0&_nkw=5v+relay&_frs=1

https://www.amazon.com/s/ref=nb_sb_ss_c_1_12/156-1749491-5956356?url=search-alias=aps&field-keywords=5+volt+relay&sprefix=5+volt+relay,aps,211&crid=393KIX9I7G1FE

Take your pick. .5 VDC to 220 VDC or 6 VAC to 240 VAC coil relays.

http://www.digikey.com/products/en?FV=fff40010,fff80368&k=relay

And those are just three of hundreds of sources that will sell you one or 1000+ of them at a time.

Not hard to find or expensive either unless you consider under a dollar expensive.

#### AnalogKid

Joined Aug 1, 2013
8,492
5 volt relays are only as common as any other relay. Just because you haven't seen them around much doesn't make them uncommon or hard to find.
In ND and OH that is absolutely true. And, I can see them just fine from where I'm sitting. Working from memory, I've got at least 4 types from project overruns. My point was that if the TS is in Lower Slobovia, he might have access to only a very narrow range of components, and that 12 V small relays probably are more available in that circumstance. This point often is made by posters in sub-Saharan Africa.

ak

#### tcmtech

Joined Nov 4, 2013
2,867
My point was that if the TS is in Lower Slobovia, he might have access to only a very narrow range of components, and that 12 V small relays probably are more available in that circumstance. This point often is made by posters in sub-Saharan Africa.
Possibly, but nothing he has said or linked to gives me any reason to think he's from some backwoods hell hole in the middle of nowhere that doesn't have working postal service to which even China won't send cheap parts to as a last resort.

I think you're just fixating on using a 12 volt relay and want to justify it with weak 'what if' based conjecture rather than admit that 5 volt relays are way more common and easy to acquire than you thought and care to admit to.

Either way in the end the OP will decide what he wants to use. Not us.

#### Thenextman

Joined Feb 3, 2017
42
Hey all,

@tcmtech and @AnalogKid - a quick search on digikey (first thing I did) did yield two 9v SPDT Relays. To Analog's point, that was 2 out of 100s and they were pricier ($7 vs$3/4) so I think it's valid to say they are not as common - but luckily available!

TCM - I prefer not to mess with the Kramer equipment's PSU - it is an expensive piece of hardware.

Analog - I think using a 5v wall wart to power relay is a good idea. The minute I get into transistors / resistors / breadboards I will fail haha. This is for a 2 week long activation - most of the time no one will be on the mat. Wall wart can be hidden and better than having the client have even the low potential of having to change a battery.

In terms of the input requirements for the unit I am trying to control, from my understanding, no power should be introduced beyond what the unit provides. In other words, to select input one on the video switch you just have to form a closed loop between pin 1 and ground. I think it calls for momentary closure of the loop, which I don't think the relay will provide - that said, I don't think it matters if it's momentary or continuous.

Thanks guys!

#### LesJones

Joined Jan 8, 2017
2,671
Why not just use two pressure mats instead of 1 ?

Les.

#### Thenextman

Joined Feb 3, 2017
42
Why not just use two pressure mats instead of 1 ?

Les.
Sorry. Not an option. It's standby mode vs triggered mode.

#### tcmtech

Joined Nov 4, 2013
2,867
TCM - I prefer not to mess with the Kramer equipment's PSU - it is an expensive piece of hardware.
The unit you linked to uses a common and cheap 5 volt 1 - 2 amp wall wart type power pack (~$5 value) with a two wire cord. About as bonehead simple to splice into as you can get assuming you can count to 2. In terms of the input requirements for the unit I am trying to control, from my understanding, no power should be introduced beyond what the unit provides. In other words, to select input one on the video switch you just have to form a closed loop between pin 1 and ground. I think it calls for momentary closure of the loop, which I don't think the relay will provide - that said, I don't think it matters if it's momentary or continuous. From what I could find in the link and related manuals I don't see the being latched to either input being a problem either. As for the closed loop that's what the relay would give you as well. Full isolation from the mat and relay coil. The 'G' line of the selector port would go the relays C terminal and the I1 and I2 leads would go to the relays NC and NO terminals. Everything else is just the connections on the power supply cord and electrically independent of the relays contacts side. That's as simple as I can make and explain it. Thread Starter #### Thenextman Joined Feb 3, 2017 42 The unit you linked to uses a common and cheap 5 volt 1 - 2 amp wall wart type power pack (~$5 value) with a two wire cord. About as bonehead simple to splice into as you can get assuming you can count to 2.

From what I could find in the link and related manuals I don't see the being latched to either input being a problem either. As for the closed loop that's what the relay would give you as well. Full isolation from the mat and relay coil. The 'G' line of the selector port would go the relays C terminal and the I1 and I2 leads would go to the relays NC and NO terminals. Everything else is just the connections on the power supply cord and electrically independent of the relays contacts side.

That's as simple as I can make and explain it.
Thanks @tcmtech - if you go back a few posts you'll see my circuit diagram (drawing). Think I got it right.

As far as splicing relay to wall wart - I rather not even risk feeding the equipment an improper voltage hah.

#### tcmtech

Joined Nov 4, 2013
2,867
Thanks @tcmtech - if you go back a few posts you'll see my circuit diagram (drawing). Think I got it right.
Yes that basically how it would be wired but with the + and - power input connected to the two relating wires of the 5 volt power pack cord.
A simple two point splice that if setup properly wouldn't even require cutting the cord in half but just separating the two side by side wires and stripping back the insulation enough on each to tie the wiring going to the pad and relay circuit into them.

As far as splicing relay to wall wart - I rather not even risk feeding the equipment an improper voltage hah.
How would you be feeding it an improper voltage?

Either you have the wires connected correctly and it gets 5 volts or you don't have them connected and you get 0 volts and the device doesn't turn on to begin with.

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#### Thenextman

Joined Feb 3, 2017
42
Yes that basically how it would be wired but with the + and - power input connected to the two relating wires of the 5 volt power pack cord.
A simple two point splice that if setup properly wouldn't even require cutting the cord in half but just separating the two side by side wires and stripping back the insulation enough on each to tie the wiring going to the pad and relay circuit into them.

How would you be feeding it an improper voltage?

Either you have the wires connected correctly and it gets 5 volts or you don't have them connected and you get 0 volts and the device doesn't turn on to begin with.
Haha. I'm sure it is an easy job - but like you said to @AnalogKid , OPs gonna do what OPs gonna do! Thanks for your help @tcmtech and analog - Kramer confirmed that this will work with essentially no latency.

Excited for the next, perhaps more complex, puzzler I can throw at AAC!

#### Thenextman

Joined Feb 3, 2017
42
@tcmtech and @AnalogKid

Great news guys - we got project! Now, like a fool, I ordered components before running them buy you (and all of the other genius) posters to this thread!

I went ahead and bought this SPDT Relay - https://www.amazon.ca/gp/product/B01MDLX3BW/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1

Now, from what I can tell, there is no way to power the relay only - it seems like power for the relay gets output to the NO / NC - this would be bad! I am only trying to form a distinct closed loop between input 1 or input 2 on the separate device - I cannot feed power to it.

Do you think this will work, will another relay work, or should I scrap this approach?

I've uploaded an image for clarity.

Thanks guys!

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#### tcmtech

Joined Nov 4, 2013
2,867
@tcmtech and @AnalogKid

Great news guys - we got project! Now, like a fool, I ordered components before running them buy you (and all of the other genius) posters to this thread!

I went ahead and bought this SPDT Relay - https://www.amazon.ca/gp/product/B01MDLX3BW/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1

Now, from what I can tell, there is no way to power the relay only - it seems like power for the relay gets output to the NO / NC - this would be bad! I am only trying to form a distinct closed loop between input 1 or input 2 on the separate device - I cannot feed power to it.

Do you think this will work, will another relay work, or should I scrap this approach?

I've uploaded an image for clarity.

Thanks guys!
It will work but it's wasted money and way over kill.

You have large and rather over priced/expensive 12 volt 30 - 40 amp relays which take a lot of power to operate doing a job that tiny cheap 5 volt 1 amp or less unit like I gave links to would have done given you are only switching a signal that is a few milliamps at most (.001 - .005 amps).

#### Thenextman

Joined Feb 3, 2017
42
It will work but it's wasted money and way over kill.

You have large and rather over priced/expensive 12 volt 30 - 40 amp relays which take a lot of power to operate doing a job that tiny cheap 5 volt 1 amp or less unit like I gave links to would have done given you are only switching a signal that is a few milliamps at most (.001 - .005 amps).

Haha - I should of expected an answer like this

I was actually asking how to wire this without feeding power to the Kramer component. Because this is an automotive accessory, the mnfctr terminal descriptions as seen on Amazon are not clear. I found a similar relay which has the same numbers on terminals so I'm assuming it will be the same. They say that:

85 / 86 are coil / 30 is common / 87 is NO and 87a is NC. I'm hoping that's the case with mine and will test with multimeter today.

I bought what I did because: I will be running it off a dedicated 12vdc 1 amp wall wart, it's rugged, the relay can be easily swapped out by our client without touching wiring, it was free next day shipping on Amazon. It won't be less reliable, will it?

Thanks!