Electronics Question

[natemoen]

I am wiring in some vehicle electronics for a friend who has a security business. I am putting some lights and a siren and such. He is just starting off so this is being done on the cheap. He has gotten some older used stuff and I am going through and installing things.

The main control box that he had gotten is similar to This and was originally set up in a rather odd way (or most likely had been messed with by a PO) and was also set up to switch the negative side of the circuits. I have rewired the box so that is it now switching the positive side, rocker switches are all set up independently now.

Now there is the 3 stage toggle switch where the question comes in. Each stage of the toggle activates a SPDT relay. I want the first stage to activate the items on the first 2 rocker switches, the second stage to active the items on the 3rd and 4th rockers, and the third stage to activate the item on the 5th rocker.

I was thinking about just running the wire from the NO side of the relays to the output side of the rocker switches. This would mean that there is a possibility there might me power coming from both the relay and through the rocker switch (if someone had the rocker switch on at the same time as the toggle switch).

So I am wondering if there is a problem if there was 2 separate circuits feeding something? Would if overload anything or possibly blow a fuse?

Don't know how well I explained that so here is another explanation. Imagine you have 2 different light switches from different circuits both feeding the same light bulb. Would that be a problem?

[TopCatGr58]

Wow Nate, 4 hours and no replies, where's CrazySteve??

Okay, let me see if I can understand what you're trying to do.

You have this 3 stage toggle switch. Does each stage only get powered when switched to ON, or does it power first stage 1, and then adds stage 2, and then stage 3 while the other stages still stay energized/switched on??

You have a series of rocker switches in the Control Panel that will be powering an assortment of devices...ie. flashing lights, siren, floodlight, etc.!

You want to be able to power these devices individually via the rocker switches in the C.P., but you also want to be able to power ALL of them thru the use of the single 3 stage switch. AND you are wondering if an item is already energized/powered via the rocker switch, will sending an additional power supply to that same device(s) via the 3 stage switch will cause a problem...ie. fuse blowing or overload.

These devices are DC devices I am assuming, and both the rocker switches and the 3 stage/relays will be providing similar DC power. The devices themselves will not care where they get their 12+ volts from. However you will need to check the current/amp draw for each device, and their totals and verify that the power supply/wire that you have feeding either the rocker switches, or the 3 stage switch/relay assembly has enough juice to power all of the devices ALL AT ONCE....otherwise THEN you could have a problem of trying to draw too much current/amps...ie. 30 amps through a circuit that can only handle 20 amps!?

Now as far as how you could wire them up! You will have a power supply line for each 3 stage RELAY that will send the power to the device. You will also want a power supply/line for the ROCKER switch for each device. I would think you could split/Y the power line BEFORE the 3 stage RELAY, one leg would still supply the RELAY that will go to the device when the relay is thrown, the other leg of the "Y" could go to the + side of the ROCKER switch. This way the same wire is supplying the power for the same device, etiher via the RELAYED side, or from the ROCKER. IF the ROCKER is thrown/ON for a particular device, and then you throw the 3 stage switch to activate the RELAY, the power will then just go thru the RELAY instead of the ROCKER...however the rocker line will still be energized, so when he then turns OFF the 3 stage switch, the device that was still ON before throwing the 3 stage switch/relays will still be on when the 3 stage is turned off. He'll just need to then throw the ROCKER swith to OFF to shut down the device(s).

T.C.

[DGXSER]

Nate,

The short answer is no. Often in older houses I have found a circuit being fed form more than one breaker. Houses have POs to you know. The same thing really. The voltage is not additive, so feeding 12 volts from two different sources in parallel does not give you 24 volts.

Putting them in series gives you a higher voltage. Much like putting multiple batteries in hand held devices, 3 1.5 volt batteries in series goves you 4.5 volts. 6 gives you 9 volts.

The only problem with the set up you have planned, the way you described it, would be that turning one switch off, may not turn off the device. If it has two sources of power, you need both off to turn the device off.

[natemoen]

You have this 3 stage toggle switch. Does each stage only get powered when switched to ON, or does it power first stage 1, and then adds stage 2, and then stage 3 while the other stages still stay energized/switched on??

Each previous stage stays energized when you switch to the next one, so when the toggle is all the way on all 3 stages are energized.

You have a series of rocker switches in the Control Panel that will be powering an assortment of devices...ie. flashing lights, siren, floodlight, etc.!

You want to be able to power these devices individually via the rocker switches in the C.P., but you also want to be able to power ALL of them thru the use of the single 3 stage switch. AND you are wondering if an item is already energized/powered via the rocker switch, will sending an additional power supply to that same device(s) via the 3 stage switch will cause a problem...ie. fuse blowing or overload.

These devices are DC devices I am assuming, and both the rocker switches and the 3 stage/relays will be providing similar DC power. The devices themselves will not care where they get their 12+ volts from.

Yup, Just wondering if having 2 energized positives going to the same thing would cause a problem.

[crazy steve]

I saw this last night, but had taken a big slug of Robotussin for a cold I've caught and coherent thought was a bit difficult.... I was in bed shortly...

A few things.... As long as the voltage source(s) is coming from the same source, you'll be ok voltage-wise. If any is coming out of any sort of electronic box, I'd be concerned about backfeed into the box. And if each power source is fused separately, you could have a problem if a short or overload develops.

Now, if I'm reading this right, you have five individual switches controlling devices, and you want to bypass/override these with the slide switch, in pairs. Relays are the right idea; what you want to do is use three 2P2T relays, connect each device to the 'common' contact, the output from the toggle switch to the NC contact, and 12V to the NO contact. Use one pole per toggle switch. Power the relay coils through the slide switch. This also eliminates any 'duplicate' feeds/backfeeds.

Did I get this right? I ain't at my best.....

[natemoen]

Now, if I'm reading this right, you have five individual switches controlling devices, and you want to bypass/override these with the slide switch, in pairs. Relays are the right idea; what you want to do is use three 2P2T relays, connect each device to the 'common' contact, the output from the toggle switch to the NC contact, and 12V to the NO contact. Use one pole per toggle switch. Power the relay coils through the slide switch. This also eliminates any 'duplicate' feeds/backfeeds.

I don't totally follow what you are saying, but that doesn't mean it is your fault.

Here is how it is currently wired up (sorry about the free software watermarks and the jumble of wires, it wont let me move them where I want)



When I rewired the box I tried to just reuse as much of the current setup as possible so I didn't have to remake a bunch of wires since I am low on connectors right now.

I have thought about using the NC side of the relay to power the switches and just put a jumper between the NO and the NC side and then the switches would be powered from whichever side of the relay was energized at the moment. Like this:

[crazy steve]

Nope, won't work. I wish my scanner worked, I could draw this up easily...

All you're doing here is moving your power supply around, the relays won't shut off or turn on anything, and the individual switches are the only thing that will operate the devices.

What I think your intent is to be able to operate each item with the switch, or if powering up a relay, the relay will turn on two items, no matter if their switches are on or off. If that's right, this is what you need...

You've got the relay control wiring right. But you just can't do this with a single pole relay unless you use one for each device. So what you need is two 2PDT relays if you only want to use three total (reusing one of the SPDT relays you have).

So here's the single device circuit; starting at your 12V source, go to the fuse. From the fuse, go two places; one wire goes to the NO contact on the relay, the other goes to the switch. From the switch, this wire goes to the relay NC contact. The device gets hooked to the 'common' relay contact.

So when the relay is off, the current flows through the fuse, through the switch, and through the NC relay contact to the device.

When the relay is on, it goes through the fuse, through the NO contact (now closed) to the device. The switch is disconnected from the circuit.

Do this for each device (you need a set of separate relay contacts for each device) and you'll be good to go...

This clearer?

[natemoen]

Nope, won't work. I wish my scanner worked, I could draw this up easily...

All you're doing here is moving your power supply around, the relays won't shut off or turn on anything, and the individual switches are the only thing that will operate the devices.

Yeah, I was out running some errands and realized that second diagram would not work, but you beat me to it!

What I think your intent is to be able to operate each item with the switch, or if powering up a relay, the relay will turn on two items, no matter if their switches are on or off.

Yes, that is correct.

So here's the single device circuit; starting at your 12V source, go to the fuse. From the fuse, go two places; one wire goes to the NO contact on the relay, the other goes to the switch. From the switch, this wire goes to the relay NC contact. The device gets hooked to the 'common' relay contact.

Ok, I get it now. I was not thinking about running the current "backwards" through the relay (not that there is a forwards or backwards really) and that is why it didn't make sense the first time.

Don't know if I can fit a pair of DPDT relays in there but I will have to go and look and see what I can find at Radio Shack. I have a little bit of time to do this since I have to wait for some backlights to show up for the box so we shall see what I can come up with.

Thanks Steve and hope you start feeling better!

[crazy steve]

Yer welcome!!! It's a bit hard to clear the fuzziness out when you're not up to snuff....

[natemoen]

Got it all wired up how you described now. Now I just have to wait for the backlights and then try and cram all the extra wires into the box.

Thanks again.