Maker Pro
Maker Pro

Relay help.

Alex Ayris

Apr 22, 2016
22
Joined
Apr 22, 2016
Messages
22
I am wondering if this is possible. I'm putting together my old car stereo system in my house, (don't ask) now I'm trying to recreate the circuit to keep the presets for radio and other settings. And to do this I'm useing 2 individual power supplies. 1 is a 30 amp supply that will be the main source when radio is on the other is a 0.5 amp supply that needs to engage when I turn the radio off. I was thinking I could use this relay, but when I look at youtube nothing seems to quite fit what I'm trying to achieve. http://m.ebay.co.uk/itm/12V-Micro-A...A-5-Pin-Car-Bike-Van-/261993828001?nav=SEARCH

If this is not suitable please let me know. If it is how do I connect it up. I'm guessing I would connect the 30 amp circuit through the coil and when I turn it off the normally closed circuit would engage which would have the 0.5 amp supply on. The thing that makes me doubt myself is that most of the videos online mention that the coil side is for a low voltage application. Can the coil side handle a 25 amp load?.

Anyway I'm babbling, any input would be a massive help, perhaps a diagram would be nice.
 

Gryd3

Jun 25, 2014
4,098
Joined
Jun 25, 2014
Messages
4,098
I am wondering if this is possible. I'm putting together my old car stereo system in my house, (don't ask) now I'm trying to recreate the circuit to keep the presets for radio and other settings. And to do this I'm useing 2 individual power supplies. 1 is a 30 amp supply that will be the main source when radio is on the other is a 0.5 amp supply that needs to engage when I turn the radio off. I was thinking I could use this relay, but when I look at youtube nothing seems to quite fit what I'm trying to achieve. http://m.ebay.co.uk/itm/12V-Micro-A...A-5-Pin-Car-Bike-Van-/261993828001?nav=SEARCH

If this is not suitable please let me know. If it is how do I connect it up. I'm guessing I would connect the 30 amp circuit through the coil and when I turn it off the normally closed circuit would engage which would have the 0.5 amp supply on. The thing that makes me doubt myself is that most of the videos online mention that the coil side is for a low voltage application. Can the coil side handle a 25 amp load?.

Anyway I'm babbling, any input would be a massive help, perhaps a diagram would be nice.
Let's take a step back and look at the parts in use. Maybe you can do this differently...

The 30A supply will not always be putting out 30A... it will be putting out 12V (most likely) and can go *up to* 30A.
This means that if you turn the stereo off, the stereo will only draw what it needs on the standby wire which is much less than an amp. The big power supply will no longer be running at fill tilt, and will be using much less power. You can leave it this way.
If you really don't want the 30A supply to remain running and ready to put out 30A, you can connect the relay's coil in *parallel* with the 30A supply. When the big supply is turned on, it will trigger the relay which you can wire to toggle between a low power supply, and the 30A supply to the stereo. Keep in mind that the 30A is what the supply is capable of, not what it's going to *push* into something. You can use a 12V relay and it will be just fine as long as you use a 12V supply. The relay will take as much as it needs to function from the 30A capability of the big supply.
 

Alex Ayris

Apr 22, 2016
22
Joined
Apr 22, 2016
Messages
22
Hi thanks for your response, I have thought about that. The trouble is my wife is a freak when it comes to turning stuff off, so when I put a big switch on the front that says off and it's not getting used she will turn it off. Lol. hear is a circuit that I think should work? 1461708575104-1395984860.jpgPlease let me know what you think. I think I'm missing a ggroundfrom the stereo back to the 30 amp supply?
 

Gryd3

Jun 25, 2014
4,098
Joined
Jun 25, 2014
Messages
4,098
On|Off switch in the picture still leaves the 30A supply on... although it will unlatch the relay and allow the smaller supply to be used. You can omit this if the bigger supply has it's own on/off switch.
Please make the following adjustments though:
- Flip the Relay... pins 87 and 87a should go to the Power Supplies. 87a (N/C) to the Smaller Supply, and 87 to the larger one.
- Pin 30 will go to the stereo.
- The 30A fuse should be the first thing connected to the big supply. It can be split to pins 87 and the coil after the fuse.

The fuse is additional protection, and it not requried to protect the relay. It should be used as close to the supply as possible if the supply does not have any built-in protection.
*You may also want a capacitor on the amplifier side of the relay... the switching action will momentarily disconnect it from both supplies while the relay arm moves. A capacitor will help smooth out this voltage dip.
 

Alex Ayris

Apr 22, 2016
22
Joined
Apr 22, 2016
Messages
22
Yeah my diagram not as clear as it should have been. The diagonal line pointing in the direction of the smaller power supply was ment to denote that. My bad.
Pin 30 will go to stereo via the Nc/ coil? As in my diagram. And the switch I was thinking the same the way I currently have it would require 2 switches. So from my main power in, put the 30 amp fuse, then split the live, and put the switch on the 30amp supply cable and that should be that?

* what type of capacitor should I use and where should I place it?
 

Gryd3

Jun 25, 2014
4,098
Joined
Jun 25, 2014
Messages
4,098
Yeah my diagram not as clear as it should have been. The diagonal line pointing in the direction of the smaller power supply was ment to denote that. My bad.
Pin 30 will go to stereo via the Nc/ coil? As in my diagram. And the switch I was thinking the same the way I currently have it would require 2 switches. So from my main power in, put the 30 amp fuse, then split the live, and put the switch on the 30amp supply cable and that should be that?

* what type of capacitor should I use and where should I place it?
Not quite. Your diagram showed a potential problem.
Pins 85 and 86 are for the coil and does not appear to be polarized, so ground and power can be provided forward or backward on these two pins.
Pin 30 is 'common', pin 87a is the Normally Closed contact, and pin 87 is the Normally Open contact.
The diagonal line you have drawn merely shows the 'internal connection' of the relay. That diagonal line will toggle between 87a and 87 as power is added or removed from the coil on pins 85/86.
At any time, the relay Pin 30, will be internally connected to either 87a or 87, but never both, and there is a very very small time-frame where it will not be touching either one while it's changing state.

Your drawing shows that both power supplied are connected to Pin 30. This is a bad decision in itself immediately because you run the risk of having one power supply back-feed into the other. If both power supplies are connected in such a manner you *must* use a diode as protection against backward current into either one of the power supplies. By putting power *into* Pin 30, you are also limiting yourself to no longer choosing which power supply to use, but you are building a circuit which *redirects* power to pin 87a or 87.
Additionally, your drawing shows that both 87a and 87 goes to the stereo amplifier... This in itself is incorrect as well, unless you want to toggle providing power to either the Power input or Standby input of the amplifier. The standby voltage simply holds clock values, and the Power input will turn the unit on and provide the current required to drive the speakers and internal circuitry.

Instead of redirecting power to go from one input to another of your stereo, you must take care of it a different way.
You *must* keep power to the Standby input 24/7.
Power only needs to be supplied to the Power input when you want to listen to music.

The question now is: How do you want to control the device?
Option A: Turn off the big power supply.
Option B: Toggle a separate switch.


So, with that said. I'd encourage you to simply leave the 30A supply on, and put a switch in-line with the Power input on the Stereo and leave the Standby input connected directly to the 30A supply... Easy. The 30A supply is capable of 360W, but it will not run like that all the time! It's simply a converter. When the stereo is on and wants 200W, the power supply will pull 210W-220W from the wall. When the stereo is off and may be drawing less than 1W, the Power Supply will be pulling substantially less as well. The exact amount will depend on how efficient the Power supply is.
*It's possible that your more capable 30A Power Supply draws less current when supplying standby power to the stereo than the less capable supply... I can't say for certain without seeing specs on the supply, but unless the 30A supply is a horribly cheap inefficient beast there really is no need to disconnect the stereo from it and connect it to a lesser power supply with a relay.

If you are still set on making it work your way:
- Connect the 30A supply + to a Fuse Side A.
- Connect Fuse Side B to Switch Side A.
- Connect Fuse Side B to Relay Pin 87.
- Connect Switch Side B to Stereo Power Input.
- Connect Switch Side B to Relay Pin 85.
- Connect the 0.5A supply to Relay Pin 87a
- Connect Relay Pin 30 to Stereo Standby input.
- Connect Relay Pin 86 to Ground.
- Connect Stereo Ground to Ground.

Sorry for lack of diagram.
The switch sits on the Power Input of the stereo. This switch is responsible for turning the stereo *and* relay on and off.
When the relay is off, it will connect the Standby input of the Stereo to the lesser Power Supply connected to pin 87.
When the relay is on, it will connect the Standby input of the Stereo to the more capable Power Supply connected on pin 87a.
In this way, the less capable supply is only ever allowed to connect to the standby input *if* the more capable supply *or* switch is turned off.
The capacitor may not be required, you can test it without first. If you need it, you should put Side A on the Standby input, and Side B on ground.
 

Kiwi

Jan 28, 2013
471
Joined
Jan 28, 2013
Messages
471
Why are you switching the low current memory battery supply?
In a vehicle this is live all the time, whether the stereo is on or off.

There are a few different ways that car stereos operate;
1 - Low current constant battery supply for memory only.
High current accessory/ignition supply to run stereo.

2 - High current constant battery supply for memory and stereo operation.
Low current accessory/ignition supply only used to wake up stereo.

3 - High current accessory/ignition supply to operate stereo.
Stereo has internal memory retention not requiring constant battery supply.

Some stereos of type 1 and 2 will retain their memory even if the battery supply is cut. Others will loose their memory if the battery supply is cut, some instantly, some after a few seconds or minutes.

How does your stereo operate?

What is the make and model of your stereo?
 

Alex Ayris

Apr 22, 2016
22
Joined
Apr 22, 2016
Messages
22
Hi thanks for reply. I think I'm going to skip the relay, and just tell my wife not to turn it off at the wall. In the last post you mentioned a low current ignition to turn on the radio. I was going to just connect this to the constant live. Is this OK as when the radio is running the constant Live could have 10 amps going through it would that mean that the ignition wire would have 10 Amps going through it aswell? Or dose it just use what it requires?
 

Gryd3

Jun 25, 2014
4,098
Joined
Jun 25, 2014
Messages
4,098
Hi thanks for reply. I think I'm going to skip the relay, and just tell my wife not to turn it off at the wall. In the last post you mentioned a low current ignition to turn on the radio. I was going to just connect this to the constant live. Is this OK as when the radio is running the constant Live could have 10 amps going through it would that mean that the ignition wire would have 10 Amps going through it aswell? Or dose it just use what it requires?
This depends on how the stereo is wired internally... It has two wires for sure, but you can't guarantee that the 'Stand-by' wire won't pull more current when it's turned on. I would suggest not using two supplies at the same time as well... as I am unsure how they are connected internally in the unit.
I would most certainly suggest getting your wife to leave it powered on, and put in your own switch in-line with the 'Power-Input' of the stereo to turn it off.

The stereo I'm wiring up is eonon GA 2114
Max current looks to be 15A
 

Alex Ayris

Apr 22, 2016
22
Joined
Apr 22, 2016
Messages
22
Yeah I think that's ambitious the fuse in the back says 15 amps so running current won't be 15 amps I'm guessing closer to 10.
Is it OK to wire the ignition live together with the constant live so that when I flick the switch it sends the signal. I have done this in the past.

Also my power supply is rated at 30 amps, it has 3 live out put terminals on it but they are all connected. Is it OK to connect a powered aerial to it as well, I'm not that clued up on electronics and I don't want to send the current I'm drawing for the radio let's say 10 amps through a device that requires less than 1 amp. Or will the aerial just take what it needs regardless of what else is being pulled?
 

Gryd3

Jun 25, 2014
4,098
Joined
Jun 25, 2014
Messages
4,098
Yeah I think that's ambitious the fuse in the back says 15 amps so running current won't be 15 amps I'm guessing closer to 10.
Is it OK to wire the ignition live together with the constant live so that when I flick the switch it sends the signal. I have done this in the past.

Also my power supply is rated at 30 amps, it has 3 live out put terminals on it but they are all connected. Is it OK to connect a powered aerial to it as well, I'm not that clued up on electronics and I don't want to send the current I'm drawing for the radio let's say 10 amps through a device that requires less than 1 amp. Or will the aerial just take what it needs regardless of what else is being pulled?
Yes, it's ok to tire ignition and constant together... but you may find when you turn it off, you loose your radio settings.
Leave the constant wire connected, and put the switch on the ignition wire only.

As far as the amperage is concerned, you cannot *push* amps into anything unwillingly unless you use the wrong power supply.
A constant current type supply can do this, and a voltage supply that is too high can do this...
Otherwise a 12V power supply rated at 1000A will be able to provide *up to* 1000A to the device(s) connected to it... BUT each device will only draw what it *needs*... so in this case... Your stereo will take up to 15A from the power supply as it needs it, leaving at least 985A available to connect other devices to. This is an extreme example of course. It's the same reason a 30W light-bulb does not explode when you put it in the socket. (Your household circuits can often provide 1500W or more... or 10+ Amps... what you plug in draws what it needs... as long as the voltage matches.)
 

Alex Ayris

Apr 22, 2016
22
Joined
Apr 22, 2016
Messages
22
OK thank you very much for all your help. I can't remember who said it but often the best solution is the simplest. Probably Mark Twain.

I do belive I have been trying to over complicate things. You would never belive this is my second time doing this. And it's basically going to be the same as the first time.
I did to much research this time from to many inaccurate sources. Damn you Google.
 

Gryd3

Jun 25, 2014
4,098
Joined
Jun 25, 2014
Messages
4,098
OK thank you very much for all your help. I can't remember who said it but often the best solution is the simplest. Probably Mark Twain.

I do belive I have been trying to over complicate things. You would never belive this is my second time doing this. And it's basically going to be the same as the first time.
I did to much research this time from to many inaccurate sources. Damn you Google.
lol. Google can be helpful if you can wade past the useless stuff.
The only advantage I see with what you originally wanted to do, is that the lesser capable power supply *might* use a little less energy while supplying the very low stand-by current to the stereo... This is a wild guess though, and I'm sure the current draw when the stereo is switched off with the switch on the 'ignition' wire will be incredibly low.
 
Top