# car audio help



## mjl (Jun 29, 2015)

Hi guys I hope you can help me out.  I have a hot tub that does not have a stereo so I built a box and used a 12 volt convertor to run the stereo.  Its on a timer that also controls the lighting on the deck so its only good for 1 hour which is fine but the problem is the stereo does  not retain the memory as there is no content power.  I have a spare auto battery that I thought i could use in combination but i was worried it would cause a problem when the 12 volt convertor is used to listen to the stereo.  The only solution is to activate the 12 volt convertor for 24 hr usage in the outdoor box that it is housed in and I don't know how safe this is.  Can I go the auto battery way and use a charger to periodically charge the battery for memory used only.  There is two lines one is the power ignition line and one is a memory line .  Any help?


----------



## Cybrnook2002 (Jun 29, 2015)

Yep, that an easy one. The car stereo you are using will have two power wires, a yellow and red. The red wire is the wire that you want to keep that one hooked up to your timer.

The yellow wire is the "memory" wire, which you can hook up to the car battery which can stay on all the time.

The only catch is you will need to ground both circuits together. Meaning you NEED to have the black wire coming out of the radio hooked up to the ground wire coming from the converter AND the negative battery terminal. This should not cause any issue as once the timer goes off, you are separated from your wall socket (which I assume you have the timer and 12 volt converter hooked up to), so the only thing that would remain "live" would be the yellow wire and the split ground hooked up to the battery. I don't think you should have much voltage bleed between the circuits (through the radio) when they are both on. Even if they do, it's all 12 volt, so not the end of the world.

Now, I would NOT have the car battery hooked up to a charger while also having it hooked up to the timer/12 converter while all being powered on. Charge the battery separate as needed.

*IDEA!!!!!!*

Or, better yet, if your familiar with car electronics (which it sounds like you might be), just use a standard 5 terminal relay to isolate your battery when the converter is on.

This, I think, is the better way ;-)















*Keep in mind, the car battery will need a charge from time to time. If you isolate it with the relay you could leave a charger on the battery all the time and be fine.*


----------



## T-Bob (Jun 29, 2015)

Cybrnook2002 said:


> *IDEA!!!!!!*
> 
> Or, better yet, if your familiar with car electronics (which it sounds like you might be), just use a standard 5 terminal relay to isolate your battery when the converter is on.
> 
> This, I think, is the better way ;-)


+1 I agree and that's a nice diagram that you put together for him. That should work just fine.


----------



## mjl (Jun 29, 2015)

T-Bob said:


> +1 I agree and that's a nice diagram that you put together for him. That should work just fine.


wow thanks for the help.  I thought of using one of those trickle chargers and leave it on all the time so I would of been in trouble.  I did not think that it was going to be  problem I will look into buying the 5  terminal relay.


----------



## Cybrnook2002 (Jun 30, 2015)

Well if you use my relay method, you can leave a trickle charger over the battery all the time.

If you find that the short millisecond it takes for the relay to switch from the battery to the power converter is still long enough to "12:00" the radio (it won't be), you could wire in line a little capacitor. Just something to hold the charge during the switch over.

Let me know if you want me to update the diagram. It would be a small cap on the yellow wire coming off the relay (30) towards the radio.


----------



## Mindweaver (Jun 30, 2015)

You could use an old/new PC power supply to power your DC car stereo, and lights.


----------



## mjl (Jul 8, 2015)

Thanks I tried hooking it up tonight.  I believe that I have it set up the way you show it.  I have power when the 12 vt conv is turned off.  The problem is that the stereo stays powered up and does not go into memory mode like when the ignition is off, it stays active.


----------



## Cybrnook2002 (Jul 8, 2015)

Can you upload some pictures please


----------



## mjl (Jul 8, 2015)

I will have to wait until tomorrow as its dark now. I have have 87  and 85 going to the 12 vt connector and 12 vt radio.  I have the centre 87 going to the pos on the battery.
30 yellow on the stereo.  86 handles all the negative.


----------



## Cybrnook2002 (Jul 8, 2015)

From your 12 volt converter, can you hit it with a multimeter when it's in the off position? I want you to check between the positive and negative (can measure between 85 and 86). If you get 12 volt, then it's not truly off. 

The idea with the relay is that when 12 volt and ground are applied over 85 and 86, the relay will close the circuit for 87 and 30. Where normally 87a and 30 are normally connected when the relay is not powered (over 85 and 86).

So if the radio is staying on when the 12 volt converter is off, either we have a wire backwards somewhere or the converter is applying enough to hold the relay open. 

Hmmmm, we could test this by you just unplugging 85 and seeing if it turns off. (Could also try 86 as well....)


----------



## mjl (Jul 8, 2015)

using a pigtail the 87 is yellow 87a is orange 30 red 86 green 85 blue.


----------



## mjl (Jul 8, 2015)

I can disconnect the convertor on off switch even disconnect 85 86 one at a time and the stereo continues like nothing happened.  I can disconnect 87a  and 30 while the 12t Conv is connected and the unit also continues without a glitch it does not go into a memory position it just keeps playing music


----------



## Cybrnook2002 (Jul 9, 2015)

Then something has to be backwards. What happens when you swap the yellow and red at the radio? (I assume this is a car stereo?)

I even went out to the garage and looked at my old relays, the diagram is right.  87a and 30 should have contact when 85 and 86 are not powered, that would allow you to get power from the battery at all times for memory.  Once 85 and 86 see 12volt and ground (respectively), then you car battery should go away (87a) and 87 should take over (all power from power inverter) as 87 and 87a swap positions to output on 30 when 85/86 are powered. Of course battery and power inverter all end up outputting on 30 at one time or another, as 30 is the constant to the radio.

The only reason I can think that your radio is staying on is because the memory and power wire on the radio are swapped (or wiring is mixed up somewhere), and for whatever reason the radio is still operating without one or the other. Do you have a multimeter?

And can you possibly provide some better, higher res pics? It's hard for me to double check your work when I can't see the "Full picture" at once, I need to be able to trace all your connections from front to back.


----------



## mjl (Jul 9, 2015)




----------



## Cybrnook2002 (Jul 9, 2015)

The radio? Still haven't seen that yet.


----------



## mjl (Jul 9, 2015)

I can switch the yellow and red and it still works the same. the same radio station continues to play.  its a kenwood x399.  I must have something set up wrong here.  I hate to be a pain but I really don't know whats the problem.  I don't have a multimeter I would have to pick one up.The three wires coming from the black cable are the black red and yellow direct from the receiver.


----------



## mjl (Jul 9, 2015)




----------



## mjl (Jul 9, 2015)

I opened the box that the deck is installed in on the deck.  The yellow is tied to the yellow the red to the red and black to black.


----------



## Cybrnook2002 (Jul 9, 2015)

Let me think on it some time. In the meantime go over my diagram again and make sure, triple check everything is exactly as is.


----------



## mjl (Jul 9, 2015)

all joints are soddered and then taped.


----------



## Cybrnook2002 (Jul 9, 2015)

If all fails, throw me a little $ and mail me out the radio harness and all and I can build you a clean harness.


----------



## mjl (Jul 12, 2015)

I tried over and over and its a no go.  I went with the first idea.  The stereo has a delay start up and shut down app 10 seconds before the music actually stops playing.  I ran another outlet that is not on that timer and put the car charger on a timer that would never conflict with the usage of the stereo.  I have it charging one hour daily.  I have no idea hour much or how often it will need a charge.  I will have to keep an eye on it.   I am going to upgrade the 12 volt converter as its only 3.5 amps and the new stereo will require more.

Thanks for all your help.  Your idea was what I actually would like but this is workable.


----------



## Cybrnook2002 (Jul 12, 2015)

Well, thanks for writing back. Ho hum on the relay :-/ I am sure with a little more time and effort we likely could get it going. BUT!!!! --> as with any hot tub<--- Down time is production downtime, and we can't have it affecting the users  If you ever want to give it a second go, PM me, and I will help with making a harness for you . (testing it at home before I send it out)


----------



## taz420nj (Jul 24, 2015)

The problem here is that car head units needs BOTH power wires to be energized in order to work.  It actually draws all of its operating power from the yellow wire, the red wire is simply a trigger lead (just like how the blue wire triggers an amp).   You can't switch between them like you have in your diagram.  The yellow wire must have power at all times.

That said, is there any specific reason why you can't just leave the power supply on all the time?  This timer + power supply + relay + car battery + charger setup is very kludgy, when all you have to do is keep the power supply on and install a switch in the red wire.


----------

