# Car stereo head unit memory circuit question...

#### Wiebenor

Joined Nov 22, 2018
7
Ok guys, I'm new here, and have seen a post here going over a memory wire connection on a car radio...

I have a slightly different question, regarding how to power the memory circuit, and have a few related questions id like an answer to, that will be listed below. But before I ask my questions, I have uploaded a picture of my setup, i made completely by hand and wired the car stereo and speakers into, and will explain below how the power is wired in...

Current setup is 1 positive and 1 negative wire going in the boombox case which will always remain the same, that gets split into 2 positive wires, one going to memory board, the other going to a power switch which then is used to turn screen off and on if I need total darkness for some reason, and the power, as is standard, then returns to the negative wire and so on...

Question 1... is the memory circuit a separate circuits from the power circuit.

Question 2... could I hook a couple of 12v(or 12v combined) (similar to C or D batteries in size) rechargeable batteries inside, to run the memory circuit.

Question 3... if you can use rechargable batteries, how would I charge them.

If you need more information let me know, but be advised that I do not check my email for new notifications every day, so i may respond quickly, or I may not... also, note that my radio in the picture isn't plugged in at the moment, so no pretty colorful lights are visible...

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#### dl324

Joined Mar 30, 2015
13,087
Welcome to AAC!

We need a schematic/block diagram showing how the memory and other circuits are powered. What is the current drain of the memory circuit and how long to you want it to retain memory with main power removed?

#### Wiebenor

Joined Nov 22, 2018
7
Welcome to AAC!

We need a schematic/block diagram showing how the memory and other circuits are powered. What is the current drain of the memory circuit and how long to you want it to retain memory with main power removed?

Well... if it helps, it's a Single DIN pioneer radio model# DEH-X6910BT, I don't know the current drain, i think, at the moment... i must disclaim, thative been making simple circuits forever, and must also say that I am mostly self taught, so am a bit behind on learning how to test circuits... i am learning though, however slow it may be... do you mean current drain/draw as in "battery amps/ current drain= hours of use"? Specifically, for for example, the Miliamps that a DC wall transformer plug outputs, and is required to run said device? Also, would the product install manual help with figuring current drain? Also, do you just need a picture of the wiring plug diagram, or were you thinking something else? How long I need it to last would be, at most, probably a week, or two, but mostly just the amount of time it is in transport to a new plugin or battery (radio has PC PSU support, as well as battery, which is another question I may put later in this thread) Remember, I'm a newbie here, and not used to running tests on circuits, just following directions to put stuff together unless I make it. But then if i make the device, its not that complicated.

#### Wiebenor

Joined Nov 22, 2018
7
Ok... forgot to add that not only will it be moved from plug to plug, or plug to battery, but it may be stored, for a few hours, or possibly days when being transported in a car, to a party for instance, or a new house. I also forgot to add a thank you for such a quick response to my post... im just tired of every time I move the radio, having to reset the time properly... the radio presets and most savable settings don't disappear, only things like time and paired BT devices...

#### Wiebenor

Joined Nov 22, 2018
7
If i understand you correctly, which as i said earlier, I may not have, these 2 images might help clear some of it up... although I doubt it...

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#### dl324

Joined Mar 30, 2015
13,087
If i understand you correctly, which as i said earlier, I may not have, these 2 images might help clear some of it up... although I doubt it...
The wire code helps a little. At least I know there's a separate power input to memory.

Do you normally connect the yellow and red wires together? If you do, you could use two diodes (so memory and stuff connected to the red wire will see the same voltage. Then put a large capacitor on the cathode of the diode going to the memory circuit.

If yellow is connected to an always hot 12V source, the diode hack can still work.

Capacitor size depends on how long you need memory retained and what else is connected to that power input.

Whenever the mechanic who worked on my first BMW needed to disconnect the battery, he stuck a 9V battery wired to a cigarette lighter plug into the cigarette lighter. He had found that that would keep the radio presets.

#### Wiebenor

Joined Nov 22, 2018
7
Hmm... i never thought about that ... but it isn't presets that dies, that is saved to ROM, or the equivalent... but no matter, I think I found a solution, albeit a partial one... i want to get a small PSU that fits inside of my box, probably with the plug showing in a hole in the rear, then id just have my battery connectors spliced in as a backup power source, same as it is set up now... the differenttechnique, that a relative helped me reach, was a battery with a barrel plug connector off of eBay or Amazon, commonly used for powering security cameras... he says that my shared negative shouldn't affect the battery any, plus I can take the battery out and charge it if need be... comments are welcome, as to the plausibility of the idea, and to answer your question, no, the 2 positives are not going to be stuck together, although they are now... but the 1 wire hooks to a switch to make my screen go dead but still power memory... as i said, my plan is to take and completely split those circuits apart by pulling the 2 intertwined wires apart... does what i just said, make any sense, or am I confusing you all???

#### dl324

Joined Mar 30, 2015
13,087
Hmm... i never thought about that ... but it isn't presets that dies, that is saved to ROM, or the equivalent... but no matter, I think I found a solution, albeit a partial one... i want to get a small PSU that fits inside of my box, probably with the plug showing in a hole in the rear, then id just have my battery connectors spliced in as a backup power source, same as it is set up now... the differenttechnique, that a relative helped me reach, was a battery with a barrel plug connector off of eBay or Amazon, commonly used for powering security cameras... he says that my shared negative shouldn't affect the battery any, plus I can take the battery out and charge it if need be... comments are welcome, as to the plausibility of the idea, and to answer your question, no, the 2 positives are not going to be stuck together, although they are now... but the 1 wire hooks to a switch to make my screen go dead but still power memory... as i said, my plan is to take and completely split those circuits apart by pulling the 2 intertwined wires apart... does what i just said, make any sense, or am I confusing you all???
Have you tried reading your posts where you put everything into one long paragraph and don't use proper punctuation?

If you had written your first post like that, you'd be on my ignore list.

#### Wiebenor

Joined Nov 22, 2018
7

I was too in a hurry to correct that, or my punctuation, which believe it or not, I know how to do correctly.
I just got used to my current style of punctuation in a game I play, and find it hard to do it the proper way when im in a hurry.(and sometimes when im not)

#### LouF1

Joined Apr 13, 2018
2
I'm going to throw this out here, and I'm going to assume this the whole radio system and not just a head unit (amp separate):
Assume the radio's memory current draw is approximately 4.5mA.

Use a 12V, sealed lead-acid battery inside the box wired in parallel to the assumed 12VDC you are supplying the box with. The supplied power will need to, then, come from a battery charger so the battery is charged properly. The batteries seem to be about 12Ah,

or

use a UPS and tap the 12VDC off the battery. A 450VA unit is about $45. These would have battery charging circuitry. Then you can plug the box into wall 120VAC. or If alkaline D-cells show ~18000mAh; you will need 8 (12V/1.5V=8). Separate the memory wire, and run it on battery only (I think the negative can remain common between the batteries and the 12VDC you're supplying, and surely that is not separated anywhere). Don't get excited because don't know if this is simply applicable, but this tells me it should last ~5.5 months. Tape 2x4 rows together, all connected in series (and the connection might be easily lost w/o a battery holder pack. I'd try this first for ~$13.