Need help with DIY Boom Box, need a way to store settings.

Reply

  #1  
Old 06-08-14, 12:12 AM
Member
Thread Starter
Join Date: Jun 2014
Posts: 21
Received 0 Votes on 0 Posts
Question Need help with DIY Boom Box, need a way to store settings.

Hey guys,

I'm designing, and will be fabricating soon, a DIY Boombox using a 12V PSU from a computer, a head unit, and some speakers. But just now, I realized something, since the box will operate solely using the PSU power, which will require it being plugged into 120V AC wall outlets, there won't be anything to store the settings stored in the head unit.

My first problem is I need a way, preferably a small and lightweight solution, to allow me to store settings, and to be able to keep that battery charged without needing to tear the box apart to change or access the battery. I can't find how many mA the HU would draw to store settings, but it can't be much. The smallest 12V solution I can find would be an A23 battery, but I can't find a rechargeable one, and I would worry about it not lasting very long. Having some sort of A23 circuit and holder mounted to the back of the box would be alright, if replacing the batteries is the only option available.

My second problem is that I'm confused about if I could even put a battery backup inline in the power circuits without it blowing stuff up. A typical HU has constant power from the battery to the red wire, and ignition power feeds the yellow remote power button, signaling the HU to draw from the red. I guess I'm planning on just wiring the remote input of my HU to the red constant 12V power from my PSU, unless you have any better ideas. But I'm perplexed about how to wire a battery backup into the circuit in a way that would allow it to store settings but not leave the HU on, draining the battery with standby or powered on amperage draw.

I'm a little frustrated, because I thought I had thought of everything, and was ready to begin. But now I've remembered this detail, and realize I still have a major hurdle in front of me. Any help you could provide would be appreciated.

FWIW, it's a 500W PSU, 22W RMS X 4 HU, 2 - 80mm fans, maybe some cold cathode tube lighting as well.

Bonus Question: If you only had 2 speakers to wire to the HU, is there a safe way I could double up and feed each speaker two channels, without it overloading the HU's amp? I suspect not, but you guys might have some ideas.

Thanks!

EDIT: Here's a crude diagram to build on, and here is how I imagine a battery backup might be wired, but don't know if that will work
 

Last edited by sv650; 06-08-14 at 12:57 AM.
Sponsored Links
  #2  
Old 06-08-14, 12:28 AM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Northern NJ - USA
Posts: 54,565
Received 510 Votes on 480 Posts
Welcome to the forums.

You're in trouble. I've done what you want for customers but I've taken the radio apart and left a separate line out for just the memory hold circuit.

Can you post the make and model of the hu ?

As far as the bonus question...... most hu's today use a four channel audio output IC chip. You cannot combine the front and rear channels. Your best best is to use the front or rear outputs and leave the fader all the way in that setting.
 
  #3  
Old 06-08-14, 12:51 AM
Member
Thread Starter
Join Date: Jun 2014
Posts: 21
Received 0 Votes on 0 Posts
Thanks for your quick reply, and for the warm welcome! I've since added a couple of diagram links. The HU is a JVC KD-X310BT.

In my second diagram, I show a proposed battery circuit. Would that work? And if so, would it require a rechargeable battery? If not, what type of solution would you recommend? I'm not sure what you mean when you say you added a separate line out.
 
  #4  
Old 06-08-14, 06:39 AM
Member
Join Date: Apr 2007
Location: Near Buffalo, NY
Posts: 4,239
Received 0 Votes on 0 Posts
The yellow wire is not a "remote power on" signal. It is in fact the "always on" memory connection that holds the settings when the ignition key is turned off. The red wire is the power supply to the HU. There is no current on the red wire when the unit is powered down. The current draw to the yellow wire is very small -- on the order of 25 to 50 milliamps -- however the A23 battery will only last about 50 hours.

Better to get a small 12v rechargeable and a charger. Plug the charger into 120v along with the PS. Connect the negative grounds together (PS, the charger, the battery and the black wire of the HU). Connect the red wire to the positive side of the PS and the yellow wire to the positive side of the battery.

The HU will pull 10 amps at full throttle, so that PS needs to be able to deliver 150 watts at 12 volts (including headroom).
 
  #5  
Old 06-08-14, 11:10 AM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Northern NJ - USA
Posts: 54,565
Received 510 Votes on 480 Posts
That's why I requested you to post the make and model. Like Rick mentioned your radio doesn't operate as you originally assumed although there are radios that do work that way.


The HU will pull 10 amps at full throttle, so that PS needs to be able to deliver 150 watts at 12 volts (including headroom).
That would be based on four speakers so your demand will be somewhat lower.
 
  #6  
Old 06-08-14, 05:27 PM
Member
Thread Starter
Join Date: Jun 2014
Posts: 21
Received 0 Votes on 0 Posts

The yellow wire is not a "remote power on" signal. It is in fact the "always on" memory connection that holds the settings when the ignition key is turned off. The red wire is the power supply to the HU. There is no current on the red wire when the unit is powered down. The current draw to the yellow wire is very small -- on the order of 25 to 50 milliamps -- however the A23 battery will only last about 50 hours.

Better to get a small 12v rechargeable and a charger. Plug the charger into 120v along with the PS. Connect the negative grounds together (PS, the charger, the battery and the black wire of the HU). Connect the red wire to the positive side of the PS and the yellow wire to the positive side of the battery.

The HU will pull 10 amps at full throttle, so that PS needs to be able to deliver 150 watts at 12 volts (including headroom).

Ahh yeah, I got the purpose of those two wires confused, thanks for the correction.

What type of 12v rechargeable battery are you thinking of? I've thought about the following options...
1. DIY several rechargeable AA batteries wired in series.

2. a 12v NiMH battery pack like this

3. a 12v alarm battery like this

4. a spare laptop battery and charger I no longer use (10.8v 4400 mAh)

You mention using a charger, and say to plug it into 120v along with the PSU, but then mention splicing the ground wire of the charger into the PSU/HU/battery ground junction, but I'm confused about how to do that if the charger is not mounted in the box, without splicing into the 120V inside the box to power the charger, and then splicing into the 12V ground to ground it, and I'm not sure if that is what you meant or not. So I've assumed that, like me, you mean for the charger to be outside the box, leaving the battery, PSU, and HU inside, but also not wiring the charger to anything inside the box, just using it to recharge the battery every now and then.

I've tried to visualize what you've recommended, amending the wiring of the charger, and that sketch is located here.

Are you sure that having the battery inline in the power supply circuit won't blow up the battery or cause any damage to anything else? And if you do mean to have the charger inside the box, can the same be said? And how would you wire that, if my above description of splicing is misunderstanding your idea.

Also, the PSU is 500W, so I've got all kinds of head room for power. There's 40A on the 12V rail, so that shouldn't ever be a problem.

Thank you!
 

Last edited by PJmax; 06-08-14 at 05:46 PM. Reason: removed board added link
  #7  
Old 06-08-14, 05:31 PM
Member
Thread Starter
Join Date: Jun 2014
Posts: 21
Received 0 Votes on 0 Posts
That's why I requested you to post the make and model. Like Rick mentioned your radio doesn't operate as you originally assumed although there are radios that do work that way.


The HU will pull 10 amps at full throttle, so that PS needs to be able to deliver 150 watts at 12 volts (including headroom).
That would be based on four speakers so your demand will be somewhat lower.


Read more: http://www.doityourself.com/forum/el...#ixzz345raZuil


Yeah, haha, it's been a very long time since I've done car audio projects, so I'm still dusting off the cobwebs from the 12V DIY portion of my brain.

I did a quick test of all my new stuff last night, and everything works. So at least I won't have to worry about anything being DOA when I actually assemble it. I can't wait to build this thing.
 
  #8  
Old 06-08-14, 06:01 PM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Northern NJ - USA
Posts: 54,565
Received 510 Votes on 480 Posts
I would use a small lead acid (gel cell) battery. You don't need 7ah. A 5ah or even 1.5ah would also be ok. That nicad pack you linked to would work. Don't forget what ever battery you choose needs a charger. A small wall cube charger is perfect. You only need to charge the box occasionally.

When you use the box on AC or as long as it's plugged in the memory battery won't be used.

I'll draw up a diagram for you to follow.
 
  #9  
Old 06-08-14, 08:20 PM
Member
Thread Starter
Join Date: Jun 2014
Posts: 21
Received 0 Votes on 0 Posts
A diagram would be greatly appreciated. Thanks for the help! Whatever battery I decide to use, I'll probably wire it to some external panel where I could plug in a barrel plug or put alligator clips on terminals to charge it without opening the box. I'm tempted at this point to use the laptop battery, since I wouldn't have to buy a battery, and already have a charger as well. But I'm also tempted to get a sealed lead acid battery, wire it to some terminal posts for charging with a charger with alligator clips, and actually having the ability to use the box without AC power, even if it is just for an hour or less. But I likely wouldn't use that very often, so I'm more likely to focus on keeping the weight down and just getting a battery that will only serve the purpose of holding memory for a few days without being plugged in.

Also, I don't guess there's any way to just use the output of the PSU to charge the battery inside the box? I'm guessing the need for the charger is because it would limit the amperage to allow a slow charge of the battery.

Are you guys certain that this won't damage anything to wire the battery into a PSU that has the ability to pump 40A, and a HU that may draw 5-10A?
 
  #10  
Old 06-08-14, 08:58 PM
Justin Smith's Avatar
Member
Join Date: Dec 2010
Location: Cressona, Pa, USA
Posts: 2,546
Received 0 Votes on 0 Posts
The PSU puts out exactly 12V. A battery needs 13.8V or more to charge.
 
  #11  
Old 06-08-14, 09:31 PM
Member
Thread Starter
Join Date: Jun 2014
Posts: 21
Received 0 Votes on 0 Posts

The PSU puts out exactly 12V. A battery needs 13.8V or more to charge.
Alright, so using the 10.8V laptop battery looks like a no-go too then, since a +15% increase in voltage appears to be the minimum for charging. I guess I'll just plan on hooking up a charging terminal on the exterior of the box. No big deal, just wanted to see if it was possible.
 
  #12  
Old 06-09-14, 04:41 AM
Member
Join Date: Apr 2007
Location: Near Buffalo, NY
Posts: 4,239
Received 0 Votes on 0 Posts
The purpose of connecting the 12vdc negatives together is to have the same zero-volt reference for the HU. The +12vdc power can then come from two different sources (PS and charger) without damaging anything. The battery is connected + to yellow and - to black (negative).
 
  #13  
Old 06-09-14, 11:12 AM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Northern NJ - USA
Posts: 54,565
Received 510 Votes on 480 Posts
With connections that I've shown below.... when you are using the radio on AC the battery is not being used or discharged. The diodes isolate the power supply from the battery. Any diode can be used... nothing critical. Needs to be at least 50v and 1amp.

Name:  memory.jpg
Views: 3576
Size:  13.9 KB

6A, 50V Rectifier Diodes (4-Pack) : Diodes | RadioShack.com
1N4003 Micro 1-Amp Diode : Diodes | RadioShack.com
 
  #14  
Old 06-09-14, 07:44 PM
Member
Thread Starter
Join Date: Jun 2014
Posts: 21
Received 0 Votes on 0 Posts

With connections that I've shown below.... when you are using the radio on AC the battery is not being used or discharged. The diodes isolate the power supply from the battery. Any diode can be used... nothing critical. Needs to be at least 50v and 1amp.
Sweet, thank you very much for that! So a 5A 400V diode would be alright? And it doesn't matter if it's a General Purpose, Zener, Schottky, etc..?

I was looking around at the Jameco site and see that they have hobby project kits, I'm thinking I may pick up a simple project on top of the diodes, and read up on the subject and maybe start a new hobby if I like it. I've always thought it would be kinda cool to be able to build my own amps and electronics, or mod existing equipment. But I always thought it would be way over my head, so I never messed with anything too complicated. But now that I'm seeing it's just a matter of knowing components and soldering them together, I'm curious to see what I can build.

Anywho, I'll probably be ordering some stuff online and will begin assembly in a week or so. I'll show you guys some pics when I'm done. Thanks for being so helpful, I appreciate a good forum and community like you've got here.
 
  #15  
Old 06-10-14, 12:14 AM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Northern NJ - USA
Posts: 54,565
Received 510 Votes on 480 Posts
Use a general purpose type diode.
 
  #16  
Old 06-10-14, 03:41 AM
Member
Thread Starter
Join Date: Jun 2014
Posts: 21
Received 0 Votes on 0 Posts
Use a general purpose type diode.
I just saw the links to the diodes in your last post, didn't see them before. I have since read something along the lines of a diode should be roughly 2.5x the rated voltage AND amperage of the transformer/power supply. So, since the HU is capable of putting out 10A @12V, should I get a diode with a minimum rating of 50V and 25A, instead of 1A? Or is it all about the wattage? In other words, [email protected]=120W, so it's only necessary to have a 50V/2.5A diode, or a 120V/1A, or 240V/.5A diode? Or is meeting or exceeding that 2.5X ratio necessary for both the voltage and amperage, even though a 50V/25A diode would equal a whopping 1250W overkill figure?

Sorry if I'm being overly cautious, I just want to make sure I select the right diodes.
 
  #17  
Old 06-11-14, 05:23 AM
Member
Thread Starter
Join Date: Jun 2014
Posts: 21
Received 0 Votes on 0 Posts
Bump for clarification on diode selection.
 
Reply

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description: