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Retro boombox - charging advice

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weaselchops View Drop Down
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Joined: 11 July 2014
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    Posted: 11 July 2014 at 6:54pm
Hi guys,

First time post...

I am currently in the research phase of converting an old Sharp Boombox into a Rasberry Pi powered device, that can get music from Wifi or local usb.

I have got most things sorted...
Amp: probably a Lepai lp-2020a+ (standard Smile)
Battery: Yuasa NP7-12, 12V 7Ah lead acid battery NP7-12
Case: Old Sharp Boombox
Speakers: Start with originals... upgrade later

Ideally I want onboard charging (trying to use the original AC input hole).
I want the Boombox to to be able to semi-permanently plugged into the mains, but able to be unplugged at time and go mobile.
I am have been reading way too much about much about SLA batteries and charging, so would like some practical advise.

What is the best way to supply power to this? A solar charging module via 12v PSU?

Any ideas greatly received

Weasel




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Shortrope View Drop Down
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Post Options Post Options   Thanks (1) Thanks(1)   Quote Shortrope Quote  Post ReplyReply Direct Link To This Post Posted: 11 July 2014 at 7:19pm
You need an spdt relay to switch between battery and mains when you plug it in and out.
Have a look back through my old threads.
I went through the exact same journey last year.
My Tinnitus is coming along nicely!!
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Post Options Post Options   Thanks (1) Thanks(1)   Quote lutkeveld Quote  Post ReplyReply Direct Link To This Post Posted: 11 July 2014 at 7:25pm
First of all; Welcome to the forum :)

Can you show us the socket which you want to use for charging?
Where would you fit the solar panel? Just go with battery for mobile, PSU for mains.
I'd just go with a MaxAmp from Accusafe, fed by a 12v 7.2ah SLA.
Accusafe also has module that provides automatic switching between mains and battery, plus it provides deep charge protection. 

And of course you need to get some kind of step down converter to provide the right voltage to your Pi. 
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weaselchops View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote weaselchops Quote  Post ReplyReply Direct Link To This Post Posted: 11 July 2014 at 9:39pm
Thank you, will take a look at your suggestions

The socket is just a IEC C7 (Figure 8) at the side. The guts of this boombox are going!
I was just going to use the solar panel regulator for charing from a 12v source as I thought it may do the job? This sort of thing  http://www.amazon.co.uk/dp/B009APJFT8 - http://www.amazon.co.uk/dp/B009APJFT8

Yeah was going to get a DC-DC convertor for the Pi... but that again seems to be a mine field Confused 
I want to add a small touch screen and mount it where the cassette window is... and "maybe" a USB DAC so might need decent USB power.

Touch screen:  http://https://learn.adafruit.com/adafruit-pitft-28-inch-resistive-touchscreen-display-raspberry-pi - http://https://learn.adafruit.com/adafruit-pitft-28-inch-resistive-touchscreen-display-raspberry-pi

When when that is all done... microswitches under transport buttons to control playback Party

But first the basics!



Edited by weaselchops - 11 July 2014 at 9:55pm
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lutkeveld View Drop Down
Young Croc
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Post Options Post Options   Thanks (0) Thanks(0)   Quote lutkeveld Quote  Post ReplyReply Direct Link To This Post Posted: 11 July 2014 at 9:47pm
That's pretty advanced. Are you sure you are capable of doing that?

For charging; get a SLA charger, take the PCB out, solder mains input from PCB to the IEC plug. Don't work on live circuits, turn it on when it's completely ready. 


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weaselchops View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote weaselchops Quote  Post ReplyReply Direct Link To This Post Posted: 11 July 2014 at 9:55pm
I actually studied electronics and electronic engineering many years ago at college and work placements (over 20 years ago!!). But went into computers instead.Big smile
Never did much battery theory hence my n00b questions and just generally rusty.




Edited by weaselchops - 11 July 2014 at 9:56pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote GEB Quote  Post ReplyReply Direct Link To This Post Posted: 13 July 2014 at 2:30pm
Yes a solar charger controller and 15v psu would work fine as thats what Ive had set up on mine for ghe last 6 months. Not sure how the charge controller would function at 12 volts though with the battery voltage being 12.1v-12.8v ish in normal operation, hence going with a 15v psu.
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