LM1875 P2P "solar powered" - diyAudio
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Old 27th April 2015, 08:39 AM   #1
Philfr is offline Philfr  France
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Default LM1875 P2P "solar powered"

Hi,
Summer is coming, I would like to listen to music for free in the garden !
So this new amp will be connect with two Li Ion batteries (near 15 volts) and recharged with solar charger.

One LM is missing at home, and for P2P I choose LM1875, and cause I have.

Schematic :

Click the image to open in full size.

Rz and Cz on output posts, distance about 5 cm between LM.
I will use two heatsinks, maybe cause pin 3 are connected to socket of LM.
I will try to have very short wirings.
Phil.
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Old 27th April 2015, 09:22 AM   #2
AndrewT is offline AndrewT  Scotland
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for the limited output of solar, I would be looking at very low quiescent current switching amplifier.
And maybe a horn loaded 3" to 4" full range driver.
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Old 27th April 2015, 11:14 AM   #3
Philfr is offline Philfr  France
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Hi Andrew,
Sorry for my poor english, but psu amp is two batteries (wiring in serial), solar charger is just for recharge the battery, like this :
12v solar panels; home solar panels; off grid solar power | Sunstore
i'ts just for example.
Phil.
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Old 27th April 2015, 11:27 AM   #4
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When it's solar powered you want to waste as less energy as possible; the logical choice would be Class-D. Look at options from TI, Tripath or Maxim.
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Old 27th April 2015, 11:46 AM   #5
infinia is offline infinia  United States
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Quote:
Originally Posted by Philfr View Post
Hi Andrew,
Sorry for my poor english, but psu amp is two batteries (wiring in serial), solar charger is just for recharge the battery, like this :
12v solar panels; home solar panels; off grid solar power | Sunstore
i'ts just for example.
Phil.
Hi
can you discuss the charger for your batteries, perhaps post your solutions in the 'Power Supply' section of this forum. This would be the most challenge in this interesting project.
I suppose you are using two identical panels > charger> batteries to support listening whilst charging?
thanks
BTW I agree with the other posters, many class D amps in the same power range have a single supply together with higher efficiencies equals smaller set-up over all.
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Old 27th April 2015, 02:53 PM   #6
Philfr is offline Philfr  France
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You are right about T or D amp, but I have the LM's and all componants for building..
Single rail vs Dual rail ?
Hum, I have two class T (Trends and chinese TDA2020) with single rail (12vdc), I found none that sounds good (mid and high), but it's my taste.
With dual rail, it's possible to have no componants in the signal path.
I try LM3886 with two batteries, I love it !
Power ? I don't need much, it's not for outdoor party, just listen music in front of a cup of tea.

At this time, I have two bat, charger, and solar panel.. Missing a converter 12 volts/230 volts.
Infinia, you are right, maybe a thread at "power suply" can help to find a better way.
Phil.
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Old 27th April 2015, 03:32 PM   #7
infinia is offline infinia  United States
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probably a pair 12V SLA directly connecting a couple of 10-20W PV panels are more universal than using the newer battery chemistries. otherwise no sense in using solar for portability eg MSW inverters and cheap AC chargers, usually a unwise mix by itself. IMO don't give upon finding a better D amp.
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Last edited by infinia; 27th April 2015 at 03:34 PM.
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Old 27th April 2015, 03:37 PM   #8
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Class AB (those LM's) use too much power for portable applications. Class-D amps aren't that expensive and can reduce consumption 5-fold.
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Old 27th April 2015, 05:01 PM   #9
tomchr is offline tomchr  United States
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How about using an LME49600? It can operate at 15 V and will provide up to 250 mA out if provided enough cooling. That's enough for 250 mW RMS, which is enough for about 80 dB SPL at 1 m with even an inefficient bookshelf speaker. That's a good 20 dB above normal background music levels.

If your question is about how to build the charging circuit, I suggest looking into peak power trackers. You want to adjust the charging current into the battery such that you get the peak power out of the solar panels.

Tom
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Old 27th April 2015, 08:40 PM   #10
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Power ? I don't need much, it's not for outdoor party, just listen music in front of a cup of tea.

With a couple of good speakers, this set up will be sure to please..

PAM8403 Mini Digital Power Amplifier Board Class D USB DC 3W 5V Supply Audio | eBay

Mini 360 DC DC Buck Converter Step Down Module 4 75V 23V to 1v 17V | eBay

5600mAh Portable External Battery USB Charger Power Bank for Mobile Phone iPhone | eBay

US Bluetooth Wireless Speaker Receiver Cordless Music Transmitter USB Power | eBay

12v 5w Monocrystalline Solar Panels; off grid energy; off grid solar

Connect the regulator board to the solar panel and adjust the output to 5 volts. (Charge controller is already in the battery) Cut one of the ends from the little male/male jumper on the Bluetooth receiver and solder directly to the amp board. (Speaker out/power wires too) Get creative and whack up a couple USB cables for charging the battery and powering the amp/Bluetooth. Use the type A USB connection at the battery for switching the system on/off..

You can either connect with Bluetooth or extend a source cable down to where you need it. It will operate from the battery for for a couple of days without the Bluetooth receiver. (Amp Only-No Charge)

I use this system myself. I have it on my screen porch. I use Bluetooth for my connection. While using, I disconnect the mini USB and run on straight battery. I pull the larger USB from the battery to shut down and plug the mini back in to charge while I'm at work during the day..

Just an idea..
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