Camping Music Box - PROJECT

[stuee]

ok thanks, thought LED was real low current, will find a LCD now. Also what else do i need for this solar panel, i have a regulator inline now, would it be ok to just leave the panel perm connected, will it not overload the battery if its full and keeps putting charge to it? im also after a simple battery power status so i can put it on the box and see the battery power.

Thanks

 

[audioguru2]

You said that your solar cell is only 4.5mw? I don't think so. The tiny solar cell on my calculator is rated the same and is the size of my thumbnail.
It is probably 4.5W, and will overcharge the battery and dry it out. You need a circuit to stop the charging when the battery is fully charged.

What are you going to do when the battery is dead and it is cloudy outside? Sing? ;D

 

[stuee]

Yer been practicing singing
Ok im slowly getting there, i got a preamp, a 40w amp and a mp3 256mb player with radio, it all works ok and volume control is ok. I have 3 more questions.

1. How do i get the stereo output to mono as the amp i use is only mono
(can i just join the 2+ of the audio together?)

2. I would like to get a sort of bass boost too or a tone control. It must be mono and <12v

3. I would like some sort of schematic for the solar panel chargig so i dont dry out the battery.

Thanks

 

[audioguru2]

Hi Stuee,
Which amp circuit do you have that gives 40W output with only a 12V battery?

You should never short together stereo outputs of anything to get mono. The outputs will fight each other and might be damaged.

I designed a passive circuit to add the channels with two 10k resistors and give an adjustable bass-boost by attenuating higher frequencies with a pot. When you turn the pot so its resistance gets lower then the higher frequencies will be reduced but the low frequencies stay the same level, therefore sound like they are boosted. I have seen similar circuits somewhere but haven't tried it. For it to work properly the amp must have more than enough gain. Use shielded audio cables. ;D

View attachment 37532

 

[ante1]

Hi Audioguru,

Don’t get me wrong here but I don’t know if the expression”boost” is correct for a passive circuit! ;D  I can’t see any problems with the circuit though. :-X

 

[audioguru2]

Hi Ante,
My modified clock radio and the radio in my old car had "loudness" controls that passively boosted the bass when they were turned down. As described by the "Fletcher-Munsen" curves of response changes of our hearing at reduced levels. The bass was always at the same level so didn't cause their amplifiers to clip.
Stuee might adjust the bass-boost control only a single time and leave it like that, then use the amp's volume control for loudness. Or he might like the "loudness control" action of the bass-boost control and use it to adjust loudness. ;D

 

[stuee]

that sounds  good to me, will make it this arvo and let you know.
Thanks all of you for your help so far, you have been great.

There was just one more thing or 2.
I want a led battery status i can turn on and see when the battery is low..  (8led)

Also what can iu use to make sure the battery isnt over charged from the solar panel thats perm connected to it i have a regulator inline at the momoent


Also the 40amp is this  KEMO #m034

 

[audioguru2]

Hi Stuee,
It is difficult to make a battery status indicator. The battery will be from 13.8V to 14.4V (if it is lead-acid) when it is fully charged. Then it quickly drops to about 12.6V for most of its discharge. Near the end of its charge its voltage quickly drops more and more.The indicator will be about the same if the battery has been used for 5 minutes or for 5 hours.

Contact the solar cell manufacturer or the dealer you purchased it from to find out how to prevent the battery from overcharge. It probably needs a circuit to multiply the charging current with charging time.

I don't read German but your "40W" amp provides about 20 watts continuously (40 peak whats) with a horrible-sounding 10% distortion into 4 ohms with a 16V supply. It will be barely clipping and sound fine at about 17W. With your 12.6V battery it will be about 10.5W into 4 ohms or about 6W into 8 ohms at clipping. ;D