Finding the correct power adapter for a no-name brand music stand light.

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The stand light looks like this:
https://images.duckduckgo.com/iu/?u=http%3A%2F%2Fwww.long-mcquade.com%2Ffiles%2F19166%2Flg_light-2.jpg&f=1
but the light I have has only 9 LED's.

The only information on the battery is 3.7 volts and it looks like this:
https://images.duckduckgo.com/iu/?u=https%3A%2F%2Fwww.pi-supply.com%2Fwp-content%2Fuploads%2F2014%2F12%2F2011-03.jpg&f=1
however my battery does not have any amp-hr rating written on it.

My question is, how can I figure out what voltage and current rating the  
power adapter needs to be in order to power the light and charge the battery  
efficiently? If I put 4.0V on the input jack without the battery installed,  
the lamps seem to light up fine. If you look closely inside the battery  
wrapper, you can see an attached pc board. The wiring from the DC jack goes  
to a series diode, then a transistor, then to the red wire extending out of  
the neck of the lamp where the LED's are attached. There is also a blob of  
round black stuff on the main pc board that looks like it could be covering  
a uP.

Thanks for your replies.
--  
David Farber
Los Osos, CA  



Re: Finding the correct power adapter for a no-name brand music stand light.
On Thursday, January 12, 2017 at 1:23:44 PM UTC-8, David Farber wrote:
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OK, that's a Li-ion rechargeable cell.
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It's not so much 'efficiency', but safety that you should be concerned with;
presumably there's voltage and current charging limitations (I'd guess
0.1 to 1 ampere of charging current), plus whatever your LEDs
require (could be up to one half ampere).   The
voltage must not get more than 4.3V, typically, on such a battery (but
that could be regulated in the power adapter, OR inside the lamp circuitry).

The circuitry and envelope around the battery are intended to prevent fire.

The prudent course is to find another identical unit, and get an exact match
to its wall tumor charger.   Otherwise, you need to reverse-engineer the
charging scheme of a poorly documented battery that has the potential
to burst into flame if mistreated.

This kind of problem is why cellphone chargers are USB micro-B with 5V output:
no one could get the right charger when they needed it, and nations passed laws...

Re: Finding the correct power adapter for a no-name brand music stand light.
whit3rd wrote:
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Thank you for the detailed explanation. I will try and get some information  
about the chargers that come with similar stand lights containing Li-ion  
batteries.

--  
David Farber
Los Osos, CA  



Re: Finding the correct power adapter for a no-name brand music stand light.
Am 12.01.2017 um 22:24 schrieb David Farber:
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can you show us the power-connector of the lamp?

peter

Re: Finding the correct power adapter for a no-name brand music stand light.
Peter Gierschner wrote:
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Peter Gierschner wrote:
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Here is the connector:
http://webpages.charter.net/mrfixiter/images/Electronics/Music_light/DC-plug.jpg

I have a 5V 1.5A power supply from an old Epson Zip drive but the connector  
is too big. The connector on the lamp seems to be on the smaller end of the  
spectrum.

Here is the pc board:
http://webpages.charter.net/mrfixiter/images/Electronics/Music_light/PC-board-lamp.jpg

Thanks for your reply.
--  
David Farber
Los Osos, CA




Re: Finding the correct power adapter for a no-name brand music stand light.
The battery cell is a rechargeable one.

This explains the diode and transistor.

So a standard 5V 3A  power supply is enough.

But according to what you say, the battery is empty ; needs a 24-hour  
recharge.


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Re: Finding the correct power adapter for a no-name brand music stand light.

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David-

I recently purchased a similar stand light, so your article caught my  
eye.  Mine is more like the 10 LED version with replaceable batteries.

Searching Amazon, I found at least four 9-LED lights that are close to  
what you have.  I think they all can be powered (or charged) from either  
an AC adapter or a from a USB outlet.

The four are:
Kootek
Sipik
Ohuhu
Lumiens L9B.

It is possible that two or more of these are actually the same light  
imported by different companies.  Is there anything about yours that  
might suggest one of these names?

Fred

Re: Finding the correct power adapter for a no-name brand music stand light.
Fred McKenzie wrote:
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Hi Fred,

I personally have the 9 LED Mighty Bright that I purchased a couple of years  
ago which uses 3 AA batteries. It also can be powered with an AC adapter  
which is 4V 400ma.
There isn't any kind of identifying writing anywhere on this other light. I  
haven't opened up the lamp compartment but I may do that just because I've  
looked everywhere else.

Thanks for your reply.
--  
David Farber
Los Osos, CA  



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