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Old Feb 15, 2003, 01:38 PM
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L200

Billy,

Radio Shack is the wrong side of the pond from me.
I suggest you check their web site. The L200 has been around for some time and is quite a popular chip so there is a good chance.

Andy.
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Old Feb 15, 2003, 04:16 PM
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@parkflyer

> i was talking about andy's

oops that was a misread on my part there.
makes since now.
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Old Feb 15, 2003, 04:34 PM
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Richmond, VA
Joined Apr 2002
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Andy,

I like Scott's charger, it works well and was cheap to build but yours is simplier. I may build that one just for the fun of it and it would give me another charger.

Is the L200 fairly available and at what cost?

thanks,
Grant
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Old Feb 15, 2003, 06:06 PM
Oxford Panic
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L200 availability

Grant,

The L200 is available from hobby electronics suppliers here in the UK for about 2.50 GBP for one off. I'm not sure what hobby suppliers of components there are in the USA, but Radio Shack was mentioned by Billy. You could start with them.

Andy.
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Old Feb 15, 2003, 09:22 PM
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here is the manufacturer of the L200
http://us.st.com/stonline/index.shtml

I checked radio shack - they dont have it
Digikey seems not to have it also but i didnt follow the links returned from the search.
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Old Feb 15, 2003, 10:10 PM
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Webster, NY
Joined Jul 2002
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The L200C retulator is available in the US from BGMicro

www.bgmicro.com

Cost is 1.99 ea plus S&H

Search on "L200". You probably need to download the pdf online order catalog to see the prices.

Do yourself a favor and get one of their 1.2 amp 12V wall warts to power the curcuit as long as you are getting the L200C.

I don't know how you would add a charging LED to the L200C circuit.
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Old Feb 15, 2003, 10:29 PM
MX
Embedded Systems Engineer
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Grass Valley, CA
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Quote:
Originally posted by Hodgepodge
@ MX

I am not by any means an expert on electronics, but to vary the voltage, why couldn't you simply adjust R4 for the correct voltage?

If the voltage wouldn't go low enough, you could simply increase the value of R4 to say 3kohm or so.

Am I missing something?
I do use R4 to adjust the voltage. I use it to calibrate to exactly
8.4 volts (or 4.2). But if I use it to change the voltage when
changing the number of cells, I would always require a meter
to recalibrate the voltage each time. With the switch, changing
the number of cells only requires a flip of the switch, which
selects one of the two precalibrated voltages.

Does that make sense?

MX
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Old Feb 16, 2003, 12:09 AM
Hornet Basher
College Station, TX
Joined Jan 2002
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Yes, that makes sense.

Could you calculate the resister value needed for 3 cells?

That was my real intention, and using a multimeter does seem a bit of a hastle
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Old Feb 16, 2003, 08:51 AM
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Mx thanks a lot for the pic, that is exactly what I was looking for. On the switches, what are you using?

Are they they single pole double throw (I confess I dont know what in heck that means, but at the Rat Shack I can find what I need if I know what to call it.)

Thanks
Glenn
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Old Feb 16, 2003, 10:05 AM
Thats NOT indestructible
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Andy

Very nice charger, i think that i will be building yours instead

Is there any way that a status led could be added, coz i dont charge without them !!

Thanks

Josh
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Old Feb 16, 2003, 11:38 AM
"Simplify, then add lightness"
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Josh,
I have not tried this so I don't know how well it would work, but BGmicro sells a 1.5 volt 75ma grain of wheat bulb. If you put one across R3, it would add about 25ma to the charging current and should light while charging and get dimmer and go out when fully charged. I don't know how bright this bulb would be on the 0.5volts across R3, but it would be a very simple charge indicator if it was bright enough, and is worth a try. Any low voltage low current incandescent bulb might work.

Jeff
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Old Feb 16, 2003, 01:18 PM
Thats NOT indestructible
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That is an idea........but i dig electronics

Come one, somone out there must be able to work out something snazy

Josh
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Old Feb 16, 2003, 04:32 PM
Oxford Panic
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United Kingdom, Oxford
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Josh,

I will think about a simple way to add a LED but it may work out as complex as the LM317 circuit.

You could just attach a DVM across R3 and watch the current drop towards the end of charge.

Adding a bulb is a nice idea but the maximum voltage across R3 is 0.45V would it glow bright enough?

Andy
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Old Feb 16, 2003, 11:45 PM
MX
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Grass Valley, CA
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Quote:
Originally posted by Hodgepodge
Yes, that makes sense.

Could you calculate the resister value needed for 3 cells?

That was my real intention, and using a multimeter does seem a bit of a hastle
You can see the charger design here:

LiIon Charger

And details on modifying for different cell sizes and number of
cells here:

Mods

330 ohms is the size of R4 for 3 cells. The only problem with
3 cells is I believe you need a power supply that can put out
higher voltage. More like 18 volts.

MX
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Old Feb 16, 2003, 11:55 PM
MX
Embedded Systems Engineer
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Grass Valley, CA
Joined Sep 2001
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Quote:
Originally posted by Depdog
Mx thanks a lot for the pic, that is exactly what I was looking for. On the switches, what are you using?

Are they they single pole double throw (I confess I dont know what in heck that means, but at the Rat Shack I can find what I need if I know what to call it.)

Thanks
Glenn
My switches were from Radio Shack. All it needs are single pole
double throw (SPDT), but I ended up using double pole double
throw (DPDT). They came in a package of two. I used one to
switch the number of cells, and one to switch the cell size
(current).

Nice switch reference here: switches


MX
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