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Old Oct 09, 2002, 07:35 AM
now that's a wattmeter...
simingx's Avatar
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Has anyone tried this Li-Ion charger IC?

How much more brainless can a circuit get?
The maximum current is only 500mA though, would that be enough for 1500mAh cells?
It's the MAX1811 from http://www.maxim-ic.com
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Old Oct 09, 2002, 07:55 AM
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500 ma would charge a 1500 ma battery in around 3 hours.

I seem to recall Maxim's Lithium Ion charge IC's are only available as TINY surface mount components. I got a big surprise when my samples arrived.

On a side note, check out the MAX713 for charging NiCads and NiMH only - works great. Don't use it for LiIon.

Jason
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Old Oct 09, 2002, 11:14 AM
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The 1811 is a surface mount device (SO). Some chips they offer both ways, but most of their stuff is surface mount.

That chip will only charge one cell (4.2V). It is designed to be powered off a USB computer port, but will accept up to a 6.5V supply.

Jimmy
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Old Oct 09, 2002, 11:15 AM
DNA
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SMT chips aren't so bad, after all they're almost as big
as the date on a penny.
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Old Oct 09, 2002, 11:18 AM
DNA
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I used that tiny little smt LM3420 to make a 1 amp Li-ion charger
using this circuit from one of National's app. notes.
http://www.national.com/ds/LM/LM3420.pdf
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Old Oct 09, 2002, 11:56 AM
DNA
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One way to handle the smt chip is to apply a teeny drop
of CA to the end of a toothpick and attach it to the TOP of
the smt chip. Tin the copper where the chip is to be soldered
with just a tiny bit of solder. Hold the toothpick and chip in
place and solder one lead of the chip then wait about 10-20
seconds for it to cool. Then do the rest of the chip leads the
same way. Pins 2 and 3 of the chip are soldered to the same
pc trace.

You will need to use a large heat sink on the LM317.

There is an extra space next to the R-Lim resistor. In case
you can't find a 1.2 ohm 3 watt resistor, you can parallel a
2.0 ohm and a 3.0 ohm 2 watt resistor next to each other.

I also changed the 1N4001 1 amp diode to a 3 amp diode
as the 1N4001 was also getting hot.
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Old Oct 09, 2002, 01:35 PM
DNA
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Charger in action, doing its thing. Total cost about $5.00
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Old Oct 09, 2002, 01:51 PM
..teach monkeys to fly..
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Thanks for posting this, DNA. It's on the top of my "parts to acquire" list.

Marten
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Old Oct 09, 2002, 07:07 PM
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DNA,
That's a good idea with the toothpick. It would make it a lot easier to work with. They definitely need a handle on them.

I kinda do it in reverse from that and glue the chip to the board first. A little smear of adhesive, set it in place and then put a small weight on it. Then I've got both hands free to go around and solder everything. I have to work through a magnifying lens though, too small for me to see without help. How about you?

Jimmy
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Old Oct 09, 2002, 07:51 PM
DNA
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Marten, you're welcome.

Jimmy,

"I have to work through a magnifying lens though, too small for me to see without help. How about you? "

LOL. If I take my glasses off I can get close enough to see the
tiny speck, but then I'm afraid of burning my nose with the
soldering iron.

So, yes, I use a HUGE magnifying glass. One of the large round jobs
with the fluorescent light around it.

I guess another caution would be to use a low wattage soldering
iron when soldering the IC. I use a 10watt Ungar Princess with
a fine tip.
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Old Oct 10, 2002, 01:01 AM
now that's a wattmeter...
simingx's Avatar
Singapore
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Quote:
Originally posted by DNA
SMT chips aren't so bad, after all they're almost as big
as the date on a penny.
Well if that's small you should try hand soldering some 0603 size components


They're only about as big as 2 grains of sand :P
I had blurred vision for about 10 minutes after soldering about a 100 PCBs full of them...
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Old Oct 12, 2002, 04:51 AM
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Hey DNA,
Any chance you could put together a "kit" for us electronically challenged folk?
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Old Oct 12, 2002, 01:19 PM
DNA
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Hi Scot,

Not sure a kit would be of much help if you're electronically
challenged, and I don't have the facilities for volume production.
All the parts are available from Digikey or RadioShack. The
pc board was one of the easiest I've made, no holes to drill.
I didn't make a photo mask for the first one, I just used a
sharpy marker to draw the trace patterns on the pc board for
the first prototype. The only difficult part is soldering the
tiny IC. But if you can read the date on a penny, and have
a small soldering iron tip, it's not so bad. A magnifying glass
helps.
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Old Oct 12, 2002, 04:57 PM
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Here is a way to solder those very small SMT's--hot air. First, admit that you are now entering the world of SMT and you will need to get some soldering paste. Yeah, I know. You have a fresh roll of good solder sitting on your bench. Just get it. Digikey KE1507-ND. Keep it in a plastic bag in the freezer when not in use. Also get one of those nifty butane soldering kits http://www.portasol.com/intro_index.htm They are widely marketed in the US by Weller (I think) and others. Be sure the kit has a hot air nozzle included. Put a dash of solder on the PC board pads. Don't worry if the paste blob covers several pads, it will not bridge! Plop down the chip. It doesn't have to be perfectly aligned and you will not be holding it in place. Use the hot air nozzle. Do a little pre-heating from a little distance, then move in right on top of the chip. Remove heat as soon as solder flows (almost instantly). The chip will align itself be capillary action. Voila. You'll be a pro in about 3 chips. With a little practice, you can even master 8 and 16 pin SOIC's by doing one side at a time.

Best,
Q
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Old Oct 13, 2002, 01:53 PM
DNA
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Thanks for the tip Mr. Quacker.
May give it try someday. Does the fact it needs refrigeration cause
any problems when using it on the workbench for extended periods?
How well does it desolder? Reflow? Not that I would ever need to do that.

http://www.partsexpress.com/pe/showd...oduct_ID=10687

You did mean the heat gun tip, and not the blowtorch tip, right?
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