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Old 11-01-2007, 12:20 AM #1
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Default 2.85 V @120mA tops? GB Diode/regulator Prob

I've built DD regulator circuit exactly as the diagram shows. GP diode in Axiz housing-OK.
I'm using 4 AA alkaline batteries for 6 volts input to the circuit. I tried two CR123 3v lithiums in series for 6v source also.
I've tried changing the 10 ohm resistor to a 5 and then none at all.
Even with the resistor removed and using the the trim pot the most I can get out of the circuit is 2.85 volts and 120mA current draw from the LD.
Any suggestions on what the heck is up?
My 1st guess would be the LM-317 is defective?

Thanks for the help in advance!


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Old 11-01-2007, 06:19 AM #2
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Default Re: 2.85 V @120mA tops? GB Diode/regulator Prob

:-/ Anybody??

So I guess I'll add 3 more volts to the power source (6AA batteries total) and replace the LM317 and see if I can get any more power out of it.

*you guys are measuring your current in mA directly in series with the LD correct?
Not just in series with the battery driving the whole circuit.

Thanks.
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Old 11-01-2007, 06:48 AM #3
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Default Re: 2.85 V @120mA tops? GB Diode/regulator Prob

Did you measure the voltage of the batteries with the diode running? I bet it's not 6 volts. If you measure the voltage between the output and adjust pins, you should read 1.25 volts.
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Old 11-01-2007, 07:11 AM #4
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Default Re: 2.85 V @120mA tops? GB Diode/regulator Prob

Quote:
Originally Posted by Gazoo
Did you measure the voltage of the batteries with the diode running? I bet it's not 6 volts. If you measure the voltage between the output and adjust pins, you should read 1.25 volts.
I'll measure the actual batt voltage under load tomorrow. And check the output/adj pin voltage to see if it is 1.25
I only measured the voltages and current right at the LD and nowhere else besides the input voltage under no load.

Thanks for the tip. I'll try it out again tomorrow. So to get 9 volts input to the driver circuit should I go with 6 AA 1.5V batteries or (3+3+3) cr123 3V lith. ?

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Old 11-01-2007, 07:32 AM #5
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Default Re: 2.85 V @120mA tops? GB Diode/regulator Prob

Yup, or you could use 2 RCR123's. Or 6 AAA's if size is a concern. You could also use 6 NIMH batteries. Personally I like NIMH batteries. It really doesn't matter as long as the voltage is at least 6 volts with the load. Once the voltage drops below 6 volts, the regulator will begin to drop out.
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Old 11-01-2007, 05:33 PM #6
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Default Re: 2.85 V @120mA tops? GB Diode/regulator Prob

Thanks Gazoo, I'll get the input up to 9v and see what happens.
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Old 11-01-2007, 06:02 PM #7
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Default Re: 2.85 V @120mA tops? GB Diode/regulator Prob

One more question.
I've read the data sheet for the GB LD and it is rated for 2.5v @ 130mA.
I know everyone is driving them beyond that and wanted to know a safe upper limit on current.

Thanks again!

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Old 11-01-2007, 06:59 PM #8
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Default Re: 2.85 V @120mA tops? GB Diode/regulator Prob

2.8v should be enough to power the diode, the ma is my question. You mentioned a pot, have you taken the pot out and used just one 10 ohm resister to see what numbers you get? the pot might not be able to wind down far enough to go below 120ma.

with 2 CR123 batteries and DDL circuit with a 10ohm resister you should be sporting about 250ma. it's the same setup I use for my GB.
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Old 11-01-2007, 07:29 PM #9
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Default Re: 2.85 V @120mA tops? GB Diode/regulator Prob

Quote:
Originally Posted by Archane
with 2 CR123 batteries and DDL circuit with a 10ohm resister you should be sporting about 250ma. it's the same setup I use for my GB.
I think 10 Ohms between Vout and Adj on an LM317 will yield 125mA not 250mA
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Old 11-01-2007, 07:46 PM #10
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Default Re: 2.85 V @120mA tops? GB Diode/regulator Prob

Quote:
Originally Posted by Grn_n_TX
One more question.
I've read the data sheet for the GB LD and it is rated for 2.5v @ 130mA.
I know everyone is driving them beyond that and wanted to know a safe upper limit on current.

Thanks again!

The diode does a nice job of burning with 160ma's. Try it there and see if you are happy. From there increase a little at a time until you get the results you are looking for, but do not go over 250ma's. IMO..250ma's is the upper limit for a reasonably long lasting diode. How long? Well nobody knows and each diode is different. Running the diode with long duty cycles will shorten the life too. If you want to jump to 250ma's, and everyone does...lol...all you need is a 5 ohm resistor between the adj. and output of the 317. Personally I am running mine at 250ma's and so far it is happy
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Old 11-02-2007, 01:11 AM #11
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Default Re: 2.85 V @120mA tops? GB Diode/regulator Prob

doh, thats right i'm using a 4.7ohm not 10. i'm getting right at 244ma give or tak which is great. Granted I have 4 extra diodes if anything goes wrong but it works like a dream.
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Old 11-02-2007, 01:39 AM #12
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Default Re: 2.85 V @120mA tops? GB Diode/regulator Prob

I tried 2 cr123's with a 6volt input to the regulator circuit and then I tried 4AA's also.
I still need to try a higher input voltage then I'll try messing with the variable resistor.

You are connecting your multimeter in series w/ the LD itself and not the battery + lead right?
That way you measure the current draw from just the LD.
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