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12-11-2007, 04:49 AM #1
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amkdeath
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Am I okay with Driver readings as follows:

Voltage across resistors: 1.25V
Voltage with ADJ and Vout: 1.25V

TOTAL resistance after pot and resistors: 5.5ohms

1.25/5.5=.227mA

Is that correct? Am I doing calculations right? Is everything okay?

This is with HUGE load on the circuit. THanks.

AMK

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12-11-2007, 05:01 AM #2
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Things
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Re: Am I okay with Driver readings as follows:

Yep, looks good!

12-11-2007, 03:11 PM #3
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a_pyro_is
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Re: Am I okay with Driver readings as follows:

Quote:
 Originally Posted by amkdeath Voltage across resistors: 1.25V Voltage with ADJ and Vout: 1.25V TOTAL resistance after pot and resistors: 5.5ohms 1.25/5.5=.227mA Is that correct? Am I doing calculations right? Is everything okay? This is with HUGE load on the circuit. THanks. AMK
What load? If it doesn't have a voltage drop of around 3V then this only tells us that with the current (Punny) load, the regulator isn't yet dropping out.

Edit
It also tells us that it is likely that you have the circuit wired up correctly. Shiny red here you come. Don't forget the 8-)

12-11-2007, 11:24 PM #4
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amkdeath
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Re: Am I okay with Driver readings as follows:

Quote:
 Originally Posted by a_pyro_is [quote author=amkdeath link=1197352168/0#0 date=1197352167]Voltage across resistors: 1.25V Voltage with ADJ and Vout: 1.25V TOTAL resistance after pot and resistors: 5.5ohms 1.25/5.5=.227mA Is that correct? Am I doing calculations right? Is everything okay? This is with HUGE load on the circuit. THanks. AMK
What load? If it doesn't have a voltage drop of around 3V then this only tells us that with the current (Punny) load, the regulator isn't yet dropping out.

Edit
It also tells us that it is likely that you have the circuit wired up correctly. Shiny red here you come. Don't forget the *8-) *[/quote]

the load is from an old toy &quot;sword&quot; with like 50 LED's in there, some in parallel, some in series. It also has this PCB with transistor and stuff, mostly to make it flash I think... I was guessing that the load was good because voltage of ADJ and Vout was 1.25, and That doesnt happen if its not regulating, right?
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12-13-2007, 04:51 AM #5
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a_pyro_is
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Re: Am I okay with Driver readings as follows:

Quote:
 Originally Posted by amkdeath the load is from an old toy "sword" with like 50 LED's in there, some in parallel, some in series. It also has this PCB with transistor and stuff, mostly to make it flash I think... I was guessing that the load was good because voltage of ADJ and Vout was 1.25, and That doesnt happen if its not regulating, right?
Correct, but can you check the voltage drop across the load? If it's less than ~2.8V then when you put the laser diode on it it will drop out.

12-13-2007, 05:01 AM #6
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Re: Am I okay with Driver readings as follows:

Quote:
 Originally Posted by a_pyro_is [quote author=amkdeath link=1197352168/0#3 date=1197419086]the load is from an old toy "sword" with like 50 LED's in there, some in parallel, some in series. It also has this PCB with transistor and stuff, mostly to make it flash I think... I was guessing that the load was good because voltage of ADJ and Vout was 1.25, and That doesnt happen if its not regulating, right?
Correct, but can you check the voltage drop across the load? If it's less than ~2.8V then when you put the laser diode on it it will drop out.[/quote]

I put DMM in parallel with the LED assembly's input, and I connected regulator in parallel with the DMM and the LEDs. I read 6v. is this normal? will it regulate to 3v upon attachement of LD?
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12-13-2007, 05:09 AM #7
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a_pyro_is
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Re: Am I okay with Driver readings as follows:

Can you take a picture? Sorry, I'm not understanding.

12-13-2007, 05:13 AM #8
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amkdeath
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Re: Am I okay with Driver readings as follows:

(- on DMM)--------------| |---- (+ on DMM)
(- on Driver output)----| |-----(+ on driver output)
(- on LED assembly)---| |-----(+ on LED assembly)

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12-13-2007, 05:21 AM #9
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a_pyro_is
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Re: Am I okay with Driver readings as follows:

If I'm understanding you, then the answer is 'yes'.
Measure the voltage across the load.

12-13-2007, 05:33 AM #10
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amkdeath
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Re: Am I okay with Driver readings as follows:

input: 6v

my DMM reads 6v, when the output from the driver, the DMM probes, and the leads from the load are all connected in parallel.

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12-13-2007, 05:05 PM #11
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a_pyro_is
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Re: Am I okay with Driver readings as follows:

I think either you've got the Adj and Vout pins mixed up, or the voltage drop of the load you're trying to use is too high.
Use either 5-10 Green LEDs in parallel, or even better use four 1N4001 and one 1 Ohm resistor all in series as a dummy load.
In order for your test to mean anything, the dummy load must be very similar to the actual load.
I've read of people trying use all sorts of things as a dummy load (DC motors, a voltmeter, even a tongue ) but unless it behaves just like the laser diode the test is invalid.
Whatever you use, you must make certain that at the current you're driving it, the voltage drop is the same as the laser diode would have

FWIW one 11.5 Ohm 1W resistor would work well as a dummy load for testing at 250mA.

12-13-2007, 10:43 PM #12
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Re: Am I okay with Driver readings as follows:

I attached a 10 ohm resistor as the load, and the lotage across the resistor was 4.5, 4.5/10=.450mA, OUCH!!

I used ohm feature, and my resistor is 10.4 ohms.
I set the pot untill the voltage across the resistor was 2.6v, 2.6/10.4=.250mA

Is this right?

I dont have any 1 ohm resisors, can I use a 10ohm instead? (for the IN4000 and resistor load)

thanks,

amk
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12-13-2007, 11:47 PM #13
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Re: Am I okay with Driver readings as follows:

I found a dead laser diode and I hooked that up. I hooked up the DMM in series with the laser diode. The DMM read 400mA, and so I turned up resistance on pot. When I adjusted pot resistance to 250mA, I disconnected DMM, attached dead diode, and measured the voltage across the diode.

Voltage across dead laser diode: 3.6v

Is this normal? the voltage drop is huge, when there is no load it reads 10 volts. with dead laser diode it drops to 3.6

is this normal? I thought the diode needed 3volts, and that anything over that would kill it...

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12-14-2007, 08:27 AM #14
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a_pyro_is
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Re: Am I okay with Driver readings as follows:

Quote:
 Originally Posted by amkdeath I found a dead laser diode and I hooked that up. I hooked up the DMM in series with the laser diode. The DMM read 400mA, and so I turned up resistance on pot. When I adjusted pot resistance to 250mA, I disconnected DMM, attached dead diode, and measured the voltage across the diode. Voltage across dead laser diode: 3.6v Is this normal? the voltage drop is huge, when there is no load it reads 10 volts. with dead laser diode it drops to 3.6 is this normal? I thought the diode needed 3volts, and that anything over that would kill it...
I don't understand. You said you were supplying 6V to the circuit, but now under no load it's puting out 10V? Can you please post a picture/pictures of your circuit showing all the connections?

12-15-2007, 05:16 PM #15
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amkdeath
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Re: Am I okay with Driver readings as follows:

Quote:
 Originally Posted by a_pyro_is [quote author=amkdeath link=1197352168/0#12 date=1197593242]I found a dead laser diode and I hooked that up. I hooked up the DMM in series with the laser diode. The DMM read 400mA, and so I turned up resistance on pot. When I adjusted pot resistance to 250mA, I disconnected DMM, attached dead diode, and measured the voltage across the diode. Voltage across dead laser diode: 3.6v Is this normal? the voltage drop is huge, when there is no load it reads 10 volts. with dead laser diode it drops to 3.6 is this normal? I thought the diode needed 3volts, and that anything over that would kill it...
I don't understand. You said you were supplying 6V to the circuit, but now under no load it's puting out 10V? Can you please post a picture/pictures of your circuit showing all the connections?[/quote]

I am using 4 AAA nimh batteries, and I found that each puts out 2.3v.
they are duracell.

so thats about 9.3 volts, which is around what its putting out with no load.
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12-15-2007, 08:41 PM #16
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Re: Am I okay with Driver readings as follows:

There is no single nimh battery that puts out 2.3 volts. I think your meter is messed up.

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