Old 10-19-2008, 03:33 AM #1
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Default voltage of DDL driver?

what should the output voltage of a DDL drive be? the one i just built started outputting 7-8 volts when hooked up to a 9volt dc power supply >.>


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Old 10-19-2008, 06:08 AM #2
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Default Re: voltage of DDL driver?

Quote:
Originally Posted by r34p3rex
what should the output voltage of a DDL drive be? the one i just built started outputting 7-8 volts when hooked up to a 9volt dc power supply >.>
INPUT should be 6v's for reds and 9v's for blu-rays. Diodes draw current NOT volts. Basically the diode has very little internal resistance so if you didn't have a driver the diode would probably kill itself quickly. Try testing voltage WHILE your running the diode and you will see it be 2.5-3v's for reds and 4.5-5.5v's for blu-rays. Diodes have a voltage drop but as long as you use a driver you should be fine.

PS: People will probably start getting angry cause they have already answered this questing before so... you may want to remove this. :-/

PS: Thanks mike

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Old 10-20-2008, 11:02 AM #3
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Default Re: voltage of DDL driver?

I don't think people would be angry about that question (at least not as much as those "Where can I get the parts to do Kipkay's flashlight hack?&quot

Anyway, yea, DDL circuit is a current controlled circuit. It tries as much as it can to deliver a certain amount of current through the output no matter what resistance it faces. Hence the voltage output will vary according to the load of the circuit. That way, the circuit can regulate the current.

For an open circuit, i.e. u didn't connect the diode, what happens is that the circuit sees a load of infinite resistance, and hence supplies the max voltage possible in effort to get a certain amount of current through, which is about 2V lesser than your supply (this is due to dropout voltage by the LM317, i.e. it "uses up" some voltage)

You'd need a load for the current circuit to function as it should.
Most would recommend getting a testload. That way, you won't blow your LD if u had the wrong current setting or something.
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Old 10-20-2008, 11:12 AM #4
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Default Re: voltage of DDL driver?

Test it as shown here,
http://www.laserpointerforums.com/fo...num=1197651171
If you want to use an 803T LD add another 2 diodes to the test load.

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Old 10-20-2008, 10:54 PM #5
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Default Re: voltage of DDL driver?

Quote:
Originally Posted by Tw15t3r
I don't think people would be angry about that question (at least not as much as those &quot;Where can I get the parts to do Kipkay's flashlight hack?&quot

Anyway, yea, DDL circuit is a current controlled circuit. It tries as much as it can to deliver a certain amount of current through the output no matter what resistance it faces. Hence the voltage output will vary according to the load of the circuit. That way, the circuit can regulate the current.

For an open circuit, i.e. u didn't connect the diode, what happens is that the circuit sees a load of infinite resistance, and hence supplies the max voltage possible in effort to get a certain amount of current through, which is about 2V lesser than your supply (this is due to dropout voltage by the LM317, i.e. it &quot;uses up&quot; some voltage)

You'd need a load for the current circuit to function as it should.
Most would recommend getting a testload. That way, you won't blow your LD if u had the wrong current setting or something.
I am not mad it him. I just didn't want him to get hurt. I posted pretty much the same thing back when I was still new to the hobby. People were a little irritated about it because they just didn't like to answer the same question over and over again.

--hydro15
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