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ddl circuit on 7.2 lithium

K

Kenneth_v

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I have the DDL circuit wired with a 100 Ohm pot and a 4.9 ohm resistor and my senkat LD/Aixiz module just arrived today.

If I want to run a 7.2V lithium battery, all I need to do is adjust my pot to ensure the voltage across the LD is around 2.9 volts correct? I'm using the dummy load of 1ohm resistor and 4 1n4001's in series to set my circuit.

I dont want to fry my LD before I get it going!! I'll also be soldering the cap and 1N4001 directly to the LD.

Sorry to ask, I couldn't find it with a search, but is there as formula to convert my mA acrossy the dummy load 1ohm resistor to mW to measure the output.

Ken
 





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chido

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Just place your probes like in the picture and set the multimeter to mV, whatever you get in millivolts will be your current when you use a 1 ohm resistor, if you use a 5 ohm then you divide the voltage by five.
Apparently the knew diodes SenKat has been sending are a bad batch and you really shouldn't put more than 180mA, it's not like that with all the diodes from this batch as someone has been driving them with currents of 280mA with good results, but just to be sure don't exceed that current.
Here's a link to a thread about that:
http://www.laserpointerforums.com/forums/YaBB.pl?num=1199990106/0
There is no formula that I know of to calculate mW coming out of a laser, and even if there was one, all the diodes are different and output at different power levels even when driven at the same current.
 

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Gazoo

Gazoo

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Kenneth_v said:
Can I safely fun this on a 7.2v battery??
Click to expand...

The 317 can be run safely on anything up to 37 volts, but if you use much more than 9 volts you will need to use a heatsink on the regulator.
 
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chido

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Kenneth_v said:
Can I safely fun this on a 7.2v battery??
Click to expand...
Wow, it's almost too good to be true, someone actually wants to run the driver with 7.2v. Almost everyone new to the driver wanted to run it at the exact 6v which are not recommended, but you my friend are the first person I've seen to differ. YOU'RE SPECIAL ;D
 
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Kenneth_v

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I like to push the envelope!!

Here is my readings though

battery 7.5v
V across 1N4001's 3.18v
mA across 1 ohm resistor 174mA

Is that too much voltage to the diode???
 
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chido

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I don't think it's right, you shouldn't get that much voltage from 174mA, then again I never worry about the voltage, just the current. Can you post pics of how you're testing the driver?
 
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Kenneth_v

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I can adjust the pot so the voltage is below 3v but at 2.97v, my mA drop to 43
 
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chido

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That's not right, what multimeter are you using, do you have it set to mV or mA?
 
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chido

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OOOOHHHH!!! There's the problem, you're supposed to set it to mV, when you put your probes like in the picture above (positive between driver and resistor, and negative between resistor and diodes) and using the 1 ohm resistor, whatever voltage you get is the current. Notice how it says mV=(mA) ;)
 
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chido

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And then if you want to see your voltage, after you're done getting the current, leave the pot as it is, set your multimeter to volts and set the probes positive between resistor and diodes, and negative between diodes and negative wire coming from the driver.
If you get 250mV when looking for the current, and then when you test for voltage you should get about 2.8-3.0v.
 
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Kenneth_v

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above numbers hold true on mV

3.18 v across the 4 diodes

174mV across the resistor

checked with 2 mulitimeters
 
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chido

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Well then I must admit I don't know what's going on. Gazoo (god of the DDL driver) do you think we should worry about the voltage, I never even cared about it, all I give a damn about is the current. ;D
 
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Kenneth_v

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It shouldn't matter cause if I was running fresh 4 AA's id be putting 3.2v into it as well
 
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