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FrozenGate by Avery
Testing DDL Circuit with multimeter
- Thread starter viroy
- Start date
so i made another DDL circuit using (2) 10-ohm resistors, this should be able to run up to 300mw right?
i harvested a 16x dvd diode and hooked it up... im reading 2.5v and at max it goes to 65ma.
so its only getting 162.5mw output correct?
the laser JUST BARELY begins to laze at the max setting... should i add another 10 ohm resistor to up the max current?
one thing i noticed... the multimeter has a draw on the current because when i turn it off, the laser diode gets even brighter.
i harvested a 16x dvd diode and hooked it up... im reading 2.5v and at max it goes to 65ma.
so its only getting 162.5mw output correct?
the laser JUST BARELY begins to laze at the max setting... should i add another 10 ohm resistor to up the max current?
one thing i noticed... the multimeter has a draw on the current because when i turn it off, the laser diode gets even brighter.
well i think i just burned out that diode :-/
i left it connected to the circuit all night but no power supply, figured it would be fine since i drained tha cap and all... then this morning i hook it back up and got nothing... then i realized i forgot to turn down the pot before connecting the power source. i thought the ddl circuit would protect it, but if the pot was at min resistance... could it still spike it?
i have alerady called it a loss because i dont get anything out of it from my other driver, and as last resort i hooked it right to batteries and still got nothing. (i rechecked all my connections too, looks good with no shorts)
i left it connected to the circuit all night but no power supply, figured it would be fine since i drained tha cap and all... then this morning i hook it back up and got nothing... then i realized i forgot to turn down the pot before connecting the power source. i thought the ddl circuit would protect it, but if the pot was at min resistance... could it still spike it?
i have alerady called it a loss because i dont get anything out of it from my other driver, and as last resort i hooked it right to batteries and still got nothing. (i rechecked all my connections too, looks good with no shorts)
rog8811
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If it was left all connected up, with a capacitor in circuit and the power off a spike is not the issue.....
How could the pot be turned right down if you were running it last night at the right ma's?
That is what killed it though, too many ma's
Regards rog8811
well i just harvested another, got it cleaned off and then dropped it... it has magically dissapeared!
unreal, i just spent an hour cleaning
well... guess ill have to do another, ive been finding good deals on broken DVD burners lately so i buy like 5 at a time.
unreal, i just spent an hour cleaning
well... guess ill have to do another, ive been finding good deals on broken DVD burners lately so i buy like 5 at a time.
ok so i just got done harvesting yet another... this time i was much more carefull with handling it 
crap, just realized i once again soldered leads on before sandwiching
anyways, its now hooked up to the ddl circuit and i also connected the multimeter.
this one shows a steady 2v draw.
i up'd the pot to about 60% which is reading 60ma (when i set the MM to 1.5v ma setting).
the laser is so dim i doubt it will even make a visible dot when collimated.
if i do the math right, its 2v x 60ma = 120mw correct?
if so... howcome its sooo dim, theres no way its putting out even 50mw of light.... actually its dimmer than a little 5mw keychain laser pointer.
fyi - im using a selectable power source, it does up to 1amp and right now its set at 4.5v
help! :'(
crap, just realized i once again soldered leads on before sandwiching
anyways, its now hooked up to the ddl circuit and i also connected the multimeter.
this one shows a steady 2v draw.
i up'd the pot to about 60% which is reading 60ma (when i set the MM to 1.5v ma setting).
the laser is so dim i doubt it will even make a visible dot when collimated.
if i do the math right, its 2v x 60ma = 120mw correct?
if so... howcome its sooo dim, theres no way its putting out even 50mw of light.... actually its dimmer than a little 5mw keychain laser pointer.
fyi - im using a selectable power source, it does up to 1amp and right now its set at 4.5v
help! :'(
viroy said:
Here's the link.
viroy said:ok so i just got done harvesting yet another... this time i was much more carefull with handling it
crap, just realized i once again soldered leads on before sandwiching
anyways, its now hooked up to the ddl circuit and i also connected the multimeter.
this one shows a steady 2v draw.
i up'd the pot to about 60% which is reading 60ma (when i set the MM to 1.5v ma setting).
the laser is so dim i doubt it will even make a visible dot when collimated.
if i do the math right, its 2v x 60ma = 120mw correct?
if so... howcome its sooo dim, theres no way its putting out even 50mw of light.... actually its dimmer than a little 5mw keychain laser pointer.
fyi - im using a selectable power source, it does up to 1amp and right now its set at 4.5v
help! :'(
First, what DVD burner was the diode taken out of?
Second, are you sure it's the red diode, you don't want to blind yourself with an IR diode.
Third, 60mA is not a lot, but I need you to tell me the speed of the burner before I tell you what current to drive the diode at.
Fourth, you can't calculate the output of your laser, you need a laser power meter.
And fifth, 1A is a bit much for the LM317, it's still within its range but you should turn the current on your power source down to at least 500mA so you don't stress out the LM317 too much.
oh and yes im sure its the red diode, i have a digital camera that can see IR... theres 2 diodes in each burner, i already tested both diodes and found the IR one... its a 9mm diode. the red one is a 5.6mm or 5.3 whichever
the red diode i was using last night was working great, even lit a match at 6 inches.
the red diode i was using last night was working great, even lit a match at 6 inches.
If you can't turn the power supply down then I suggest you either get some batteries, or buy a heatsink for the LM317 and don't let it run for too long.
I suggest you drive the 16x diode at 200mA, you can turn it up higher if you want to, just don't go over 250mA.
I suggest you drive the 16x diode at 200mA, you can turn it up higher if you want to, just don't go over 250mA.
rkcstr
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- Dec 1, 2007
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viroy said:
Your calculation is for the power output of the driver. You could theoretically calculate your laser output power by multiplying the output power of the driver by the efficiency of the laser diode, but you probably don't know that value.
Also, if you're trying to power an LM317 with 4.5V, it's not going to put out the current you're expecting. I believe you need an input voltage of at least 3V more than the output, so in your case, about 6V to the driver. If you don't have a couple lithium batteries to hook up, just hook up 4-6 alkaline batteries in series.
Well I have an adjustable voltage regulator I bought from Radio Shack. It has a selectable voltage output from 3v to 12v, but the current is fixed at 1amp.
Individual settings are 3v, 4.5v, 6v, 7.5v, 9v 12v. I used 4.5v since the diode appears to draw 2v + the LM317 comsumes 1.5v = 3.5v
I think I understand what you mean by the diode effeciency... I've read that most DPSS diodes are only about 50% - 60% effecient at producing light which means the rest gets converted to heat (explains why cooling is necessary in high current diodes). I haven't run my newest diode for more than 30 seconds and thats at about 60ma off the DDL driver supply.
What I don't understand is, Why... if im giving more than 120ma to the diode, do I get such a dim light?
is it... the diode has a very small tolerance between what will make it fully laze and burn out?*
is it... something with my circuit?
is it... something with the way im reading my MM?
Another thing I dont really get... Why does my MM have seperate Ma settings for 1.5v and 9v?... Do I need to calculate the difference if I set the MM at 1.5v and the diode draw is reading 2v? Should I be adding 25% because of that?
(When set at 1.5v Ma, I get a readuot of x.xx whereas 9v would always give 0.0x, So obviously 1.5v is the correct range setting)
* When I say 'Fully Laze', I mean... At the DDL's circuit max resistance setting, the diode emits a very VERY dim red glow from the aperture. When I start reducing the POT and reach near 0-5% resistance... It will all of a sudden get EXTREMELY bright! I mean night and day difference!!! I was able to light a match in less than a second from 6 inches!
I let this one do a die hard test and kept it on for about 5 minutes... After that, the collimator housing (Aixiz brass, plastic lens) started getting very hot to the touch and I decided to shut it down.
I turned it on again after about an hour and it still worked great! very strong red!
but... it's never been a visible beam. I have a 50mw output 532nm green laser and it has a very visible beam for a very long distance. so this just makes me question the power rating based on the green lasers performance.
The last red 16x diode that burned out... I ran that all the way up to 12v from the source before the DDL circuit!, I had the MM hooked up the whole time and I saw no fluctuations in voltage! the LM317 appears to do an excellent job at vreg.
Individual settings are 3v, 4.5v, 6v, 7.5v, 9v 12v. I used 4.5v since the diode appears to draw 2v + the LM317 comsumes 1.5v = 3.5v
I think I understand what you mean by the diode effeciency... I've read that most DPSS diodes are only about 50% - 60% effecient at producing light which means the rest gets converted to heat (explains why cooling is necessary in high current diodes). I haven't run my newest diode for more than 30 seconds and thats at about 60ma off the DDL driver supply.
What I don't understand is, Why... if im giving more than 120ma to the diode, do I get such a dim light?
is it... the diode has a very small tolerance between what will make it fully laze and burn out?*
is it... something with my circuit?
is it... something with the way im reading my MM?
Another thing I dont really get... Why does my MM have seperate Ma settings for 1.5v and 9v?... Do I need to calculate the difference if I set the MM at 1.5v and the diode draw is reading 2v? Should I be adding 25% because of that?
(When set at 1.5v Ma, I get a readuot of x.xx whereas 9v would always give 0.0x, So obviously 1.5v is the correct range setting)
* When I say 'Fully Laze', I mean... At the DDL's circuit max resistance setting, the diode emits a very VERY dim red glow from the aperture. When I start reducing the POT and reach near 0-5% resistance... It will all of a sudden get EXTREMELY bright! I mean night and day difference!!! I was able to light a match in less than a second from 6 inches!
I let this one do a die hard test and kept it on for about 5 minutes... After that, the collimator housing (Aixiz brass, plastic lens) started getting very hot to the touch and I decided to shut it down.
I turned it on again after about an hour and it still worked great! very strong red!
but... it's never been a visible beam. I have a 50mw output 532nm green laser and it has a very visible beam for a very long distance. so this just makes me question the power rating based on the green lasers performance.
The last red 16x diode that burned out... I ran that all the way up to 12v from the source before the DDL circuit!, I had the MM hooked up the whole time and I saw no fluctuations in voltage! the LM317 appears to do an excellent job at vreg.
Your diode is so dim because you're only inputing 4.5v, set the power source to 7.5v and set your pot to let through 200mA. 
Like I've said before don't worry about the voltage, think current. If your diode measured at 2v it's probably because it was being under driven, most 16x diodes draw around 3v when being driven at around 200mA, it depends on the diode. If you set the power source to 4.5v, as soon as you turn up the current on the diode and it starts taking more than 2.5v it won't go past those 2.5v because the power source won't be providing the power needed to get past that point.
If you're testing for current like in rog's schematic then I don't see how your readings could be wrong.
I don't understand what you're saying about the DMM, could you post a picture of it?
You shouldn't have let the other diode run for 5 minutes, that is way too long for a diode in an aixiz module alone. I'm surprised you didn't kill it but I'm sure you severely shortened its lifetime.
You can see your green laser's beam simply because green is more visible to the human eye than red is.
Like I've said before don't worry about the voltage, think current. If your diode measured at 2v it's probably because it was being under driven, most 16x diodes draw around 3v when being driven at around 200mA, it depends on the diode. If you set the power source to 4.5v, as soon as you turn up the current on the diode and it starts taking more than 2.5v it won't go past those 2.5v because the power source won't be providing the power needed to get past that point.If you're testing for current like in rog's schematic then I don't see how your readings could be wrong.
I don't understand what you're saying about the DMM, could you post a picture of it?
You shouldn't have let the other diode run for 5 minutes, that is way too long for a diode in an aixiz module alone. I'm surprised you didn't kill it but I'm sure you severely shortened its lifetime.
You can see your green laser's beam simply because green is more visible to the human eye than red is.