Current?

The_Muffin_Man · Nov 20, 2008

Hey guys,

Ok so I am making a red laser and I have heard in a bunch of places what current to run my diode at (red senkat...its from stontek..) I have heard 250ma and 300-350 ma i do have proper heatsinking..(its a labby)

1) what current should i run it at?
2) How do i get this current? I have a rkcstr driver and a DMM from radioshack. Should i just put the DMM probes onto the driver (positive goes to LD and negative goes to GD) and read the output and adjust it until i get to whatever current to put it at? or do i need to make a test load? If so how do i make this (I have read about this. You hook up 4 1N4001 Diodes in series with a 1 ohm resistor on the end. I dont understand what this does...if anyone could explain it would be greatly appreciated)

Thanks

ElektroFreak · Nov 20, 2008

If you're going for a labby then install the diode in an Aixiz module and get this heatsink:

http://www.z-bolt.com/MODIIIbg-green-laser-module.html

Look at the heatsink that is under the three green modules.. I have one and its AWESOME!.. Pre drilled for a fan, also.

As far as current for those diodes, someone else will have to help you there..

EDIT: sorry I thoght you were asking if you should heatsink.. seriously though, check this one out..

The_Muffin_Man · Nov 20, 2008

Yep i got that heatsink (i think) it was from z bolt anyway...it has room for the top half of an aixiz module and a rkcstr driver...Super nice! My diodes are coming tomorrow so im gonna put it all in there...Any ideas on current and how to set it/Test loads?

Thanks

jonrobertd · Nov 20, 2008

So you read the thread on the test load and need help or havn't read it and need to?
Not being mean just need clarification.
and if you haven't read it here it is : http://www.laserpointerforums.com/forums/YaBB.pl?num=1197651171.
If you need help understanding it I will be glad to help but getting bed time here 1:30 got work later

The_Muffin_Man · Nov 20, 2008

Thanks for responding
yes people have mentioned it on other threads and I have read through it but it doesn't make very much sense.. Also I don't see the need for a testload...why can't you put the DMM probes right on the pads? Also any ideas on current?

Thanks

ElektroFreak · Nov 20, 2008

In order to correctly read current, you must wire the meter in series with the positive input of your driver. Disconnect the battery/power source, and connect its positive lead to the positive input on the DMM. Connect the negative input on the DMM to the positive input on your driver. Connect the negative input of the driver directly to the negative output of the battery/power source. This way the positive current flows through the DMM before it arrives at the driver. DO NOT try to connect a meter between the driver and the laser diode.. this has the effect of killing your diode unless you are VERY careful. You'll get the same reading either way.

lasersbee · Nov 20, 2008

Wouldn't connecting the DMM between the laser and diode give a more accurate
current reading... since the current the driver uses wouldn't be included in the
reading... :-?

But I agree... it is more risky to the Laser Diode....

ElektroFreak · Nov 20, 2008

In my experience, the driver doesn't use any current at all except what the diode demands of it while powered up. If you remove the diode, then the power supply is an open circuit, and draws no current at all, even if it is still hooked up. Even while in operation, I don't think the driver circuit itself draws any extra current (and if it does, it is such a negligible amount as to be ignored).

lasersbee · Nov 20, 2008

ElektroFreak said:
In my experience, the driver doesn't use any current at all except what the diode demands of it while powered up. If you remove the diode, then the power supply is an open circuit, and draws no current at all, even if it is still hooked up. Even while in operation, I don't think the driver circuit itself draws any extra current (and if it does, it is such a negligible amount as to be ignored).

Yeah you're right... I just did a test with a Blu-Ray set at 100ma... there is only a 0.1 ma difference..
measuring the current at the LD or at the battery..

That was with an LM317 Driver..

The_Muffin_Man · Nov 21, 2008

lasersbee said:
[quote author=ElektroFreak link=1227161304/0#7 date=1227200662]In my experience, the driver doesn't use any current at all except what the diode demands of it while powered up. If you remove the diode, then the power supply is an open circuit, and draws no current at all, even if it is still hooked up. Even while in operation, I don't think the driver circuit itself draws any extra current (and if it does, it is such a negligible amount as to be ignored).

Yeah you're right... I just did a test with a Blu-Ray set at 100ma... there is only a 0.1 ma difference..
measuring the current at the LD or at the battery..

That was with an LM317 Driver..[/quote]

So you are saying I don't need a test load? I can just measure right off the ld/gd pads on my driver? Still trying to find the current for my diode lol

Thanks again

ElektroFreak · Nov 21, 2008

Yup. That's exactly right. The purpose of a test load is to check your circuit for voltage/current spikes during powerup and powerdown and to make sure the driver is providing the proper current. You typically perform this step right after you finish building the driver but before you connect it to a diode for the first time. Under these circumstances you do want to connect the meter between the driver and the test load. This is best done with an oscilloscope, but may be done with a DMM instead. Once you've connected a diode to the driver, it's best left alone until it dies and must be replaced.

I think you might be able to find the proper current requirements for your diode in either the red laser section, the general section, or here in the tutorials section. I'm sure there is someone who can tell you but I've never used those diodes before so I can't help you..

The_Muffin_Man · Nov 21, 2008

Thanks for responding

I have found the current 300ma

Just to clarify just to be safe ... I do NOT have to hook my diode up to a test load to measure the current output.I can hook it up to a preset driver..correct?

You would be surprised how few people know how to spell solder...I have heard sawter and sauter..LOL

ElektroFreak · Nov 21, 2008

The_Muffin_Man said:
You would be surprised how few people know how to spell solder...I have heard sawter and sauter..LOL

I know what you mean! sauter?? come on.. that's just ridiculous.. :-?

As long as you're sure the driver is properly set and not producing any power spikes, then you can hook up the diode. After the diode is hooked up then you need to connect the meter the way I said earlier between the battery and the driver.. MAKE SURE YOU SHORT OUT ALL CAPACITORS ON THE DRIVER!!!!! This is a shockingly common cause of diode death due to capacitors discharging just as you hook the diode up. As long as everything has checked out up to this point, you should be good to go...

The_Muffin_Man · Nov 21, 2008

My driver killed my last diode that way LOL

Umm ok sounds good...I'll tell you guys if it works and I'll post some pics....
How do I short the driver? Touch a piece of metal to the ld and be pads linking them?

Thanks

ElektroFreak · Nov 21, 2008

The_Muffin_Man said:
Touch a piece of metal to the ld and be pads linking them?

Yes. Sort of. But be sure to short each one out before you connect them together. With no power applied, connect the positive and negative terminals of the power supply together briefly. This will discharge any remaining juice from the capacitors..

The_Muffin_Man · Nov 21, 2008

what do you ran short each one out? How? I thougt you just linked the ld/gd pads and that did it...

Thanks

Current?

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