Testing Driver Output - PLEASE Help

[BrewCityMusic]

Here's my dilemna - I have a dual-diode driver board with 7VAC input and outputs for (2) 80Mw red diodes (it's in a Shinp DL22 laser display) and I also have (2) 803's in modules with custom heatsinks/mounts all ready to go - but I need to confirm the output current and voltage and I have no test load. Is there an easy way around this - I have read that an LED can be used (and I have several of those that will take 200Mv) but I need confirmation. I would love to just measure the current load before the driver but can't in this situation because it's an AC input so I don't believe I can test it as you would in line with the positive input in a DC situation...Aaaargh - I SO wish I'd have paid more attention to electrical theory back in college! Any suggestions or ideas before I get impatient or stupid and end up blowing one or all of my diodes? Thanks!

 

[ElektroFreak]

You won't have to worry about blowing your 803s with a driver for red diodes. Red diodes require considerably less voltage than blu-rays, and so I doubt your drivers would work at all (although you could try, just to see). My recommendation to you is to build a 405nm blu-ray DDL driver (aka LM317 driver) for each diode. You can find the schematic here: http://www.laserpointerforums.com/forums/YaBB.pl?num=1185701612

Replace the 4-ohm resistor in the first schematic with a 10-ohm to give the right current for blu-rays.

You can power the drivers with a 1 amp 9VDC wall wart.

 

[pseudolobster]

If you'd like to test the output of your drivers you can build a dummy load with roughly the same characteristics as your blue diodes... Wire 6 diodes or low-brightness LEDs in series, attach them to your driver and put your multimeter in series with the circuit (ie, the multimeter closing the circuit), set your multimeter to amperage, turn it on, and hook up the driver to power. Alternatively if you have a 1ohm resistor, put that in the circuit instead of your multimeter, then measure the voltage across the resistor, since at 1ohm, 1mv=1ma... This is really the preferred method since a lot of cheaper multimeters can only handle up to 200mA before you blow the fuse, and aren't very accurate.

 

[BrewCityMusic]

Thanks for the pointers - Another question though, the driver board also is populated for a green diode (the company that builds the displays uses the same driver boards for their green, red, and rgy lasers in the DL series) - would it be possible for me to utilize that circuit to power the 803's? If not, I'm assuming I'm in for a real mess because the driver boards are also (I believe) TTL controlled as the displays are DMX/Sound activated so for me to put in new driver boards might be a mess unless I can find some that are able to be controlled by the DMX board...

BTW, just for fun (and of course observing all precautions for ESD, etc) I took the chance and tried one of the 803's (Yes, I'm a glutton for punishment) and it does lase, just at a very low output (not "blown diode" low, just "vastly underpowered" low)

Well Hell, at this point I'm comitted to the project - I think what I'm going to do is tear into one of the single red displays we have laying around and try refitting the driver, etc and seeing if I can make it work ... Not too sure about the "wall wart" though, the displays have 120VAC input that goes into a transformer that outputs 7VAC for the driver boards and 12VAC for the DMX board, and they're a pretty tight fit so there is little chance to do an internal power supply, and being as we use these systems 5 nights a week in our shows the hassle of an external supply would be more than it's worth (all our lighting trusses and rigs are set up for the existing power requirements and have no extra outlets available without a pretty serious rewire - all power is run internally and is coded so whomever "bangs in" the show can't mess things up)

If all else fails, I guess I have a pair of nice diodes in focusable modules for sale cheap... LMAO

Thanks again for the help - if anyone has more pointers or direction I'd appreciate it!