need driver help schematic with diagram has no protection diode

ok i ordered a kit off ebay, i know dont flame me......
and the schematic looks good but it has no protection diode in it....should i add one?

and also they say i can set the output current with a 1 ohm resistor by measuring the mV across the resistor, do they mean parallel the DMM to the resistor? or how else should i set it?

it calls for around 90mA for this 150mw 405nm

kit:
150mW 405nm Blue-Violet "blu-ray" Laser Diode in Module - eBay (item 170385523927 end time Sep-27-09 23:13:43 PDT)


schematic: http://img33.imageshack.us/img33/2142/0921091501.jpg

That diode is there to protect against reverse polarity, so unless you're 110% sure you'll never hook it up backwards, I'd put the protection diode in. You can use pretty much any diode for this application.

ok what about setting the current?

Search the forum for the terms "dummy load" or "test load". You'll find information about how to build and use a test load to set your current. The load will contain a 1 Ohm resistor which you use a DMM to read by connecting the DMM leads on each leg of the resistor. The reading (in mV) will equal the current (in mA).

here is a link to the page that talks about setting up the test load and how to test with it.
this is not my page it is another members page (pls don't flame me) and the guy does an excellent job telling you how to use it etc.
It can be done - Laser driver
I built that test load just maybe 2 weeks ago on some perfboard
perfboard plus electrical components less than 10 bucks. as well there is someone in the buy sell trade area that has several of the 1 ohm 1/2 watt resistors I could be wrong but I think even free.
I know that was the tough one for me to find at the local radio smack.
for blue you would use all 6 diodes set in series as in the schematic in the link. to test the voltage your diode is getting test (dmm set to volts) in series across all six diodes. to test you current output you test across the resistor with you dmm set to mv and the mv=your ma output. and adj the pot to adj your current output.
easy as that. as well the driver you picked up is pretty much the exact as the standard ddl driver you see all over the forums.

if you would like I could post some pics as to how I set my test load up for both red and blue lasers. with my jumpers etc I just use alligator clips to connect my driver and have diff wires coming off it for the dmm.

ok new problem, got the current set where it needs to be at 90mA but my voltage is at 6.7v which from what the specs say is way too high, its looking for 5v, btw its all powered by a 9 volt

the extra voltage should be dissipated from your current regulator as heat someone pls step in if this is wrong but that is what I have been reading. if you want to reduce your voltage you would need to change your batteries to something with a lower voltage that driver generally takes about 2 V to power your diode says 4 volts so you would need 6 volts. but I believe the voltage you are reading is what you are capable of getting from the driver.

You can't accurately measure the voltage without a load in place. The way the LM317 regulator works in that configuration is it supplies a fixed amount of current and basically lets the laser diode take whatever voltage it needs. Worry about the current, not the voltage. As long as you have the circuit built correctly, you'll be fine.

ElektroFreak said:

You can't accurately measure the voltage without a load in place. The way the LM317 regulator works in that configuration is it supplies a fixed amount of current and basically lets the laser diode take whatever voltage it needs. Worry about the current, not the voltage. As long as you have the circuit built correctly, you'll be fine.

Click to expand...

bs i tested everything, reference voltage, i had the current set at 90mA, used a 9v batt like the diy driver post said, and now im out a 405nm diode

IDK.... wouldn't the first choice be to contact the seller....:thinking:

Or am I the only one that goes back to the Seller/Manufacturer
if something is questionable about a product...
Then... if it doesn't pan out... I will look elsewhere for answers...

BTW.... looks like someone didn't discharge the 47uF cap....
before connecting the LD... :cryyy:

Jerry

BTW.... looks like someone didn't discharge the 47uF cap....
before connecting the LD... :cryyy:

Jerry

Click to expand...

Exactly what I was going to say. Common mistake, well you'll never forget to do that again at least. Consider it a lesson learned. Don't worry I'm sure you'll have a second chance soon. Sorry to hear that.:cryyy:

You could solder a resistor, perhaps 470Ω, across this capacitor, to keep it discharged. A surface mount resistor isn't big. Gives you a little insurance.

That's what I do.. works great. Haven't lost a diode to cap discharge in a long time. Sorry to hear you lost your diode, that's a classic first-time mistake. Did the instructions that came with the driver talk about discharging the caps before connecting the diode? If they didn't you should send an email off to whoever sold you that driver and tell them they should include instructions to that effect.

The eBay auction Description for that driver does...........
The seller pretty much covered himself....
Like every other bit of information anywhere.... "ya needs to read it"


Jerry

I want to add that if you want to replace your diode, don't go back to ebay. Try the buy/sell/trade section here or try modwerx.com or hightechdealz.com. You'll save a bit of $.

yeah if you go to the buy sell trade area you can get some nice diodes there cheaper than ebay.
don't feel bad about the diode. I had taken my red out to work on the driver and killed it in the process. well I had a working laser for about 2 weeks. but I paid 40.00 for that diode. last time I will pay that much for an ebay diode. I know it wasn't the sellers fault it just happens.
as with most hobbies
you build it, you break it, you fix it. almost always in that order.
I think dark lasers still has PHR 803t diodes for sale between $10 and $15.00 and alot of peeps like them. I am patiently waiting for christmas from the postal service.