- Joined
- Sep 22, 2010
- Messages
- 1,360
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- 48
I hate to bump this back up but it appears I'm an idiot twice over. I had planned on building two of these drivers -- one for a red and one for a BR diode. I ordered some 10 ohm and 5.1 ohm for the drivers (should have been just 5 oops) and forgot to order the &%&* 1 ohm resistors for the test load. The readings I got were using a 5.1 ohm resistor and not with a 1 which explains why things didn't seem to work right. Using I = V/R the driver was actually outputting 49mA. I'm not sure what the threshold for a 16x red diode is to lase but since the 5w I have on order is 30mA it has to be a lot more than that since 250 seems to be the recommended setting.
:banghead:
Unfortunately I'd need to push 1275mW across the resistor for 250mA which would smoke my 1/4w resistor. If I use two 1/4w 5.1 ohm in parallel I'd only have to push 638 mV which would be ~160 mW which would be fine. Hmm. Yeah. That *should* work. I could put 5 of them in parallel to get 1 ohm but I'd be out of room on my breadboard for other connections. Maybe I'll up it to three and redo the calculations. Wish we had something other than rat shack here so I could get a package of 1 ohm resistors. Oh well I'll get some next time I order from digikey. At least now I know what I need to do to calibrate my driver correctly.
:banghead:
Unfortunately I'd need to push 1275mW across the resistor for 250mA which would smoke my 1/4w resistor. If I use two 1/4w 5.1 ohm in parallel I'd only have to push 638 mV which would be ~160 mW which would be fine. Hmm. Yeah. That *should* work. I could put 5 of them in parallel to get 1 ohm but I'd be out of room on my breadboard for other connections. Maybe I'll up it to three and redo the calculations. Wish we had something other than rat shack here so I could get a package of 1 ohm resistors. Oh well I'll get some next time I order from digikey. At least now I know what I need to do to calibrate my driver correctly.
