Request: 5-mode driver @ 1.8A

[grainde]

So it does output 700mA correctly when using the 445 setting, right?

Yup.

Edit: Im just checking it, but as each diode should be 0.7 V it possibly means that the 445 (pin 4) setting doesnt actually run the driver at 4.5 V....So the stated pin 3 (Red), pin 4 (Blue) and pin 6 (Bluray) might not be correct, or Ive got something wrong? Will post back with an answer..:thinking:

 

[ryansoh3]

Yup.

Edit: Im just checking it, but as each diode should be 0.7 V it possibly means that the 445 (pin 4) setting doesnt actually run the driver at 4.5 V....So the stated pin 3 (Red), pin 4 (Blue) and pin 6 (Bluray) might not be correct, or Ive got something wrong? Will post back with an answer..:thinking:

Thanks for your info. I get something like that as well, so that's why I was wondering. My stab at it is that the diodes have a variable forward voltage as the current changes I think. Are you using your DMM to measure the voltage drop? So was I, and that may be the reason why we're getting that result.

Cheers! :beer:

Edit: Maybe check out the upper right graph on the second page here:
http://www.micropik.com/PDF/1N5400_8.pdf

Is this it?

 

[grainde]

Thanks for your info. I get something like that as well, so that's why I was wondering. My stab at it is that the diodes have a variable forward voltage as the current changes I think. Are you using your DMM to measure the voltage drop? So was I, and that may be the reason why we're getting that result.

Exactly, I saw a similar graph on Jufrans sales thread too, but it suggests a VF of 0.8 - 0.9 at our currents. So yes it does change as you up the current. It just seemed a little low however. In your pdf they actually state VF is 1.2 V @ 3 A, which would be fine if we used currents that high! If that is correct however, then it could mean its around just over 1 V @ 2 A and hence 4 diodes will total ~4 V. Could also explain why I was able to run the driver using 1 battery on the test load too.

I dont think we can use the DM to check it, because its not under load ie running at 2+ A and itll give the wong value. :beer:

 

[ryansoh3]

Exactly, I saw a similar graph on Jufrans sales thread too, but it suggests a VF of 0.8 - 0.9 at our currents. So yes it does change as you up the current. It just seemed a little low however. In your pdf they actually state VF is 1.2 V @ 3 A, which would be fine if we used currents that high! If that is correct however, then it could mean its around just over 1 V @ 2 A and hence 4 diodes will total ~4 V. Could also explain why I was able to run the driver using 1 battery on the test load too.

I dont think we can use the DM to check it, because its not under load ie running at 2+ A and itll give the wong value. :beer:

Yup, thanks for your confirmation.

I really do hope the Vf vs Amp slope is consistant with that of the M140's, because if not... :evil:

Cheers! :beer:

 

[landswimmer]

why cant we just make our own "LPF" DIY variable driver?

there has to be someone here who knows enough about them, to either make and sell them, or to make a tutorial and post it.

to me it seems like a pretty good thing to have a variable driver for the M-140 diodes, so you can drop the power low enough that looking at the dot wont blind you, while still having the ability to crank up the power to full.

 

[The Baron]

That sounds like a great idea for all M-140s to have variable current. It would be very useful.