Learn me something electronical...(Flexmod)

[Bradfo69]

No... I haven't hooked anything up yet. I'm just saying the resistor says .200 ohms. I have no idea what sort of voltage I should be expecting to see. I just used 12 volts as an example since that's what the power supply is. I have no idea what actually runs through the resistor. I'm guessing based on your reaction that its a lot less voltage than that!

[DZ]

No... I haven't hooked anything up yet. I'm just saying the resistor says .200 ohms. I have no idea what sort of voltage I should be expecting to see. I just used 12 volts as an example since that's what the power supply is. I have no idea what actually runs through the resistor. I'm guessing based on your reaction that its a lot less voltage than that!

Indeed! That is the current sense resistor and is in series with the laser diode. So the voltage you measure divided by the 0.2 ohms will give you nearly the exact current going thru the diode. I say nearly because the meter isn't perfect and the 0.2 ohm resistor isn't going to be perfect either. But close enough.

[Bradfo69]

(I can see this is going to end up going back in the box and up on the shelf before this thread is done. )

So to do what you are describing... I forget what the instruction manual says about a load of some sort where the diode gets hooked up and, I don't need to bother with the modulation line. I just apply power from the 12V supply and then measure the voltage going through the resistor, do the math and adjust the pots that way?? (There is something to be said for buying completed, working projectors. LOL)

[DZ]

LOL! Ok, so I typically turn down bias and gain a few turns. Hook it all up, connect leads across the current sense resistor and power it on. I then set my lower limit with the bias pot (just below lasing threshold), no real reason to measure current here since you are below lasing threshold. I then apply +5V to the modulation input and see where the current is. That part is kinda dangerous, if the gain pot is still turned up and it tries to send 4amps down a diode that can only handle 250mA, then it will likely kill it. So you can either "shotgun it" and apply the +5V and hope for the best or you can send it a variable voltage and start at around 0.5V for the modulation input, check your current. Then turn up the modulation input voltage until you get to +5V while monitoring the voltage across the current sense resistor. Then adjust the gain pot as necessary. It all sounds complex and a pain in the ass, but really after a few times you'll find that it's very easy.

[Bradfo69]

I'll see about giving it a shot tomorow. I'm done my cursory 15.5 hour work day... time for zzzzz...

[WolfMax]

Attachment 43763

Your all forgetting one thing. The flexmod will stop working if there is an open circuit or a dead short on the diode output (normally accompanied by a red LED being lit on the board). Therefore you have to have ether a dummy load or the current meter across the output connection for it to work at all.

Using the notation from your picture, connect 'Pos' and 'Neg' to the current meter. Connect V to +12v on the supply. Connect G to FG on the supply. Connect INT to +12v on the supply or solder it to the leg of the big black resistor nearest V+ on the board. Then you have to have a 5v supply and common its ground with the 12v supply ground. Now you're ready to do the setup of the Flexmod.

To set the threshold, connect 'M' to the common ground. Turn the 0Bias clockwise to increase or anticlockwise to decrease the current till you get the reading you want on the meter.
To set the max current, connect 'M' to the 5v supply. Turn Gain clockwise to increase or anticlockwise to decrease the current till you get the reading you want on the meter.

You're done!

Things to remember:
There is a start up delay of 7 seconds unless it has been disabled by shorting pads on the board (see the manual)
If the Red LED comes on, there could be a problem with the output connection. Power down, check the connections, Power up.
Make sure the fuse in the meter is ok (caused me to think I had fried 2 of my Flexmods as it caused an open circuit on the output)
If you have obtained pre-owned (secondhand) Flexmods, check to see if the 'Beam Suppression' mod has been made (see manual). This may affect the output when setting the threshold as it turns the laser beam from 'LED' mode to fully off. But I will admit I don't know exactly how (however, if I had to guess I'd say voltage suppression).

Hope this helps.

[Bradfo69]

Thanks Colin.

That should probably be made into a sticky!

[WolfMax]

Don't know about a sticky but you're welcome.

[norty303]

To be honest (and you may not want to do it this way) but after I did my first ever FM2 using a meter, every one after that has been done by simply hooking up the laser diode and using a power meter.

Bias is done visually, and I know what power I want out of it, so I just set it to that on the power meter.

Obviously, if you're running your diodes on the ragged edge this may not work for you, but for the higher tolerance diodes it should work just fine.

IF you end up fine tuning your bias, etc for colour balance and modulation matching you'll end up doing it like this anyway.

[m0f]

Just to clarify as I don't see your earlier question answered. Ground on the P3, goes to V- on the power supply. Nothing goes to power supply ground except chassis ground of your laser projector later on, but ignore power supply ground for now. Just V+ and V-. The 5V modulation signal goes to Mod+ and Flexmod Ground

Ground on the p3 is shared between modulation ground and power input ground. You can either solder in 2 wires to the p3, or what's easier is a short lead to the p3 and split it off to 2 wires, or even just run your modulation ground to V- on the power supply.

Interlock either goes to V+ on the power supply or some other options listed earlier. I run it to the power supply v+ that way if ever I want to use the interlock feature I already have a wire in place making it easy to run it to wherever I need.

I've never had a problem just hooking up a current meter directly to the outputs. The flexmod does heat up that way quickly, especially at higher current settings, but just make sure to heatsink it well first and don't leave it on too long (plug the power supply into a power bar so it's easy to switch on and off as needed). I've never had a problem running it for a minute or so to set the current, even at higher current settings. I've probably setup about 12-13 flexmods this way without any failures. I use this methods as I just find it so easy, but for sure use whichever method your most comfortable with.