flexmod issues

I built a small 2W laser and have been using it sucessufully on my cnc to engrave pictures into wood. I have removed my laser and flexmod from my cnc to trouble shoot some issues. My laser can handle up to 1.8 amps. I have been running it at 1 amp but decided it is time to turn the power up. If I remove the diode from the flexmod and connect my amp meter it reads 1.8 amps when the potentiometer is at 5V. If I reconnect the diode and turn the potentiometer to 5V the flexmod shuts off and the red light comes on. With the diode connected I can not take the current past 1.14 amps or it will shut off. I have tried 5V 12V 19V and 24V power supplies thinking it could possibly be a problem of overcoming the internal resistance of the diode but this did not help. I really hope someone has some suggestions? I am knowledgeable in electronics but this one has me stumped.

http://www.ebay.com/itm/2W-445nm-M-T...item2a2158fe9d

This is the diode that I am using.

I have removed every possible variable from the system by getting the circuit down to the minimum components.(removed fans displays ect) I have drawn the circuit I am using and will post it below. With the output shorted and the potentiometer output at 5V I can adjust the flexmod gain so that the meter reads 3 amps. This successfully proves that the flexmod and the power supply can handle a 3 amp load with no issues. I adjusted the flexmod gain back to 1.8 amps then I connected the diode. Starting with the input potentiometer at 0V and slowly ramping it up the flexmod will shut off when the current reaches 1.4 amps. When this happens the red light comes on. All connections are soldered and all wires are less than 1ft long.
Attachment 46312

Hello,

I had this same issue a few years ago because the voltage of the power supply was too low. I tried to power a flexmod @t +5V with a blue laser diode connected. I started to increase the voltage of the modulation input. The driver shuts off and the red LED lighted.
Everything has been sorted by replacing the +5V power supply for a +12V. For a blue laser diode, the minimal voltage of the power supply should be around +7V (there's a -1,5V drop in the driver).


EDIT : I just saw that you feed the interlock with 5V. I always connect the interlock to +V of the power supply. In your case you have to feed this input with +12V.

Tell us if it solves the problem ;).

SUCCESS!!! That fixed it thank you for your help.

I use 5V SMPS for my blues but i turn the adjuster all the way up which gives ~5.8V
This works just fine.

Now I can get back to engravingAttachment 46313.

http://www.o-like.com/images/mce_upload/445-1.6-1.jpg

I took the worst case = 5,5V accross the diode + 1,5V drop = 7V.

Norty, do you use FM P3 drivers for your blues ? Maybe the voltage drop is lower with yours.

OK- This has been helpful. After artfully machining a heat sink of copper and managing to keep my remaining fingers, I went to hook up the flex mod and noticed the instructions say to connect your meter in current mode ACROSS THE OUTPUT of the flex mod. Uhh, always thought you measure current in series with the load.
Before I blow up an expensive diode, I'd like to test the driver with something else- someone suggested I use a high power led as a load for testing.
Any thoughts?

Quote:

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Originally Posted by MIIKKKLLLL

I took the worst case = 5,5V accross the diode + 1,5V drop = 7V.

Norty, do you use FM P3 drivers for your blues ? Maybe the voltage drop is lower with yours.

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Maybe the new revisoin P3's are different but when I tested it there was only about a 0.5V dropout. Check out this video. The diode had a 4.8V voltage drop @ 1.6A and when I lowered the supply voltage currrent did not start dropping till around 5.4Vish.

https://www.youtube.com/watch?v=9U_rRbclKBk

Quote:

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Originally Posted by glorocks

OK- This has been helpful. After artfully machining a heat sink of copper and managing to keep my remaining fingers, I went to hook up the flex mod and noticed the instructions say to connect your meter in current mode ACROSS THE OUTPUT of the flex mod. Uhh, always thought you measure current in series with the load.
Before I blow up an expensive diode, I'd like to test the driver with something else- someone suggested I use a high power led as a load for testing.
Any thoughts?

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the idea is to set the current before you attach the diode... it's really late but if my brain is functioning... when you measure across your meter will look like an electrical short so your diode will do nothing and your meter will measure the current the driver is putting out (into the short which is the meter in current mode)

I appreciate your input. I'll give this a try, but I now have to get a decent meter. For years I carried Flukes, only to have them disappear on job sites along with SureFire flashlights. Got into the habit of buying "disposable" meters. Not exactly the reference standard for accuracy. Again, thanks.