LED that decreases in intensity when excitation is increased on DAQ software

[dlee7]

Hi Daniel,

I've been experiencing a strange problem of LED light intensity getting weaker when I increase excitation % on the DAQ software (0% being the brightest and 40% and above the dimmest). When I compared the default LED intensity on this miniscope with the default LED intensity on the other microscope which behaves normally with good light intensity, it was much weaker. I tried resoldering with a new set of LED+LED PCB, resoldering wires that connect CMOS and LED PCBs, and even using new coax cable + new CMOS PCB the problem persisted. I received these two presumably problematic CMOS PCBs from the same source (neighbor lab) and the other one that works fine from another source. So I've been thinking that these two particular CMOS PCBs could have been from a defective batch or of version that is not compatible with the DAQ hardware+software. Did you have a similar experience, and if not what do you think could be a possible explanation? Currently I'm using old version DAQ PCB.

Best,
Don   

[Daniel Aharoni]

Hi Don,
Can you upload a picture of the problematic PCB? There are 2 possible problems that could cause what your are experiencing:

• If you are using the newest CMOS PCB version, you need to make sure to add a little solder ball across the 2 half circuits on the bottom of the PCB to short the 2 pads together. Look here, http://miniscope.org/index.php?title=System_Assembly, under the section titled "Soldering the solder-jumper on the bottom of the CMOS PCB (v3.2)".
• The other possible cause is a damaged LED or slightly shorted LED wires or some short around the LED driver circuitry (left over flux residue can cause this). I know you tried a brand new LED and LED wires but you might want to try 1 more time.

Please let me know as you make progress or keep running into issues.