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hzeller / ldgraphy

Simple Laser Direct Lithography / Laser Direct Imaging for PCB manufacturing
http://ldgraphy.org/
GNU General Public License v3.0
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Not an issue, but a (stupid) question #3

Closed Pepetruen0 closed 6 years ago

Pepetruen0 commented 6 years ago

Hi, I'm seeing that the laser driver has a note stating "there is now a cap accross R3." As I'm a newbie and English is not my primary language, can I have a brief explanation of what this means? Also, what size capacitor do I need to use for this?

Thanks.

hzeller commented 6 years ago

This means that there needs to be an additional capacitor in parallel to R3, which has not been reflected yet in the schematic or printed circuit board. I have fudged the capacitor in with what I had lying around, I think it was around 100pF.

Pepetruen0 commented 6 years ago

Wait, when you say "fudged" do you mean "I got away with" or "totally destroyed"? Just to be sure. Also, would something like this work? capacitor

hzeller commented 6 years ago

'fudged' means that I choose the value without much calculation after having measured the outcome on an oscilloscope. I hacked it into the existing board by just soldering the capacitor on top of the R3. It works well.

Not sure what you want to do with your circuit above, but the 100pF needs to be across R3 not R2.

Pepetruen0 commented 6 years ago

Whoops, my bad. I meant something like this, would it work?

cap

hzeller commented 6 years ago

Yeah, this looks good. The value is somehwere in the order of 22pF to 100pF. They will essentially suppress unstable behavior like this:

https://plus.google.com/u/0/+HennerZeller/posts/g9reVCg4bnE

Pepetruen0 commented 6 years ago

Awesome, thank you so much for your patience!