Adam, I have Cambridge's old procedure for finding the first shaft resonance and designing/tuning the notch filter components without a Dynamic Analysis machine. I won't post it, on-line, but PM me with an email and I'll send you a copy.
~
It is one of those procedures I do not post because if done by the "wrong" immature person with the wrong equipment, then posted on line in a FAQ or Youtube video as "Gospel" , it could do a lot of damage. Especially as each notch is a bit different from galvo to galvo, model by model, and mirror by mirror, and in some cases from production run to production run... Cookbook designs for high Q (Quality Factor) notch filters are not a good thing.. While doing the test procedure manually, it is really easy to miss the correct resonance while watching the oscilloscope and twiddling the knobs on the signal generator.
~
Cambridge stresses that a notch filter is the last thing you touch while working on a galvo amp, nand really stresses the point about calling the factory before doing so.
~
There are two procedures I wont post, and one of them, position sensor calibration, requires you to know a constant from the factory a priori, and the second is the notch.
~
As the clone design will never have the same photodiodes or vanes in the position sensor used by the mother factory, using the published Cambridge numbers while bringing a new, untuned, or repaired board up from scratch can set you up for real bad juju... A bad sensor constant really ripples through the whole analog PID portion of the amplifier.
~
Tuning /finding the notch needs serious bench experience and strong technical skills. It is far easier and safer to use a Dynamic Analyzer . PS, before some one chimes in and says I could just run a "FFT" on a sound card while the galvo is running closed loop, well try it some time. HA! Good luck reading that picture!
~
Usually on a on clone amp notch board there are five pins. +15V in, -15V in, Ground, Signal in, Signal out. Each brand is different, and you HAVE to find the pins by inspection. You can find the power and ground leads with an Ohm Meter, measuring from the 7815 and 7915 output pins. Ignore them. The remaining two pins are notch in/out and in many cases can just be jumped, for testing, but you may have to retune. IN some cases a commercial system Could oscillate if the notch is jumped. REMOVING the notch without installing a jumper will result in a mirror that does not move. Jumping V or V- to the output stage by mistake will fry something, usually the galvo.
~
Keep in mind a notch board may have more then one notch (N=3 some times), and there will be trim pots for notch center and notch depth for each notch.
~
NOT something to play with unless you have a spare scanner system.
~
Steve
.
Last edited by mixedgas; 07-06-2018 at 08:26.
Qui habet Christos, habet Vitam!
I should have rented the space under my name for advertising.
When I still could have...