Hi all, you'll like this. I have build a MCU-driven circuitry for driving those ancient split-flap units from a train station. My problem is that each display unit is driven by set of eight 48V signals that power a built-in relay which switches 110V AC built-in motor (1W-2W-3W, depending on unit size). When the display unit reaches the appropriate position, it turns the relay off, stopping the AC mottor.
When the relay goes off and the motor stops, it must induce all kind of EM noises that apparently propagates to my 5V circuitry (wasn't a problem back in 70's), namely to one 74HC164's clock input. I know of various techniques of supressing these transient effects and have indeed employed some (ferrite cores on both ends of cables, 100n decoupling capacitors for each IC), but still the problems persist, because I don't know what frequencies I'm supressing.
Instead of blindly trying snubbers, various capacitances, inductors everywhere, shielding, multiple PCB layers etc., i would like to SEE the transient effects on an oscilloscope and I want to SEE the corrective effect of any action. I'd like to spend like $500.
The Question: Are oscilloscopes in this price category able to record such transients? I have NO IDEA what frequencies may be involved here. Do I need 1Gsamples/s? Do I need an equipment for $100.000?
I'm already fed up with EMI, it is destroying my second project, but this time I'm not giving up :-) I don't really need to complete it anytime soon, it's 80% learning.