- I have an RC circuit delivering a square signal via a standard 555 timer set in monostable.
- I am powering the 555 with 4.88V DC directly from the Arduino, which itself is taking its power from the Serial USB cable connected to my computer, running on battery power (i.e. = not mains).
- I did my homework and selected appropriate decoupling/bypass caps directly across VCC-GND to help with power smoothing. All fine.
- Arduino triggers a set of 6 consecutive reads to calculate/average the time constant and then goes quiet until next request. Nothing fancy.
Now: When I put a probe on the capacitor and observe voltage, I see little ripples that almost look like a heart beat...(Figure 1.) They are spaced 25.5uS apart.
Q: Could someone tell me the origin of the ripples?
Editions: - Added Schematics following requests.