Humbled by 555 Circuit Problem

Well, why wasn't my 555 astable circuit tranferring from breadboard to proto circuit with strip style power rails? That had me baffled for over a day.

This was for a longish delay of over five plus minutes, R1+R2 to be 3M plus, and C1 of 150uf. Clean up tracks, inspect for solder bridges, check. Add bypass caps across V+ and gnd, check. Add bypas cap from control voltage pin to ground, check. Using same power supply, check.

I remember someone mentioning the use of home run wiring on a smps circuit I was working on a while ago. Huh, maybe the ground bus was messing with C1 somehow? Ran a home run wire for the 555 gnd and C1- pins to power input pin, and BINGO! works like a charm now.

Apparently, all the stuff hanging off the multi strip ground (approx. 15" total length) rail was upsetting C1, and the astable circuit function.

Your problem was probably caused by the very high output current available from an ordinary 555 (200mA) which causes it to create a power supply spike of 400mA when its output switches states which messes up many circuits that do not use a supply bypass capacitor directly at the supply pins of the 555.
It is mentioned in the datasheet of the LM555.

As mentioned previously, I put the bypass caps on per data sheet. Also, distance to power supply bypass caps of 100uf and 100nf < 2 in. The circuit would actually trigger with a C1 value of 100uf, but the period was too short for my liking.

With the circuit working properly, pin 2 (trigger) would would be on a steady march up in voltage, and then trigger. Prior to fix, and using the larger than 100uf caps, pin 2 would rise, and then ping pong back and forth in voltage, never reaching the trigger point.

The data sheet says that R1 + R2 can equal 20MΩ max. So perhaps the way to have done it was to use a 10MΩ resistor for R1 and backed off C1 to 100uf with less leakage. Since the circuit works currently, not going to revisit.