Maximum Number of Zones

[HereComesTheRain]

In general, if you want to stabalize power you need a large and a small cap. The large cap handles ripple of lower frequencies the smaller cap is faster and will handle higher frequencies but with a limit. If the noise or spikes are to large than it is better to use a LC (coil/cpa) or RC (resitor/cap) circuit. Therefore the suggestion of the 100 Ohm resistor in series with a 0.1 uF cap behind the R (on the hc595) side. Several cases of unwanted behaviour of the hc595 can be found on the internet and are solved with this RC circuit.


I was also wandering if all 4 boards are showing erratic behaviour or is the first board different?  The data from the Pi is clocked in on the first hc595 (pin 14) and the overflow bits are exitting on pin 9 which is connected to the next hc595.  If the noise/spikes are on the data, clock or latch pins than you could a test with connecting these pins to gnd. Of course the circuit does not work but I 'm curious if you pull the black and brown wire from the Pi and connect them to GND what happens if you do what you do (pull fan?) to generate the issue.

The above might not solve the problem but is merely to identify the entrypoint of where the problem enters your circuit.

"For me it is quit difficult to handle the issue without having the stuff on my workbench." 

PM me your address and I will be happy to send it to you.   

"If it makes abolutely no difference than you can eliminate the psu (for now)."

No Change in outcome. 

"I was also wandering if all 4 boards are showing erratic behaviour or is the first board different?"

As I unplug and plug in the USB power wart from UPS (GROUNDED ONLY OUTLET)  the triggering appears to start on the FIRST RELAY MODULE. As I continue to unplug and plug in the USB power wart from the UPS the triggering progresses thru to the other RELAY MODULES.  Sometime it triggers one optocoupler sometime it triggers multiple optocouplers.

"Another experiment you could try is connecting the hc595 to +3.3V instead of +5V."

I just say that from one of your earlier post.  Have not tried that yet.  Would I need to reconfigure how the optocoupler(s) are powered?

"Of course the circuit does not work but I 'm curious if you pull the black and brown wire from the Pi and connect them to GND what happens if you do what you do (pull fan?) to generate the issue."

I will give that a try.

You have been very helpful and I value the time you have spent with me on this issue.

Hope to have time later today to install the resistors and capacitors.  

If you are inclined feel free to dumb down where I need to connect what to what.    

For example:

"Therefore the suggestion of the 100 Ohm resistor in series with a 0.1 uF cap behind the R (on the hc595) side."

Do I need to solder a 100 Ohm to a 0.1 uf and then where do I make the connections?

"could connect the top 5v also to the bottom rail and put 2 caps (0.1 + 47uF) on it"

Do I put the 0.1 + 47uF in the pin holes of the BREADBOARD or to I solder the 0.1 + 47uF and the attach to the 5v wire connecting the top and bottom power rail.

"To be sure you coud add on pin 11, 12, 14 on the hc595' a resistor of 4k7 or 5k6 to +5v "

Would that go on each of the SHIFT REGISTERS or just the first one? And would that connection be made between each of the pins and the TOP POWER RAIL (+) 5v?