Maximum Number of Zones

[HereComesTheRain]

Although I don't like Fritzing I did try to make a new drawing like the one in the SIP wiki but with the wiring as shown in the schematic diagram. Hopefully this makes a little more sense to you.

While recovering from surgery I ordered some hc595'. In the coming days/weeks I will try to find the time to make the same circuit and see if I can make it fail too.

Let me know when you have done some testing. 

Hello Gerard

Your Fritzing, had to look that up, is great.  It's like paint-by-numbers for those of us who are not EE nor play one on TV.

Fortunately I purchased a pack of three BREAD BOARDS so I can start fresh.

Would you mind clarifying what wires the three 4.7(s) are connected to?

I see the first 4.7 is connected to Red +5 and Green (SER14)

Is the second 4.7 only connected to the Red +5 and the Brown (RCLK12) and not the Green (SER14)?

Is the third 4.7 only connected to the Red +5 and the Black (SRCLK11) and not the Green (SER14) and Brown (RCLK12)?

Can I power the RELAY MODULES by daisy chaining the Red wire from +5 pin to +5 pin to +5 pin to +5 pin or do I need to splice into the Red wire coming from the TOP POWER RAIL?

Is it me or is your current Fritzing significantly different than what I was attempting to construct/replicate?  Change can be a good thing.

Thank you again for your assistance.

[astrogerard]

Would you mind clarifying what wires the three 4.7(s) are connected to?
Sure, the point is that all pins of the hc595 which are connected to the Pi have a 4K7 resistor to +5V

I see the first 4.7 is connected to Red +5 and Green (SER14)
Yes
Is the second 4.7 only connected to the Red +5 and the Brown (RCLK12) and not the Green (SER14)?
Yes, but "behind" the 100 Ohm resistor, so directly connected to the hc595
Is the third 4.7 only connected to the Red +5 and the Black (SRCLK11) and not the Green (SER14) and Brown (RCLK12)?
Yes

Can I power the RELAY MODULES by daisy chaining the Red wire from +5 pin to +5 pin to +5 pin to +5 pin or do I need to splice into the Red wire coming from the TOP POWER RAIL?
Depends on what you mean by "power the relay modules". If you mean VCC next to DI8 then Yes. But only with jumper removed. Later when everything works you can connect another power supply (so NOT the Pi) to JD_VCC. JD_VCC is powering the relay board while VCC is only providing +5V for the onboard leds and optocouplers

Is it me or is your current Fritzing significantly different than what I was attempting to construct/replicate?  Change can be a good thing.
It's you 
The only thing changed is removing the purple wire and pulling this wire to GND to permanent enable the HC595.
Additional to the original drawing is the R100 and 0.1uF filter. Also added are some stronger pullup (4K7) resistors since the inputs of the HC595 have a very high impedance, therefore a bit sensitive to noise or spikes.


--Gerard

[astrogerard]

Hi Rob,

I did a lot of testing with the shift register setup. Bottom line of all the hours of testing is that the schematic I made some time ago works as expected.
But.... also the original drawing which is in the wiki works with some minor remarks.

First of all, the optional capacitor of 0.1uF is not optional. additionally a series resistor as drawn in my schematic is also advised to include. The values however must be a little adapted. When using a 0.1uF cap it is better to use a 47Ohm resistor. With my oscilloscope I checked the timing on the GPIO ports but when using 0.1uF and a R100 resistor the latch(Pi pin 15) needs a little too much time to go from high to low or vice versa. So a resistor of R47 (or two R100 in parallel) is a safer choice. 

With both my drawing and the (slightly modified) wiki drawing I did a lot of testing with external devices like fans, motors, relays and other stuff to try to fail the circuit. With the not-optional cap connected it didn't fail even once. Without the cap the circuit sometimes goes bananas.

When I had the scope connected I do see unexpected signal levels in the sense that when everything is at rest the data, latch and clock signals remain high. You would expect these signals to be low. I'm not sure if this could make the circuit extra sensitive to noise or spikes so additional testing is needed. I will make some changes to the code and see if it is of any influence.

So, what can you do? 
1. make sure the psu of the pi is from a decent quality or change the psu and see if it makes any difference. I powered my test Pi3b with a Samsung 5v phone charger. This (dodgy) charger is not suitable to power a Pi but did way better than expected.
2. recheck if the (non) optional capacitor is connected between pin 12 of the hc595 and GND. With preferably a series resistor of about R47 to P15 on the Pi.
3 recheck all the wiring if firmly connected. Be aware that using a breadboard and breadboard wires you will never get a solid/permanent solution. It (usually) works on the bench but in the field I would definitely solder the components on a perfboard.
4. If everything fails first try to simplify the setup to 8 channels by using only one hc595 and one relay board. Disconnect everything else and see it this works without any problem. From there expand the setup.

As we discussed via mail we both are a bit busy this and next month so lets take the time we need and update this thread when you or I have any news on this topic.

--Gerard