2021 Jun 24, 09:58 PM
(This post was last modified: 2021 Jun 24, 10:27 PM by astrogerard.)
Should I anticipate that the 47uF will resolve the issue at hand?
In general, larger capacitors (47uF.. 100uF) are used to stabilize (flatten) the power. In other words, compensate against small fluctuations. Smaller capacitors are used to reduce noise. Since noise or spikes are fast events the capacitor needs to be smaller otherwise charging the cap takes too long and the noise is still there. Depending on the type (frequency) of the noise/spikes values between 0.1uF (100nF) and 0.01uF (10nF) are a good start. According to the datasheet of the HC595 0.1uF between pin16(+5) and pin8(GND) is recommended.
Just to verify I make the connection between the POSITIVE and the NEGATIVE using the 47uF on the TOP RAIL?
Yes. When using longer rails you could use two, on either end one
Doesn't there need to be a common GND between the Pi powered shift registers and the secondary powered RELAYS?
No, there should be absolutely no physical (electrical) connection what so ever. The only connection between the output of the HC595' and the relays is optical through the optocouplers (small 4 pin black devices on the relay boards).
btw, do you have the "optional" 0.1uF capacitor connected as described in the Wiki. That capacitor is in fact mandatory and not optional.
In general, larger capacitors (47uF.. 100uF) are used to stabilize (flatten) the power. In other words, compensate against small fluctuations. Smaller capacitors are used to reduce noise. Since noise or spikes are fast events the capacitor needs to be smaller otherwise charging the cap takes too long and the noise is still there. Depending on the type (frequency) of the noise/spikes values between 0.1uF (100nF) and 0.01uF (10nF) are a good start. According to the datasheet of the HC595 0.1uF between pin16(+5) and pin8(GND) is recommended.
Just to verify I make the connection between the POSITIVE and the NEGATIVE using the 47uF on the TOP RAIL?
Yes. When using longer rails you could use two, on either end one
Doesn't there need to be a common GND between the Pi powered shift registers and the secondary powered RELAYS?
No, there should be absolutely no physical (electrical) connection what so ever. The only connection between the output of the HC595' and the relays is optical through the optocouplers (small 4 pin black devices on the relay boards).
btw, do you have the "optional" 0.1uF capacitor connected as described in the Wiki. That capacitor is in fact mandatory and not optional.