Relay Board for 24VDC Solenoids

[Nick0341]

Jon

My apologies, probably a difficult project to use as my first one. Let me see if I can walk you through the grounding.

I have a three prong 120VAC plug to supply power to the control panel. One of the lines in a ground. My PS is a DIN rail mounted PS so there is no screw terminal for ground, but I assume the ground is to the railing. I have everything grounded to the ground wire on the plug coming in.

One thing I noticed is that when I turn off the switch, the green power light on the PS takes a while to turn off. I'm thinking it could be a grounding issue. Should I disconnect the ground wire to the back plate?


Thanks

[JonW]

You say your PS is a DIN rail mounted one and that there is no screw terminal for ground, but the negative terminal on the PS is the ground!

A wiring diagram or pictures showing how you have things connected would help as I think there are things getting lost in translation.

VCC on relay board to 24VDC positive.
GND on relay board to 24VDC negative/ground.
GND on relay board to BCS negative/ground.
IN-1 on relay board to a BCS output (or 5V+ for testing)
GND on BCS tied to earth ground.

[Nick0341]

Thanks Jon

I'll try to sketch something out in a bit. For the PS, I have a negative wired to the solenoid valves, is that not correct or does it just need the positive?

I have two positive and two negative/ground coming out of the PS. Assuming the solenoids need both +/-, can I just ground the second negative/ground to ground. I've also grounded everything to the back plate (panel) and the ground coming from the plug to the same terminal for earth ground.

[Nick0341]

Wiring Diagram Attached

[JonW]

It still appears that you've not attached the BCS ground/negative to the relay board ground and to earth ground.

[Nick0341]

Is the ground coming in on the AC plug not an earth ground?

[JonW]

Yes.

[Nick0341]

Jon

The internal AC plug that I plug the BCS into is grounded to the panel that is grounded to the AC plug coming in. I assume that is good. Do I need to ground one of the BCS grrounds to the panel as well?

I just wanted to be clear that you stated the AC plug's ground coming in is the earth ground.

If so, looks like I need to ground the DC power supply and I'm good.

[JonW]

Please make the connections that I previously listed:
VCC on relay board to 24VDC positive.
GND on relay board to 24VDC negative/ground.
GND on relay board to BCS negative/ground.
IN-1 on relay board to a BCS output (or 5V+ for testing)
GND on BCS tied to earth ground.


I feel you don't have a clear grasp of AC vs DC power and wiring. Plugging the BCS power supply into an outlet does not "ground" it. Yes, the incoming AC ground wire gets connected to the chassis and that is an "earth ground".

You need to tie the DC negative outputs together which can be done by the two connections I listed going from the BCS negative (GND) to the relay board GND and the 24VDC power supply negative output also to the relay board GND. Additionally, while not required, I would add a jumper between the BCS GND and the earth ground. This is useful for smoothing the temp probes since everything will be tied to the same ground reference.

[Nick0341]

Thanks Jon!

That totally works! To say that I don't have a firm understanding of DC vs AC power would be a major understatement. Thank you very much for your help on this. I tested on the 5V test as well as the solenoid and it's all good.

This is something I am learning and would really like to learn more. Can you refer me to any references/books that would be able to help?

Thanks a ton!