Unexpected results using dual power adapters, diodes and relays

Thread Starter

eSk8orDIE.Net

Joined Mar 16, 2023
3
So I have a couple water level sensors(4 wire, vcc, signal(vcc clone), ground, mode(NO/NC) , a 10w water pump and a couple 12v SPST relays powered by 2 seperate power adapters (12v 5A and 12v 1.5A)

The way I have them hooked up is so that the low level sensor is always on and plugged in. If water gets low, it triggers and fills to the minimum line.

The upper sensor is on a timer and cycles on 2min every 3hrs. This one fills the container full or as much as it can in 2min. Then all power is cut from the circuit and relay.

The manufacturer had me put a diode (1N4001) between the relay trigger wires in case of a short on each relay seperately.

The issues I've had are that I figured like many circuits I've worked on, a common ground is fine. So I hooked up the power adapters and relays ground all together to the water pump.

Then I proceeded to make sure the relays input were attached to each adapter seperately and the signal wires were also seperately attached.

The output wires of the relays were joined and sent to the water pump since they would likely join anyway and only one sensor would trigger regardless and it was rare that both sensors would trigger at once unless the tank was both empty and scheduled on time overlapped... At which point I assume nothing but the pump would be activated and 12v and 7A available for use (which it would still only use 0.8A)

The first issue I got was that sometimes one of the relays saw something like 36v while one sensor and adapter was off. So I isolated the relay output on some diodes (1N5822) and it worked for a while.

Then suddenly the bottom sensor stopped working(vcc only received a few mV when powered on like something is causing a short) ... This is where I am now. With one adapter off (upper) the bottom sensor doesn't get power from its own adapter... I'm not sure why...

I'm thinking of maybe adding diodes to the grounds and also isolating them but at this point it's a shot in the dark. I'd like to know why I keep getting issues that come up a few days later...

I have a few snap connectors where I can join leads together for testing.. But I've never heard of a circuit being so finicky over having common ground...

I now suspect the signal wire is Not actually a signal wire but a bridge between vcc.... So this may be a culprit and it was somehow sending power backwards from the triggered relay back into the sensor via the signal or vcc wire when one activated... But with diodes this should help...

But is the relay diode somehow screwing things up?

Or what?

Thanks

This is all I got from the sensor manufacturer so I had to figure it out as they kept pushing use of a DPDT Relay but couldn't figure out why not just use a SPST.. But now I'm thinking ground is somehow screwing things up... 16790250047815032535444506916721.jpg
16790253828062803785923602701942.jpg

On my relays input is on the bottom red wires, right green wires are joined and ground, left wires are (yellow or blue) both "signals wires" (I should of made them both yellow in retrospect), upper wire is relay output to pump (red and white).

The ground splices are joining the common grounds to the adapter grounds and to the sensor grounds. Then the other larger splice adapters have 2 diodes in them to accept power to feed to the pump without reverse bias being an issue.
 

Thread Starter

eSk8orDIE.Net

Joined Mar 16, 2023
3
I just checked the diodes at the relay... One works fine. The other seems to amplify voltage!... What's that about? Is it because it's broken or due to being a rectifying diode or what?

Voltmeter test shows 0.6v and 0.0v, the other is 0.6v and 2.2v.. Instead of stopping power its amplifying it...
 

Thread Starter

eSk8orDIE.Net

Joined Mar 16, 2023
3
I unattached the diode from the circuit and it works fine... Is the voltage on the diode too low or is something else going on here?
 
Top