Heating valve control

Other Hardware Home Automation
1

Hello

I’m working in a small project that consist in using the PID climate in ESPHome to control a heating valve.

My project is the following:

  • my valve (Frese 48-5529) is power with 24 VAC – I’m using a modular 24 VAC 8 VA transformer to power the valve
  • the control signal to the valve is 0-10 VDC – I’m using the DAC output from my ESP32 and an Operational Amplifier TLV2371 to do the control
  • the Operational Amplifier TLV2371 is power through an LM7812 regulator module (like this) – the LM7812 is power by the modular 24VAC 8 VA transformer the same that I use to power the valve
  • The ESP32 is power through an LM7805 regulator modulo (like this) – the LM7805 is power by the LM7812 module

I’m having difficulties about the following: to control properly the stroke of the valve my 0-10 VDC signal must have the same GND of the power supply of the valve (24 VAC). My Question is it’s possible to connect the GND from the 24 VAC transformer to the 12 V DC GND? Which terminal should I use?

Valve connections:
image

Example of the connections between the transformer 24 VAC and the module 7812:

image
image867×313 36.4 KB

Thanks a lot for the help!
André

2

Use a relay between esp and the valve

I won't recommend you to connect both ground.

A relay will be best for your project as it separate your esp from the High voltage.

3

There isn't enough information to answer your question. First understand that 'ground' is a point in the circuit designated by the designer. Ground is not synonymous with negative. The lower circuit you show does not have a ground because you have not specified one. If a part of the circuit is connected to the case or chassis or other metalwork, or to safety earth, or the actual earth (the muddy stuff outside), then that part of the circuit will be ground.

In the top circuit you have designated a ground but the circuit is incomplete, is it just a designation that could be changed or is it connected to earth or metalwork?

Provide the above information and it should be possible to answer. Really what is missing is knowing the overall context of what else is connected to both circuits and what, if anything, makes a particular point in each circuit, ground.

1 Like
4

Maybe you have solved already, I saw this because looking for ESPHOME applications.

If you have a transformer as in scematics there is no galvanic connection to ground. If you have isolated powersupply to ESP there is no galvanic connection to ground. The ground will be floating so it should work with no groundcurrent. I think you should have one point somewhere to ground (maybe already in the valve)

Do you use an OP amp to multiply output from ESP 0-5V to 0-10V ? Just curious

5

Clarification Groundcurrents creates problem must avoid. There will be voltagedrop over groundcables disturbing control signals. Not good. Also the AC 24V must have no galvanic connection betewen primary and secondary coils.

6

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