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:

Example of the connections between the transformer 24 VAC and the module 7812 (I'm not sure that the LM7812 that I use have this exact configuration but should be similar, is just to better understand):



Thanks a lot for the help!
André

 

You can if you remove the bridge and use a single diode half wave rectifier.

 

You can if you remove the bridge and use a single diode half wave rectifier.
View attachment 286033

Hello sghioto

Thanks a lot for your help. It's not easy to replace the bridge by a single diode because, my LM7812 is a complete module ( like this). I would need to replace all the components, but if it's the only solution I will need to go by that way. It's ok to power my ESP32 and Ampop TLV2371 with just a single diode half wave rectifier?

Thanks

 

That looks easy enough to modify IMHO. Can the valve run on 24 volts DC?

 

That looks easy enough to modify IMHO. Can the valve run on 24 volts DC?

I do not think so. Mine is 48-5529 not 48-5529-1:

Do you think I can test to power the valve with 24 V DC? Or it can destroy the actuator?


Regarding the single diode, just to test it's possible to do somethin like this?

 

What is the point of the D3 FW bridge?
You cannot use DC for an AC solenoid, much too low a resistance.

 

I do not think so. Mine is 48-5529 not 48-5529-1:

Do you think I can test to power the valve with 24 V DC? Or it can destroy the actuator?
View attachment 286038

Regarding the single diode, just to test it's possible to do somethin like this?
View attachment 286039

That will work to test.

 

What is the point of the D3 FW bridge?

12 volt supply for the op amp circuit

 

What is the point of the D3 FW bridge?
You cannot use DC for an AC solenoid, much too low a resistance.

Thanks Max, I won't test with DC in AC solenoid
I think the point of D3 FW bridge is to rectify the 24 VAC to a full-wave but I'm now a specialist in electronics. I didn't know that a half-wave rectification could work like sghioto told.
Where is a picture of the board LM7812 that I have:

 

12 volt supply for the op amp circuit

YEs, correct. I need 12 VDC to power the OpAmp and 5 VDC to power the ESP32

 

Thanks Max, I won't test with DC in AC solenoid
I think the point of D3 FW bridge is to rectify the 24 VAC to a full-wave but I'm now a specialist in electronics. I didn't know that a half-wave rectification could work like sghioto told.

1/ You have one leg of the bridge unconnected, essentially doing nothing, the single diode is just going to make it Half wave rectification.

 

1/ You have one leg of the bridge unconnected, essentially doing nothing, the single diode is just going to make it Half wave rectification.

Sorry, o didn’t understand you well. Your suggestion is to connect just one leg of the bridge to the 24 VAC transformer and the other one to the GND in output?

 

Remove D3 and connect directly to the top of the bridge

 

Understood!
Thanks a lot for the help