Correct but the opto in the relay module is not isolated. It's referenced to the negative supply.

So? Does that make my statement incorrect somehow?

 

So? Does that make my statement incorrect somehow?

It does in reference to working in the circuit as shown in post 36.
However this circuit might work if the sounder is configured as shown.
Several more voltage measurements from the TS will confirm and may provide other options.

 

It does in reference to working in the circuit as shown in post 36.
However this circuit might work if the sounder is configured as shown.
Several more voltage measurements from the TS will confirm and may provide other options.

View attachment 299713

Thank you, I can see how this will trigger the relay but I have an observation. The positive to the sounder also comes from the driver circuit and I expected to use this positive side to the IN.

 

View attachment 299712

I feel this is exactly the circuit required, I see the LTV814 has a diode with the LED which I assume does the rectifying. I’m buying a LTV814 now.
Thank you.
Peter

 

I feel this is exactly the circuit required, I see the LTV814 has a diode with the LED which I assume does the rectifying. I’m buying a LTV814 now.
Thank you.
Peter

Question, what is the requirement for the1N4001 diode on the positive to power the relay?
Peter

 

You may not need the PC814 if you can get me a few voltage measurements.
Diode is to drop the voltage to appx 5.3 volts for the relay module.

 

You may not need the PC814 if you can get me a few voltage measurements.
Diode is to drop the voltage to appx 5.3 volts for the relay module.

I’ve bought the PC814 as I do like the way it isolates the relay on both the + and - sides. I will try the relay supply from the batteries (6v) which may be lower with the circuit and sounder drain once triggered. If I can, I have a PC oscilloscope on an old notebook which I’ll connect up and get some data and the wave, I’d like to use it after a very long time.

 

I’ve bought the PC814 as I do like the way it isolates the relay on both the + and - sides. I will try the relay supply from the batteries (6v) which may be lower with the circuit and sounder drain once triggered. If I can, I have a PC oscilloscope on an old notebook which I’ll connect up and get some data and the wave, I’d like to use it after a very long time.

Well I’ve managed to get something, not sure what it’s saying but here’s a screenshot from my notebooks oscilloscope. Hope it gives you some information.

 

Is that the waveform across the sounder?

 

I do not know why it says, "3890V". It might actually be 3.89V peak at a few mA.
Do you want the relay to turn on and off at its frequency?

 

Is that the waveform across the sounder?

Yes, across with the sounder sounding

 

I do not know why it says, "3890V". It might actually be 3.89V peak at a few mA.
Do you want the relay to turn on and off at its frequency?

No, I want the relay on solidly whenever the sounder is active.

 

How were you measuring the voltage across the sounder when you read 29 volts?

 

I’ve bought a smart meter and now have these readings with the sounder disconnected:

 

I do not know why it says, "3890V". It might actually be 3.89V peak at a few mA.
Do you want the relay to turn on and off at its frequency?

The scope is set (incorrectly) for X1000 probe?

 

I’ve bought a smart meter and now have these readings with the sounder disconnected:

Are you planning on disconnecting the internal sounder?

 

I have a bad feeling about this. Driving and LED or opto coupler is likely to have a large effect on the transducer. I suspect we are going to need amplification.

 

Are you planning on disconnecting the internal sounder?

No, I want that sounding

 

For a test place a 10K resistor across the sounder and measure the voltage when activated. Want to see if that loads the sounder too much.

 

For a test place a 10K resistor across the sounder and measure the voltage when activated. Want to see if that loads the sounder too much.

As I have already bought the optocoupler I’m going to wait until it arrives and see if it works. I think I’ll try your circuit as in post 36 unless you have any modifications.
Thank you for your help and time.
Peter