John Dent avatar image
John Dent asked

Programmable relay assistant driven by temperature sensor — what does "open/closed" mean?

I have a MultiPlus-II 5000 GX, which came with a two-wire temperature sensor.

I have no need of the sensor to monitor the battery since my battery has inbuilt monitoring (Pylontech US5000), so I've employed it to measure the temperature of the free air around the unit. This seems to work well. It shows up on VRM as "battery temperature" but the unit itself is quite aware that it should ignore the sensor input, and refer instead to the BMS-reported data.

I drive a second (external) fan using the programmable relay base on the Multiplus-II's fan state. This also works great.

I thought I'd extend it to turn on the fan in case the free air temperature rose. Hence exploring the programmable relay temperature sensor input.

When the assistant's "input signal (aux 1, aux 2 or temperature sensor input)" option is selected, it will later offer a panel titled "Drive based on input signal", with detail then when "Aux 1/Aux 2/Temperature sensor input" is "open/closed" for "(some number)" it will drive the relay.

Obviously I want "Temperature sensor input".

But what does "open/closed" mean in this context?

And what does the number mean?

I wonder if it is a mis-translation? Could the open/closed be intended to mean "above/below", and then the number would be the temperature in ºC? But that seems a bit of a leap in the dark.

Has anyone any experience or idea?

My other idea is to write a small Node-RED flow that monitors the temperature input, and drives the relay on the Smart Solar instead. Might switch over to that if I can't find out how the assistant works.

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kevgermany avatar image kevgermany ♦♦ commented ·

Open - relay passes no current

Closed - relay passes current

But in terms of sensor not clear. Perhaps @JohnC can help.

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JohnC avatar image
JohnC answered ·
I don't think Assistants can deal with Temperature. That port can be used in open/closed mode, like the Aux ports, but if used for Temp then that's it. Can be a global Temp (probably even with Pylons), so switching from it could conceivably be sourced via GX (etc), processed externally, and the result fed back to Assistants via an Aux port.
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John Dent avatar image John Dent commented ·
Oh, I see.

So in this mode, the assistant isn't actually intending the temperature sensor input to be connected to a temperature sensor.

Instead, it's seeing it just as a port that gets taken open or closed. And the port happens to be one that is normally used for the temperature sensor. But in this mode, of course, it cannot be connected direct.

OK. That's clear.

Slightly disappointing, but clear. Thanks.

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sharpener answered ·

AFAIR all 3 inputs - Aux 1, Aux 2, temp - are basically digital with 0 = <1V, 1 = >4V (there is an internal pullup resistor) and this is what the Assistants use.

The way to interface the temp sensor to do what you want would be with a simple external circuit using an op amp or just two transistors in a long-tailed pair configuration to compare the voltage across the temp sensor with an adjustable reference and use this to drive one of the three inputs.

I agree, it's a pity this functionality isn't built in, it wouldn't take very much to put an adjustable analogue threshold into the relay assistants. How about it @Matthias Lange - DE?

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