Dummy question: non-zero voltage between off OUTPUT pin and GND?

[ocramius]

I'm currently toying around with the T16M before putting it into a wall and calling my project "working".

While experimenting, I started messing around with measurements ( hence my questions on https://www.kincony.com/forum/showthread.php?tid=7423 ).

I've wired my board similar to what I've found in these posts:

* https://www.kincony.com/forum/showthread.php?tid=7211
* https://www.kincony.com/forum/showthread.php?tid=2221 (this schematic is really clear, by the way, thank you!)

While testing out the board, I noticed that the voltage between `V-` and a disabled `V+` pin (see picture below) is **non-zero** (measures 2.385V).

I'm wondering if something is wrong with the board, or if the ESPHome settings don't completely disable the pin?
It may also be a misunderstanding of mine in how MOSFET-based switching works, so feel free to also tell me that my use-case is wrong



https://snipfly.io/pEQGS2V.png

[admin]

you should connect with a load to test. such as a DC24V relay or contactor.

[ocramius]

In my case, I'm waiting for some 24V electronic valves: will report back once they're here once I have them :-)

[admin]

ok

[twostar]

I ran into something similar recently while helping a friend set up a KC868v3, with one of the outputs connected to an LED and dropper resistor and the output set to off there was around 7.5V on the output and the output LED was lit even though it was set to off.

Looking at the circuit diagram, the p-channel MOSFET switches the voltage from LO0/LO1 onto the output Y1, Y2, etc, and also onto the output LED via a dropper resistor.  If the output already has a voltage on it, in this case via another LED and a dropper resistor, it'll light the output LED even with the output off.

I don't know exactly what the setup was with the external LEDs so I'm reverse-engineering things based on the observed behaviour.

[admin]

here is T16M mosfet output circuit.
   

[ocramius]

I've just tried attaching a load to the circuit (a small 24V light), connecting `-` (negative), `DC` (positive) and the light OUTPUT01.

The light goes correctly on/off in my case, but I noticed:

* when any of OUTPUT01~OUTPUT08 are enabled, all other non-enabled OUTPUT01~OUTPUT08 pins jump to 2.5V between `-` (negative) and the pin.
* same applies to OUTPUT09~OUTPUT16
* any pins attached to the load stay at around 0.5V between `-` (negative) and the pin
* the other pins stay at ~3.65V between `-` (negative) an the pin, when the pin with an attached load is disabled

In my case, this is mostly OK: I'm just worried about the amount of power that gets consumed passively this way, for a device that will sit in a rack, on 24/7...

EDIT: I'd love to help with the circuit schematic above, but I don't have the experience/knowledge for that, sorry :-\

[twostar]

What happens if you try this with 12V input instead of 24V?  The reason I ask is that the HSS4P06 is specced for a max gate-source voltage (V/GS) of 20V while in this case it could be 24V (depending on what effect the 5.1K pullup has).

[ocramius]

Unfortunately, I don't seem to have a 12V power supply sitting around ^^

Will certainly report if I can find one.