the symmetrical output is indeed a plus

Comparatively, since my 2*N output connector and decoupled channels allow connection with any polarity.

It almost seems like a job for a relay.

Sorry, I had to explain


2*8 terminals as inputs and 2*8 terminals as output. Quick enough to exclude relays, but must be ready to switch external relays.

Well, I lost some time to decide among MCUs, the cost of decision was about $0.80. And now I want to choose G3VM - it makes a $16 additional price per my 8 channels

 

See

 

Дякую!
Thanks, added to my library. It's a very good transistor.
It's a rare occasion to see such a characteristic: "Emitter-Collector Breakdown Voltage (Base Open)" Profound datasheet!
Still, 2 points are embarrassing.
1) In open state the residual voltage on a switch (Vce) is not a "Collector-Emitter Saturation Voltage" from a datasheet, but a sum of photo transistor Vce and switch's Vbe. It will be more than 1 V anyway. So the power dissipation is up to 0.5 W with my 400 mA max current.
From this point of view a "Collector-Emitter Saturation Voltage" is not a vital in such "Darlington" configuration.
It is a new info that this thread (and #12) has brought.

2) I believe that ZXTN07045EFF can dissipate 1.5 W. But I think the printed board will be very hot. It darkens with time under such conditions and I don't know what else happens - and the reliability may degrade. That was a reason to me to open this issue.

I began to draw a board. If anybody cares, I can show the result here.

 

Make sure to design your board to help the transistor dissipate the power.
Lot's of copper leading the heat away- this will make a big difference in the temperature of the transistor.

 

See

 

Make sure to design your board to help the transistor dissipate the power

I've chosen mosfet opto couplers.
Here is almost complete schematics (w.o MCU programming terminals)

 

And like this:

 

That is exactly what #12 proposed, with MOSFET switch transistor. And it is very good.
But I want a module that behaves as if it has relay outputs. No place to any additional power source. Look at my module - just 2 terminals for a channel.
BTW, what do 70 and 28 mW mean? Why there are 2 values?

 

Voltage=70.56mV and Power=28 mW.
The winding of the relay have shunted diode? If so, then everything is in order.
Model for optomos CPC1018N-R05.
VCC is a 5V microcontroller power supply. A V2 - output of the controller.

 

Voltage=70.56mV and Power=28 mW.
Model for optomos CPC1018N-R05.

Thanks, bro! Your opto is better than my OMRON one