Now that I think about it maybe a ptc fuse could fit the bill.

 

Dissipating heat is not a real problem in this particular case. The valve will be activated only about once or twice a day, and the duration of the activation pulse is in the range of 150 to 200 ms, so not enough heat will accumulate for it to become a menace.

I've just looked up the ptc fuse you've suggested, it's a very interesting alternative of which I was unaware of. I'm going to give it some consideration.

Many thanks!

 

As for "keep your face out of circuits when powering",
as things like that sometimes happen with some delay, and it's hard to keep the face away when inspecting stuff:

A pair of ballistic glasses is what I use And I'm not kidding. I also tend to use them when soldering, to not get biting fumes or little flying balls of flux and stuff into the eyes - but holding a slipping away soldering iron at bay for at least a short impact is also not something I'd complain about.

 

From your data sheet. Gate-Source maximum is +/-8v and Drain-Source is 12V. You are running the circuits from a 16V volt supply. I would use a larger margin of safety and choose a FET that has the maximums significantly above 16V.

 

From your data sheet. Gate-Source maximum is +/-8v and Drain-Source is 12V. You are running the circuits from a 16V volt supply. I would use a larger margin of safety and choose a FET that has the maximums significantly above 16V.

Good catch, thanks for that. I actually built the original circuit using DMG2302U-7 nFets on the bridge's low side, which have a 20V rating drain to source. Somehow I forgot to update that detail in my sim.

 

Need to check the back of my shed for that last one ... maybe I'll find an Apollo 11 surplus space suit that I could use.

I actually worked with an engineer that would lift the soldering iron to his nose and sniff it to see if it was hot. Saw him with a blister on his nose once or twice.

 

I actually worked with an engineer that would lift the soldering iron to his nose and sniff it to see if it was hot. Saw him with a blister on his nose once or twice.

... well, I guess that's fine as long as he never used someone else's nose for that ...

 

For the record. I decided to build the circuit in post #26. Maybe later on I'll build the super-simplified version of it, but right now I have to make sure I'm on the safe side of things.

The circuit is working as expected, and the transistors are not even warming up at all.