Question for the Home Builders out there…….

[Andy_Corkill]

Hi

I intend to put an Electronic O2 injection system onto my KISS. I’m looking at my solenoid. This solenoid will be in a canister mounted at the bottom of my unit. I don’t think I can rely on being able to hear when it’s firing. So I want something to indicate when the solenoid is open. An LED in my HUD to tell me when the solenoid is open is what I want.

This needs to be controlled independently from the power supply to fire the solenoid, as I need to cater for when the solenoid fails open.

Yes I should be monitoring my PPO2 carefully, but want to be able to identify a soleniod failure very quickly. I think this may help.

Has anyone fitted a sensor to their O2 injection system to monitor if the solenoid is firing or not ?

Any ideas

Thanks Guys

Andy

[beanie]

would you not need to measure the gas flow from it to know that?

[Andy_Corkill]

Hi Beanie

Yes thats what I'm after, a sensor which would be activated when a gas flow occurs. Don't really need a gas flow measurement as such, I just need to know if it's flowing or not.

Andy

[Mdemon]

A baffle over the solenoid would do it - with a v. small magnet. You can get DIL-packed hall effect monitors (if I got the words right) that will register when the magnet moves. Or mount a reed switch on the baffle and a magnet on the closed position - test for an open circuit.

Or some other method of measuring gas flow?

This is all guesses on my part though. I wanted the same thing and decided that I wanted to measure an actual gas response, not the current going to a possibly-seized solenoid.

[nigelH]

Originally Posted by Mdemon

A baffle over the solenoid would do it - with a v. small magnet. You can get DIL-packed hall effect monitors.

Problem.
The flow is small and you are working in a condensing humidity environment. A simple flapper vane with a magnet on it is going to rock and roll with every movement and then get all wet and stop. I wouldn't like to promise it would work all dive let alone all week.

My first guess as the instrumentation man would be to use the cooling effect of dropping from IP to ambient and put a little bead thermistor in the gas path.
Audio would be another way, a tiny mike just next to it but they don't like the damp and if they are sealed they don't like the pressure.

My HUD is still stalled under lots of work...

nigelH
Combro: Instruments 'r us 8-)

[Brian Garner]

How about an O2 cell facing the injection point. It should spike every time O2 is introduced in to the loop.

Brian Garner

[beanie]

Originally Posted by nigelH

My first guess as the instrumentation man would be to use the cooling effect of dropping from IP to ambient and put a little bead thermistor in the gas path.

I like this as an idea anybody got any idea what kind of temperature change you get, and what sort of response time you can get out of a thermister?

Originally Posted by Brian Garner

How about an O2 cell facing the injection point. It should spike every time O2 is introduced in to the loop.

hmm pricey though and prone to failure oh and a little large really.

[Brian Garner]

Originally Posted by Brian Garner


How about an O2 cell facing the injection point. It should spike every time O2 is introduced in to the loop.


hmm pricey though and prone to failure oh and a little large really.


I agree but I was considering ways that do not use any moving parts. It would mean that you always had a cell handy if one of the main ones went funny. I do think the temperature idea is beat and I would have suggested it but Nigel beat me to it by seconds.

Brian

[beanie]

Originally Posted by Brian Garner

I agree but I was considering ways that do not use any moving parts. It would mean that you always had a cell handy if one of the main ones went funny.

Sorry to piss on your fire but the cell would decay rapidly if your squirting O2 at it , well more rapidly than your normal cells anyway.

the thermister wouldn't need any moving parts either, so if the temperature change is detectable on the thermister its the way forward.

might just have to look into this myself another beepy thing

[Brian Garner]

Do you really need a sensor at all? If you measured the average po2 over a few seconds ( this will remove any fluctuations caused by a hot area going round the loop) Then compared this with the value after the O2 injection, again averaged over time, there should be a PO2 change. If this is not detected then bleep away. Should be easy to do in software and have no extra parts.

Brian