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Super simple low cost ZERO SOFTWARE ventilator controller
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MisterDiodes:
I thought I'd post a fun circuit for people to play with - it was inspired by the University of Florida Open Source Emergency Ventilator project.  But really it's just an adaptation of a handy 555-driven low power timer pulser circuit for AC or DC loads.

This could be used on other sorts of emergency ventilator designs - could be a piston-actuateg bag squeezer, peristaltic pumper, blower or some other breathing aid device.  Could also be a roadside light flasher, Halloween decoration, or whatever you want.

This is only meant to be an example schematic and learning tool- users can develop their own modifications and Bill of Materials to suit whatever parts are available and whatever need they have. 

Sometimes in this age of cell phone apps people forget how simple a timer circuit can be...

I'm not against using CPU's and MCU's in all sorts of systems - I make my living doing that at all levels.  BUT SOMETIMES software just isn't required - and in the case of a product that needs emergency FDA clearance for cybersecurity, it's really handy to kick out an old school quickie 555 circuit.  Just eliminate the software hacking problem altogether.  Don't even need a PC board made either. 

I know some readers might not be completely familiar with 555 timer circuits, or how to adjust the duty cycle of a timer with a simple comparator, or how to easily control a low power AC load with a small SSR chip.  Here you go...  Here's a super simple, super reliable and inexpensive way to help save someone's life - or make a cool gadget for a science fair or Halloween prop.

Link to a Google drive with example open source schematic, complete circuit description, oscilloscope shots taken during testing and an exciting demo movie.

https://drive.google.com/drive/folders/1wJ81SEzPLlEspD-UX3PU1LFRpdiZRutf?usp=sharing

Link to Open Source Ventilator project:
https://simulation.health.ufl.edu/technology-development/open-source-ventilator-project/

AGAIN:  This is only an example that was built and validated based on parts we had in stock, and looking around at parts distributors to see what was in plentiful supply that's inexpensive.  There are a million ways to do this circuit; this is ONLY an example.

Another note:  Already I've been asked "Why not use a zero-crossing TRIAC chip to control the AC coil"?  Because this circuit is designed to drive low power AC loads at 24VAC - namely a low power sprinkler valve with AC control coil.  The zero crosser won't even work correctly at low AC voltages, and it's really not desired anyway for this use.

Have fun!
drussell:
timer ≠ ventilator controller
MisterDiodes:

--- Quote from: drussell on April 14, 2020, 12:27:57 am ---timer ≠ ventilator controller

--- End quote ---

Please see the University of Florida project.  It's an EMERGENCY ventilator design.  Nobody (even project managers) claimed its a good device, it's just something that can be cobbled together if required without waiting months for manufacturers to catch up.  It just needs the valve to operated in a timed fashion - as are just about all of the open source emergency designs.

If you're drowning and have a chance to be attached to a real ventilator, use that.  If it comes down to a last ditch effort to keep you breathing with a sprinkler valve, some PVC parts and a good luck 555 timer - well that's where this circuit comes in.  Maybe this is all that's available to someone in certain parts of the world.
doktor pyta:
Welcome back MisterDiodes !
Edwin G. Pettis:

--- Quote from: drussell on April 14, 2020, 12:27:57 am ---timer ≠ ventilator controller

--- End quote ---

If you had taken the time to actually read and understand the project first before commenting, you would have seen that it actually works, it's simple and reliable and would work in a pinch until the real thing was available, that is all it is.  A ventilator doesn't have to have a CPU and a hundred bells and whistles to work, check out the older models that didn't have CPUs or even electronics, just a mechanical machine to do the work and that likely wasn't as reliable as this circuit and cost a lot more.....so where's the beef?
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