So ! it's done now ?

 

Yes, it is done and working on the breadboard. Just got the tiny solderable breadboards today to transfer the circuit to something a little more secure.

Thanks a bunch to everyone, and big kudos to Ron H for the diagram we worked with.

 

Yes, it is done and working on the breadboard. Just got the tiny solderable breadboards today to transfer the circuit to something a little more secure.

Thanks a bunch to everyone, and big kudos to Ron H for the diagram we worked with.

I'm glad it worked for you. It was cookbook. Someone just needed to post it for you.

 

So, I just received some new IV pumps to get ready as props with an apparent software revision that is causing a problem if anyone can help.

The error I am getting is:

"During power-up the A/D converter expects audio transducer input voltage to be >0.2VDC during audio activity. If not, blah blah blah"

If I power up the unit with the stock Piezo (same make and model as the original pump) give it a moment and then hot swap for my circuit it works fine. So It is definitely something not allowing enough voltage through at startup. Any thoughts ?

I've re-attached the circuit diagram for reference.

 

It sounds like you just need more amplitude. Have you measured it, both stock and modfied? Can you post a schematic showing how the modification is connected to the existing circuit and that excludes any original components that have been removed or are disconnected?

 

So, I just received some new IV pumps to get ready as props with an apparent software revision that is causing a problem if anyone can help.

The error I am getting is:

"During power-up the A/D converter expects audio transducer input voltage to be >0.2VDC during audio activity. If not, blah blah blah"

If I power up the unit with the stock Piezo (same make and model as the original pump) give it a moment and then hot swap for my circuit it works fine. So It is definitely something not allowing enough voltage through at startup. Any thoughts ?

I've re-attached the circuit diagram for reference.

I would lift the left end of C14(?) and connect the output of the 555 to that end of the capacitor. Is this what you have done?

 

All I had to do with the original was replace the existing piezo with my circuit to the existing connector. I did not have to modify the existing circuitry of the device at all.

For now I have just added a DPDT ON-ON Toggle into the mix so I can switch between the piezo and my circuit. I start it up with the piezo, and once it has done it's startup I switch it over to the bypass. Seems stable enough. Was hoping to find something a little more elegant and "dummy proof" for the boys out on the film set.