Electronics > Beginners
How would you make a heart rate simulator that would plug into an oscilloscope?
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janoc:
Probably a phone with a pre-recorded audio file and connected to the scope using the headphone jack would be the simplest and fastest way to do it (tape recorder in the past but these days people are more likely to have a phone than a working tape deck!).
trophosphere:
Here you go: Frank's ECG Simulator
IanB:

--- Quote from: Beamin on March 09, 2019, 09:12:23 pm ---The purpose isn't to make it look real it's to learn how to manipulate voltages and slow oscillators built from very simple parts with the most complex being a 555. The cam/light idea sounds novel but I'm more into electronics then mechanical bits.  It will also give me practice with my scope as I never did get to play with it much since I bought it. Plus it has the occasional dreaded fan noise that goes on and off since its an older Tek, usually a light tap or angle adjust makes it go away.

What kind of LC circuits? uf sized Electrolytic caps and hand wound toroid style inductors? Would one 555 control a group each of which makes one part of the trace? Or would it be better to cascade them? I really don't know where to start.

--- End quote ---

The way I would approach it would be to build an analog model of the system. The way the heart works is fairly well documented. There is a pacemaker that sets out the basic rhythm like a metronome. Signals propagate out from the pacemaker and trigger other events in a cascade that generates the various parts of the waveform (P, Q, R, S, T). Roughly speaking, the triggered events are things which charge up slowly and discharge rapidly when triggered. These could be modeled perhaps with capacitors that have charging and discharging circuits. The various parts are all superimposed to produce the final waveform.
Beamin:

--- Quote from: trophosphere on March 09, 2019, 11:19:08 pm ---Here you go: Frank's ECG Simulator

--- End quote ---


That's exactly what I was looking for. I didn't think the IC could have powered those caps but I always think you need to add transistors for amplification. If you wanted LEDs to go off with each pulse then the IC would need amplification at each "step" of the wave? How many mA can an IC put out and do you need to current limit it like an LED? IF you did this with 555 timers would you need to cascade them?
Rick Law:
If the output is all that is important, this looks like an easy job for an Arduino to handle.

One may need a capacitor to smooth the rise/fall, besides that, how the "patient is doing" can easily be programmed in your Arduino - you can make your custom "death scenario" : from a very excited state, to erratic movement, to flat line, then come back with a few random beats, then flat line again... then ... RIP!

I like a random single/double/triple beats after a random 10's of second pause, you know, to keep the relatives hopeful, then quiet...  Just as they begin to count their inheritance, it beats normal again.  Grandpa is back...  You'll have to wait a bit longer for your Gran Torino after all.
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