| Electronics > Beginners |
| How would you make a heart rate simulator that would plug into an oscilloscope? |
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| Beamin:
I was watching a old TV show where a person was in the hospital or something and the heart rate monitor was just an analog scope. But they did go through the trouble to make the trace look real. How could you build that using analog parts? You want a flat line to peak up, go down, go up a little bit and ring, then go flat for a second before repeating. The whole thing could be a ring if you could control the signal enough. I'm guessing you would have a signal that only goes to 0V at the very bottom. The flat line part of the "heart beat" would be at say 2V on a scale of 0-5 volts. Of course adjusting the scale of the scope is the easy part. Could you do this using a 555 timer, some caps, and some coils to make it ring? Or would this be way too complex and finicky using analog circuits? Beep Beep Beep BEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEP Time of death is thirteen forty eight hours. |
| Doctorandus_P:
You can have one 555 oscillate at the heart rate, and then a handfull of 555's cascaded, which trigger each otther. Then each 555 can have some resistors / capacitors / diodes to generate a flank that is one part of the ECG. https://en.wikipedia.org/wiki/Electrocardiography You can probably substitute the cascaded 555's for a single 4017, but with 555's you have independent control of each timing period. Either way ti will take some fiddling to get it to work. You can also simply buy a ECG simulator, including buttons for simulating a bunch of different heart conditions. Or: For something that somwhat resemles a heart rate on a scope you can hack something together, but for more accurate signal a uC with DAC becomes attractive rapidly. (Or use an AWG.). |
| Zenith:
No doubt it could be done with a 555 timer or two and a few extra bits and pieces. It could also be done with an arbitrary function generator, or several function generators with something to control them, which could be a load of TTL . All this has been around since at least the 70s. There were audio synthesizers in the 60s which I'm sure could have done it. The easiest way to do it for a prop in an old TV show, would have been tape record an hour or so of someone connected to a heart monitor. That would be doing it with analogue parts. |
| rstofer:
Some Arbitrary Function Generators, like the Siglent SDG2082X (and similar models), have this waveform built in. In fact, it has 15 ECG waveforms, plus 9 others. |
| nali:
Depends how old the show was, but as Zenith says above probably just recorded. ECG/EKG recorders have been about for quite a while - I was working on some about 30 years ago which used a slowed-down audio cassette tape in a portable recorder. https://en.wikipedia.org/wiki/Holter_monitor |
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