Hey All- I figure this would be a great place to get some much needed advice. Basically I need to create a remote controlled pulse. Ive done a bit of research and I think I could make it work with a coin shaftless vibration motor, a transistor, battery source and bluetooth module. But I need a little help with the coding, AND how to set it up fully to do what I want.
What I need to be able to do is simulate a human pulse in a dummy that I could change via remote control or bluetooth app (ideally an app so I could add other controls in the same program). It needs to be battery operated and it needs to be affordable.
I think I would need to have PWM in order to create the variable heartbeat rate, of x pulses per minute. Since Im new to all of this, all of the individual components make sense, but when you start adding it all together I get a bit confused.
A pulse is typically 60-120 bpm, so 1-2 Hz. So you need to produce some kind of "pulse" 1-2 times a second. So I figure you want to run this vibration motor to produce this pulse? Did you try this already? I doubt it stops spinning (and vibrating) fast enough to be a pulse.
Actually I'd be thinking of doing it a little more lifelike. Use a flexible tube, fill it with water, close on one end, a bit larger bladder on the other end, and have a solenoid produce an actual pulse by pushing down that bladder creating pressure in the tube. The expanding tube should feel very much like a human pulse, which if felt at the wrist or neck is just that: a tube (blood vessel) expanding due to water (blood) pressure suddenly increasing.
PWM doesn't make much sense here.
All you need to tell your Arduino is to operate that motor or solenoid for a certain time (10-100 ms or so) at your desired frequency (every 500-1000 ms for 1-2 Hz). Sending a new heart rate over Bluetooth is easy, the hard part there probably lies with programming the sender side (mobile phone?).
Just about anything can be battery operated - you may have noticed battery operated cars on the road nowadays, so no problem there. Just make sure your battery is big enough to last long enough for the intended use.
"Affordable" is a completely meaningless word without budget. What is affordable to me may not be affordable to you. An amount of $5 is a huge amount for some, $5000 is just pocket change to others.
We’ve tried the tube + fluid combination and unfortunately it’s not strong enough to be felt. (This is going in a medical mannequin) I haven’t tried the setup yet, mostly I’ve been trying to figure it out in my head before buying components, but maybe i just need to jump in and see what i can put together. As for cost- as cheap as possible and must be under $25. We even considered using a hydrolic micromotor, but haven’t found anything small enough.
Look for a pager motor. One very small example. There are bigger ones, or use a few in parallel.
I am pretty sure that at least some types could be pulsed at 2 Hz (2 x per second), but you will probably need to use a motor driver with a brake function to stop the motor quickly, e.g. this one or this one (for two motors).
It’s less about the haptic feel of the pulse and more about trainees being able to feel and recognize tachycardia vs bradycardia (60bpm vs 120). The vibration motors seemed the be the easiest cheapest, quietest solution and seemed like it may be straight forward to program into an app (similar to what the new pulse metronomes are doing).
I thought about a servo, but I worried that the additional pressure against it as someone felt it would burn the motor out.
If the little extra pressure of someone feeling burns out a servo it would burn out without that extra pressure just fine. Solution: get a halfway decent or better servo.
Quite sure a solenoid is cheaper than a servo, by the way. If only for the simpler construction. In any case you have to buy a bunch of parts and start experimenting.
I would bite the financial bullet, go buy a motor, a transistor, a diode and a couple of resistors, and hook it up like this to a power supply of suitable voltage. (If you need 12V, hook it up to the car....)
To start with, simply use Blink to pulse it on and off, fiddling with the two delay()s in there for the timings.
If as you say you don't want it to feel like a real pulse, you'll know soon enough if you're anywhere near close enough to what you are looking for, with very small financial and almost nil intellectual investment.