I bought an exercise bike a while back. It had a pulse meter which clipped onto your finger. The bike sucked and the heart monitor was inaccurate. I bought a new bike and it’s awesome. It didn’t come with a pulse meter, but it has a jack for one which fits the one from my old bike - still inaccurate though.
So that’s how it stood until a buddy upgraded his super duper heart monitor watch thingy. His is all fancy and stuff, connecting to the computer and what not. His old one is so old you can’t even buy batteries for it. So he gave it to me, complete with dead battery. It has a transmitter gizmo you strap onto your chest. The watch is the receiver. Neato.
No prob. with the battery, though. I soldered a pair of wires, added a couple of AA and voila - it works. And how! It is bang on accurate.
Now to the point: My bike has a program that adds resistance if your heart drops below your target. I’ve now got a gizmo that accurately measures my heart rate. It would be a cinch to intercept the signal going to the watch battery, and tell the watch to beep out in time with my heart. Can I just slap on the right jack and plug’er in?
In short: What does my bike expect signal-wise? My google-fu only comes up with gizmos to buy, no specs or schematics.
I don’t have a EE answer to your question but you might want to check your bike’s manual to see if it already has a receiver. What brand and model is it? The elliptical trainer I use at the gym has a receiver for those chest strap transmitters. I found out by accident when I wore the strap and the watch, and started getting the pulse readout on the elliptical machine as well.
Does your bike’s manual say anything about what kind of input it expects in the jack? Or at least what kind of devices you can plug in?
I’m afraid I know nothing about the signals, what comes out of a finger cuff or is transmitted by the strap. I would think that building a device to receive the signal from the strap then output it in a form suitable for the bike is nontrivial if you are not an electronics hobbyist.
I bought the thing “as-is” from National Sport. No manual. I’ll definitely try putting into heart mode while wearing the transmitter - wow wouldn’t that be cool if it worked.
I’ll try a couple things: fashion a jack leaving the ends open, then touch the ends together 80 times per minute and see if it registers. I’ll measure the voltage the watch sends to the speaker, but I can’t imagine it’s very high - probably safe enough to just plug’er in to the bike.
But I no longer have the finger cuff (giggle) from my old bike, so I have no way to measure what the thing does. When it was plugged into the bike it reported my pulse with numbers that centered around my actual pulse, just highly sporadic (either that or I should see a cardiologist).
If anyone has one of those finger cuffs (not you, Amy! I don’t want to chase you… giggle) and a multimeter and a couple minutes to spare… couldja? I suspect it varies resistance, but by how much and in which direction?
Yeah, I could see problems here, you start cycling to pump your heart, your leg muscles demand more blood, so you cycle harder to supply it, then your body demands more to cope… I can see its a question of whether or not your bike gives out before your leg muscles :dubious:
The jack on the bike is a 2-conductor sub-mini. I used this to attach a momentary contact switch. When the switch is closed, the little heart icon appears on the display, then disappears when the switch is open. By pressing the switch once per second the numerical display reads 60 bpm.
I couldn’t accurately measure the voltage going to the speaker inside the watch because the beeps are too quick - my mulitmeter is digital and takes a second to register. The watch takes a 3V battery, so it’s probably reasonable to assume the speaker receives 1V to 3V.
So at lunch today I’m running to Radio Shack to pick up a low voltage relay. [Peter Lorre]By setting the watch to beep with each pulse, connecting the speaker outs to the relay I should finally be able to destroy life. Do you despise me Rick?[/Peter Lorre]
Look, I think we’re all sympathetic if you can’t afford a pacemaker, but (A) this is not a sound medical procedure, and (B) the SDMB is not the place to ask for medical advice.
I’ve dabbled a little in electronics, and I think you may be able to use a transistor or op-amp for something like that instead of a relay. A mechanical device that has to activate once each heartbeat will not last that long. (that kind of says something about how robust the human body is) You may want to ask about it on an electronics hobbiest forum.
