Hi all
This is more of a general electronics problem and not arduino related (yet), though I may incorporate an arduino at a later stage.
I have an oldish exercise bike with a large UI made from leds and membrane buttons.. its a self powered device the type you might have found in the gym circa 1984
it has a 3 pin din input for a hrm and 3/4 of the programmable options depend on its input. But no Hrm came with it.
the only badge/label on the thing is a single brand name 'aerobike' and google has failed me for a simple buy n use solution.
So i could? fabricate a HRM perhaps? well i could if i had a clue how to.. can anyone shed light on the issue and perhaps even guide me or point me to a simple solution ???
many thanks in advance, and if this is an inappropriate forum for this Q? Sorry, only place i frequent that i have confidence that someone will have an inkling
ps i need to use the bike, had a heart attack.. and am totally bored using its single (No-hrm-requierd function...)
As you have not defined what HRM means, I wil take a wild guess that you want an hour meter.
This should not be a difficult task. There are electro mechanical hour meters available and they would be the simplest solution. This would not however give any programable functions.
If my guess is wrong please let us know what you want.
By HRM, the OP means Heart Rate Monitor. It generally comprises a pair of electrodes held in place on the chest by an elasticated belt. The heart signal picked up by the electrodes would then be passed to the (presumably in this case) the exercise bike electronics.
'Fraid I've no idea if one of the commercially available HRMs (Polar, Garmin etc) could be made compatible with your exercise bike tho - sorry.
It probably uses a monitor similar to this: Heart Rate Ear Clip - 6030206 | Fitness and Exercise Equipment Repair Parts I'm guessing that is an electro-optical device similar in concept to an opto isolator, so an LED on one side of one's earlobe and a photo transistor on the other side. If you could identify the model number of your bike those guys might be able to supply a direct replacement.
Current generation equipment uses wireless heart rate monitors that are a battery powered chest strap transmitting pulse data via a simple LF pulse (5000 Hz?), bluetooth, or ANT standards. This wouldn't work directly as a replacement in your case, though building a receiver that translates to a signal compatible with the OP's equipment might be feasible.
There's also been a wave of wrist monitors using reflective electro optical including the Apple watch and Fitbit among others. Again, probably not directly applicable.
I doubt it is "self-powered" - though it may be. Battery more likely.
It's pretty common for "health club" level exercise bikes to use what amounts to a generator and an electronically controlled variable load to provide resistance for the user. Power from the generator is also used to power the user display.
I agree with MrMark. In an old bike, the HRM almost certainly has been an infra-red sensor that is clipped on a fingertip or ear lobe. Some of these kind of HRMs might have the needed filtering, amplification, and DC-removal circuitry embedded, but my guess is that this one is just a 'dummy' sensor with maybe a pull-up resistor.
I recommend that you measure the DIN pins (when the bike is powered). See if you can find Vcc (3/5V most likely) and GND. The third pin would then be then signal input. If you can identify the pins (and a wired solution is acceptable), just buy a generic ear lobe HRM, and either solder/connect a female 3.5mm stereo plug into the DIN connector, or cut the male 3.5mm plug from the HRM off and connect individual wires.
If the above fails, you might need to build or buy a board that does the signal conditioning, or an HRM that has all the stuff embedded. All this gear can be found on the net. For example eBay has a ton of generic IR HRMs for sale for just a few bucks.
If you want a wireless solution, then the issue becomes a bit more complicated and costly, but not impossible.
