How to modernize an elliptical trainer...?

[StrandedonEarth]

So as the Covid weight piles on, we decided to buy an elliptical trainer  . Used, of course; I have no idea when it was made aside from being in that curious technological overlap area when the manual I downloaded mentions both ifit.com and videocassettes. The control console is a typical old-style with black-on-grey LCD display, some blister buttons, and some colored workout-intensity LEDs. So I started pondering the how relatively simple it would be to just sell upgraded consoles for these things. After all, the only wires coming from it would be for a speed sensor, a heartbeat sensor, and the little motor that controls resistance. Aside from power, which can be supplied by 4 D cells or the wall AC adapter (presumably 6v, haven't botherer to look). But why make a new console in this day and age?

I soon realized that it could be as "easy" as rigging a dongle (to connect those two I/O's to an iPad, then writing an app to interface with the machine. My main roadblock here is that while I get the concept of using Arduino's and Raspberry Pi's to interface between computers and hardware, I know pretty much nothing about them. Ditto for writing apps. Not to mention no fine soldering skills.

This is probably more of a mental exercise than actually intending to replace the control console with an iPad. But how hard would it actually be? A microcontroller to feed data to the iPad (via dongle or Bluetooth) and control the resistance motor on command from the iPad is probably the easy part, but I don't even know if I'd use a Pi or an Arduino for that. After that, it's writing the app, which could be as simple as overlaying performance data over YouTube videos, up to a more virtual "walk"

So, any ideas on how I would go about this? Or suggestions for a website/forum that specializes in this sort of thing?

It would be nice if it had a generator to charge a battery bank....

 

[Shpaget]

Well, the choice between Arduino and RPi is simple. RPi is a huge overkill for this. You don't need a full blown computer to control one motor and a few LEDs. The power requirements alone would be a deal breaker here. Arduino is more than enough for this.

Bluetooth for Arduino

https://www.ebay.com/itm/HC-06-Wireless-Bluetooth-Arduino-PI-JY-MCU-Serial-RF-5V-Transeiver-Module-AU/272770538949?hash=item3f82641dc5:g:CtoAAOSwTCZZcU7B

Note it's 3,3V device so you'll need a level shifter to bring it to 5V if you're using some 5V Arduino. Something like this:

https://www.sparkfun.com/products/12009

As for a mobile app, perhaps check this:

A forum that specializes in Arduinos is official Arduino forum https://forum.arduino.cc (it throws a 504 error at the moment, but the link should be fine).

Unfortunately, the community there is a little weird. There certainly are knowledgeable guys there, but sometimes you keep getting cryptic answers that require an already existing knowledge of some (to newbies) obscure component behavior/characteristic which makes the answer practically unusable. Some of the guys there expect you to know a lot of theory before they are willing to help you, and just point you towards a (very) general direction, which I suppose is somewhat fine (noone should be doing your homework), but directing a newbie that asks about using a MOSFET to read up on transistor doping, is ridiculous, and doesn't help at all since the guy asking will not only fail to understand it, but has no need for it anyway. 

Better community is eevblog.com/forum/ but they are oriented towards more professional aspects of electronics, so a lot of them might not be interested in meddling with Arduinos. There are some that will help you there.

Alternatively, why not stay here? There are a handful of us here that like to play with magic smoke.

[Gargamel]

Be careful with the motors on exercise equipment, they're designed (the good ones are) are designed to dish out a lot more oomph than you'd think.  There's a reason these types of motors are used for building robots and go carts.  I don't know the mechanics of your machine, but just imagine how much force your legs can exert, and the motor has to be able to counter that force, and then a not insignificant margin of error on top of that.  Most machines I've looked at are direct drive, usually there's not a gear box involved, so the motors are usually quite hefty. 

I've always had good success on the arduino.cc forums, but as @Shpaget mentioned, you can get some weird answers.  But if your arduino skills are lacking (or Nill), I would recommend getting the Arduino for Dummies book, and a good starter kit.   And practice those soldering skills. 

On 5/17/2020 at 9:05 PM, StrandedonEarth said:

But how hard would it actually be?

You might find this rabbit hole is a lot deeper than you think though.  Those are custom built micro controllers already in place in the machine.  Trying to swap out a single component might lead you to swapping out multiple components.   If it ain't broke don't fix it.   If it is broke, then possibly swapping out the knobs or switches would be the way to go, as even the very light duty ones end up being rated a lot higher than you really need (but make sure you check!), just due to the size of the human finger.   You might find your quest to 'modernize' your machine might cost you more than a new modern would be. 

I think step one should be designing a really good mount for a tablet, and then get it working, even if it is just for streaming video for now.   Making an elegant and functional mount in itself can be a good project.  It's a really good way to get into 3d printing, woodworking, or metal working, depending on the route you go.