Let's Make Robots!

"Pedometer" for roller skates?

So as I mentioned a few months ago, I'm currently training to join a local roller derby team. I am, for lack of a better word, quite out of shape. I can only afford to go skating once a week, and want to make sure I am getting the most of my sessions.

I've seen pedometers for runners, and even small GPS units for skaters going outside, but what if you're inside?

I'm a quad skate snob, and will use my indoor skates for INDOOR ONLY. However, I really want a way to track how far I've gone during my sessions. Even the knowledge that I'm going a wee bit farther every time would be exciting. I get disheartened easily and want something to keep me going.

I'll first post pictures of my skates to get creative juices flowing, then spout off my own ideas:



OK. So I'm thinking one idea would be to paint on the inside of one wheel and use an encoder, but I'm not sure how high I need the proc to count.

The top two pictures show where ideal proc placement would be between the shoe and plate. I want it in a place that is easy to get boots on, and won't hurt me if I fall, because I WILL fall.

Waterproofing isn't a big deal, but if it works out well, I'd like to eventually make a waterproof version for when I can afford a second pair for outdoor use.


Any thoughts guys?

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I think that would make it a little akward.


"'scuse me while I stick my hand down my pants to run a wire." :P

no kidding: wearables are all the rage, even in the diy scene.

but my vote is for the awkward wire

I think starting dirt simple may be best. You could start with an off the shelf pedometer. From the pic, it should fit in the gap between the bottom of the boot and the frame. It already has a nice counter, display, and reset. It should be simple to bypass the defult input and trigger the counter with a microswitch. Then there are two simple options for counting.

1. you could put a small bump on the wheel(small epoxy lump maybe?), and mount a microswitch so that it is triggered by the bump. I think that this may be a bit too much for the microswitch since the rpms of the wheel will be pretty high.

2. Again with the microswitch, but drag a small feeler, so that the switch is triggered when your foot is lifted.

You could try this for $10 or less in parts, and just take a look at the data. Do a fixed number of laps and look at the count, then try again. I imagine that you will find a relatively consistent number of counts per lap. I know that this is not the exact solution you are looking for, but it should give you some useful result, and it is cheap.

Very cheap idea! I like!

Quite simple to compared to the others.

Now I'm tempted to go buy a pedometer just to hack it and see what I can do.

ooh, that's a cool idea!

It might be a good idea to do both. I'm not sure if it would register though. the bottoms of skate shoes are quite tough. I might just have to buy a pressure sensor just to see.

How about a couple of neodymium magnets fixed to the wheel somehow and a hall-effect sensor to detect them?  I'm suggesting two magnets, or maybe four, to keep the wheel in balance.
I'm not too sure about magnets. First there's not much room between the wheels and the trucks. I also don't want any to  possibly fly off. It only takes a very small pebble to catch a wheel and cause a faceplant into the floor (I did this when they didn't clean all the cake off the floor from a birthday party).
I haven't made use of one yet, maybe someone else has. what about an eccelerometer?

did you mean an accelrometer?

that might work  but i wouldnt know how to calculate distance without calculating speed  but it might be able to detect when your foot goes up or down 

why not look into the bicycle meters that do distance it might give you some better ideas i think they use a roller that has an encoder on it, if you add a roller  put enough tension on the wheel so it doesnt roll  when  lifted off the floor

I've actually been researching this. There's a very long equation to figure out velocity using an accelerometer. I've been trying to find websites that go more in-depth, but am coming up empty handed.

It might make everything TONS easier if I forgo putting something on the skat and just clip an accelerometer to my shirt. That way there would be much less calculations with my foot going back and forth, and if I put it on my shoulder on the shirt-collar, it would be out of the way if I fell. AND I could use it for biking/walking/etc.