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Looking for a sensor to detect the foot movement and connect to an app

bhl3302

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Hi All,

There are a lot of apps in the smartphone that can be used to count the walking steps. I am trying to archieve a similar target but want to use a real sensor wearing in my shoes or tied to the legs/feet.

(1) Would anyone give me a recommandation for such a sensor that I can use to count the physical movement such as the steps that I walk?

(2) Similarly, if I am riding a bike, if I want to count how many cycles I have gone through, can I use the same sensor as the first one, or I should use a different sensor? I still want to have this sensor attached to the body, instead of installing it on the bike to count for the cycles.

Thank you!
 

KlausST

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Hi,

Generally every acceleration sensor should work.

But you don't give true specifications.
As you have written you want just count steps
But mayou you should be interested in
* step length, running speed
* force
....

What about power supply, data transfer, accuracy, ruggedness, price, ....

Klaus
 

bhl3302

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Hi,

Generally every acceleration sensor should work.

But you don't give true specifications.
As you have written you want just count steps
But mayou you should be interested in
* step length, running speed
* force
....

What about power supply, data transfer, accuracy, ruggedness, price, ....

Klaus
Hi Klaus,

Thank you for your advice! Currently, I have not got into the specs yet. But all the points you mentioned are very important.
(1) I do want to know the step length and the running speed so the total walking/running distance can be calculated.
(2) I have not thought of the force issue but I think I will get to this eventually.
(3) The power supply can be a 3V lithium coin cell battery. Data transfer from the sensor to the phone can be relatively low frequency, say, 1 Hz. Accuracy, ruggedness, and the price are not critical at this moment.
Do you have any reference design that I can start with to find out more details? The power supply does not have to be the one I am thinking about.

Thank you again for your help!
 

KlausST

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Hi,

If you want stepsize, then you need an analog sensir (while a pure step counter sensor could be digital).

Because mounting is not the precise, I assume it needs to be a 3 axis sensor, so software can compensate.

With an analog sensor (it may still have a digital interface) you need a much higher sampling rate than 1Hz. Thus I assume you need to process sensor data at a microcontroller close to tge sensor ... then sending the data once per second to the cell phone should work.
You should look for low power sensor, low power microcontroller and low power (wireles) data communication with cell phone.
In my eyes this is important in the early design stage, because a later change of sensor would propaply change overall performance, too. This also is true for accuracy and ruggedness.

If you want your device to be a good tool for fitness it needs to be rather precise (not necessarily accurate).
My target would be a speed precision over a complete run of maybe 1%. (My personal opinion, targeting high quality...and from my own running experience).

Specifications:
Maybe not specifications, but at least the requirement/goal should be the starting point of every design... with values and units.
Otherwise the development will take longer and you will become disappointed inbetween and need to start anew.

Klaus
 

bhl3302

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Hi,

If you want stepsize, then you need an analog sensir (while a pure step counter sensor could be digital).

Because mounting is not the precise, I assume it needs to be a 3 axis sensor, so software can compensate.

With an analog sensor (it may still have a digital interface) you need a much higher sampling rate than 1Hz. Thus I assume you need to process sensor data at a microcontroller close to tge sensor ... then sending the data once per second to the cell phone should work.
You should look for low power sensor, low power microcontroller and low power (wireles) data communication with cell phone.
In my eyes this is important in the early design stage, because a later change of sensor would propaply change overall performance, too. This also is true for accuracy and ruggedness.

If you want your device to be a good tool for fitness it needs to be rather precise (not necessarily accurate).
My target would be a speed precision over a complete run of maybe 1%. (My personal opinion, targeting high quality...and from my own running experience).

Specifications:
Maybe not specifications, but at least the requirement/goal should be the starting point of every design... with values and units.
Otherwise the development will take longer and you will become disappointed inbetween and need to start anew.

Klaus
Hi Klaus, thank you very much for your insights! This is super helpful!

I am specifically curious about the operation of the analog sensors from your advice to measure the steps:

1. if the fitness application is at the treadmill, and I have to tie the sensor to the person instead of measuring from the machine, how will the 3-axis signal generated be useful for the microcontroller to process and calculate the step size?

2. similarly, if the fitness application is at the cycling station, and I have to tie the sensor to the person(say, under people's feet inside the shoes) instead of measuring from the machine.
--- 2.1 if we can use the sensor as that of point 1, how will the raw signal generated by the sensor be useful for the microcontroller to calculate the distance that bike travels?
--- 2.2 if we cannot use the same sensor of point 1, what another sensor I can use, and what is the useful signal generated by it?

Thank you!
 

KlausST

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Hi,

1) 2nd integration of acceleration is length, (1st integration is speed)

2.1) possible only if there is fixed gear. It can just measure RPM of pedals ... then needs a fixed factor for "distance/revolution"

2.2) Difficult. Maybe "force" can give a feedback about gear or "distance/revolution".
But there is no fixed physical or mathematical relationship as with 1)

Klaus
 

danadakk

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