how to measure the weight of pushing on every pedal of a bicycle?

It's for a school project..
I thought the FSR sensor and arduino.
I would like to measure the weight of a person for example 100kg.Maximum value of the FSR sensor is 10kg.
I would like something more in detail if you could help me.

sort by: active | newest | oldest

A Let's Make search for, "force sensor", returns some relevant instructables, I think.

From just looking at the pictures, we can see a lot of these are some kind of project that involve, what I think is, the specific FSR sensor you are writing about.

It kind of looks like there are exactly two of those, a circle shaped one, and a larger square shaped one. I have also seen these in's pages, here

and here,

There may be other vendors selling the exact same same thing.

I could not help noticing, on Adafruit's page for the larger square one, this text in the description,

FSRs are basically a resistor that changes its resistive value (in ohms
Ω) depending on how much its pressed. These sensors are fairly low cost,
and easy to use but they're rarely accurate. They also vary some from
sensor to sensor perhaps 10%. So basically when you use FSRs you should
only expect to get ranges of response. While FSRs can detect weight,
they're a bad choice for detecting exactly how many pounds of weight are
on them.

If I have not already mentioned it, the grown up version of this FSR thing is a device called a "load cell"

These might be expensive though, or hard to find, or both.

So what alternatives are left?

I thought that 'ible by MechEngineerMike, was rather clever.

What he has built is essentially a steel spring connected to a slider potentiometer, and he is using an Arduino Uno to measure the position of the potentiometer. So this is kind of old school (observing Hooke's law in an actual steel spring) and new school (Arduino plus LCD display) at the same time.

Also there are stories of people who have hacked their bathroom scale, for to get data from it, into some other device. It seems like had a few tutorials, of this kind.

I dunno. Are there inexpensive and accurate, load cells out there? It would be weird if the cheapest way to do this was by hacking a bathroom scale.

I dunno. Are there inexpensive and accurate, load cells out there

Yes, Lots I have a drawer full for a mirror support project I want to try out

OK. Do you recall where you got them from? Or can you point to an example of the same thing, or similar, being sold somewhere, today? Or a link to a data sheet would be nice.

Just Ebay, they're inexpensive, and the electronics to interface them costs about a dollar. Ridiculous, but true.

Toga_Dan20 days ago

those Sensors might be usable even if they are too low for the force on the pedals. Secure a 10 to 1 lever to the crankset, to the sensor and multiply the reading by 10. This will get you a ballpark number. Some backpressure on the trailing pedal may add some force to the crankset, but I think this will be slight.

I keep telling ya, force is measured in newtons (N), not kilograms (kg).

W = m*g

which is essentially just a special case of F = m*a.

Also be careful with that acronym, FSR. In the context of your question, it stands for, "force sensitive resistor"

However, if you listen to nerdcore hip-hop, then FSR stands for, "Futuristic Sex Robotz". Their single, "Snakes on a Plane", based on the movie with the same name, has some clever lyrics, and a surprisingly sick beat. But I'm not going to link to FSR, because their songs contain a lot of profanity. Thus FSR is NSFW. Looking them up is left as an exercise for the interested reader.

Joe Average tends to think of F in terms of kg or lbs. That's OK for the layman. But, yes, newtons are the accepted scientific metric measure of force.

1 newton is approx 1/10 kg (weighed on earth

It's called SI, which is short for Système International.

Although I must admit, I have never seen a bathroom scale that can display weight in units of newtons (N). Usually it is a choice between pounds (lb) or kilograms (kg). If it is a bathroom scale with a digital display, usually there is a little switch on the back, with exactly two choices: (lb) or (kg).

Also, I suppose it doesn't help when the vendors who sell force-sensors, load cells, etc., also use mass units, like pounds and kilograms, in their documentation.

when Neil armstrong first set foot on the bathroom scale on the moon: "that's one smmall step for man, one giant leap for weight watchers annonymous

That reminds me: There is a song by KMFDM, titled "Risen", that includes lyrics which make pun of two of the well-known quotes from the Apollo 11 mission. These puns are short, and they appear seemingly randomly in the flow of the song, so I have included some time marks (in minutes plus seconds notation) for the interested listener.

At t = 2m+52s,

A small step for mankind
A giant leap for a rock'n'roll

At t = 4m+5s,

The ego has landed

YT link to an AMV (anime music video) with this song as the audio:

One Newton is roughly the force one apple exerts on the earth....

orange piping? Granny smith?

good question. What kind did William Tell use when shhooting the apple off Isaac Newtons head?

oooh. I like that. As seldom as I use newtons, I sometimes forget: 1/10th kg? Or 10 kg So, next time I need to deliver apples with rockets, that will help.!

Toga_Dan21 days ago

sometimes on a hill, a rider will stand on pedals, putting their whole weight on 1.

rickharris22 days ago

Deleting the original question and answers won't get you better ideas.

We may be oldish but the memory still works.

Not worth repeating what I said before

What was wrong with the answer you got yesterday ?