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[on:]

Hy,

We neet te measure weight in arduino for a school project.
The idea is how more you weigh how brighther the licht becomes.

Does anyone have an idea how to do this?

[Reply #1 on:]

Yes -- lots of people know how to do this.

But... you need to explain the project much better. What weight, what are you measuring and so on.

Is your native language English? If not tell us -- maybe someone speaks your language and can help you more.

[Reply #2 on:]

We want to weigh up to 3 people. So the measurment dusn't have to be real precisely.
We measure with steps of 60kg.

My native language is dutch, but reading englisch isn't hard for me.
Writing englisch is still a litle dificult for me. So this is a good exercise for me as well.

[Reply #3 on:]

We want to weigh up to 3 people. So the measurment dusn't have to be real precisely.
We measure with steps of 60kg.

My native language is dutch, but reading englisch isn't hard for me.
Writing englisch is still a litle dificult for me. So this is a good exercise for me as well.

Will they be standing on each others shoulders? Hanging from a rope? All sitting on the same chair? Standing on a platform you will build -- With force sensors (strain gauges) at the corners?

"doesn't have to be real precise"  Steps of 60Kg? Why bother? It seems useless. That is plus or minus the weight of a teenage student is it not?

Now do you mean the display is in steps of 60Kg -- or the sensors? I am not aware of how to build any weight measurement device with that level of inaccuracy. Maybe +- 6KG-10kg???? Base on say three people of 60-80 kg each then... say 240KG +- 5% would be about right for a simple "dumbed down" project.

Always separate the "working part" from the display. Just like object oriented programming.

Why build something of say 30-50% accuracy. Use a weight guesser at a local carnival... it would be more fun and just as instructive.

Now if this is a project for kids under 13 OK -- but if this is a "High School" (Grade 10-12) project maybe you should define it a bit better.

[Reply #4 on:]

have a google for "DIY pressure sensor" 

I believe I saw something with a wet sponge, and the arduino measured the resistance of the sponge.
that varied when the sponge was compressed.

or this
http://www.instructables.com/id/DIY-Force-Sensitive-Resistor-FSR/

or just put a wooden plate on something soft like rubber tiles or a few pillows
and measure the compression/movement of the wooden plate by means of a potentiometer   

now where can I send the rest of your homework ;-)