digital weiht scale

[feldspar]

i would be glad to get any ideas, or circuits, senosors e.t.c. to build a digital weight scale. thanks

 

[Optikon]

i would be glad to get any ideas, or circuits, senosors e.t.c. to build a digital weight scale. thanks

Strain gauge sensor in a bridge.

A simple design is here:

**broken link removed**

There's an idea and circuit.

 

[zachtheterrible]

Check out allelectronics.com, i think they have a digital weight scale, if you dont want to build one.

 

[feldspar]

almost but...

i dont want to go all the way to a chip thanks though O. but... :roll: im still stuck.

 

[Nigel Goodwin]

Re: almost but...

i dont want to go all the way to a chip thanks though O. but... :roll: im still stuck.

The only tricky part is mechanical, how to get a reliable and accurate electrical signal based on weight.

You need to either buy or build a suitable sensor.

One simple (and crude) way of doing it is using black conductive foam (as used to store IC's), you place a metal plate either side of the foam, and connect a wire to each plate, place it on the floor, one plate downwards. You then measure the resistance between the two plates, this is your 'no weight' reading, you then apply the weight on top of the upper plate - this compresses the foam and lowers the resistance reading.

I've never done it (or had any reason to), but I've seen comments from people who have - with varying degrees of success!.

 

[Roff]

i would be glad to get any ideas, or circuits, senosors e.t.c. to build a digital weight scale. thanks

Do you want to make one, or do you just want to own one? What is the weight range you want to cover?

 

[jnegowski]

you need the tinker toy or block system.. one sensor one power supply very stable and one digital metter that you buy for 9.95 .. the sensor can be many different types based on how you apply it , but you will want to select one based on it's output . most of the time millivolts is pretty standard like 0 to 30 mills for what ever range you want to weigh, sensors come in different ranges of force that can be used on them like 0 to 100 lbs ect ect. some limits are set by the type of sensor ,ring, button,bar ect ect for scales on a small scale button compression rings are used. all sensors of this type have a excitation voltage applied to them most of the time 10 volts is pretty standard. it's a bridge 10 volts across the circuit apply force to the sensor from 0 to the high range end and millivolts out linear to force. then all you need is a digital meter to read the millivolts 0-10 pound sensor with 0 to 30 mills out =3.33 mills to the pound of force applied to the sensor so you can use a mulitiplyer or electronic scaleing for direct reading in pounds .