need a simple digital weight scale schematic

[basel]

can anyone please link me a simple schematic for a digital weight scale which work according to this ( "weight sensor" analogue signal >> analogue to digital converter >> micro-controller >>lcd screen) i just need simple schematic which can be easy to make and do the purpose because i cant seem to find a good one

 

[shrtrnd]

I don't think you're going to find a 'simple' schematic for this.
My advice is to find an existing scale that you believe most closely approximates the
features you're looking for, and then search (Google) the model number for it's schematic.
I don't know your weight range.
Laboratory grade scales are used for very small weight measures, and industrial scales
are used for large to very large weight measures.
Somebody here might have some suggestions about which manufacturers to start
searching for, if you tell us the approximate weight range you want to work with.

 

[(*steve*)]

I remember many years ago a kit that used tracks on bith sides of a PCB in a bridge arrangement.

Pressure on the pcb (they were actually "fingers" that bent under load) would compress one side and stretch the other.

The slight change in resistance would unbalance the bridge and produced (small) a voltage reasonably linear with weight.

 

[GonzoEngineer]

First, you need to define the sensor...(Google is your friend!)

Strain Gauge for light to medium weights.
Load Cells for the really heavy weights.

I found this on the first page....

http://www.nerdkits.com/videos/weighscale/

 

[basel]

any weight will do , i just need a simple circuit with the components i mentioned above for a digital measurement circuit project , btw isnt the circuit below complicated?

 

[basel]

never-mind the above circuit , can i connect this circuit to a a/d then to a micro-controller to show the weight on a lcd screen?

 

[GonzoEngineer]

That is a good start. I would check to see what the excitation voltage requirements are for your particular strain gauge, and whether or not your MCU can drive it.

If you go to Digikey.com, and search for Strain Gauges, you will find that they are usually a low resistance (the first one I checked was ~350 ohms.

You might want to put drivers on the MCU outputs. I would use a TC427, but that's just because I have thousands of them in stock.

Good luck!