A SIMPLE ANALOG-TO-DIGITAL CIRCUIT/ \STRAIN-GAUGES

[HANDzCLEANx]

HI
How can I convert analog to digital without the use of an ADC(an ADCand it's pin-connection seems way too complicated to figure out without any help and with a limeted budget :wink: )?
-I want to build 2 voltage deviders , each containing one varaible-resister(LDR or strain guage) and
one normal resister, then the problem is how to test wich one is the biggest?
Then converting it to a suitable input supply for digital components.

I recently opened up a calculator and found that the "button" looks like a strain-gauge, is it a strain-guage??
I can buy strain-guages, because I cant find any here in the RSA.
If it is in fact strain-guages, can I use them and how will I get the protective layer of the copper so that I can solder a wire to the gauge??

Thanx for reading this post.
CHEERS
*******

 

[laroche73]

analog to digital without ADC

How can I convert analog to digital without the use of an ADC

The simple answer is, you can't, since an ADC is an analog-to-digital converter . The good news is that ADCs can take on many different forms (V/F converters -> flash), some of which are inexpensive and fairly accurate, at the expense of lower conversion speeds than the ICs you're referring to.

Here's a cheap, simple A/D design that has fairly good accuracy, simply measure the duty cycle with the micro you're using.

**broken link removed**

I don't know much about strain gauge converters, but this A/D (and most others) would require a pre-amp. Conversion speed is more than adequate.

 

[Klaus]

HI


I recently opened up a calculator and found that the "button" looks like a strain-gauge, is it a strain-guage??
I can buy strain-guages, because I cant find any here in the RSA.
If it is in fact strain-guages, can I use them and how will I get the protective layer of the copper so that I can solder a wire to the gauge??



*******

I would think from your comments above that you are confusing etched switch contacts with strain gauges. There are no strain gauges inside calculators.

Strain gauges are very small and basically consist of a long track, etched in a zig zag pattern, inside a protective plastic foil sleeve. These are bonded to the part under measurement in an arrangement to sense the mechanical strain. They are usually connected in a wheatstone bridge array, and thus can detect minute mechanical elongation or contraction of the part.

Since the whole set up is subject to temperature variations, there are gauges available that are compensated for the type of metal they are to be used on.

The output from the strain gauge bridge bridge is fed to a precision amplifier with a gain of around 1000 to result in a varying voltage output that corresponds to the applied strain on the part.
The whole set up requires precision and is therefore not cheap.

You can get simple A to D converters in a chip, it all depends what accuracy you are looking for.
Klaus