How to use AD 676 Analogue to Digital IC

Question

I want to measure degrees using linear potentiometer, so I thought to use the AD 676 analogue to digital converter (ADC) IC.

Is this a good ADC for monitoring a potentiometer?

If so, how can I use it? A schematic of an example implementation would be helpful.

Answer 1

Why did you choose the AD676 in particular? It's a 16-bit ADC, which is much more than you need. A potmeter rotates over about 270°, so an 8-bit ADC would give you a resolution of about 1°. Nowadays it's often easier to find a 10-bit ADC, and they don't cost much more.

Normally you should also look at the ADC's speed, but for reading a potmeter 10 samples per second should do and any SAR (Successive Approximation) ADC will do here (most will easily be a thousand times faster).

How do you want to interface it to your microcontroller? I2C, SPI?
A standard serial protocol makes it ridiculously easy to interface your ADC with your microcontroller. As an example the following "schematic" from the Microchip MCP3021 datasheet:

The MCP3021 is a 10-bit ADC which interfaces through I2C. It comes in a 5 pin SOT23 package:

2 x power (Vdd, Gnd)
2 x I2C (SDA, SCL)
1 x Analog input

That's all you need.

Answer 2

This data sheet contains one example circuit. You will need to specify a bit more on your requirements to get a better answer.

I think that particular chip is a bit overkill if you just want a simple measurement of a potentiometer. I would go for a chip with 1) a breakout board and 2) sample code if this is your first chip you're talking to. It's just easier to get started and will save your potential problems the your first time around.

Answer 3

A AD676 ADC is way too extreme for your purpose of reading an analog potentiometer signal. If you'd use the full scale of your ADC (so if it can read 0 - 5V, you would use min 0V and max 5V), you have over 65000 positions.. and a lot of noise to deal with.

A 10 bit ADC has about 1024 positions. If you want to encode 360 degrees , you could get up to 0.36 degrees resolution. However, potentiometers don't turn full 360 degrees or circles, so you will likely be limited to about 270 degrees.

Stevenvh showed a simple example of how to connect the ADC. Connect the SDA and SCL signals on your microcontroller on the appriotate pins. Look up the datasheet for your devices to see what pin that is, that's different for every chip. The analog input would just be the middle tapoff from the potentionmeter, and just apply +5V and 0 to it (if your potentiometer can read up to +5V)