PIC Sensor Interface

[amdkicksass]

So i have the need to build a digital circuit that can incorporate external analog sensors. The application needs to be so that a sensor with a analog voltage output for example 0-10V can be inputted in a PIC and then using the pic and 2 external buttons, the user can set Zero and Span.
My understanding is that certain PIC modules can accept an Analog signal and the pic can interpret the digital signal as well as calculate offsets and gains needed to create the correct zero and span condition and then output the signal into a small d/A unit that report a signal with the corrected zero and span ?

Is this possible ?

Thanks
PEte

 

[donniedj]

Not only possible but also typical. Most PIC series are capable of what you want. First get a pin count requirement, speed, and size. Like 8-pin, 18-pin, 28-pin, Soic, Ssop, internal clock (4 or 8 mhz), external clock, and finaly the means of communication. Once you have these criteria you can start to choose which micro to use.

You have it good, assumming you have no PICs in stock or prefered type. We vets will go through all matter of code tricks to the extend of using (wasting) external parts just because we have developed a preference and refuse to buy a PIC thats not in our current stock or wisdom.

 

[Pommie]

You have it good, assumming you have no PICs in stock or prefered type. We vets will go through all matter of code tricks to the extend of using (wasting) external parts just because we have developed a preference and refuse to buy a PIC thats not in our current stock or wisdom.

LOL, but oh so true.

Mike.

 

[amdkicksass]

Well to be honest i havnt worked with PICs that much most of my work involving them has been using the 16f628 model. As far as size and pin count well actually whatever is the smallest (in dip package) that will do the job. I am thinking that one I/O port i going to be used for the analog input and two others for the zero/span switches. Whatever is leftover can be used for the output.
Will i have to use another D/A IC in addition to the PIC ? Also do u guys have any model suggestions ?

Thanks
pete

 

[Pommie]

You couldn't use the 16f628 as it doesn't have an ADC. If you are happy with 18 pins then the 16F88 would suit you. It has a 10 bit ADC and the spare outputs could be used with a R2R DAC. The main problem would be that the output would be 0 to 5V but this could be rectified with an opamp.

Mike.

 

[ericgibbs]

hi Pete,
What DAC resolution do you require? ,, also whats the update rate?

Eric

 

[amdkicksass]

To be honest with you i am not sure what is an acceptable resolution and refresh rate. Given the chips we have been looking at what is some acceptable and doable rates ?
Also my programming will be done with the pickit2 so whatever ICs we pick must be compatible with it ?

Thanks for your continuing help..
pete

 

[amdkicksass]

Any further suggestions ?

Pete

 

[Nigel Goodwin]

Any further suggestions ?

As you yourself don't know what specs you need, it's pretty well impossible to make suggestions - but the 16F88 already suggested should be a good starting point.