Micro controller voltage measurement + output to a LCD project

[danrogers]

Hi all.

I'm looking at designing a device for testing hall sensors that we produce at work (2.5v vRef & Vout). I came up with the idea of using some LCD voltage measurement displays, but they are not cheap and not very flexible.

It was suggested by my boss that I use a Micro controller (they prefer either Atmel or PIC) and one of the LCD screens that we already have (RS232) to display the two voltages, then we could even interface with a PC in future for logging results etc.

Now, I'm at the beginning of the project and have not started to look for processors yet but if anyone has any useful advice or direction that would be great because I'm new to processors and programming but eager to learn.

Thanks

 

[Sceadwian]

What kind of resolution/accuracy do you need? PIC or AVR the industry standard for ADC's is 10bit's for a general purpose micro controller, they're generally accurate down to 8bits although you can squeeze decent 9th and 10th bits (sometimes more) out of them with some care when you take measurements and basic statistical averaging.

 

[danrogers]

Hi Sceadwian, thanks for the reply. I really have zero experience with uC's so I'm going to find this task quite a challenge. I need to select a controller by mid next week!

Resolution, at least down to two decimal places so 2.54v for example but 3 would be a bonus. As for accuracy would it be possible to calibrate the measurement?

So.. 8bits please excuse my ignorance but what would that mean in terms of scale?

Thanks

 

[SneaKSz]

What kind of resolution/accuracy do you need? PIC or AVR the industry standard for DAC's is 10bit's for a general purpose micro controller, they're generally accurate down to 8bits although you can squeeze decent 9th and 10th bits (sometimes more) out of them with some care when you take measurements and basic statistical averaging.

Don't you mean ADC?

Usually the resolution of a PIC is 10 bit, so there are 2^10 steps=1024 .With a (usual) voltage reference of 5V means that the voltage step = 5V/1024=4,88mV, you're able to visualice with an accuracy of ~5mV. That would be 2.54xV ,these ADC's are onboard.

kind regards

 

[crutschow]

If you are thinking about interfacing to a computer why not just use an A/D USB interface adapter. That would be very simple to use and allows easy display, logging and manipulation of the data. If you want the LCD display also, you could connect it to the computer via RS-232 and program it to display the measured voltages. (If it's a new computer with no RS-232 ports, you can buy an inexpensive USB to RS-232 adapter).

For example this unit has four 10-bit differential analog inputs and two digital inputs including software for $29.

Edit: For more resolution (and more money) this unit has eight single-ended or four differential 12-bit inputs.

 

[danrogers]

Hi, I should have mentioned that the unit needs to be able to operate on its own (stand alone) and needs to be portable or at least semi portable.

Has anyone got advice on choosing a micro controller - things to look out for and things to avoid?

Thanks all

 

[Nigel Goodwin]

Hi, I should have mentioned that the unit needs to be able to operate on its own (stand alone) and needs to be portable or at least semi portable.

Has anyone got advice on choosing a micro controller - things to look out for and things to avoid?

Thanks all

Check my PIC tutorials, which pretty well cover all you need.

 

[Sceadwian]

There are other micro controllers out there you can use such as Atmel's AVR line, but if you want quick results Nigels tutorials will do very well for you; Microchips PIC line is well supported. There are reasons for looking elsewhere if you delve deeper into micro controllers but this is not what you're looking for, so exploring the vast field of them would be a waste of your time. From his tutorials and code you can use immediatly, or adapt what he has to do exactly what you want.

 

[OlPhart]

I splash in a different pond... Freescales' 9S08 series has a Bunch of candidates with multiple 10 bit ADCs and a serial port (USB may be available...).

The serial port would allow PC interface now, mgt by VBasic quite easily.

The learning curve won't be easy, but once accomplished, PICs will reset themselves into a new roll in your toolbox...

Assistance in the Freescale arena available (I'm neither employed by nor seek compensation for). However, if you want me to build it for you... that's different (it IS my day job). Good Hunting... <<<)))

 

[Sceadwian]

It's all about choice OlPhart, I'm sure that Nigels tutorials will set danrogers on his way though.

 

[danrogers]

Thanks, I will start taking a read through Nigel's tutorials. Will post back if(when ) I have any questions lol. Thank you all