Hello forum,

Can you please advise me on either, how to make a voltage reference using a zener diode (Philips BZV55 voltage reference diode), or how to use the Zetex ZR431 zener shunt regulator as a voltage reference.

I need a voltage reference to measure when the supply voltage (battery supply) reaches a certain voltage. I'm using a PIC with ADC and need a voltage reference for it. My battery supply can vary from 4V to around 10V (different number of cells being used).

I have access to both the BZV55 and the ZR431 and I have played around with both of them, and I just can't get a stable reference voltage.
I would like the reference voltage to be 2.5V with the ZR431 and any value below 4V for the zener (I have different zener voltages to choose from).

A circuit diagram would be much appreciated.

Thanks.

Regards,
Futterama

 

Check my analogue PIC tutorials, which use the 431 - this is a precision reference, a simple zener will be pretty poor as a reference.

__________________
PIC programmer software, and PIC Tutorials at:
http://www.winpicprog.co.uk

 

Hello Nigel,

Could you please post a direct link to the page where I can find circuit diagrams using the 431? I'm having trouble finding it on your website, sorry :roll:

 

OK
http://www.winpicprog.co.uk/pic_tuto...ogue_board.htm

__________________
PIC programmer software, and PIC Tutorials at:
http://www.winpicprog.co.uk

 

Nigel, it works just fine!

The reference is 2.58 at my multimeter, regardless of input voltage variations. It should be a 0.5% reference (I use the SOT23 package), perhaps my multimeter is incorrect.

Thanks Nigel!

Edit: My multimeter must be out of adjustment! I just borrowed a FLUKE 87 that should be correct, it showed 2.497V.

 

That's always the problem, you don't really have an accurate way of adjusting a voltage - unless you send your meter for expensive annual calibration, which isn't really worth it for domestic use (or most professional use either!).

__________________
PIC programmer software, and PIC Tutorials at:
http://www.winpicprog.co.uk

 

It's not a bad idea at this point to check out the Maxim and Analog Devices sites for IC voltage references. They make very accurate references available in a selection of voltages and will usually provide free samples.

Dean

__________________
Dean Huster, Electronics Curmudgeon
Contributing Editor emeritus, "Q & A", of the former "Poptronics" magazine (formerly "Popular Electronics" and "Electronics Now" magazines).

R.I.P.

 

Or you can get them out of many scrap TV's and VCR's. The 431 is often used as a PSU feedback reference.

__________________
PIC programmer software, and PIC Tutorials at:
http://www.winpicprog.co.uk