Low Voltage Detection - 16F628A

[paul borgmeier]

... detecting a low voltage condition , to blink an LED. ...
regards.

It is still not clear (to me) what you are trying to do - Are you trying to detect a low voltage condition of your 6V battery supply? In other words, do you want to monitor the 6V battery supply and then blink an LED when the batteries have reached 3V?

If you are detecting a low voltage condition of something else other than the Vdd of the 16F628A then Melanie's comparator primer (as suggested by Steve) is the approach and method you want.

If you are trying to do what I asked in my first paragraph of this post, then the internal comparators will not work without additional "efforts" because the internal reference voltage for the comparator is based on the Vdd supplied to the PIC.

Are you using a voltage regulator?
(6V is too high for a PIC and will damage it with time)

Paul Borgmeier
Salt Lake City, Utah
USA

[Acetronics2]

[QUOTEIf you are trying to do what I asked in my first paragraph of this post, then the internal comparators will not work without additional "efforts" because the internal reference voltage for the comparator is based on the Vdd supplied to the PIC.

Hi, Paul

Just compare a 2.5v ref ( or a Zener !!! ) to Vdd ( through a res. divider ...) and comparators will work fine here !!!

That's also how you can detect voltages w/ Logic CMOS, connecting a Zener to an input. ( input "level" changes at VDD/2 ... )

More difficult ( just a little ) is to play with Pics TTL inputs trip point that is a function of VDD ...
Experience shows the trip point is precise enough.

Alain

[paul borgmeier]

Just compare a 2.5v ref ( or a Zener !!! ) to Vdd ( through a res. divider ...) and comparators will work fine here !!!

Alain,

That is exactly what I meant in my post by "additional efforts." I did not want to go through the formal explanation if Charudatt was doing something different (which still is not clear to me from his/her posts). If it were me, I would ADC measure a reverse Zener or forward LED voltage. When the ADC value rose to a cutoff level (because the Vdd would be decreasing), I would flash the LED. You also could use the internal comparator in a similar manner. However, the specifics depend on whether or not Charudatt is using a regulator, anticipated temperature conditions, the problem Charudatt is trying to solve, etc. - I was looking for more input before providing more options. I think we match on how we would solve the scenario asked in my earlier reply. Now charudatt has lots of options.

Charudatt, please let us know how it turns out.

Paul Borgmeier
Salt Lake City, Utah
USA

[charudatt]

Sorry for the late reply,

Yes, I am using a LF series 628 in my application. My application works on 6V and I have a LDO for 4.5V to the PIC. I am building a Smart sensor for Crane Safety (which is battery Operate) and requires a HPWM output and a LO BAT Voltage Indication.

Melanie's excellent tutorial, helps me think in this direction more positively. Initially I planned to use a 16F676 and use the onboard ADC. but the software PWM gave me a problem. The Only next option was to use the LF628 with onboard comparators.

I have gots some excellent advise (as I always have) to try it out and see what suits me the most.

So now I can experiment with all your advice and post my results on it.

regards