Low Voltage Detection - 16F628A

[charudatt]

Sir, considering i am using a 16F828A, i can detect a min of 3V.

Any idea on how to use the internal Comparator for detecting a low voltage situation.

Thank you for your help.

regards.

[mister_e]

a regular 16F628, depending of the crystal speed, is suppose to work from 3V to 5.5V. Detecting a 3V may work great or not. What i'll personnaly do is to use the 16LF628 wich work down to 2V. That's my own opinion.

What i usually do, and some may have another opinion, is to use an LF serie and a LDO voltage regulator. This give me a stable voltage reference to compare against the battery voltage. That way it work.

One way to do it...
Datasheet section 9.1 use mode 101 (one comparator)
Poll C2OUT bit of CMCON

OR Interrupt
Enable Comparator interrupt (see PIE1 register 4.2.2.4)
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your code.
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Interrupt routine
Blink your LED
Clear Comparator interrupt flag CMIF (PIR1 register 4.2.2.5)
Resume Interrupt.


Without any voltage regulator it's not impossible but you need a stable voltage reference... i remind one of my bench stupid idea in the past : use an I/O to supply a Resistor + Zener Diode for the voltage reference... worked. But as Zener diode need few mA to work properly... it's not suitable for a battery powered system... IMHO

[Jerson]

Take a look at the MC34064 low voltage detector. Connect this to a port pin and check the pin to decide if you want to blink the LED

Jerson

[Melanie]

Use the 16F628A's COMPARATORS, this is exactly what they can be used for...

Many years ago, I did a Comparator tutorial on the piclist, a link to the archive where it can be found is here...

http://list.picbasic.com/forum/messa...tml?1020960642

By configuring the internal Voltage Reference Module (Datasheet secion 11), you can detect voltages as low as around 208mV, by using two Resistors (Potential Divider from 5v rail) as external Reference, you can get even lower. See the Datasheet (Table 17-2) for the Comparator Specification for exactly how low. Theoretically by setting the Reference to 0v you might be able to detect a positive going voltage as low as 10mV, though I haven't tried that.

[Acetronics2]

Take a look at the MC34064 low voltage detector. Connect this to a port pin and check the pin to decide if you want to blink the LED

Jerson

Hi, Jerson

As the 34064 detects 4.65v ... how do you do this kind of miracle ???

Alain

[Jerson]

Hi Alain

Since Charudutt did not specify how low is low voltage for him, I assumed. Anyway, I have a similar app where I use 6V for supply and 4.65 is low enough for the circuit to stop operating correctly.


Jerson