I'm building a battery pack, and I need it to become open circuit as soon as it goes below 20v. My battery Is normally at 24v-22v.
What would be the easiest way of achieving this?
I imagine some sort of relay would somehow get switched somehow...😕
What would be the easiest way of achieving this?
I imagine some sort of relay would somehow get switched somehow...😕
Consider a micropower comparator driving a MOSFET. Otherwise you would need a latching relay because standard relays would draw substantial power continuously and would drain the battery.
Hold on, gotta find it again... I used a derivatie of this circuit for a low battery detector on model aircraft to sound a piezzo...
You should be able to knock one together from the LM311 datasheet..
You should be able to knock one together from the LM311 datasheet..
K, I'll check out the data sheet.... If you have a link to the circuit tho that would be great🙂Nordic said:
The problem with a comparator is you need a reference voltage. You could use a switching voltage doubler and then a regulator to get a 20 volt reference. This method has the potential to be very accurate.
Or a 20v zener diode could be used.
Or a 20v zener diode could be used.
Check LP2950, it's a micropower 5V regulator. Once you have a 5V supply and reference, a PIC micro with built in comparators may be much more functional than a plain comparator. All this is posible with less than 0.5mA battery drain.
Ok, I'll check out the comparators...
For a reference could I get away with cr2032 cion cells in series? I could use a few diodes to drop 21v down to 20v...
For a reference could I get away with cr2032 cion cells in series? I could use a few diodes to drop 21v down to 20v...
A relay drawing 50mA to 100mA will drain the battery quickly. Not to mention that relais usually close at 75% rated voltage and open below 50%.
The "micropower" way with 5V reference, hysteresis comparator and power MOSFET can do accurate switching without draining the battery.
The "micropower" way with 5V reference, hysteresis comparator and power MOSFET can do accurate switching without draining the battery.
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