Low Voltage Cutoff

[crutschow]

According to my calculations, R6 would have to be a 40W resistor...

R6 is a dummy load representing the real load.
It isn't on the actual circuit.

It does not shut off until about 12V..

If you are using the circuit in post #13 then it should trip at about 17V.
If not, then you have a wiring error or an incorrect resistor value.

 

[LukeKnepp]

I made this board, and the first time it shut off at 16.1V.
I was like "YAY"

However, after that, it did not work again.
I took off the MOSFET and tested it. It does not work.

I tried this twice and have 2 non-working MOSFETs.

Does anyone know what is wrong?

 

[crutschow]

What was the MOSFET load?

 

[LukeKnepp]

It was a 10k resistor, and that was only for a test, I was going to hook it up to my fan, but I certainly do not want to cause my fan damage.

 

[crutschow]

I see no reason for the MOSFET to fail, unless there is a wiring error.
Sounds like the drain might be shorted to ground.

 

[LukeKnepp]

Hello Everyone!!!
It's me again, wanting a little advice...
This low voltage protection board has a lot of drain after shutoff, and it also has about a 2 volt voltage drop across the MOSFET...

Are there any integrated circuits I would not have to program that would work for a low drain shutoff??

 

[crutschow]

This low voltage protection board has a lot of drain after shutoff, and it also has about a 2 volt voltage drop across the MOSFET...

What board?

 

[LukeKnepp]

What board?

 

[crutschow]

Here's my simulation of the circuit.
The voltage drop when the MOSFET is on is only about 30mV, and the OFF battery current drain is only 44uA, so I don't understand the problems you say you have (?).

Note that a value of 10k ohms for R1 is too large for proper switching of the MOSFET due to the current draw of the TL431.
It should be no larger than 5k ohms.