I used the AND gate because otherwise if the OpAmp is powered off both LED's would be lit. Though it is probably reasonable to assume the circuit would be powered off in whole and not in part.1. The AND gate is superfluous. Join R3 to the output of the op-amp.
2. To make it work better at low current, replace the zener with a bandgap reference. Some of them will produce an accurate reference down to 10uA. A zener is only accurate at its rated current - usually 5mA.
The circuit will work pretty well but give false reading due to the internal resistance of the battery if a heavy load is connected.
NO sir. I am using normal batteries . 9v batteryWelcome to AAC.
There are many ways to do that. Perhaps the simplest is to get a battery management chip (BMS) that includes both charger and low-voltage indicators.
Are you using rechargeable batteries? If so, what type? If not, I would delete the green LED as that will only hasten their discharge. What battery capacity and voltage are you using?
That was the concern I had in post #2. Leaving an LED on will drain the battery. Heck, the anti-theft in my cars drains the battery in a few months. A 9V battery is rated about 900 mAh. That is, it will 1 mAh of about 900 hours or 10 mA for 90 hours. You can see how an LED that was on continuously would drain it. Flashing the LED is one way to conserve life. You might also consider using an LCD (liquid crystal) indicator that has very low current drain, and only show battery status when you turn it on.NO sir. I am using normal batteries . 9v battery
Since that's just a two-terminal reference how did you get the sharp switching needed for the MOSFET gate?I have tried a LM385 (which works the same as a TLV431 but attached to the positive rail) driving a p-channel MOSFET.
There are quite a variety of LM385, both fixed and adjustble. The adjustable one is much like a TL431Since that's just a two-terminal reference how did you get the sharp switching needed for the MOSFET gate?
Or did you add a comparator to the circuit?
But see the difference in price between a TLV431 plus CD40106 versus the price of a LTC1442.
by Jake Hertz
by Duane Benson
by Jake Hertz