I'm trying to make a simple charge indicator using a transitor on a 12v project that will turn on a led or flash a led once it gets to 10.5-10.8 volts!!

 

use an op amp as a comparitor.

opamp

 

Would like to make blink at the given voltage drop? Would you have a schematic of a built circuit for a 12+ volt system that will indicate at 10.5-10.7 volts to blink led.??

 

You need a 555 timer IC circuit to build yourself an LED flasher. Just look for it on this site, authored by Bill Marsden. Lots of options.

As noted, you can then use a comparator to turn the flashing circuit on when the system voltage sags. You need a voltage reference to "calibrate" the comparator. I would use resistor voltage dividers to divide down the system voltage, to compare to your reference. For instance if you use a 5V zener diode as your reference voltage, you will divide your system voltage by ~2 to tell when the divided voltage falls below the reference. With a variable resistor as your divider, you'll be able to dial in whatever setpoint you want.

 

Would like to make blink at the given voltage drop? Would you have a schematic of a built circuit for a 12+ volt system that will indicate at 10.5-10.7 volts to blink led.??

Flasher circuit

Simply make the comparator circuit , set the preset VR2 to make the op amp go high(pin 6) at 10.8v, and then connect it to the flasher circuit on pin4 of the timer ic, this will make the flasher work at the set voltage, use a 6v1 zener for the reference.

 

You can use one of these..... http://www.radioshack.com/product/index.jsp?productId=12708931
instead of the 555 circuit to get the flashing function.