Question Low battery indicator

[Bakuku]

http://modretro.com/xen/index.php?t...sion-of-daftmikes-low-battery-indicator.3640/

Im trying to make this. I'm using 4x panasonic NCR18650B 3.6v batteries but I don't really know how to make the circuit.

Any help is welcome!

 

[Herma]

The schematic really says most of it. Are there any particular questions? You should just need 2 of the same NPN transistors and a few resistors and a trimmer pot, as are listed.

If you're curious about orientations, you can find the orientations of various components online. In general for diodes the longer lead is the positive terminal (the side without the bar on the schematic), as for the transistors, it depends on the package, but the standard types people generally see are, if you're looking at the flat side with the leads pointing down, collector, base, and emitter respectively from left to right.

 

[Bakuku]

Do I connect it between console and batteries or just to my power switch?

The first resistor is calculated on your power source. But fully charged or advertised capacity.
7.2v or 8.4v?

 

[Herma]

2-12 goes to the positive voltage of your batteries, or your switch so the circuit is only consuming power when you are not wanting. The ground goes to the 0V (common/ground) of your batteries. You select R1 based off of your battery voltage. And I'd say the LED should be calculated at around the value you expect your batteries are low. That's because the LED doesn't light up until the batteries are low, so you would calculate it on your low voltage level. You could be safe and calculate it at a higher voltage, likely the LED will still conduct but will just be a bit dim.