This battery monitor circuit is used for monitoring the battery’s condition through the three LEDs. The threshold level of the red LED is controlled by potentiometer 2, yellow by P1 and green by P3.

The setting of each pot is quite critical and must be adjusted repeatedly until the correct threshold level is reached. Finnaly, the pots must be replaced by fixed value resistance values. These resistance values can be found by measuring the actual resistance setting of each pot.

This level battery indicator circuit that lets you know the battery level of a device from the number of LEDs that are glowing, it uses ten LEDs in all. So if three LEDs glow, it indicates battery capacity of 30 percent. Unlike in mobile phones where the battery-level indicator function is integrated with other functions, here only one comparator IC (LM3914) does it all.

This is a simple DIY iPhone charger circuit that can be built with a few resistors.
First, you need to buy 4 resistors with this values: 2 of 50 kΩ, 1 of 100 kΩ and 1 of 150 kΩ.
Ok, you got 4 resistors, now you need a 5V power supply, you guessed it, another USB cable. An USB cable has +5V on pin 1 and -5V (or ground) on pin 4.

If you can handle a cutter, gently cut off the isolation and reveal the wires inside. See what colors the wires have that are connected at pin 1 and 4. Note or remember and then with an soldering gun solder the cables to the iPhone charger circuit like in the schematic.