How to Make a Battery Level Indicator

This project is a battery level indicator or a battery tester. The circuit take the input voltage from the battery that is connected and tests the level of voltage left in the battery through the use of diodes and an integrated chip. The circuit works to show you the remaining battery capacity by the use of the LED's. Each LED represents 10 % of the total battery. The Circuit is designed around the LM3914 IC, which is an integrated chip for a LED dot/bar display driver. The integrated chip can work under an effective voltage from 3 volts to 15 volts, but its breakdown voltage theoretically is up to 25 volts. The circuit worked as planned for both a 9 Volt battery source and a 12 volt source, as tested by two different batteries.

• LM3914 IC
  • If you are interested in the data sheet for the Integrated Chip the download link is here:
    • https://www.ti.com/lit/ds/symlink/lm3914.pdf
• LED's
  • Red 3
  • Yellow 4
  • Green 3
• SW-SPST Switch
• Resistors
  • 18 K Ohm
  • 4.7 K Ohm
  • 56 K Ohm
• 10 K Ohm Potentiometer
• 12 Volt Battery
• Connecting Wires

To set up the breadboard you first want to create a jump from positive to positive and negative to negative.

This will connect both sides of the the breadboard so you can plug each component into the same power and the same ground.

You then want to put in your battery connector with the red wire to the positive and the black to the negative side. This will supply power to the circuit and will also ground it as well.

Starting with your green LED's first, start at node a-19 and place the positive side in the (+) column and the negative side in the node. Each LED should be spaced one pin apart for each other, so your first LED is on node a-19 the next one will be placed on node a-21.

You will start with all the green LED's first then move on the the yellow LED's next, followed lastly by the red LED's.

Your last LED should be in node a-37.

Take your LM3914 IC and place it on nodes e-f 52 to nodes e-f 43.

In this step we will place all of our resistors into the circuit.

• Place your 18 K Ohm resistor with one end on node g-52 and the other end to the (-) ground.

• Place your 53 K Ohm resistor with one end on node g-51 and the other end in g-57.

• Place your 4.7 K Ohm resistor with one end on node i-27 and the other end to the (-) ground.

Take your 10 K Ohm Potentiometer, and wire your ground to the (-) ground.

Wire your output to node g-47.

Wire your Vcc to node i-57.

In this step we are going to wire all the LED's to the IC. Each wire will go from the node next to the LED to a spot on the IC.

Below is the list of which node on the breadboard to wire together:

• b-19 to d-43
• b-21 to d-44
• b-23 to d-45
• b-25 to d-46
• b-27 to d-47
• b-29 to d-48
• d-31 to d-49
• d-33 to d-50
• d-35 to d-51
• d-37 to g-51

In this step we are wiring all the resistors to the IC.

Each wire node connection is as described bellow:

• j-50 to (-) ground
• i-49 to (+) power
• g-46 to f-27
• g-45 to g-27
• g-44 to (-) ground

This step is to wire in the switch. What the switch does in the circuit is to switch from dot display more on the LED's to bar display more on the LED's. With the change is displays the current draw from the battery is also different.

To wire in the switch place the switch with one terminal on g-i 43 and place the other terminal on g-i 40.

Wire from node j-40 to (+) power

Now you can test it out!

You will want the potentiometer at about 48% for a 12 Volt battery.

Just attach the battery to the battery connector and see you can see how much life it has left!