Low Battery LED Indicator Board [OSHPark]

[Helder]

Hey guys I have this board I whipped up that I have tested on breadboard and it works good but you need to adjust the value of when the LED turns on with the Potentiometer. I ordered 3 to come in so I can test it and get some proper values but I know some people have been looking for something like this for their builds.

SMD Version:
https://oshpark.com/shared_projects/Q2XKys7X



Parts list for this project:
Transistors:
http://www.taydaelectronics.com/t-trans ... b-215.html

33K Resistors:
http://www.taydaelectronics.com/resisto ... -0805.html

10K Resistor:
http://www.taydaelectronics.com/resisto ... -0805.html

47k Potentiometer (Variable Resistor):
http://www.taydaelectronics.com/potenti ... r-6mm.html

Red LED:
http://www.taydaelectronics.com/leds/ro ... m-red.html





Through Hole Version:
https://oshpark.com/shared_projects/btIHScY7



Parts list for this project:
Transistors:
http://www.taydaelectronics.com/t-trans ... istor.html

33K Resistors:
http://www.taydaelectronics.com/resisto ... istor.html

10K Resistor:
http://www.taydaelectronics.com/resisto ... istor.html

47k Potentiometer (Variable Resistor):
http://www.taydaelectronics.com/potenti ... r-6mm.html

Red LED:
http://www.taydaelectronics.com/leds/ro ... m-red.html




Now the way this circuit works is the two transistors are configured as voltage sensor and inverter.

The first transistor on the left senses the threshold voltage level as per the setting of the 47K preset. As long as this transistor conducts, the second transistor on the right is held switched OFF, which also keeps the LED switched OFF.

As soon as the battery voltage falls below the set threshold level, the left transistor is no longer able to conduct.

This situation instantly triggers the right hand side transistor, switching ON the LED.

The LED switches ON and provides the required indications of a low battery warning.





-----------------------------------------------------------------------------------------------------------------------------------------------------


I got some solid values to make the board a little more low profile without the pot and it comes on at 3.26V so no need to tweak the pot.

SMD Version:
https://oshpark.com/shared_projects/KtfWqSdE






Through Hole Version:
https://oshpark.com/shared_projects/N6qwkU4V

[Lanceomni]

You are awesome. Ordered.

[username 123]

So we buy the board from there and then populate it ourselves?

[Lanceomni]

Yep

[Helder]

Updated first post with a friendlier through hole version and explain what and how the circuit works plus added parts links. This can be built for less than $4 for 3 boards.

[Ganreizu]

Where do the bat+ and - lead from? Something from the pwrboost?

[Helder]

Where do the bat+ and - lead from? Something from the pwrboost?

You connect the battery leads to this and obviously you need to add the battery leads to the charge/boost board.

This isn't for the powerboost1000c since it has a low battery LED, this is more for the cheap alternative that costs $3 since it lacks this feature.

[Ganreizu]

You connect the battery leads to this and obviously you need to add the battery leads to the charge/boost board.

This isn't for the powerboost1000c since it has a low battery LED, this is more for the cheap alternative that costs $3 since it lacks this feature.

Ahhh i see. Good stuff! I got a batt_dmg from kitsch-bent and was going to hook that up to the LBO, hoping that will give me a good battery indicator.

[Helder]

You connect the battery leads to this and obviously you need to add the battery leads to the charge/boost board.

This isn't for the powerboost1000c since it has a low battery LED, this is more for the cheap alternative that costs $3 since it lacks this feature.

Ahhh i see. Good stuff! I got a batt_dmg from kitsch-bent and was going to hook that up to the LBO, hoping that will give me a good battery indicator.

That's a bit pricey and not sure what the IC draws but I know this circuit (the boards in first post) draws 1.5mA to function and go as low as 1.4v for the threshold sensor but obviously we don't need that as that is way too low.

[Ganreizu]

That's a bit pricey and not sure what the IC draws but I know this circuit (the boards in first post) draws 1.5mA to function and go as low as 1.4v for the threshold sensor but obviously we don't need that as that is way too low.

Yeah i'm not sure if batt_dmg is appropriate for GBZ build. Just kind of bought it for the hell of it so if it worked great if not oh well. Looking like it won't work at all since it's connected to the original circuitry and is based on the batteries it's supposed to run from. Got this quote from the installation doc:

if you replace the LED with your own, assume the forward voltage to be 4.6V @ 20mA (the IC will not connect the circuit until engaged at 4.6V). use this for your calculations. the resistor is 0603 package. the included red LED is rated at 2.5V @ 20mA

the light will illuminate when the batteries can only supply 4.6V. the DMG is designed to run at 5V, with a voltage input tolerance of +/- 10%. meaning, (some of) these ICs are suggested to operate at 4.5V – 5.5V. this low-power indicator will alert you when the batteries can only supply 4.6V, so that you may extend the life of your equipment and are not surprised by a weak battery when it matters most (like a performance)