Lipo low voltage alarm

m.alldatasheet.com

Search for BC847 and find the adjustable parameters

This is a Battery Low voltage output sensor/indicator... The first transistor was set to sense the battery if the voltage is getting low.. When the set low voltage level (can be adjusted by changing the values of the first 2 resistors) was reached by the battery, the first transistor will be “switched off" and the second transistor will be "switched on" by the third resistor causing that 4 LED to lit..indicating that the "set" low voltage was met

By the way.. I was confused with the title you gave to this circuit.. This does not offer any protection to the battery.. Even if it shows you that the battery voltage is low, it does not stop the battery from discharging.. It purely senses voltage level and will not switch off your rc..

I think he means to save the lifetime of lipo battery. He aims to protect it from overdischarging. İt harms lipo batteries.

BEC for battery eliminator circuit

Reducing the 1 k ohm resistor to 900 ohms does turn the diodes on. Drones have a return to location if loss of contact. Might look over drone circuits for ideas.

This is only a simple low voltage alarm circuit used for small rc planes. But as I said above, I couldn't enter the correct values to the transistors in the everycircuit to make them like bc847. Because I couldn't understand the values like emitter resistance, forward beta... I read the datasheet of bc847 but there is no value like in the everycircuit.

Forward beta will be labeled as HFE on datasheets. It's one of the most important parameters to consider when selecting a transistor, and I've never seen a datasheet that didn't list this value. Don't worry about the other stuff, just find the HFE of your chosen transistor and adjust the value here to match..

I would change it so that the LEDs are off when the battery gets low, to stop the leds draining the battery.

the default settings in EC for NPN is reasonably close to a BC547/BC847. the minimum forward beta (hFE) for that transistor is 110. that means 1mA of current passing through the base will sink 110mA of current through the collector. but when you buy a real bc847, the hFE could be anywhere up to 880, so 1mA of current into the base will sink 880mA of current! all of this means you don't have to worry too much about parameters in EC just yet

anyway the best website I've found that explains transistors simply is this one http://www.talkingelectronics.com/projects/TheTransistorAmplifier/TheTransistorAmplifier-P1.html

Is this bc847 desired for the three separate bases having three different gains? The LED will be a visual indicator for the pilot to know they are running low, not at the point for the battery to shut down yet.

Anyway, it's not a bad idea for a project, but is it really necessary? I fly electric R/C helicopters and I've found it pretty easy to tell when the battery is getting low-- first it begins to lose power (noticeably so) and then it simply won't fly anymore. Unless your plane is just really friggin cheap, its internal circuitry shouldn't allow for the battery to drain anywhere near critical. So if you've noticed that your plane is killing batteries, forget this circuit and get a new plane lol!..

@faceblast thank you for your comments and all others

@Sine_eyed I know maybe this circuit is not really necessary for my plane. But I am really interested in electronics and only want to understand basic things like this circuit. Also I have a airbrush compressor and getting really hot when I am painting my scratch build planes. So I have built a simple cooler with two 12v computer fans and a 3s lipo battery. This circuit will also work for this battery.

@dtserkanozkhan- were all here to learn, and if we are able, help others to learn as well. So if I came across as dismissive I apologize, that was not my intent. In electronics, in many cases there are many ways one particular task might be accomplished. Among these different solutions there will be some that are more simplistic, and some that are overly complex. This applies to choosing a specific circuit to implement, as well as circuit design itself. As a beginner, these options are limited due to inexperience, but will grow with time and practice. There is much to learn, so keep at it- you'll find it quite rewarding if you do.. X^)

For a quad a low voltage alarm is critical and this is an excellent alarm. Good job!