How could I make a low battery indicator?

aoLhaTer · 12-02-2006, 09:47 PM

I'm not talking about the accurate ones which take into consideration discharge history, temperature, chemistry, etc. I'm talking about just terminal voltage (ie battery hits X voltage and an LED goes on)

I found this schematic http://www.maxim-ic.com/appnotes.cfm...te_number/1872 but the IC required is absolute TINY, no possible way to solder it

Wiredwrx · 12-02-2006, 10:36 PM

Quote: Originally Posted by aoLhaTer

I'm not talking about the accurate ones which take into consideration discharge history, temperature, chemistry, etc. I'm talking about just terminal voltage (ie battery hits X voltage and an LED goes on)

I found this schematic http://www.maxim-ic.com/appnotes.cfm...te_number/1872 but the IC required is absolute TINY, no possible way to solder it

You can try the one on this page,
http://ourworld.compuserve.com/homep...den/page11.htm

Actually, you should

http://www.google.com/search?hl=en&q=led+voltage+meter

Michael

2k1Toaster · 12-02-2006, 11:00 PM

Quote: Originally Posted by aoLhaTer

I'm not talking about the accurate ones which take into consideration discharge history, temperature, chemistry, etc. I'm talking about just terminal voltage (ie battery hits X voltage and an LED goes on)

I found this schematic http://www.maxim-ic.com/appnotes.cfm...te_number/1872 but the IC required is absolute TINY, no possible way to solder it

There is this pretty nifty solder goop stuff for small IC's and you squirt it on the contacts once placed in a PCB, and stick it in the toaster oven (No joke) and the solder beads up around the IC's pins, and sticks it to the PCB. Soldered! Then the PCB can have big globs for you to manually solder to.

I'll try to find the link

aoLhaTer · 12-04-2006, 12:31 AM

Quote: Originally Posted by Wiredwrx

You can try the one on this page,
http://ourworld.compuserve.com/homep...den/page11.htm

Actually, you should

http://www.google.com/search?hl=en&q=led+voltage+meter

Michael

That first link has a nice one, thanks (IC can be bought at Radio Shack too)

Was googling for "low battery indicator" opposed to voltage meters since thats more along the lines of what I want but I will definitely settle for that simple voltage meter if need be. Only reason I wouldn't use it is because it consumes more power. All I really need is an LED to come on when some voltage level is reached. This is for a bicycle lighting project so battery life is a major consideration.

Wiredwrx · 12-04-2006, 12:42 AM

Quote: Originally Posted by aoLhaTer

That first link has a nice one, thanks (IC can be bought at Radio Shack too)

Was googling for "low battery indicator" opposed to voltage meters since thats more along the lines of what I want but I will definitely settle for that simple voltage meter if need be. Only reason I wouldn't use it is because it consumes more power. All I really need is an LED to come on when some voltage level is reached. This is for a bicycle lighting project so battery life is a major consideration.

I don't think there is a way to trigger/light an LED when voltage drops (a battery dies because/when the voltage drops below a certain level) to a predetermined or specific level, with out being powered. Perhaps you can just add some sort of button, that when pushed, will light an LED, unless it is below a certain voltage. You can do this with a large value resistor in series with the LED, that won't light when the voltage is too low.

Michael

davesaudio2 · 12-06-2006, 07:34 PM

http://www.electronics-lab.com/projects/models/004/

ramy_zohair · 12-06-2006, 10:57 PM

Quote: Originally Posted by Wiredwrx

I don't think there is a way to trigger/light an LED when voltage drops (a battery dies because/when the voltage drops below a certain level) to a predetermined or specific level, with out being powered. Perhaps you can just add some sort of button, that when pushed, will light an LED, unless it is below a certain voltage. You can do this with a large value resistor in series with the LED, that won't light when the voltage is too low.

Michael

There are negation gates (ICs) that can be used for this. give you an output if there is none and vice versa... basic digital electronics. or you could use a relay.