Newbie needing some assistance with a project.

[Aperturelab]

I want to create a battery tester. Consisting of multiple LED's that go of as the power deplets. id say a 1/2v jump from one to the next. ranging from 1/2v - 4v. Im very new to electronic work, so any help is much appretiated

 

[chopnhack]

Welcome to the forum Aperturelab.

To clarify, a battery tester or a battery power level meter? Is this to be in circuit continuously or will it be used like a tester, and put across the terminals when in use?

 

[Aperturelab]

Youre right, It will be in circuit constantly

 

[chopnhack]

So to clarify, you are looking to produce a battery level meter.

 

[Aperturelab]

Yep

 

[chopnhack]

Ok, what research have you done so far to come up with a solution to your problem? There are many ways to approach this problem from μcu to op-amp and other methods in between. What are you comfortable working with?

Edit: Does the LED indicator have to be fed off of the battery or will there be another power source and what would the maximum allowable consumption of this circuit be if there is no additional power source?

 

[Aperturelab]

Well, i was looking into these schem's, but im unsure how to step them down. They're not sensitive enough.

http://hackaday.com/2008/07/03/led-battery-level-indicator/

http://www.eleccircuit.com/simple-voltage-indicator-by-led-and-zener-diode/

It would have to be self powered as well, trying to keep my setup with least amount of replacement requiring components as possible. As for consumption rate, im assuming if i use very small LED's, it wouldn't draw much power, so i didn't really consider it, to be honest. As for what my actual plan of attack is? I honestly haven't the faintest.

 

[chopnhack]

The main problem I saw from your initial request is that LED's require a forward drop of about 2 volts. Do you understand what this means?

 

[Aperturelab]

ah, i see. so if i do want 1/2 volt increments, it would definitely need an external power source.

 

[chopnhack]

Correct, you would be able to sense from 4 to about 2.5, but lower than that and the diode would not become biased, thus no current would flow and the LED would fail to light up. Even if you used something like a LM3914 you would need an external source, since this IC can run on no less than 3V.

What are your thoughts now?

 

[Aperturelab]

yeah. the battery im wiring is 4v at full charge. I can make space for a 9v.. hm... Mind if we continue this tomorrow? Im going to do some testing with the battery i have, at the moment. You've given me a lotto consider, thanks!

 

[chopnhack]

Sure, post when you can and lets see what you are thinking!

** I am going to ask the mods to move this from offtopic to perhaps circuit help**

 

[Aperturelab]

So i did some testing of the battery voltage, when my device (the one for the battery) says its almost dead, and when its full. At supposed 20%, its at 3.1v. at full, its 4.1v roughly. So i suppose that's fine for self-powered meter. I guess my new question is can i get smaller than half volt increments wired to LED's, and what id need to do that. I just dont know how complicated it would get for a more sensitive step up/down

 

[chopnhack]

Have a look at the chip that I linked in post #10, I think this is pretty much what you are asking for in a ready made package.

 

[Aperturelab]

took a gander when you posted it, it seems like it was made specifically for this as well. Says it can output 2ma to 30 ma, which sounds like what im looking for, if my understanding is correct

 

[chopnhack]

It's an ideal solution I think. Just needs an additional power source, so your 9v should work just fine. Incidentally, why not just use a voltmeter when you want to check the status? Is it hard to reach? This device will consume some energy as will the LED's

 

[Aperturelab]

well, i mainly just want the ability to tell the battery life at any moment. its also something i keep on me quite frequently, so i feel like itll be a very usefull addition. Functionally and aestheticlly

 

[Aperturelab]

im willing to trade in ther battery for something a bit heavier, but for now its a trial and error kind of project. seeing how far i can take what i have, and improving on it

 

[chopnhack]

Cool. There are many LED's that are of higher efficiency that don't need a full 15mA to be bright. Look around for superbright or clear lens type LED's many of those should give ample illumination at about 7-9mA so that should help extend your second source's life. The IC itself doesn't consume much from the spec sheet. If you can wait a bit, super cheap.

 

[Aperturelab]

ahah, way ahead of you. funnily enough, i bought from the exact same seller. Ill start looking for the LED's now too. Youve been so tremendously helpfull and patient with someone that barely knows anything of this world. This project of mine was the first time i needed electronics in my pieces, I found this portion so daunting but I couldn't let a moment to learn something new, slide.