Battery Indicator

Thegamer3000 · Post by **Thegamer3000** » Fri Jan 05, 2007 1:53 pm

I want to make a battery indicator for my N64p.

All I want is a green LED when all is well, and a red LED to replace the green LED when you are going to lose power soon.

Does anyone know how to do this?

Post by **gannon** » Fri Jan 05, 2007 2:00 pm

Well, you could do what the original gameboy did and tap a LED directly to the batteries with the right value resistor so it'd fade out before the batteries were dead.

timmeh87 · Post by **timmeh87** » Fri Jan 05, 2007 11:48 pm

you can get leds with a green and a red built into one lens.

there was some chip that was brought up before that was an analog voltage level meter with 10 lights. you could hook the red and the green up in such a way that it goes green>yellow>red. dont remember the name of the chip though.

Turbo Tax 1.0 · Post by **Turbo Tax 1.0** » Sat Jan 06, 2007 8:40 am

i think kurt had it, it was from battery space, but it only works with their stuff i think

blackbox_dev · Post by **blackbox_dev** » Sat Jan 06, 2007 8:53 am

Probably a little over kill, but you could use a PIC with internal ADCs...

Thegamer3000 · Post by **Thegamer3000** » Sat Jan 06, 2007 10:36 am

That idea where the LED just fades out sounds fine to me.

I'm going to use this battery http://batteryspace.com/index.asp?PageA ... ProdID=385

Could you give me a Mouser part number for a LED to use and tell me what type of Resistor to get.

I assume I just hook it up to the battery.

Thanks

codeman · Post by **codeman** » Sat Jan 06, 2007 11:12 am

well...can i make a suggestion? Why have a green LED to say "everything's fine"? Why not just have the red LED come on when the batteries are low. The green LED would just waste power, which is bad for a portable.

Also, probably the simplest way to do it with one or two LEDs is just to set up an op-amp as a comparator. You want to know when the batteries are low before the regulators stop working, so you know you'll always have a regulated 5v rail (or whatever voltage you're using). So you can just set up voltage dividers on the inputs to an op-amp. One input is the known constant voltage from the regulator, the other one is the changing battery voltage. When the battery voltage crosses the threshold you set up from the regulated voltage divider, the op-amp output will change state (from 0v to 5v for example), turning off the green LED and turning on the red one. Or just turning on the red one if you take my advice

Thegamer3000 · Post by **Thegamer3000** » Sat Jan 06, 2007 11:23 am

One Red LED is fine, just give me a diagram and a part number for mouser. Please

Super Cameraman · Post by **Super Cameraman** » Sat Jan 06, 2007 1:50 pm

codeman wrote:well...can i make a suggestion? Why have a green LED to say "everything's fine"? Why not just have the red LED come on when the batteries are low. The green LED would just waste power, which is bad for a portable.

The battery's dying, so let's turn on MORE LED's!!

Makes sense to me!

-Super

codeman · Post by **codeman** » Sat Jan 06, 2007 2:05 pm

well turning on a battery warning LED is better than "i wonder if my batteries are low...crap my game just died and i didnt save", or at least i think so

Thegamer3000 · Post by **Thegamer3000** » Mon Jan 08, 2007 12:58 pm

How do you do it?

Please tell me

codeman · Post by **codeman** » Mon Jan 08, 2007 7:04 pm

sorry, i forgot. Here's a schematic you can use. The LED might flicker a bit if the voltage "bounces", if that happens and is really annoying let me know and i'll draw up a schematic with a schmitt trigger for debouncing. I didnt do that now because it would take some research on my part...i kind of forget how to do it.

It's set up to turn on the LED when the battery voltage drops to about 6.25volts. If you need to change that value let me know. You'll need an op-amp that can handle the current of the LED, which is about 20mA or so. R1 is just a protection for the op-amp and LED, but it might not be needed if you get an op-amp that can handle a continuous short circuit and limits at about 20mA[/img]

Thegamer3000 · Post by **Thegamer3000** » Tue Jan 09, 2007 2:45 pm

Sorry if this sounds stupid but what Is that triangle thing in the middle is it a transistor? And also what is an op-amp or whatever? Can you give me a part number for that? Also I see these areas where 5V come off of this circuit. Where do I wire those on my portable?

Sorry if this sounds stupid, but could you explain this a little better? Also I don't think I care if it bounces. Another thing, I think the system will not work at 6.25V I'm powering a N64 and PSone Screen which I think will die at 7.2 V.

Thanks for your help.

codeman · Post by **codeman** » Tue Jan 09, 2007 3:07 pm

Ok, to get it to give you an indication at about 7.2v, you need to change R3 to 14k and R2 to 40k. That will give a trip point between 7.1 and 7.2v approximately.

The triangle thing in the middle is the op-amp (short for operational amplifier). To find one just do a search for "op-amp" on digikey or something and you'll get tons of options. As for the 5v, i was assuming you had a 5v regulator somewhere, do you not? Or are you using 3.3v?

Post by **gannon** » Tue Jan 09, 2007 3:25 pm

The n64 has 1 7805 and the psone lcd has 2.