12 Volt battery meter with output?

[dhcomp]

Ok, so i would normally post this in the garage, but the audio form is dead, no one is ever in there

So, newly installed remote start has a trigger wire that will start the truck when grounded. I thought it woudl be cool to put this to use.

Anyone know of a battery meter or the like that would operate on 12v, and output a signal i could use when the voltage drops below a preset value?

I'm thinking that i could wire it to start itself and charge (for 20 min, the current remote start run time) whenever the battery got low. I don't have normal issues wiht the battery getting low, but i do often use the lights/stereo at night in party situations. Would be sweet to not have to monitor it and to just let it play.....and start itself as needed.

Any ideas? I think it would be pretty trick. Also the words most fuel inefficient generator/radio.....but whatever.

I have a 2nd battery if i happen to kill my primary by lights/stereo, but its not exactly hooked up. It just sits there....until i jump myself manually.

Thanks guys!


EDIT:

Maybe i could do something like this, wish i hadn't done so bad in circuits

http://www.reconnsworld.com/power_12vbattmon.html

Would really prefer a manufactured setup, but i could probably get someone to make it for me. I guess i could test it on a breadboard setup.

 

[dremu]

It's so ridiculously cheap and relatively easy to DIY, I donno why you'd buy pre-made.

That circuit actually is prolly the simplest electronically, but what you're asking for is screaming for a comparator.

The venerable LM341 would do what you need, IIRC. You'd need some way to set the comparison voltage, i.e. a zener diode and maybe a resistor, and then a resistor/transistor to amplify the output to drive a relay wired into the ignition.

If you want the truck to turn OFF at some point, you'd either need a timer or another comparator, bascially turn the motor off when the voltage goes above, say, 13.5 or whatever. That might be a bit tricky, as the alternator might peak the charge voltage briefly ... the timer idea might be better.

You'd also need a latch or something for the on/off bit.

Anyway, it's less than ten bucks in parts but does involve some time in designing and soldering... but yeah, breadboard it

[And I forget, are you still up there in bicycle town, or are you down in the Bay more now? Or am I thinking of someone else from Davis?]

-- A

 

[dhcomp]

Thanks for the response man. Ive been slow at work and posting some on here before researching i guess.

I technically still have a place in Davis, but have been living in Fremont and working in Milpitas. But in davis on the weekends.

Anyways, after i reread that schematic, there is a Potentiometer in there to adjust trigger voltage. I figured i could use a dimmer switch or somethign to test the circuit with different voltage levels to see what point it is triggering at.

Main reason i am considering this, is all i need to make it work is a pulse at low voltage. The remote start does not need a latched signal, just a momentary trigger to tell it to start. It also times itself, and i can set it to run for 5, 10, 15, or 20 min. Its set at 20, cause ive walked outside too many times in the morning after getting ready to find it shut down 2 min before, haha.

I figure i could just replace the LED with a relay, will i get enough current out of a circuit like this to make it click? Or really, it might be able to trigger the alarm start directly.

Basically, i could build that schematic w/o problems. I am just worried i'd have to alter it in some way, cause i seriously remember next to nothing from circuits.

Are most of those compnents available at radio shack? I shoudl "hire" someone to build it for me, solder it up, and put it in a little box. Haha.

Thanks man!

 

[dremu]

Thanks for the response man. Ive been slow at work and posting some on here before researching i guess.

I technically still have a place in Davis, but have been living in Fremont and working in Milpitas. But in davis on the weekends.

Anyways, after i reread that schematic, there is a Potentiometer in there to adjust trigger voltage. I figured i could use a dimmer switch or somethign to test the circuit with different voltage levels to see what point it is triggering at.

Main reason i am considering this, is all i need to make it work is a pulse at low voltage. The remote start does not need a latched signal, just a momentary trigger to tell it to start. It also times itself, and i can set it to run for 5, 10, 15, or 20 min. Its set at 20, cause ive walked outside too many times in the morning after getting ready to find it shut down 2 min before, haha.

I figure i could just replace the LED with a relay, will i get enough current out of a circuit like this to make it click? Or really, it might be able to trigger the alarm start directly.

Basically, i could build that schematic w/o problems. I am just worried i'd have to alter it in some way, cause i seriously remember next to nothing from circuits.

Are most of those compnents available at radio shack? I shoudl "hire" someone to build it for me, solder it up, and put it in a little box. Haha.

Thanks man!

Aha! Ya know, I was gonna suggest a remote starter, 'cuz it would make things a LOT easier.

You're on target with the dimmer ... except your basic AC light dimmer won't work, and you need a potentiometer =))

All of that stuff is available at Radio Shack, or at Fry's. You'd have to cross the 2N3904 to an NTE number, but they should have a book there or you can do it online (or I can

Sure, the transistor can drive a relay. Your basic Bosch style ice cube relay has a coil current of 70mA or so, IIRC. Take out R3 along with the LED, as it's just a current limiter for the LED.

You might be able to take the collector of that transistor and drive your remote start directly (keeping the LED, or something else as a pull-up load), but it depends on whether your remote box wants a negative pulse or positive or what, so the relay is simple, cheap, and easy

If you get totally stuck, I can help; worst case, you come up here and buy burritos and I can prolly set you up.

-- A

 

[dhcomp]

Sweet, thanks man. I wonder if i have my breadboard from school kicking around davis somewhere.

I'd love to set it up and give it a shot. I may look into it in the next couple weeks, might be a good "i'm living at home and missing most of my tools" project.

The more i thought about it though, i really need the whole thing on a switch....so its not just randomly starting if the battery gets low....and i'd turn it on when im gonna run it low. If it seems to work well though, i would leave it connected all the time.

I'll keep you updated. Appreciate your responses!

 

[dremu]

Sweet, thanks man. I wonder if i have my breadboard from school kicking around davis somewhere.

I'd love to set it up and give it a shot. I may look into it in the next couple weeks, might be a good "i'm living at home and missing most of my tools" project.

The more i thought about it though, i really need the whole thing on a switch....so its not just randomly starting if the battery gets low....and i'd turn it on when im gonna run it low. If it seems to work well though, i would leave it connected all the time.

I'll keep you updated. Appreciate your responses!

Umm, yeah ... you'd want an override for it OTOH, that's a $2 toggle switch to the circuit. Easy peasy.

And no worries -- at one point years ago I was gonna get a PE, either EE or ME, maybe even at Davis. That doesn't seemed to have happened and I'm now pushing 40, but I still do some soldering in my spare time.

-- A

 

[dhcomp]

I do NO soldering in my spare time. Just one of those things i have never taken the time to learn to do right. Guess everyone has that one or two tasks.....