Hi everyone,
Simply, this is what I'm looking to do.
I have a 12v usb socket charger for my phone and I've been using that to power up my arduino. Can I connect this usb charger directly to the battery to keep my arudino on all the time? Will it drain my battery quickly? Or is there a better way to do it?
Thanks!
It probably won't drain your battery much faster than your onboard clock will. This question entirely depends on your power draw. What does your arduino do? How much current is it drawing?
Most cars however turn off the usb/cig lighter charger when you turn the car off. A possibility would be to get it its own battery, and run off the battery when the car is off, and off the charger when the car is on. This means that you need to use your car every so often or the arduino will die, and sometimes quick trips won't recharge the battery very much. This shouldn't be a problem for most people, but I know some weekends I don't use my car from getting home Friday until I leave again on Monday.
Say your arduino draws 50mA when on.
If you leave it on for 72 hours, that's 72 * .05 = 3.6AH drain from the battery - which typically has hundreds of AH of cranking power to turn the engine over.
So you'd probably be okay.
My 2004 Jetta Wagon's 2 power outlet's are on all the time.
CrossRoads:
My 2004 Jetta Wagon's 2 power outlet's are on all the time.
My 2009 Hyundai requires the car to be turned on in some form. I want to say my '00 Honda was also off when the car was off, but its been too long for me to be sure.
Easy way to test: Take your phone charger, plug it in while the car is off, and see if the phone charges. Also make sure it doesn't change states somehow when you crank the car, as that might give a brief power surge or interrupt the circuit. You can always run wires from someplace, though I would make sure to have significant filtering and protection to protect your Arduino from your car's power.
I think get a USB car adapter, those have switching power supply built in, then power your arduino via a USB cable.
I leave my sirius satellite receiver and my Garmin Nuvi plugged in all the time, the socket is live all the time.
Other cars may be different.
All kinds of adapters are available:
http://www.amazon.com/s/ref=nb_sb_ss_c_0_15?url=search-alias%3Dmobile&field-keywords=usb%20car%20adapter&sprefix=usb+car+adapter%2Caps%2C365
My local hardware store had them in a basket by the checkout desk even, $5 each.
CrossRoads, car batteries can be as small as 50 Ah on smaller cars. "Hundreds" is a bit of an overestimate even for larger diesel engined cars.
That could be a problem if there is additional power consumption hooked to arduino.
All that being said, there is always a fuse box that is powered all the time. It is usually near the steering wheel or in the glove compartment area.
SeanD:
Simply, this is what I'm looking to do.
- Keep arduino always on even when car is off.
Why? What function will the Arduino be performing? Unless it's performing some sort of alarm function, can't you preserve whatever data needs to be preserved in EEPROM at power down instead?
As has already been mentioned, an Arduino Uno draws about 50mA. If you park your car at the airport for 2 weeks to go away on holiday, I wouldn't be surprised if the battery is flat when you get back. If you really must run the Arduino all the time, then you need to:
Use an Arduino that doesn't draw a significant amount of power for anything other than the MCU. So not a Uno, Mega, or anything else that has a separate USB-to-serial converter.
Run the microcontroller at a low clock frequency to reduce power consumption, and/or have it in one of the sleep modes most of the time.
Rechargeable battery box connected to your car adapter in turn connected to Arduino?
My car shuts off all power outlets when the ignition is off. The external GPS's work in the same way, no?
My Garmin GPS is connected to cigarette lighter. It recharges when the car is ON but I can still use it when car is OFF.
Ofcourse it will help if you know 1) your normal mode current draw and 2) your worst case expectation of car being unused. But there are some D size rechargeable cells that claim capacity higher than 10AH!
I was thinking this
"With 640 cold cranking amps (CCA), this battery performs well even during the harsh winters."
but it doesn't indicate for how long, so "hundreds of AH of cranking power " was not quite correct.
I do know my two electronics that go into some kind of standby/charging mode when turned off never drained my Jetta battery over a weekend, and it lasted about 8 years in New England before I replaced it early last winter.
Hello everyone.
Thank you all for your insightful replies. I am using an Uno R3. The reason I will need it to be on at all times is for security purposes. It's only going to draw enough to use the arudino normally through a usb. Any other high current will be trigger through the digital pins to a reed relay.
I guess my ultimate question is whether or not anyone has tried this before. And what I mean by this is hooking a 12v usb charger directly to the battery terminals. Is the cigarette lighter the same voltage and current as directly off the battery? I'm just not too sure on this one because I'm not too techy on cars. I'm just afraid of frying my usb charger.
You've never said what kind of car, so who knows?
Got a meter? Go out & buzz your lighter, see if you have power.
If its really a Lighter it's probably fused, and may or may not come direct from the battery.
Newer, higher end cars likely have some thing powering the power socket indirectly so as not to damage anything with startup/shutdown transients.
SeanD:
Is the cigarette lighter the same voltage and current as directly off the battery? I'm just not too sure on this one because I'm not too techy on cars. I'm just afraid of frying my usb charger.
Yes for the volts, not necessarily for the current. But the latter is irrelevant
The current at the lighter is limited by its fuse, the current at the battery is determined by the fuse in the charger. Either way it should be far more than you need, hence irrelevant.
Be aware that accessory circuits are often on timers. My Ford Falcon has power available for the windows and on-board phone for ten minutes after the key is removed. It will also turn the interior lights off if a door is left open for ten minutes. Connecting directly to the battery bypasses all this stuff.
Obvious sources of permanent power are the supplies to an existing security system, the memory for the radio or the doorlocks.
Also note that a high CCA for the battery only reflects its cranking ability, and does not reflect its suitability for long-term use. The latter is best reflected by the physical size of the battery, and modern compact batteries don't take much to flatten them. In short, you need to be a bit careful about accessory loads.
I have a Honda Civic '96 Sedan. One example is to keep the device always on and implement a proximity sensor where it will trigger a reed relay to send the Horn on. Do you guys think it will be safe enough for me to wire a usb adapter directly to the batter terminals?
Ahr is usually only a small fraction of the CCA. After all, you aren't going to turn the starter for an hour.
what is Ahr and CCA? Sorry I'm not familiar with the abbreviations.
SeanD:
I have a Honda Civic '96 Sedan. One example is to keep the device always on and implement a proximity sensor where it will trigger a reed relay to send the Horn on. Do you guys think it will be safe enough for me to wire a usb adapter directly to the batter terminals?
If you mean the little bullet that plugs into lighter socket, yes. You can replace the contacts and springs etc. with flying leads. Include a fuse in one of the leads..
SeanD:
what is Ahr and CCA? Sorry I'm not familiar with the abbreviations.
CCA cold cranking amps is the short surge of power available to start the engine.
AH is amp hours - a better indication of its ability to deliver long term power. 50 AH is one amp for 50 hours or, hopefully, 50 amps for one hour.
CCA is what you want with a car battery, and I understand they are often only identified by that these days.
Amp-Hour and Cold Cranking Amps.
If you connect to the battery, be sure to use an inline fuse in your positive lead wiring.
Can pick one up a car parts place like NAPA.
Ahr means Amp Hour - How many amps can the battery put out for one hour. However, the number of Ahr (pronounced "Amp Hours") you can get out goes down the faster you draw current, so it is generally rated at the 10hr discharge rate.
CCA means Cold Cranking Amps. How much is the maximum current that your can starter draw and remain at a high enough voltage to turn the starter. So you could have a 50Ahr battery that is rated at 270CCA.
Generally, as a battery ages the Ahr rating goes down much more quickly than the CCA rating does.
Sounds good, guys. I will give it a try tomorrow.
Thanks!