Also, the thought of using resistors as a voltage divider has brought up the fact that the battery may only last as long as a 5v.
So I can just wire a positive wire to the Vin on the arduino and a negative wire to the ground pin from a 12v battery? I was worried that the arduino would fry up or something.
I will take that as a complicated way of saying yes. Lol.
The battery we have is a NP7-12, 12v, 7.0Ah : Sealed Rechargeable Lead-Acid Battery. It says genesis on it and www.enersys.comWe need the Arduino to pull information off (separate) 12v car batteries and send that information wirelessly through Xbee for an hour.I have not had the time to look up the battery's specifications yet, but I will later.Any help is appreciated.
The battery we have is a NP7-12, 12v, 7.0Ah : Sealed Rechargeable Lead-Acid Battery.
Well a basic arduino board draws about 50ma for it's own uses, so maybe 140 hours from that battery. But I suspect you may be powering other external devices and components that draw power from the arduino +5v pin or directly from the +12vdc battery? If so that current consumption would also have to be factored in to get a total battery run time estimate.Lefty
It's not clear to me from this, but I assume the overheating problem is on the 5V regulator onthe Arduino board, due to its dropping a full 7V when the 12V battery is used.7V * (whatever current is being drawn) = Pd, the power-dissipated in the v.reg.For tiny SOT223 v.regs used on Arduino boards, Pd can be only .3W or .5W before the regulatorstarts getting really hot. So, that means current in the range of only 50-mA or so before heatstarts rising. XBees and XBee Pros draw a lot more current than that when transmitting. As others mentioned, linear v.regs are not very efficient. As you mentioned, 9V batteries like the little 1" sized things, won't run your system for more than a few minutes.Short of going to a switching regulator, I would try a series-R rather than a voltage divider, pre se. With a full v.divider, the resistor going to ground will suck your battery dry in no time.Rather just try using a series-R alone, with 4-5V being dropped in the resistor. Then, theseries-R will get hot instead of the v.reg, and that's a much better deal. 4V/.250Amp = 16 ohms or thereabouts. It needs to be at least 2W size.You're still wasting a lot of battery in the series-R, as compared to using a switching supply, but at least it should work.
I would just get one of there:DC-DC adjustable switching regulator module.
Or one of these if you'd like to get it sooner rather than later.
Your battery is 7 Amp hours, which means that it can more or less deliver 7 Amps of 12 Volt power for one hour. You should have plenty of power for what you want to do. UPDATE:Let me give you some figures. I looked up the XBee and XBee Pro. They take 50 mA and 300 mA (respectively) of 3.3 Volts. The Arduino will take about 50 mA of 5 Volts. Your battery will provide 84 Watt hours of power. So if you use two relatively high efficiency switching voltage regulators (one to give 5 Volts to run your Arduino and one to give 3.3 Volts to run your XBee), in theory the XBee will take 165 milliwatt hours, the XBee Pro will take 990 milliwatt hours, and the Arduino will take 250 millwatt hours. So the XBee/Arduino combination will run for about 200 hours, and the XBee Pro/Arduino combination will run for about 65 hours. Even if you just use linear voltage regulators instead of switching regulators, you should have plenty of power. The XBee/Arduino combination will run for about 70 hours, and the XBee Pro/Arduino combination for 20 hours.
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