Okay, I am working on a monitor for my camper. I plan to set it up to monitor A/C voltage and current, D/C voltage and current, inside temp, (at some point outside temp and A/C frequency as well as WAY in the future, the volume of my three water tanks).
I was initially planing on powering the Uno directly from the 12 power of the battery side. But I see two potential problems. One I have read differing specs on the max voltage to the Uno and one of them was 12 volts. A 12 volt deep cycle marine battery will charge at 14 volts or more and a full battery will have 13 or more. Second, even it 14 - 15 volts was okay, there is a potential heat issue. Now if I use a voltage regulator such as a 7805, I think I will still have a heat issue, just on the VR not the Uno. Also as a concern is wasted energy as power conservation is important when you are camping far from a power source.
Also how long can I run the wires from the Uno to a 16x2 lcd display?
Use a USB adapter (switching regulator) and power it via the USB port.
Length of wires - probably depends on the display. A unit that you connect to via serial interface would probably be pretty tolerant of longer wires.
While 12v is a practical limit, the Uno is good for 20v. The 7805 has been around a long time and there are probably better ways to do the job. There should be plenty of good 5v switchmode power supplies around but the project does not appear to include any real power hogs, and running it off a 1A USB car adapter should suffice.
No comment on the 1602, except that a Nokia 5110 is probably a better bet. You get at least 72 characters, and the backlight is more or less redundant.
distance of 15 feet okay? I am trying to keep the sensors as close to the power distribution as possible a while still putting the display where it would be easy to see. Would also have buttons and probably temp sensor with display.
Probably, but you know best by testing it. LCDs consume so little power that they can't put much demand on the cables., and any button connection should be quite tolerant about losing a volt. DS18B20s are available with 5m of cable.
Current Uno/Mega use LM1117 regulator I believe, and they are Not rated to 20V except as an absolute max, in which case "Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for
which the device is intended to be functional, but specific performance is not ensured. For ensured specifications and the test conditions, see the Electrical Characteristics."
Here's the regulator on the schematic:
NCP1117ST50T3G
For 5V operation, same Absolute Max, 20V: Stresses exceeding Maximum Ratings may damage the device. Maximum Ratings are stress ratings only. Functional operation above the
Recommended Operating Conditions is not implied. Extended exposure to stresses above the Recommended Operating Conditions may affect
device reliability.
Fixed device operation is spec'ed at up to 12V:
5.0 V: Vin = 6.5 V to 12 V, Iout = 0 mA to 800 mA: Vout = 4.9 to 5.1V
CrossRoads:
Here's the regulator on the schematic:
NCP1117ST50T3G
For 5V operation, same Absolute Max, 20V: Stresses exceeding Maximum Ratings may damage the device. Maximum Ratings are stress ratings only. Functional operation above the
Recommended Operating Conditions is not implied. Extended exposure to stresses above the Recommended Operating Conditions may affect
device reliability.
Fixed device operation is spec'ed at up to 12V:
5.0 V: Vin = 6.5 V to 12 V, Iout = 0 mA to 800 mA: Vout = 4.9 to 5.1V
So I could run the arduio off the 12 volt battery, knowing that the actual voltage should be under 15 but at most times be in the 13 to 14 volt range. BUT, probably better still to use a 12V 1A USB charger?
parrst:
So I could run the arduio off the 12 volt battery, knowing that the actual voltage should be under 15 but at most times be in the 13 to 14 volt range. BUT, probably better still to use a 12V 1A USB charger?
You can run it off 12v battery. I only mentioned 20v because it is a bigger number than 12, and it clearly means that you aren't going to fry it with 14v. I wouldn't ask where you would get the 20v from anyway. I raised the USB charger because
it delivers similarly to the PC you are likely to be using already
the situation is testable
your power requirement is not likely to embarrass the supply
they cost about $3
They appear to be a lot more efficient than the on-board regulators
The last is noteworthy. You only have to stick your hand on an Arduino being fed with 9v to conclude that long term supply at 12v merits some thought. USB adapters on 12v are good for 1000mA and can stay a lot cooler than Arduinos on 9v while charging Apple devices which have a similar power demand.