Leaving Arduino Permanently On

Hi Folks,

I was just wondering if it would be a bad idea to leave my arduino running nonstop without turning it off for extended periods of time (Maybe for days or even indefinitely). I was thinking of keeping it in a type of suspended mode until it reads an input value and have found a link to some suspend mode, but am already using an interrupt. I did find a website (http://www.arduino.cc/playground/Learning/ArduinoSleepCode), but power isnt really an issue. I was just wondering if leaving my arduino MEGA running would decrease its life or break something.

As of now, I am using it as a speedometer in my car and have a switch to kill the power. I would like to make it sit there and wait until the car starts before it activates to make it more streamlined. Would you suggest using a sleep mode, leaving it on, or just using the setup I have now with the manual activation of the switch.

Note: The arduino is also connected to three seven segment displays which are constantly on, displaying zeros if the car is at a standstill, but I think I can modify my code to turn them off after displaying zeros for maybe more than a minute.

no the microcontroller is pretty much designed to be used 24/7 so as long as you have power figured out it should last 20+ or so years depending if the capacitors crap out first or the avr starts loosing its memory (I bet the capacitors)

personally in a car I would just hook it up to the fuse where your radio attaches, its switched by the key

I wonder if with ROHS compliance if tin-whiskers would kill it much sooner…

:-?

/have they figured out a solution to this problem, or do they consider it a built-in obsolescence switch? Maybe I am just being cynical… :wink:

Consider the temperature range the board will be exposed to. Most electronic components not rated for automotive applications are not designed for the hot and cold extremes of a car. Generally they can be stored in those temperatures but not expected to operate in those extremes.

tin whiskers - many companies have tin whiskers mitigation plans as part of their design criteria. I believe that conformal coating a board can provide resolution.

As to leaving the arduino on, I have one data point for you: I have a 3.3V Promini running from 3.7V 1000mAH LI Ion battery, it wakes on keypress and goes into powerdown mode after transmitting a button push. Has been powered up like that for several weeks now with no issue. Battery voltage still reads 3.78V.

figured out it should last 20+ or so

Designing anything with a 20 year life is going to be tricky.

Also there is no way of telling how long one of any design will last, it is down to a probability or how many out of 100,000 will fail per year.

I have a clone that's been running continually for more than a year. Fully powered up at all times and used several times a day (electric gate contoller). I've had to 'fix' it about 3 times. Once for a sticky relay, once for a failed thermal cut-out and the last time as a wire that had come loose.

I've got an Arduino based controller running 24x7 for a couple of years now - no problems.

As other mentioned, automotive temperatures could be a problem.

I suspect a more likely problem would be the Arduino killing your car battery - especially shortening the battery life. I had a surplus GPS unit (old one, but of a power hog compared to current models) that I powered with a 7805 circuit, 24x7. That battery lasted about 2 years. I installed an APO (a newer model than mine here) and the next battery lasted 5 years.

-j

The ATMegas (328P) are spec'ed for up 85C (185F) operation. So, not quite boiling water hot, but pretty warm!

I imagine if you powered it with switching regulator vs a 7805 it'd be easier on the car battery long term, especially if you went into power down sleep mode when not active.

How are you controlling the seven segment displays? If you have dicrete chips, you may be able to write an F to them blank them, or if you have something like a MAX7221 that can also blank them for less current draw.

The ATMegas (328P) are spec'ed for up 85C (185F) operation.

That just means that they will work at that temperature not that you get the maximum lifetime at that temperature. As an approximate rule of thumb the life time doubles for each 10C cooler you can make it run.