Operating temp for a Picaxe

[meridian]

I am planning a controller for my diesel generator. Probably a 20M to measure various temp inputs and control relays for throttle, alternator, etc.

Anyway, in the engine room after a couple of hours running, the temp is about 45C. After many hours of the Detroit Diesel running (up to 24 if there is no wind) the temp can reach 55C.

Is this a problem for an 'axe?

paulr
Bali, Indonesia

http://www.winlink.org/dotnet/maps/PositionReportsDetail.aspx?callsign=vk2ahb

 

[westaust55]

From the datasheet for the 28X1/40X1:


Absolute Maximum Ratings (= NEVER TO BE EXCEEDED)
Ambient temperature under bias.......................................-40° to +125°C
Storage temperature .................................................... -65°C to +150°C

Standard Operating Conditions (unless otherwise stated)
Operating temperature
-40°C ≤ TA ≤ +85°C for industrial
-40°C ≤ TA ≤ +125°C for extended


TA = ambient temperature

 

[Dippy]

For the latest and straight "from the horse's mouth" info then download the Microchip Data Sheet.

The 20M is based on the PIC 16F677.

Whilst Westy's quote is correct we sometimes need to look a little more deeply.

Firstly, PIC numbers have a suffix defining whether 'commercial' or 'industrial' grades.
These grades have slightly different temperature ranges where the performance is in spec.
(Sometimes specifications are not absolute, but a figure +/- something , a statistical spread)

Secondly, (for Internal oscillators) where oscillator speed is crucial then we have to study the change in frequency with temperature.

It is possible to lose comms if the temperature is excessive in either direction. Many specs are listed at a certain temperature.

The 'safe' range of operation is usually -40oC to +85oC ('Industrial' grade), so you should be OK.


Heat dissipation is another issue when pushing things but that's for another day.
And, in some situations for battery powered devices, it's an idea to study battery performance too.

Sorry for long post. I only make these points as general comments and something you should note for the future.

 

[hippy]

The 16F677 datasheet is the best place to look as recommended by Dippy. Note there are a whole range of tables and figures showing what changes with temperature. As well as operating speed the voltage points for inputs indicating high or low can change. ADC readings may change. None of that may be a problem but depends on your circuit and how it is meant to work. Similar issues arise at lower temperatures. Most components are affected by temperature.

You can mitigate the problem by mounting the PICAXE lower to the floor, even outside, to keep the PICAXE controller cooler, but longer cable runs may mean more interference and susceptability of EMI which has to be taken care of.