I am working on a machine for use in 90% humidity and up to 110 F temperatures. The machine is controlled by arduino. Can anyone tell me if I need to add anything to make sure an arduino can handle that environment?
A dehumidifier and an air conditioner.
Check the datasheet.
Which arduino? what does the spec says about the working conditions?
you'll likely need to protect it from moisture and heat. As @jim-p said,
How long does it need to run?
Adding conformal coating on the Arduino board can protect it from moisture and of course Power supply and connectors should also be rated for that environment... May be using a sealed enclosure with proper ventilation and a desiccant to reduce humidity inside would work for some time?
I cant fin about humidity. (UNO)
It would be the control system for an industrial sewing machine in a Mississippi factory with no climate control. Used for a shift a day, 5 days a week, all year.
Would just a constant fan work well enough, or do I need to increase the price with a dehumidifier?
Blowing around humid air does not make it less humid. Humidity is a bigger problem that temperature because you may have water condensation on the board.
Which arduino are you using?
Working with arduino 3 and 4 at the moment. A fan would keep the board free from liquid water.
Not really, you are just blowing more hot humid air on the board. Conformal coating as @J-M-L suggested would be a good solution but I don't know of anyone who has actually tried it on an Arduino.
The problem is not what you listed, but when the temperature drops, then the RH will be 100%.
To avoid problems, conformal coating is the answer, but only after you have prepared for it. First there can be NO connectors of any kind because they cannot be coated. So, all connections must be soldered using lead-free solder if possible. Only then can you conformal coat the circuit boards. Use spray polyurethane so you get all the nooks and cranies coated. But, that only takes care of the Arduino board. What of all the other components?
Other components like step motors will be IP rated as appropriate.
What about the stepper motor driver and the power supply?
The power supply I can get IP rated. The driver is a simple chip on a breadboard. Conformal covering time.
I'm not an expert on conformal coating but coating devices that dissipate a lot of heant like voltage regulators amd motor drivers could be a problem.
You cannot be serious about environmental problems and are using a breadboard!
110F is far short of AVR heat limits.
If you put the electronics inside of an enclosure, you could cool that with a Peltier wafer and a large passive heat sink.
Humid air transfers heat quicker than dry air. It's got more latent heat capacity.
If the factory was roofed with solar panels, it wouldn't be so hot.
The large drive and its motor will have to be bought IP rated. The small stuff doesn't turn out a lot of heat. There is a good boundary between summer temp and max 185 temp. I will also have a fan on it continually from on until cool again.
There are no air conditioned room in that facility? (Install the critical stuff away from the sensors - use an industrial bus to transport the signals)
Putting in that much wiring would kill the deal. AC is not close. That far away the signal delay would also cause problems.