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Author Topic: Vivarium humidity and temperature controller  (Read 989 times)
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Hi, i'm an Alevel student doing design technology, I am trying to make a vivarium temperature and humidity control system for it, I have a DHT11 temp and humidity sensor and I have code working for that giving me serial output. I am using the Arduino Uno micro controller by the way. What I need help with is connecting a Nokia lcd 5110 display to it so it displays the serial output from the sensor, and also I am trying to connect a '2 relay module' to a bulb and mains so that when the temperature goes below a certain point it turns the bulb off and when it goes above a reading it turns it off. I would appreciate anybody's help with some code, libraries and connection diagrams, and a list of any other parts that I may need, for example a resistor for backlighting?

p.s I am very inexperienced in this field this is the first coding type project I have ever done, so i would appreciate it if you are undersatnding that I done know most of the terminology used.
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I am trying to connect a '2 relay module' to a bulb and mains so that when the temperature goes below a certain point it turns the bulb off and when it goes above a reading it turns it off.

Make sure you use a relay module designed to switch mains voltages and to isolate them from your control circuits. Don't leave any mains conductors exposed.

To switch your bulb on and off do not use a single temperature value or your bulb will flicker on and off as the temperature rises slightly above and falls slightly below the value. Instead have an "on" temperature setting and an "off" temperature setting with a decent gap between the two. Your bulb should come on when the temperature fall belows "on" and stay on till it rises above "off" it then stays off till it falls below "on".

The same applies to humidity, you don't want to be continuously inputting tiny amounts of water. What you want is for the humidity to oscillate slowly within a comfortable environmental range for your reptiles.
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For the bulb, I recommend you get a mains to DC transformer and use a low voltage bulb. Then control it by a transistor (or transistor + relay) on the low voltage side. You really don't want to combine mains voltages with home made circuits and moisture. For example, transforming the mains voltage to 12V DC would enable you to use any automotive bulb, giving you a wide choice of wattages.

I don't know how to drive a Nokia lcd 5110 display but there are plenty of small LCD displays that are easy to drive, and if you can't find how the Nokia screen works then using a known display might be the easier solution.
« Last Edit: November 01, 2012, 02:24:39 pm by PeterH » Logged

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What PeterH is saying makes sense to me, not just about the LCD and for safety but because a mains bulbs will probably give you far too much heat if the tank is small. It might be worth scouting the internet to look at the specifications of commercial units to get an idea of power requirements.
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