16x2 LCD driven by Pro mini

Hi All,

I am going to put a 16x2 LCD inside a DIY home appliance. The appliance has a 1000VA transformer inside it so there will be some heat generated as well(50-55 degrees Celcius max). I need the LCD module+pro mini to be extremely reliable as I might sell a few of these.

  1. Besides LCD and Pro Mini do I need anything else. I mean resistors or capacitors to make sure the duo works within safe limits?
  2. There are plenty of options on web to buy pro mini and LCD from? Any suggestions about where to buy these from a quality point of view.
  3. Should I use a separate Fan for the pro mini?
  4. Is there an alternate programmable arduino board(low cost) that I can use in place of Pro Mini? Space is not a constraint for me as there's lot of room inside the appliance.

Thanks for the time.


  • You haven't mentioned the critical thing - what you are going to use to power the Arduino and display?
  • I am not going to be held responsible for their reliability, but I think "Alice" AKA "TxHang" seems to be a good supplier. Or G&C (not quite as cheap).
  • I would do some testing to see what temperature the displays can tolerate before going black. Not sure about a separate fan, but you may choose to fan cool the whole unit.
  • I should be very surprised if you would find a cheaper ready-built assembly than a Pro Mini.

I am going to put a 16x2 LCD inside a DIY home appliance.

Can we assume that you got it running? --> http://forum.arduino.cc/index.php?topic=280193.msg1968556#msg1968556


Sorry for the late response.

I checked my connections a number of times. They were all ok. except the V0 which I had some doubts about.

I am guessing that there is some short circuit one some pin on the 16x2 LCD which I cant fix. So I have ordered a new one and I am still waiting to get that.

Once I have that I will solder it neatly and will try again.



  • You haven't mentioned the critical thing - what you are going to use to power the Arduino and display?
  1. The appliance is a power inverter which must have +5 volts available somewhere on the PCB for the pro mini and the LCD to run. If not can i connect the batteries +12V/Mains to a voltage regulator 7805 and power the LCD+mini with this.

Normally speaking, when people complain of a broken 16X2 LCD there is either a wiring or soldering fault.

A picture or two will clear that up.

Attaching the 2 pics of the 16x2 and connections
I have wired breadboard jumper wires stripped on one end directly onto the connection points.

BTW, I tried the nokia 5110 graphic LCD and Pro Mini duo and tested it out for 12 continous hours(powered by a 9V battery with 7805) and it worked perfectly fine.

You appear to be using a strange combination of LCD data pins. As far as I can tell you are using DB0, DB1, DB2, DB3, DB6 and DB7. I don't see any connections to DB4 or DB5 although there are solder blobs at those locations.

I don't think you will win any prizes for neat soldering either!


Yes you should be using the 4 data pins at the high end to use the module in 4 bit mode. (D4 to D7)

I took a break for some time due to my job so i am posting a little late. sorry aboutt that.

The LCD worked and I have permanently soldered a female berg strip on it so that i can be connected to bread board easily.

(1) Now the next thing i have to do is to read voltage from Analog input pins. when I tested my arduino board's AO pin OPEN i.e. without any voltage on it, still then it returns a value between 200-300 which is not encouraging for me.

But it is correct.

An open pin has has some static noise on it and you are measuring that.
If you put a piece of wire to the A0 pin, shortly touch a piece of bare metal of your PC to discharge static electricity, and then touch the piece of wire, you'll see the values fluctuate a lot more because you'll be acting as an antenna.

Connect the pin to GND and test again.
Connect the pin to 5 volt and test again.
Compare the results with what you expect them to be.

These are simple tests to have fun while learning.