3 pin Fan temperature control box for cabinet w/LCD

thingiverse

As mentioned in my other thing herehttp://www.thingiverse.com/thing:2236078 I need a temperature control for my Prusa cabinet. I re-designed it now using an atmega 328p. Attached are the eagle files as well as the electronics case. As a LCD case that fits a 1602 w/I2C connector, use this one:http://www.thingiverse.com/thing:90592 Important: 1) The IRF540 MosFET which is shown in the designs is not being used. I use the IRFZ 340 which is a TTL MosFET, quite cheap, but I could not find it in Eagle and did not want to draw one. Yes, it is is much much oversized, you may use a smaller one, if it is TTL N-Channel Type and pin compatible. 2) Print the top first and then cut the PCB to its final size, so you make sure the cutouts fit the connectors 3) Mark the connectors where pin 1 is, so you do not mix up directions of the connectors 4) The .ino file is for I2C Version 1 of the connector, read here:https://arduino-info.wikispaces.com/LCD-Blue-I2C?responseToken=03e6accfe0582e9bb3beca7e9e664216e If you have a different one, change the programm to your needs. 5) Use a long enough display cable so you can place the LCD where you like it 6) Yes, I know you should NOT use polarized capacitors with the 78L05 as it could swing. Use ceramic ones. I only had those 1µF ones lying around. Normally you SHOULD use 0.33µF as C1 and 0.01µF as C2. 7) As the 3 pin fan is controlled via a PWM pin on the atmega328p, it is hard to read the tacho signal (it is being chopped up by the PWM). I use pulse stretching to get a clear signal. This influences RPM a little when using lower PWMs. 8) Yes, the PCB requires a few wires to be connected on the top side of the PCB. The two resitors below C1 have to be connected on the left side. It is easy to overlook this, in the picture you can see it.