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I've been working in my thesis project which consist on a PID controler to mantain a certain temperature in a case. The heater module is made of two 40W-12V 3D printer resistors and one 15W-10 Ohm wirewound resistor. In addition to these, I have an Arduino Uno, a 20x4 LCD screen, two temperature sensors and two PC coolers (2W each) which all sum up in 5W (rounding up). I'm using a 12V-10A switching power supply.

When the PID is at 100% the tension in the resistor (Rparallel= 1.5 Ohm) is supposed to be 12V, but due to the cables and transistor (IRF540N) drop, the maximum tension is 10V. So, all in all, in maximum behaviour I would be drawing 66.6 W + 5W= 71.6W.

My problem is that I want to be sure that the system can work for a long period of time without overheating/exploting/breaking. My question then is where and which fuses should I use?

In the following picture you can see a section of my board, more specifically where the power supply and heater module connects to the board. In total I found 3 places where heat gets high: power supply connector, heater module connector and power supply (switching) case. I have one cooler flowing air to the transistor and the power supply connector but I don't know if that's enough. The 3x2 connector datasheet is this

Section of my PCB board. Green arrow indicates the power supply connector. Red arrow indicates the connection for the resistors for the heater module. The white arrow indicates the transistor (IRF540N) that regulates the current trhough the heater module

I was then wondering, should I only use one 10 A cartridge fuse right after the power supply ?Where? Should I add a thermal fuse somewhere near the transistor? How can I ensure that the device can work for a long time?

Shupper
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  • Welcome to EE.SE. Is Q1 on a heatsink? What is the current limit for *one* of these connector pins? (Find a datasheet for that exact connector, edit your question, and include a link to it please.) You may have to use more pins for that much current. Note, pin 1 of incoming ground is square, but on all other connectors is positive - they all should match (pin 1 = square = positive.) Also making the island ground bigger will help to "suck away" more heat from the pins. – rdtsc May 26 '20 at 19:26
  • Hi! Yes Q1 is on a heatsink. the current limit for the connector pins is 5A theoretically, so I think I'm okay. Regarding the island, thanks, I'm going to enlarge it a little bit, both GND and VCC should be larger? – Shupper May 26 '20 at 21:18

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