Hi everyone! It's been some time since I've last posted here, because I haven't had to work with Arduino for a while. However, for my current project I do and I'm stuck with the schematics. I've spent several hours searching for a solution, but it seems I can only find partial solutions to my problem. I need to design a circuit that reads in the temperature using a thermistor, prints this to the computer and lets the user control a peltier element to gradually cool a surface. No problem with the first two parts, but the last one seems quite challenging. I've started with the following circuit, using a DS18B20 digital thermistor and controlling a LED with PWM, using two pushbuttons:
I figured if I got the code working with a LED, I could just replace the LED with the ordered peltier elements when they arrive and I would be done. However, I discovered the lab where I work has some spare peltiers lying around, so I decided to do already do some first tests. I have an education in electronics-ICT (graduated a couple of months ago) so the people at the lab expect me to know how to build this kind of circuits. Unfortunately, my education was highly IT-oriented and we never got to build more than the most simple of analog circuits. I have a theoretical understanding on how peltiers and MOSFETS work, yet I can't seem to turn this knowledge into practice. I've been given a peltier with no datasheet or type on it, just a label stating: I(max) = 6.4 A, V(max) = 14.9 V, Q(max) (delta T = 0) = 53 W, delta T(max) = 68 °C, R = 1.98 Ohm. I've also been given a box of IRL530 MOSFETS, which should be sufficient for this circuit and told to “look up a datasheet and check it for yourself”. I've found the following datasheet: http://www.datasheetcatalog.com/datasheets_pdf/I/R/L/5/IRL530.shtml. However, I cannot figure out how to check whether this should suffice. What I see is that Id @ Tc = 25 °C = 15 A @ Vgs = 5 V; I guess this is okay since the peltier will draw 6.4 A max and I can provide 5 Vgs with an Arduino output pin. What about the voltage, though? What I'm asking is:
a) How do I correctly interpret the datasheet (practically no experience in doing this, we just used examples from the textbooks)? Which values do I need to look at? b) If this indeed a good MOSFET for this application, how do I connect the Arduino, the IRL530 and the peltier? c) Am I correct in assuming I can control the amount of cooling using a PWM signal or is there a better way to do this?
Like I said, I've spent a couple of hours on forums trying to find a solution. I've found some related posts using PWM and a FET to control a motor or a LED array, but they mostly deal with to some specific components or connections in the circuit, not with selecting the right components or building the entire circuit. I've been hesitant to ask anyone for help, because I have the strong feeling that I should already know these things. However, I have to acknowledge that I don't and this seemed like the best place to ask. So, can anyone please provide a practical explanation (or point me in the right direction)?