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I would like to use an arduino system to control a heating pad that I will be using in my system.

http://www.amazon.com/Signswise-200x200mm-Silicone-Heating-Printer/dp/B00ZP3XCS4/ref=sr_1_fkmr1_1?ie=UTF8&qid=1447442029&sr=8-1-fkmr1&keywords=400+200+silicone+heater+24v

Although it says 24 v in the link when I click it says 12 v so I don't know whether the heater I got 12 v or 24v. Perfect :) Now the question is... How do I turn this thing on and off so that it stays at 37C in my system. I have seen various mosfets but I couldn't find any that support 150W. I also don't know how to set up the mosfet system but I can look up the diagrams online so that's not a big issue... I have seen some logic level mosfets but people raised concerns about some "charging" and "protecting the pin" and all that... so idk. I am a biochemistry student trying to build a nice arduino system and not completely clueless but fairly inexperienced with these systems. so if anyone can explain how can I use mosfets/relays (i think relays only work with ac not like my heater (dc)), I would be really happy. Thanks a lot. Have a great day.

Mr_DOdoska
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The MOSFET doesn't have to dissipate 150 watts. The heating pad does that. The mosfet only needs to flow the 12.5 amps when heater is on, and then block the 12 volts when you want the heater off.
The Rds (resistance) of the mosfet could typically be 31 mohm (0.031 ohms) when on. The power that the mosfet would have to dissipate then would be about 4.8 watts. http://www.mouser.com/ds/2/200/irfz44npbf-222819.pdf

Choose a mosfet with blocking voltage higher than 12 volts. The above mentioned link is for a 55 volt mosfet.

Regarding protecting your arduino (or other system), there are lots of driver circuits you can find here on EE stack exchange that discuss the matter.

As regards relays, there are many many relays that can be used in DC circuits.

Marla
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  • Thanks a lot but this thing says 2v min 4v max for activation so I don't know how to set that up either since arduino output is 5v or 0v. I was considering https://www.sparkfun.com/products/10213 but the sparkfun technical support answered me like this.. looking at the datasheet, I don’t think that it is able to handle that amount of power. The datasheet states that the power dissipation has an absolute maximum rating of about 96W. If you were to send that much power through the N Channel MOSFET, you would probably need a heat sink to keep the MOSFET operational. – Mr_DOdoska Nov 18 '15 at 23:53
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    The 4v you mention is in the gate threshold specification. Thus it is the Maximum of the gate threshold (to turn on), not the Maximum applied gate voltage. Maximum gate voltage is 20 volts. The "sparkfun" mosfet you linked is very similar and has an even lower "maximum gate threshold" of 2.5 volts. Your selected mosfet will work nicely. Yes, you will need a small heatsink – Marla Nov 19 '15 at 00:00
  • Read my answer again, the mosfet only needs to dissipate about 4.8 watts, NOT 96W, NOT 150W. – Marla Nov 19 '15 at 00:03
  • @Mr_DOdoska: See this previous question on how read a MOSFET datasheet: http://electronics.stackexchange.com/questions/195073/is-mosfet-gate-threshold-voltage-a-limit-or-minimal-full-on-switching-voltage/195080#195080 – Fizz Nov 19 '15 at 00:05
  • @Mr_DOdoska: Oh, and even for 5W dissipation you still need a heatsink for a TO-220 package or else it will be toast. See http://electronics.stackexchange.com/questions/16882/dissipating-1w-on-a-to-220-without-heatsink – Fizz Nov 19 '15 at 00:14
  • 3d printer heated beds may use PWM, if the Arduino doesnt have current to turn the fet fast enough the fet can spend considerable time turning on, so I can see some scenarios in which the fet will dissipate more than Rdson*Iˆ2.. In my experience with heated beds and 3d printers thought, current requirements arent that high (once it heats up current draw diminishes a lot) – Wesley Lee Nov 19 '15 at 02:08