HIMNL9
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The BC337 does not need to dissipate power, is only for invert the driving signal of the 555 to the mosfet ..... the mosfet can require some heatsinking, but if you use a high current one, probably it does not need too much of it (after all, it's drived mainly in on/off configuration, it dissipate power mainly in the transition times) ..... no, resistors does not need to be high power ones, i used all 1/4W, and yes, i powered it at 12V.
Just be sure that the power supply can give enough current without "sit" when the TEC is in "on" state ..... or, also better, you can decouple the two power lines, for avoid problems, or at least for try to reduce them ..... the positive for the TEC can be hooked directly, where instead you can place 3 or 4 diodes (1N400X, no matter the exact type) in serie to the positive line that power the 555 part, and a big enough capacitor or bank of them (like, 470uF25V, or more) on it, so the switching cycle of the TEC does not influence too much the 555 part.
About the mosfet, i used a PHD78NQ03, a 60A one, but just cause they was easy to find here ..... anyway, more ampere they hold, more low is their internal RdsON, more low is the power dissipated from them ..... there are so much types of them, that i cannot imagine a part number to suggest you, cause this mainly depend from the availability of them in your electronic shops ..... also, mine was in SMD, but for hook it on an external heatsink, you probably prefer to find one with TO220 case.
Last, the NTC resistor, i used a standard model, miniature, with a common value of 10 Kohm at 25C, that is one of the more common types available around ..... if you use a different value, you may need to change also the trimmer value.
Just be sure that the power supply can give enough current without "sit" when the TEC is in "on" state ..... or, also better, you can decouple the two power lines, for avoid problems, or at least for try to reduce them ..... the positive for the TEC can be hooked directly, where instead you can place 3 or 4 diodes (1N400X, no matter the exact type) in serie to the positive line that power the 555 part, and a big enough capacitor or bank of them (like, 470uF25V, or more) on it, so the switching cycle of the TEC does not influence too much the 555 part.
About the mosfet, i used a PHD78NQ03, a 60A one, but just cause they was easy to find here ..... anyway, more ampere they hold, more low is their internal RdsON, more low is the power dissipated from them ..... there are so much types of them, that i cannot imagine a part number to suggest you, cause this mainly depend from the availability of them in your electronic shops ..... also, mine was in SMD, but for hook it on an external heatsink, you probably prefer to find one with TO220 case.
Last, the NTC resistor, i used a standard model, miniature, with a common value of 10 Kohm at 25C, that is one of the more common types available around ..... if you use a different value, you may need to change also the trimmer value.
