Blower doesn't stop

[Michel Kraaij]

I just finished my heatermeter 4.3.4 build and adapt-a-damper build. When connecting them everything seems to work fine. Board and buttons work, lcd display works, servo works. Except for the blower. Well it actually works a bit too good. It goes in full speed the minute i power up the heatermeter and doesn't throttle down. Not even when I activate the lid open option.

What am I missing?

 

[Michel Kraaij]

Never mind! I found several topics on Q1 (the BS170), so i replaced it with the Q2 (from the alarm). Guess what, it works! Time to order a few extra BS170's ;-)

 

[Bryan Mayland]

Doh! Glad you got it figure out. The BS170 is the same as a 2N7000 except the pins are mirrored (so just face it the other direction when installing) if you can find those more easily.

 

[Michel Kraaij]

Thanks @Bryan Mayland! I found three types at the store here in the Netherlands. Can you help me out which one is the correct one?

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What are the specs I have to look out for?

 

[Bryan Mayland]

Iiiiiii have looked at all three of those and don't see any difference apart from power dissipation. The version I get from Mouser is listed in their specs as being the higher dissipation (850mW) but the datasheet says it is the low dissipation (350mW). The HeaterMeter circuit never expects to even reach the low dissipation number (120mW pulsed) so any of those should be fine, I'd go with the cheapest I guess?