RE: Pas Home / Home ventilation demo + cellar door demo

mcb1 — Fri, 10 Oct 2014 10:28:13 GMT

Pascal

Nice work, its coming together.

re transistor, diodes.

The diodes aren't achieving anything, BUT you could use a diode across the transistor (C-E) in reverse to ensure that any spikes form the ventilation control (if it has any) don't damage the transistor.

I'm picking the output at Pin2 of P12 is 5v, which means that 5 - 0.6 (B to E) = 4.4 I =E/R = 4.4/330 = 0.0133 Amps base current (13mA) NOTE the GPIO is only 8mA

At the worst gain of 40 for a 2N2222, that gives you 0.5333 Amps collector current which is all that the 2N2222 is capable of.

IMO R6 = 330 is the right value, but just check on the ventilation control current required, as you might need a higher gain transistor.

Mark