12v layer fan control for E3D converted Davinci 1.0's

Don't know if anyones mentioned this before(if so plz delete)

But the Davinci 1.0's 5v fan control is negatively switched
it has an NPN switching transistor.

how does that help us get 12v fan control?

the negative side of the 12v and 5v rails are common(tied together).

and the particular NPN switching transistor is automotive grade.

0-40v tolerance, 600ma current.

which means if we feed the positive side of the fan 12v, and leave the negative attached where it was when it was 5v

you have a perfectly functional 12v speed controlled 0-255 style fan setup.
this lets us use all those much more powerful 12v 40mm fans easily and cheaply brought.

Unlike the 40mm 5v version's that either cost an arm and a leg, are hard to get, or are too weak, or a combination of all 3
(I had been waiting for 3 weeks for one when I discovered this while doing another mod)

if you already did a E3D hotend conversion, you'll have a 30mm 12v fan, with 12v wires run for the heatsink on the hotend.

tap the 12v+ wire for the layer fan and leave the negative alone(use the original negative I mean),(and obviously make sure your layer fan is 12v)

Source: I'm using a fan from a dell powerconnect switch(they were too powerful and noisy for my switch's use case, so I swapped them for quieter mag lev bearing lower speed fans, leaving me with 2 powerful 40mm 12v fans laying around.)

NOTE: This is an original Davinci 1.0, first gen board(has removable stepper drivers on little pin headers) Check your board near the cable that goes to the extruder to see if yours has the same NPN transistor

This may even be the same for other models, checking needed.