DIY fan controller- zero hum variac.

[bigbadbillybob]

hello stoners, im going to edu-medicate you today in the ways of the 3 wire voodoo.

thats right it is electrics day and to kick off im going to show you all how to make the best fan controller you will ever own. well its possibly not, but it is cheap simple and effective, and best of all for those running bigger fans, there is zero hum from it.....at all.....guaranteed.

ive built a few of these, and if you want i can post up my 2nd guide to making a twin fan controller, with a seperate temp controller, high and low speed settings ATC800 control module for heater etc etc, but this is going to be a simple one, not worked off a temp probes, just worked off your hand and a thermometer in the room. once you get it dialled in you will love it.

How does it work? it works off a variable transformer, or variac for short. i do not think this will work on USA electrical systems, (110v to uks 240v) so dont try and sue me if you build one in the USA and your house melts.
im also not a qualified sparky, but im also not a brainless gibbon with the IQ of a lettuce. i know a little bit about a lot of things, and have been verified by no less than Nanook to be "not full retard", which is nice.

let us begin, you will need some tools.
a drill
hole saw for cable glands fitting
pliers - sidecutters and small ones for variac nuts
stanley knife
cable strippers
electrical screwdriver
flat screwdriver for knob fitting (ooooh matron....)
4 x M6 bolts nyloc nuts and washers
2 x cable glands
1 x terminal block
lots of small crimp on eyelets m4 i think, 2 @m6 for earths , and crimps to connect them
1 x 2 gang trailing lead (this is for plugging in an intake and outtake fan to - check the AMP pull first tho, off your fan)
1 x 3 pin plug
a metre of 1.5mm square cable..
an electrical enclosure box 230 x 180 x 130. it must be 130 deep, to fit the variac into.

next.....dont bloody post while im typing the next bit out....

[bigbadbillybob]

Theres always one.


right for this example i used a 2 amp variac, a ravistat 2F1 i think its called, this will safely run most combinations of RVK fan
im going to be using a 5 inch intake and 8 inch out take, and it will be fine for these. ive another one using a 10 inch intake and a 12 inch extract, but would not really recommend it, as on full pelt the box gets pretty hot, ahem

anyway, first up measure the mounting holes for the variac on the lid of the box. TIP> Dont be a dick like me and plonk it right in the middle, better to put it up a bit, so you can fitt all the cables, terminal block etc in there.
heres some sizes.
ook the 4 outer holes are for the mounting bolts, the middle one is for the dial/ knob. you need to remove knob by unscrewing this
so now you can bolt the variac in , make sure the knob can turn freely and the bolts can be tightened up, but leave one, for the earths later.
more coming dont post

[bigbadbillybob]

now make up 2 leads, one with the twin trailing socket on it, and one with the plug. heres how to wire a plug, for the full retards out there you should end up with these.

now to get them into the box, you need cable glands, these need holes in the box - to be hole sawed 22mm in this case.
try to make sure they arent in line or people will think you're an OCD twaaat

[bigbadbillybob]

right heres the wiring diagram, ill go through it for the hard of thinking

[bigbadbillybob]

hopefully you can make out the plug and trailing lead?
these are stripped at the ends of the cables and connected to the terminal block, from the left, it goes earth , nuetral, live, earth ,neutral, live.
the3 wires from the plug , the live needs to have a 2 amp inline fuse, like so. with a quick blow glass fuse,
this will save your house from burning down as the fuse will go melty melty before the variac goes boom/ fire / ambulance etc. .
the earths have a m6 terminal crimp and are put to the mounting bolt of the variac, this prevents you getiting fried.
the variac has A B C and D on it. D isnt used.
A is for the neutral wires
B is for the live from the trailing lead
c is for the live from the plug.

connect it all together and congratulations, you have mastered the voodoo, and have a simple variac controller.
just like mine

[bigbadbillybob]

for the twin variac controller, you will need a ATC800 control module, another 2 amp variac, a 10 amp non latching relay and you will need to wire it like this.


oh except you need a 10 amp fuse from the bottom right , not a 2 amp one, okay dokay?

thank you and goodnight

[bigbadbillybob]

the variac looks like this ignore the earth cable, it shouldnt be there hahaha

next week; how to make yourself a replacement head, out of cornflake packets, play doh and a few straws.

[bigbadbillybob]

Nah..... nah,.............. yours is rubbish ,................ mines much better .............yellow box.....really?........

[Nanook]

good post thank you :)

[Keeno]

Bloody good write up BBBB. Think you just gave me an idea for this weeks light a week entry