Thanks to David N.
and Doug
Smith for their help in getting me started on this project.
The commercially available X-10 compatible fan speed controller is the
6381-U from Leviton. Unfortunately, this switch causes the fan motor to
hum loudly. When I installed one in my bedroom, I found it nearly
impossible
to sleep with the fan on. This was very annoying since I have very tall
ceilings in my bedroom, and a lot of warm air is trapped up high in the
winter, while we are chilly a ground level. The room gets noticeable
warmer
when I turn on the fan. After receiving a copy of a circuit from one of
the gentlemen mentioned above, I decided to build my own version.
Ceiling fans that are controlled by the switch like Leviton's buzz due
to the PWM action of the wall switch's TRIAC. On the other hand,
cheaper
manual fan speed controllers that feature discrete fan speeds allow the
fan to operate completely silently by switching capacitors in series
with
the fan. The project described here combines the two units. An X-10
controllable
fan speed switch that allows the fan to operate silently by switching
in
capacitors.
Giving credit where it is due, I used the same approach for controlling
the fan (capacitors in series with solid state relays) as a circuit
posted
on AOL, they however used a series of opamps and a discrete voltage
divider.
When I saw the schematic I remembered from my bag 'o tricks that there
is a chip to do this job, the LM3914. It can even drive loads directly.
As a result the circuit is more compact. I also used a real power
transformer,
instead of the resistor/capacitor type power supply of the AOL circuit.
Implementation
I used an 'old work' box as the enclosure, screwing a four terminal
barrier
strip onto the back. The whole unit can then be slid out of the wall,
and
disconnected for service or assembly. It can also easily be mounted
back
into its intended location. The box is then covered by a blank plate
with
a few holes drilled so the LEDs can stick out.
The main challenge in construction is fitting the whole thing into a
wall box. I used two circuit boards, one to hold the capacitors, solid
state relays, and the power transformer. The other holds the LEDs, the
IC and the dummy load for the inductive module. Each board stands
vertically
on the left and right side of the box, and the dummy load resistor is
put
in the back where holes have been punched for air flow. The power
resistor
should be rated for 10Watts, it dissipates less than 1.6 Watts in the
circuit.
There is only one adjustment in the circuit. With the inductive switch
fully on, adjust it until the hi-speed led indicator lights up. With
the
circuit in use, and an ON command is received, the leds will ramp in
order
red-yellow- green to full speed. An off command will also cause it to
ramp
down. Now you can send bright / dim commands to change the speed of the
fan, and the LEDs will ramp up and down accordingly. Had I used a
microprocessor,
I could add a chime to click everytime a change of state occurred, but
I resisted the temptation to overdo this job.
When you build this thing, I urge you to put together a project board
like I did. Using a 2' by 1' piece of plywood, I put an GFCI outlet on
it, with a mini-controller and a circuit bread board. Since you will be
working at line voltage, you want to be able to unplug the whole thing
when you touch it. The GFCI will help protect you from shocks. As you
test
and assemble, you can pick up the board to your ceiling fan for tests.
Since there is a mini controller right on the board, you don't need to
walk across the room for an X-10 transmitter. I would also add a fuse,
something I did not initially do, causing me to ka-blow the Leviton
switch
during development (I repaired it).
Photo of the
finished installation. The
Fan Controller
is on the right, and the controlling
wall switch on the left (along
with the light
switch).
Correspondence
>From: rod@mail.delnet.com (rod)
>Ed. Did you modify your inductive load wall switch with a
different
>TRIAC.
The design of the inductive wall switch allows the use of a 9k resistor
as the dummy load. Power dissipation is low enough not to be a concern.
Long term update
The unit was installed in 7/96. After more than eight months of usage,
especially thru a winter, I am extremely pleased to have built this
unit.
The fan operates completely silently, and we are saving energy. We can
control the fan speed from bedside, and it is probably one of the best
uses of X-10 in the home (3/97).
September 2000 - I replaced the inductive dimmer module with a regular
wall switch modified to add a neutral wire. The Leviton unit
stopped
working due to an ESD incident. The No-Hum Controller has
performed
flawlessly for these five years, and is used every night.
Schematic of
original no-hum circuit.
The image
is chopped off on the right.
The value of the zener is
5.1Volts, and its
cathode is
the '+' terminal of the
power supply.
The adjustment pot is 200k.
Video of one unit on the repair bench showing its operation (6/2012)
If you are interested in a kit with all the parts to build your
own unit. Click here.