Now that Puck's formula is available I was all set to post a circuit diagram that connected the vibration sensor to the PowerFlash when I realized we have another problem to overcome. Since the same switch controls both the light and the fan how will the sensing circuit know that the light switch has been turned off so it can turn it back on?
In a way this is similar to the problem I had in one of our bathrooms with the same set up. I wanted a timer on the fan independent of the light switch. I had to install a second electrical box above the original one to install the mechanical timer for the fan.
Let's assume you do the same thing but the second box contains an appropriate appliance module or wall switch instead of a mechanical timer. The wiring would now be that BOTH the light switch and the appliance module/switch be wired to the fan in parallel (not per code!) I did this for a different application in our last house and it worked perfectly for years. You just have to be careful to get the polarities the same.
Now whenever anyone comes into the bathroom and turns on the light the fan goes on. Whenever the dryer goes on the fan will go on per the yet to be published external circuit. If either goes off while the other is on the fan will still operate.
If this modification is acceptable I'll publish my time delay diagram. Actually I may anyway since someone else may be interested.
Time (seconds) = Resistance (Ohms) X Capacitance (Farads)
This is the time for the Cap to charge to 63% or discharge to 37% of the voltage thru the resistor[/b]. Depending on how the PowerFlash works, you might need to build a Comparator Circuit.
Using Puck's formula above and the second box per my other post above, this is the circuit I would try first. This assumes that the PowerFlash (PSC01/PF284) will be set to Mode 3 (6-18 V DC):
(http://www.sfpasc.com/x10/DryerSensorSmall.jpg)
Parts List:
- Wall Wart = Probably 12 volts DC or more.
- S = The switch in the vibration sensor.
It'll be interesting to see how long this lasts considering that one dryer load produces more vibration than the sensor would normally see in a lifetime in its intended application. I don't think you'll have trouble however. - C = Whatever appropriate "super" capacitor you can get surplus.
Its rated voltage will have to be the same as your Wall Wart, or, if it's cheap enough get four and hook them up in series parallel to up the voltage rating. - R1 = Time delay trimming potentiometer.
- R2 = PowerFlash voltage input trimming potentiometer.
NOTE: The combined resistance of R1 as adjusted and R2 is the resistance value to plug into Puck's formula.
You'll need to do a little Googling to find these parts, particularly the capacitor, without spending an arm and a leg, but they are out there.
With the wiring scheme in my other post, above, you may not need a very big capacitor since you only really have to smooth out the momentary ons and offs of the vibration sensor, although I might shoot for 10 to 15 seconds. Play around with the capacitance/resistance values you find on line and see what you come up with.
The other thing to keep in mind is that the vibration sensor may have a prefered motion sensing direction. That would control whether you mounted it on the back or side of the dryer. I suspect you'll end up on the side.
[TTA Edit: Added some formatting. ;) ]