Fan speed controller night/day idle HELP

Ok, I've been looking at Phason and Quantem speed controllers with idle settings.

The problem is, I don't want only a temp based controller, I can even do without the temp control. I want to be able to run at a user-set idle speed during lights off and full blast (or temp controlled) during lights on.

Seems I could build something using a SPDT relay and a std "dial a temp" solid state type speed controller...but I'm just not quite seeing it. Can't figure out how to wire it all. Thinking something like this:

outlet plug->DialATemp->bare wires
/ \
power->SPDT relay ==>receptacle->fan
\ bare wires---------------------->/


The idea being that the SPDT relay would switch between the dial a temp side and a "normal" full power side, both feeding a single plug/receptacle, based on my lights on/off timer. That would effectively give me an user setable lights-off idle speed.

Input?

Already have a dial a temp, and noticed that in all the speed controllers I've seen there are none with a specific night idle. There are some with day/night temp settings, and with idles but nothing quite does what I want.

Use the timers live output to control the relay coil. Tap a live feed from the timers input to the n/c relay contact. The live from the speed controller goes to the n/o relay contact. The common contact of the spdt relay goes to the fan live.
Its much easier to explain with a pic :wink:
Don`t forget to use a relay with a coil voltage matching your supply.. 120v or 240v (Lights are off in the diagram so the fan speed is dictated by the setting on the controller. When timer is on..relay coil is on, the fan speed controller is disconnected and replaced by full supply voltage..fan runs flat out)
Your dial-a-temp can go in line to the fan (after the relay) so its active lights on and lights off

Perfect, 100% clear. Thanks for the help!

Think I'll actually use a DPDT and just switch the neutral along with the hot, instead of just switching between the hots. Should make the wiring a little more tidy and the relay prices are basically the same.

I enjoy the DIY stuff, even if I weren't a frugal type. Still, I figure this design will save me about $150 vs an off the shelf temp-based controller w/ 30' probe.

I once made something similar using just a cooling stat and fan speed controller. Basically wire the cooling stat and speed controller in parallel, electricity takes the path of least resistance so when the cooling stat says I'm hot the fan kicks in to full speed, when it's satisfied goes back to idle. Here's a drawing, but where it says power in, that is from the timer.

Be safe

Lightning,water and air will take the path of least resistance, electricity will flow wherever there is a conductor. Wire a 25w lamp and a 1000w lamp in parallel and see if the electricity ignores the 1000w with its higher resistance.
If you wire a stat and speed controller in parallel,when the stat closes you have the same situation as plugging both sides of your active speed controller into the mains versus the usual mains to the input and a load (the fan) to the output.

True, but 1000w lamp would have less resistance than 25w lamp given that both lamps work at same voltage.

Me2 said:

If you wire a stat and speed controller in parallel,when the stat closes you have the same situation as plugging both sides of your active speed controller into the mains versus the usual mains to the input and a load (the fan) to the output.

Click to expand...

So is that a bad thing? I'm not an electrician by any means but it works and doesn't seem to hurt the speed controller to have both sides connected to the hot side of power when the stat closes. I know the speed controller has electronics (solid state) so can it be damaged by wiring this way?

just get a user controllable rheostat to controll fan speed and forget about breaking open and rewiring things together specially if you are not "electrical savvy". could cause fires, could work fine , or might not work at all. but on the flip side if you just use a dial type speed controller everything will be fine.

or get a little 4" vortex or similar and run it on a photo cell at night and use a big six inch vortex full bore during the day on a seperate photocell to disable it at night.

I've found that solid state speed controllers do not like to be hot on either side if they are not controlling the fan.
For a single fan, to be run either full-on (lights on) or user-set idle (lights off), use the light timer (or another timer set the same) to control the coil of a suitable DPDT relay.
Have the power (hot-side only) feed the center pin of one of the switches, so that when the relay is off the power is connected to one of the leads of the controller through a pin, and when it is on, the power is connected directly to the fan input through a pin.
Connect the other side of the controller to the center pin of the other switch, and jump the input of the fan to the pin of that switch that is connected to the center pin when the relay is off.
What happens is: when the relay is off, the power is connected to one side of the controller, and the other side of the controller is connected to the fan. When the relay is on, the power is connected directly to the fan, and the controller is completely disconnected from the circuit.
There is no need to switch either the green or white leads in a 110 circuit.
I've built many controller boards. I usually like to use two thermostats (one for when the lights are on, and one when the lights are off, selection made through a relay that is controlled by the light timer), and two to four speed controllers, so that the high (cool-down) and low (idle, or prevent over-cooling in cold weather) settings always provide a little negative pressure. Oh--these controllers are for active intake and exhaust, that's why there are so many individual controllers (triacs).