Photo sensitive switch

[DocTim420]

So something like this cheapest relay I could find would work?

WIth some sort of 120v photo control..

It makes perfect sense now. I haven't worked with relays but should have know better.

Let me see if I can make this muddy water clear.

You have a timer that turns lights ON and OFF at specific times. A photocell will let you know when the lights are on. Instead of relying on the photocell to determine when lights are on...I would use the timer. How can you do this?

Your wall light switch has two positions, up or down....on or off. We call this switch a SPST (single pole single throw). Instead of getting up and turning on the light switch at night, you can replace the light switch with a photocell device (like the one Queeg discussed) and the lights will turn off and on all by itself.

Now, lets suppose you want to control two sets of lights or 1 light and 1 fan with a single switch (without wiring the two appliances together) then a DPST switch (double pole) is what you would use. If you wanted to connect three items (1 light, 1 fan and 1 heater/humidifier/dehumidifier) then a TPST switch (triple pole) is what you would use. A normal light switch has 2 wire connectors, double pole has 4 wire connectors (two for each appliance) and triple pole has 6 wire connectors.

Now, if let's discuss "throws"--a single throw (basic light switch) has two conditions: On or off. A double throw also has two conditions: On1 or On2--depending if the coil is activated. This requires three contacts: On1, On2 and Post. When the coil is not activated (OFF), the relay contacts for Post and On1 are made and the device connected to On1 will operate. When the coil is activated (ON), the contacts for Post and On2 are made and the device connected to On2 will operate. It is an either or situation--depending if the coil is ON or OFF; both devices can not turn on at the same time, just one or the other.

A relay has two parts: Coil and contacts. In this instance you can wire the coil directly to your timer and avoid the photocell (duplication). Got an extra electric cord with a plug laying around? Connect the two wires directly to the relay's coil contacts and plug the other in to your timer. Now your timer is controlling the relay.

As for the other contacts--let's use your diagram to resolve this.

The contact identified "120v+" inside your "light controlled switch" box is connected to the relay's POST (power source). The contact identified "light" (Speed 1) is connected to the relay's On2 (lights on & coil on). The contact identified "dark" (Speed 2) is connected to the relay's ON1 (lights off & coil off). The common wire connection (120v-) is the same for the relay.

Now will the relay you found on Ebay work, yes...but it is only a 5 amps. What are the amps for your fan? For safety purposes (avoiding excess heat), I would select a relay that has at least twice the amps of the fan. Relays are rather cheap--and it would be a shame to let a $5 relay go "post toasty" and burn up...thus undoing your hard work

Hope this helps.

 

[Phychotron]

Well the fan wall dials are rated for 1.5 or 5A. I opted for the 5A version when I got the one. I couldn't find one with a higher capacity.

The fan operates at a maximum of 210w when full blast @120V, so 1.75A.

I could very easily wire the power to the coil to a separate power cord and just plug that into the same power strip my lights are connected to. I think that would end up saving a lot of heart ache of relying on keeping that control box in the light.

 

[DocTim420]

You're good...see how easy this turned out to be. A simple device with a bit of re-wiring--and a basket of knowledge you did not expect to get...lol.

 

[Phychotron]

I ordered three of those cheap relays to play around with. I knew the concept of relays but without the experience never thought to implement it. Funny cause I've been thinking about relays for my truck and for use in other electronics but never thought about it having the double throw option. It was after I hooked up my ozone generator to a cycle timer and ordered that cheap photo controller that I realized a relay of some sort would work. I was just stuck on the idea of controlling it with a photo sensor which would require some sort of electronic component.

Sure its a little odd that it's going to have two power cords but it beats having to implement a bunch of extra components.

Thanks. I'll probably post the build when its all done for. Might take a month or two to get the parts from China though.