# incandescent light dimmer to off/on by proximity or photo sensor

#### bostonkorn

Joined Jan 4, 2012
3
please note that i am as beginner as it gets-

i am an artist looking to have an incandescent light(available power source is standard residential outlet(120?)) be normally on and dim to off when someone approaches and peers through a porthole window. i am hoping to install a sensor below the window that would work by light(photo sensor?), or proximity(optical sensor?), but not have to have a broken beam as in a garage door safety switch. i can read basic schematics and can solder. if anyone has any suggestions they would be life savers. Thanks

#### wayneh

Joined Sep 9, 2010
16,114
Do you need it to fade (as in slowly) to off, or just go off? The latter is simpler, and you might consider hacking a motion detector light from the hardware store. I've never done so, but maybe you can reverse the logic so that the light goes off when motion is detected, instead of the normal reverse operation.

Anyway, you'll get more help if you can give more details, such as how much space you have, whether you can add a DC power supply, how much light (wattage) you want to control, etc. Diagrams are a good way to communicate and save a lot of back-and-forth here.

Welcome and good luck!

#### bostonkorn

Joined Jan 4, 2012
3
Thanks.
- it does need to fade to off.
- there will be four of these lights total, but they will work independently so i figured i just make four of the same thing
-the lights, sensors, and any converters, circuitry, etc. will all be housed in a 6' x 6' cube placed in the middle of a room over a floor outlet
- so space isn't much of a concern
- the outlet is AC but could a converter be used if DC is easier?
- wattage could be anything from 4(like a night light) to 20.

sorry if i'm leaving anything out. thanks for any help. next one will certainly be posted better.

#### Bernard

Joined Aug 7, 2008
5,285
To avoid messing with 120 V AC, use a dusk to dawn photo sensor adapter, one that you screw in a bulb & screw adapter into a socket. A LED is placed over photo sensor & then can control light from a low voltage source. A PIR, passive infra red, module, obtainable from Radio Shack, will detect an approaching body. A dimming ckt. can go between the two.

#### R!f@@

Joined Apr 2, 2009
9,682
One thing we do not encourage for n00bs to do is meddle with AC mains Voltage.

If you a beginner, there is likely chance that this thread will get locked.

But if you start to learn about the dangers involved and tell us how old you are may be we might consider.

As for ur post.
Using standard lighting units off the shelf will only switch it on and off. You cannot fade out. If you need to fade out have to use an additional circuit or modify any off the shelf one.

Fading means u need to limit the voltage the Mains to 0V slowly which can be accomplished using Triacs. Which I am sorry to say that you will be dealing with AC mains level voltage.

This can be done quite easily and very little effort.

Only question is how confident you are handling mains voltage.

If you are scared or is like too eager to do this then this thread will be locked.

#### bostonkorn

Joined Jan 4, 2012
3
Thanks for the concern. I understand completely. I am a grad student with experience in repairing motorcycle electronics and some basic music instrument stuff, pedal projects,etc. but i do consider myself a beginner. and, it is the dimming, or fading, that is the part i need help with. using a sensor as a switch i should be able to do. but, i don't know how to get it to dim and then return to "on".

#### R!f@@

Joined Apr 2, 2009
9,682
OK then...
Show us what u already have.

#### strantor

Joined Oct 3, 2010
5,158
any experience programming? could be done fairly easily with some LEDs, a microcontroller, and an ultrasonic sensor.

#### Bernard

Joined Aug 7, 2008
5,285
Here is an adaptation of Sgt Wookies voltage controlled PWM to dim & brighten a LED, which in turn controls a lamp dimmer. A PIR module, R-S 276-0033, or Parallex #555-28027, with jumper set to H, output will be high with intermittant motion,slowley charging C2, causing U1b output to be mostly high, dimming LED, brightning lamp. The IC is either LM2903 or LM393. C1 can be increased to give PWM a clock rate of about 50 Hz as the LDR in lamp control is a little slow. R8 may need to be adjusted so that LED matches lamp control.

#### Attachments

• 82 KB Views: 42

#### Bernard

Joined Aug 7, 2008
5,285
An old difused red LED with current of 2.7 to 5mA caused full dimming of two different dimmers. LED placed about 1/8 in front of window. 5 V, 680 Ω, gives 5 mA.
Outdoor / Indoor Light Control Socket, # G15455 @ $1.49, Electronic Goldmine. Dusk to Dawn Light Control # 33701 @$ 9.99, ACE Hdw. Has nice recess to hold light shield- makes mounting LED easy; but a little paper & hot glue also works on other.