# I NEED Help (Circuit For DIY At Home Project)!!

Discussion in 'The Projects Forum' started by hellohellosharp, Apr 19, 2011.

1. ### hellohellosharp Thread Starter New Member

Apr 19, 2011
27
0
The goal of my project is to make a circuit with a photoresistor that can turn my bedroom light on and off.

I will be pointing a laser at a little photoresistor. If my bedroom light is on, I want it to turn off, and vice versa.

To make things simpler, lets just forget the photo resistor and say I'm using a push button switch (because I can setup a push-button switch with a photo resistor and a relay). I want to be able to push the button and have the light turn on/off (kind of like a TV power button). I have outlined the circuit I need in the picture below.

So like I said, push (and release) the switch and the light turns on. Push (and release) the switch again, and the light turns off. Any help would be GREATLY appreciated.

2. ### R!f@@ AAC Fanatic!

Apr 2, 2009
9,666
1,110
Hi, welcome.

First of all did u know that you will be meddling with the mains in order to complete the project.
If you dunno how to wire a simple series circuit, I have doubts in ur ability to handle live circuits.

Unless you tell us ur experience in this area, we cannot help you.
Let the Mod's decide what to do with ur thread

3. ### magnet18 Senior Member

Dec 22, 2010
1,232
125
Was 40Hz just a random number?

4. ### Wendy Moderator

Mar 24, 2008
21,417
2,948
What part of the world are you?

Your use of 40Hz for line frequency marks you as a beginner, and you are wanting to mess with line voltages right off, this is not good. We like beginners at this site, but safety is always an ongoing concern.

You need to start with the photocell (AKA LDR, Light Dependent Resistor), there are several significant differences between an LDR and a switch.

There may be be a way of doing this using line voltage, but my inclination is to use a low voltage power supply for the solid state electronics. Have you put any thought into this?

You will need to prototype a circuit to see if it does what you want. There is a component called a SSR (solid state relay) that is ideal for this kind of project, but you won't need it until the final phase of the project.

Last edited: Apr 20, 2011

Apr 20, 2004
15,815
293
6. ### Bernard AAC Fanatic!

Aug 7, 2008
4,926
541
One way to stay safe is to use a dawn to dusk lifht control that you screw a bulb into & it into a socket; add an external light source, white or red LED controlled by a toggle flip-flop. Input to FF from a light dependent resistor or photo transistor- all operated from a low V wall adapter.