A photocell device to light a small bulb

[wdavidleeii]

Hello, this is my first post. I googled it, and searched the forums, but no luck.

I want to know what I need to build a device, that can light a small light bulb. Something rather small, such as a flashlight bulb. But I need the on/off switch to be a photocell that is sensitive enough to make the bulb light, when a laser pointer hits it. If that doesn't make sense, think of it this way. I want a to make a small light bulb light up whenever the laser pointer is hitting the photocell.

I assume I need a few batteries to light the bulb. Also, a photocell of some kind, but I don't know what kind. Would I need anything else?

If I need to be more specific about anything let me know.

Thanks in advance.

 

[mdjensen22]

Start with a nightlight circuit and flip the logic (a simple transistor should do), or you could use a comparator and flip the pins.

 

[wdavidleeii]

Okay. I guess I should have stated that I am not an electrical engineer, nor do I have very much knowledge on the subject. I am an electrician's apprentice, and I understand ohm's law and comprehend circuits. But I don't know what a logic is, or a comparator is either.

Also, exactly what would that do? Would that make it so the photocell from the nightlight is switched on when light hits it, or what?

Thanks

 

[mdjensen22]

Yes - currently nightlights turn the light on in the absence of light.
You want a circuit that will do just the opposite.

Essentialy, you just want to invert the signal of a the circuit.
The approach I was giving you was a simple way to hack something you could inexpensively obtain.

The question becomes, do you want to build something, or hack something you can buy?

If you want to build something, I would read on phototransistors and LEDs. That more/less is all you'll need to build your circuit (assuming you have DC power available).
It seems that you've got some interest in electronics, which is a good start. If you Google night light circuits, you might be able to find something with a full circuit description you can build with a few minor tweaks.

 

[wdavidleeii]

Right. So do you think a laser pointer would be a strong enough source of light to make it work? Do you think it depend at all on the light around the photocell relative to the brightness of the laser? Am I going to have to experiment? Sorry for all the questions. I just have a very specific idea and I want to build it but I don't know exactly how to begin.

 

[mdjensen22]

The laser pointer should be plenty good. It is far brighter then the nominal ambient lighting in a room (which it currently responds to).

You should always experiment to find out though. It is better to know something will work, than to construct a circuit and hope it works.