In this issue of the useless electronic circuits blog, I'll show you how to create a little infrared lamp.
So why is the post title Night vision? well, it just happens that digital cameras can "see" infrared light, thing that the human eye cannot do. There are other things you can do with IR light but i'll leave that to you to investigate, here we'll make a infrared light source that does nothing without some extra gear.
To get started you will need to get about 10 infrared leds, two 1.5 batteries (AA recommended), a push-button and a on-off switch. If you want your lamp to be fancier you can make a digital gate with transistors to only turn the lamp on when you have the on switch and push the button.
To get a bright and reliable IR light that doesn't turn off when one of the leds fail, we are going to wire them in paralel and in two different circuits, like so:
This diagram doesn't have the switches, that is up to you to decide what type of swith you want.
When you turn on this lamp and see where you are pointing it to with a digital camera you'll see a purple light, that's the infrared. The cool thing is that you cannot see the light with just your eyes, so you won't bother anyone when you are using this thing.