Electronics 2000

Hi Guys,

I am working on a project where I need some battery powered LEDs to switch on as a result of something being knocked three times. for example:

I have a set of flat LEDs in a book cover, but they only turn on after the book cover has been knocked 3 times, and after a given number of seconds the lights turn back off again.

What do I need to get to achieve this, I really appreciate your help.

WS7

guys I really need help for this, have been looking around for gadgets which have a similar function so I can pull it apart, but not found anything yet, any suggestions would be great.

Thanks again

Hi whitestar,
What you want to do is a little complicated. Are you planning to actually put it in a book?

You need to convert the "knocks" to a trigger pulse. Count them through a shift register. Enable a timer with the output from the counter (shift register. It can be done, but getting it flat enough to fit in the cover of a book....well, that is advanced design. That would require a little circuit like you find in singing greeting cards. I think they are called "chip-on-board", and are custom designed and printed micro-circuits, sealed under a dab of epoxy. You find them in many small battery operated items these days such as bicycle light flashers, greeting cards, Tele remote controls, etc. You will also need to house a battery or other power source. So again, are you planning on putting this in a book? If so, to get them built will be several thousand pounds!

Now then, if not in a book, there is more to discuss....

You could also adapt a 'clapper' circuit by replacing the microphone with a peizo buzzer circuit
to pick up the knock instead of the sound of the clap.

This is a two clap circuit for switching on lights, you could make it a 3 knock circuit by the addition of another 555 chip and the piezo buzzer amp I would presume.

http://www.electronicsforu.com/electron ... p%20Switch

obviosly the mains bit on the output is not needed for your circuit

hi Guys,

thanks loads for the advice, I didnt realise who complex this would be! please excuse my ignorance on it, I am very new to all this.

The device will be used in a pair of shoes, was just thinking maybe I could tear apart some of those shoes which light up, and modify them. I like the idea of the clapper, I think I am kinda outta my depth here by a long shot