Christmas Vacation Project - Building a Clap Switch Light

RE: Christmas Vacation Project - Building a Clap Switch Light

fmilburn — Thu, 28 Dec 2017 18:36:00 GMT

Great project John and Ivan,

I was fortunate enough to spend time with my grandson this year and we always do something with engineering when we are together. Really enjoyed seeing your project.

Frank

RE: Christmas Vacation Project - Building a Clap Switch Light

jc2048 — Thu, 28 Dec 2017 13:48:04 GMT

"It is a simple 2 stage audio amplifier ..."

Except that it isn't. I'd have said the same at a quick glance, because it does look like the kind of circuit shape an amplifier would have, but in reality the first two transistors are a monostable with a very fine trigger. The first transistor is biased so that it normally conducts and it holds off the second transistor. A signal from the microphone starts to turn it off, the second transistor turns on and the collector voltage falling is coupled to the input by the 1uF cap, massively reinforcing the original trigger.

Then it's a matter of waiting until the 1uF capacitor charges to the point where the first transistor will turn on again, returning the second transistor to its normally off state.

Try looking at the collector of Q2 with a scope and you'll see what it does each time you clap. The collector goes low for longer than the clap lasts (that avoids multiple triggering of the output bistable). The output bistable is toggled by the negative going edge of that collector waveform, which you'll see if you compare the two.

RE: Christmas Vacation Project - Building a Clap Switch Light

ntewinkel — Thu, 28 Dec 2017 06:14:32 GMT

What a great project!

And the customization makes it that much better with an even greater sense of accomplishment at the end.

You can tell Ivan is really proud of the result!

-Nico

RE: Christmas Vacation Project - Building a Clap Switch Light

shabaz — Thu, 28 Dec 2017 05:17:25 GMT

Hi John & Ivan,

Excellent project and demonstration!! It works really well!

Regarding the holding wires thing, I too have that problem, sometimes I'll use blu-tack (temporary putty) to hold things in place while I solder. It softens slightly admittedly when the heat reaches it, so I still have to be quick to complete the join, but it seems to hold for long enough.

RE: Christmas Vacation Project - Building a Clap Switch Light

DAB — Wed, 27 Dec 2017 20:02:34 GMT

Great project John.

Well done.

DAB

RE: Christmas Vacation Project - Building a Clap Switch Light

genebren — Wed, 27 Dec 2017 16:16:37 GMT

What a fun project to share with your grandchild. I am so looking forward to doing something like that with my grandchildren (still in the blocks and clay phase, but soon???).

Enjoy!

RE: Christmas Vacation Project - Building a Clap Switch Light

jc2048 — Wed, 27 Dec 2017 09:35:37 GMT

Cool! Sound, light, and transistors - almost the perfect project.

Why the inverter? Why not drive the MOSFET with the other side of the bistable, or doesn't that work for some reason?

RE: Christmas Vacation Project - Building a Clap Switch Light

mcb1 — Wed, 27 Dec 2017 07:57:43 GMT

That's pretty neat.

Obviously he likes spending time with you, and the electronics is a bonus.

I can see a few other uses for those, so I might need to add them to the next order.

Well done Ivan.

Cheers

Mark