build circuit

how involved can you get? Do you know how to get parts, and solder a simple circuit? Or, do you want an off-the-shelf solution?

If you can build circuits, you can use a relay, an electret microphone, a transistor, and a 555 monostable (along with a few resistors and capacitors) to build something that would work.

If you are interested in a circuit to build, please reply here.

Regards Bob Monsen

... or for something in between, the PICAXE might handle this & be fun to learn at the same time.

Hotwire one of those clap on clap off things.

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I can solder but I have never built a circuit. If it's fairly easy I would love to give it a try. Can you get me started? Thanks gina

(First, read this message in courier font, because there are ascii diagrams in it, which will make no sense unless you are reading them with a fixed width font.)

Here is what you need:

The power supply:

1 12V DC wall adapter. Only needs to support about 100mA (more is fine). The cheaper, the better. 1 7805 integrated circuit 1 0.1uF (uF stands for microfarad) capacitor (10V minimum rating) 1 0.33uF (25V minimum rating) capacitor. 1 1N4148 diode (or any old diode, it does not matter much)

The sound detector:

1 electret microphone 1 15k Ohm resistor 1 2N3904 NPN transistor (or equivalent, small signal transistor, three terminals) 1 1Meg Ohm resistor 1 10k Ohm resistor (10,000 ohms) 1 0.1uF capacitor

The timing element:

1 cmos 555 integrated circuit (see here for more info: 1 220uF electrolytic capacitor (6.8V or higher voltage rating) 1 1Meg Ohm resistor 1 0.1uF capacitor (6.8V or higher voltage rating)

Connecting the detector to the timing element:

1 1uF capacitor 1 220k variable resistor trimmer you can set with a screwdriver

The light switch:

1 12V 'normally closed' relay that can handle the current for your light bulb. A 220V/1A capable relay should do it easily. 1 2N3904 NPN transistor (or equivalent) 1 1k resistor 1 1N4001 diode (or equivalent)

The circuit board:

1 prototyping board you can solder everything to. I like 'stripboard' for this kind of thing.

Tools:

wire cutters a digital multimeter a soldering iron + solder

1 1k resistor 1 cheapo red LED a tool to trim leads (wire cutters, but must be able to cut things very short)

-------------------------------------------------

Step 1: the power supply

Diode .------|

info:

Wow, nice work Bob. That gets my vote for the comprehensive reply of the week!

Dave.

Thanks. Seems like lots of people ask these kinds of questions, but haven't a clue about where to start once they get the 'answer', which is mostly an indecipherable ascii circuit diagram. So, I thought I'd try making it easier. It took way longer than I expected to anticipate all the details and type them in. I actually had to breadboard it as I was writing it.

Anyway, I hope it helps somebody get into the groove of hobbying with electronics.

One thing I forgot was where to get the parts. I was assuming radio shack, but I don't think they have a really good selection anymore. So, unless I've scared off the OP, here is a list of mail-order places: