Experimenting means there will be casualties :-)

I don't understand that circuit. He talks about a BC547 and then shows 2N7000 in the schematic. He goes on to do a poor job of showing the connections to the laser. It should be two separate circuits. The first one is your laser, a resistor and the battery. The second would look something like the circuits here.

I suggest you build one of these, the first one should be fine. Shown here,

Replace the LED with your buzzer.

Mikek

Can you show a picture of what you've connected?

What are you using for a supply voltage?

The 2N7000 is a N channel field effect transistor and the BC547 is a bipolar transistor (if I understand it). Those aren't exactly interchangeable parts.

Bipolar transistors start conducting with a specific current in the base to emitter junction and a voltage of ~.6 volts. (Point six volts) Mosfets will start conducting at ~2-4 volts with no current flow to speak of. Different animals...

Don't get discouraged, it takes a degree of patience and perseverance to learn electronics by building things. You will fail, but if you learn from the failures they aren't really failures. Book-learning can help.

I found a better documented project.

Mistakes enlarge your knowledge. Successes enlarge only your pride.

But you already have the parts for the circuits I posted. Why not put it together. Mikek

I do not have a potentiometer.

Andy

You can substitute a resistor for the potentiometer. But I note the circuit is probably backwards from what you want.

This circuit will turn on the buzzer when light hits the LDR. I suspect you want the Buzzer to turn on when the laser beam is broken. So, reverse the positions of potentiometer and the LDR. For clearity we will label the resistor R1. Now, when there is no light on the LDR it has a high resistance, this means there is less voltage drop across R1. Because there is less voltage drop, the voltage on the base of the transistor is high and it conducts causing you buzzer to buzz. With light on the LDR it has a low resistance, lots of current flows through R1 and it has a high voltage drop. So much that the transistor is off and the buzzer does not buzz. Remember this is with the R1 and the potentiometer reversed.

If you build it and it doesn't work, give me the base voltage with and without light on the LDR. You might even give me the voltage, dark, with ambient light and with the laser shining on the LDR. Mikek

Do you have any electronics books? For a beginner I'm going to suggest "Practical Electronics for Inventors" If you don't buy the latest edition, it's only $5-10. With lotsa good stuff.

George H.

Thanks, i will look for it.

It is available for download as a bit torrent file too. (if you use torrents)

The magnet link:

magnet:?xt=urn:btih:7912823298f185188593ec36404b15e73fde50db&dn=Practical+Electronics+for+Inventors+provides+step-by-step+instru&tr=udp%3A%2F%2Ftracker.leechers-paradise.org%3A6969&tr=udp%3A%2F%2Ftracker.openbittorrent.com%3A80&tr=udp%3A%2F%2Fopen.demonii.com%3A1337&tr=udp%3A%2F%2Ftracker.coppersurfer.tk%3A6969&tr=udp%3A%2F%2Fexodus.desync.com%3A6969

ical+Electronics+for+Inventors+provides+step-by-step+instru&tr=udp%3A%2F%

2Ftracker.leechers-paradise.org%3A6969&tr=udp%3A%2F%2Ftracker.openbittorr ent.com%3A80&tr=udp%3A%2F%2Fopen.demonii.com%3A1337&tr=udp%3A%2F%2Ftrac ker.coppersurfer.tk%3A6969&tr=udp%3A%2F%2Fexodus.desync.com%3A6969

Thanks a lot. I am reading it now.

Andy

Not even *remotely* interchangeable!!

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Hi Andy,

Firstly, please continue to ask questions, and surf around finding interesting websites of projects.

Be slightly aware though, that a lot of websites (especially from the less IT switched on parts of the world) are mostly set up to make their operators money, or get them recognised as "employable" by their peers.

The information shared is often junk regurgitated from content other folks that have shared.

A very worthwhile source of tutorials

or google "Getting Started in Electronics by Forrest M. Mims III"

Seriously, I'd buy a copy. If I had the last book as a kid[I], I would have been a very different kid.

([I] Apologies if you are not a kid.)

--
Adrian C

Thanks.

I am a kid in an adult body. :-)

Andy

Ain't we all :)

--
Adrian C