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The Magic Cafe Forum Index :: The workshop :: Need electronics help!!! (0 Likes) Printer Friendly Version

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freefallillusion1
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Elite user
Cincinnati, OH
446 Posts

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Hoping someone knowledgable with electronics can help me-

I'm working on an effect which involves a laser pointer. Here's what I need to accomplish- I have the laser beam on a pre-determined spot, and when I move it away, a buzzer sounds. Now, I happened to be at the dollar store and found some yard stake-lights which are all pre-wired with a photo sensor, so by day, the light is off (and the battery inside is charging), and when the daylight is gone, the LED kicks on. I tried shooting the laser at the top and it worked great. Upon moving the laser, the LED came on. Perfect!

So, I thought it would be easy. My plan was to hack this setup and replace the LED with my buzzer, and since the buzzer requires 6 volts, replace the 1.2 volt battery with six volts. In theory, that should work- but apparently everything is rigged to work with the 1.2 volts instead of six, and when I connected the battery pack, everything got really hot!

Is there something simple I can adjust to make this work?

Thanks for any help!
magicwatcher2005
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Elite user
Washington state
446 Posts

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Yes. A solid state relay that uses the LED's 1.2 volts to trigger a separate circuit powering the buzzer on 6 volts. Any well-stocked electronics supply house should be able to guide you.
Anverdi-museum
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Inner circle
1200 Posts

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Radio Shack sells a Reed Relay that should do it.
Christopher Taylor
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V.I.P.
British Columbia Canada
2321 Posts

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Don't know of a relay that will function on less than 3 volts but there certainly are buzzers that will. Look for a "Piezo low voltage buzzer" which will generally operate on anything from 1 to 30 volts.

All the best,

Christopher
Christopher Taylor

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www.taylorimagineering.com

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jolyonjenkins
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Inner circle
United Kingdom
1183 Posts

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You don't need a relay, you can use a transistor. Google "transistor switch".
Jolyon Jenkins
mrmetropolis
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Regular user
who has only made
155 Posts

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Get an Arduino or something similar. Google: arduino light sensor to buzzer. Personally, I would use something else cheaper than arduino and they are kind of overkill but they will get the job done easily.
"For those who believe, no explanation is necessary, for those who do not, none will suffice".-Joseph Dunninger http://www.youtube.com/watch?v=K4wL5fX3xGQ
jolyonjenkins
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Inner circle
United Kingdom
1183 Posts

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Arduinos are wonderful things but I would suggest that they are not appropriate here. The OP would need to learn some basic coding, would need to get a separate 5V power supply, and might still find that it couldn't deliver enough current to drive his 6V buzzer. Plus the input from his lights won't be enough to drive the arduino input so he'd have to give up on that too. You'd be talking about spending about $30 for a problem that can be fixed for a couple of dollars.
Jolyon Jenkins