Lockout buzzer

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Joined Sep 26, 2008
I am working on this same project to use for Jeopardy-style reviews in a class that I teach. I wanted to make a few modifications including putting it in a project box with the switch and LEDs mounted to the outside, and extending the answer and reset buttons. I'm also using this as an opportunity to learn about more complicated electronic circuits and their components (haven't had any of this since college physics...trying to learn how/why diodes, transistors, etc. fit into all this).

I first tested the project with the parts it came with to make sure everything worked, and then desoldered the LEDs and buttons to make my extensions. I purchased larger LEDs to use instead so they would be more visible to the students. Here are the stats from Radio Shack:

Size: T-3-1/4 (10mm)
Typical Voltage is 1.9, with a maximum voltage of 2.2V
Typical MCD: 5000
Typical wavelength: 660mm
Viewing angle: 30XXX°
36mA (max)

Do I need to make any changes so that these get the voltage they need compared to the small ones that the the kit came with? I'm not quite sure how to make these calculations.

Here is a copy of the circuit diagram:


Joined Apr 20, 2004

We prefer that you don't hijack existing threads by posting onto them. Always start a new thread for a new question.

The previous thread was this one - http://forum.allaboutcircuits.com/showthread.php?t=9029.

Here is a link to our Ebook on figuring LED resistors -http://www.allaboutcircuits.com/vol_3/chpt_3/12.html. You don't state the circuit voltage or desired current in the LED's, so we can't help further.
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