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BEAM Pieces is a BEAM Reference Library site.

What to buy, how to apply

Diodes (including LEDs and Photodiodes)

Since BEAMbots don't have very high current requirements, we'll be using diodes optimized for fast, low-resistance switching of low currents.

Three particular Silicon diodes seem to be the most-popular ones in BEAMbots:

  • 1N914, 1N4148
    These guys are interchangeable, small signal diodes. You'll use these for most of your circuits since they're small and work for logic, or loads to 200 mA.

  • 1N4001
    This guy is a rectifier diode, and doesn't show up as often in BEAMbots, since its only advantage over the 1N914 / 1N4148 is in current capability -- up to 1A. BEAMbots never draw nearly this much power, but remember this diode for loads near (or over) 200 mA.

If forward voltage drop is an issue, you can use a Germanium diode (tho' they're much more expensive than their Silicon cousins). The most common is the...

  • 1N34A
    Small-signal Germanium diode -- sometimes salvageable from a variety of circuit boards

In some instances, diodes are marked with part codes; a guide to deciphering them is here.


LEDs (Light Emitting Diodes)
A tutorial on using LEDs is available here. The things you'll need to consider are current drain (general rule: small is better than big), and LED type (regular vs. infrared vs. flashing).


Most any photodiode will do for BEAMbots; I'd suggest you select one based on what has a convenient "field of view" (some are sensitive to light from such a broad field that you'll need to build them "blinders" so they'll only respond to light from a given range of directions.

For more information...

Details on the physics of diodes, and the background of the various types are available both on the BEAM From the Ground Up diode page, as well as in the EncycloBEAMia.

And don't forget to visit the online "LED Museum"

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Page author: Eric Seale
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