Proto 2000 and White LED Headlights

Puckdropper · 2007-02-03T08:03:55+00:00

I'd like to put a White LED headlight in my FA1 Proto2000 locomotive. The circuit board provides 1.5 volts for a headlight, but the White LEDs I have want 3 volts.How can I go about doing this? Are there reasonable sources for 1.5V White LEDs, or does someone make an inexpensive kit to support this?Puckdropper

Feb 03, 2007 25 Replies

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Joe 19 years ago

Whether currently produced or not, both Fairchild and National currently show LM317 in a TO-92 package in their data sheets.

Here's the URL for the National datasheet:

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--- Joe

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Joe 19 years ago

A correction:

LM317L is the low power version of the LM317.

LM317L "guaranteed" outputs 100mA which makes it ideal for LED current regulation. I have used it to plug various types of LEDs (red, white, yellow, green...) into a breadboard with the LM317L wired for 15mA output current, without having to change components to adjust for the various forward voltages of the LEDs.

Another nice feature of using the LM317L in constant-current mode is that LEDs can be wired in series, as long as the input voltage is high enough.

--- Joe

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Jon Miller 19 years ago

I should have replied this way first as I use this circuit all the time. Go to;

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I use a SMR between the two legs and it makes for a small package.

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Puckdropper 19 years ago

"Jon Miller" wrote in news: snipped-for-privacy@corp.supernews.com:

That's nice and small, looks like it'd be a good fit. Thanks.

Puckdropper

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David Nebenzahl 19 years ago

Joe spake thus:

So would you recommend using the LM317L (as a constant current source instead of as a voltage regulator) over the LM334?

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Joe 19 years ago

Can't say that I would. I haven't used an LM334. Jon Miller apparently has, and quite successfully. The fact that a reverse connection to the input of the LM334 is well tolerated may actually convince me that the LM334 is a better choice.

--- Joe

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