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Yet more LED questions

Marty RMarty ROGR Forum Member
quote:
Originally posted by DaveJfr0:
This is what I use to plan my LED circuits' resistance.

http://led.linear1.org/led.wiz


Awesome, a site that will draw me a picture! The picture is for DC, but it is a start. It leaves me with the following:

1) What input voltage do i use, considering I run conventional and will be running DCS with variable loops included? At 8 V my 2 30 mA bulbs call for a 68 ohm resistor, but if I go up to 18V it calls for a 470 ohm resistor.

2) What do I need to add to run AC?

3) How can the LED be made directional in AC (Tender tail light)?

Added after initial post.
Dale H's site clears up some of this (wow, you did a lot of work, thank you Dale)
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S stan2004OGR Forum Member
quote:
Originally posted by Marty R:

3) How can the LED be made directional in AC (Tender tail light)?



Is this a DC motor? If you connect the LED to the motor in the proper polarity, it will light when reverse voltage is applied to the motor. LED current limiting and reverse voltage protection as described in the tutorials is done with an additional resistor and diode. The downside is brightness varies with speed and will be off when stopped such as just after switching into reverse.

If your reversing-unit has a relay, you can probably tap the signal that drives the relay and also have it drive the LED - may need to add a couple of components. A close-up picture of what you have might help drum up some ideas.

If it's an older mechanical reversing stepper, more info on what you have would help.
FM Former Member
quote:
Originally posted by stan2004:
quote:
Originally posted by Marty R:

3) How can the LED be made directional in AC (Tender tail light)?



Is this a DC motor? If you connect the LED to the motor in the proper polarity, it will light when reverse voltage is applied to the motor. LED current limiting and reverse voltage protection as described in the tutorials is done with an additional resistor and diode. The downside is brightness varies with speed and will be off when stopped such as just after switching into reverse.

If your reversing-unit has a relay, you can probably tap the signal that drives the relay and also have it drive the LED - may need to add a couple of components. A close-up picture of what you have might help drum up some ideas.

If it's an older mechanical reversing stepper, more info on what you have would help.


But if you use command you just hook your LED to the board most of them have a constant voltage output so it won't dim.

If you use a 3MM W/W 3.5 volt LED and a 750 ohm 1/4 watt resistor it'll come on at about 6 volts and work up to 18 volts and it won't dim hardly any.

David
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