Powering leds and relays from dual rails

[JAY X]

Hi!

I'm drawing a 500 series module, and I'm going to use +/-16v to power relays and leds.

Relays are 24v types 2880R coil, and leds are typical 3mm 2v types and 20ma IF current. So I calculated the drop resistors for leds to be 1k5 maybe 0.5w. For relays I calculated 1k drop resistor, maybe 0,25w. As i never powered leds and relays this way, I don't know if there is anything to watch for...

Thank you very much!

Jay x

 

[Bo Deadly]

As long as the LEDs are not quickly flashing on / off you could use +16 or -16 and not the full 32. Just use a separate ground wire back to the edge connector ground.

If an LED is used to indicate the relay is energized, just put it in series with the relay coil.

If you have a string of LEDs where multiple ones can be on at the same time, put them in series and then use a transistor to bypass them to turn them off.

If the LEDs are for something with a lot of blinking LEDs like a VU meter, then I would use a small DC converter to make 5V for a PIC and slew rate limiting LED driver and then drop down into code.

If you post a schematic, I might be able to direct you more specifically.

 

[JohnRoberts]

There are different strategies for managing this... depends on what is important to you.

JR