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[boz6906]

Good day to all, I have a simple question some may be able to answer.

I'm looking for an easy way to run an LED on phantom power.

I work with visually impaired folks who sometimes have difficulty maintaining proper mic positioning, a bit of illumination at the mic would really help.
I've used a battery powered light but it's too large and batteries get expensive,

I've seen several mics with LEDs, operated by phantom.

Standard is 48Vdc at 10 mA, converted to 4.8 Vdc at 100 mA would operate the hi-efficency CREE and OSRAM LEDs with no problem.
A voltage divider won't work, not enough current, I think it would need to be some kind of dc-to-dc converter.

Thanks for any info!

Boz

[klaus]

Tracy Korby used blue LEDs in several of his mic models. Maybe you could contact him? The cause is certainly honorable enough that thoughts of competition should not stand in the way of his cooperation.

[David Satz]

Be aware that the majority of phantom power supplies in the real world don't meet the IEC/ISO/DIN standard's requirement to provide (up to) 10 mA per input channel. There are still some that can't even supply 4-5 mA without falling out of regulation.

Also, be aware that 48 Volts is the specified open circuit voltage. Under load, that voltage drops, sometimes considerably due to the 6.8 kOhm phantom feed resistors that are in series with the 48 Volt supply. If a microphone (or other device) were to draw 10 mA, the phantom feed resistors would each pass 5 mA, so the drop across each of them would be ca. 34 Volts, leaving you with only about 14 Volts. (That's one reason that few well-designed microphones draw more than 7 mA--that being the point at which the maximum power is made available.)

--best regards

[boz6906]

Yes, not all phantom supplies can deliver 10 mA but most LEDs only use 2-10 mA at 5 Vdc.

I'd use an LM317 but their input max is 37 Vdc.

I've seen many mics with LEDs, the newest is the TLM107, I know it can be done.

[Jim Williams]

Why does the mic need to have it's own light source? Fitting a visually handicapped person with a strap on head lamp works in a variety of darkened places, all while leaving your hands free to work.

Once the job is done, lights go out, mics look dark on stage. Glowing microphones could be another distraction for those that can see well.

[boz6906]

Interesting idea, but I don't think it would be appropriate to ask vocalists to wear a "strap on head lamp" in studio or live situations...

[boz6906]

So nobody here knows how to run an LED from 48Vdc phantom?

The sigers love the idea, here's a comment about the Cathedral Pipes mics with LEDs:

"Anyone who discounts it because of its' styling is missing a trick and actually, the LED is kinda cool particularly, for those of us who prefer a subdued atmosphere for recording voice. You can virtually turn the lights off and the vocalist can clearly see where they are meant to be singing."

It seems even those with good vision would like a positioning LED for subdued studio lighting.

Maybe Chuck at Cathedral Pipes will share the secret knowledge...

[Jim Williams]

A pair of resistors will do it, match them so the CMRR of the mic isn't degraded. Pull off the phantom power input (pin 2+3) and wire a 18,000 mcd white led and you will see how brite an led can get. I would sand the led to difuse the light as those can burn a hole in your retna.

[rammy]

Why does the mic need to have it's own light source?

To use it as a direction indicator in the way Sennheiser does it ih the MKH80...