Looking for info on power switch LED powering

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Redtns

Member
Joined
Apr 11, 2017
Messages
20
Hi all,

I was replacing the main power switch (a combo LED/latching push switch) on an old mic amp I have a few weeks ago, and realised that the "power-on" LED was powered by the same 15V rail the rest of the LED circuitry used.

For me it doesn't make sense that the mains-on LED indication isn't "pre-power supply", if you know what I mean. I'd assumed it'd be fed from a half rectified, post power transformer point.. Because it is after all indicating whether power is being supplied to the power supply, not whether one rail of the supply is working.. What's the normal way to power something like this? Or is this normal?!

Cheers!

R
 

Rob Flinn

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Joined
Jun 3, 2004
Messages
4,557
Location
Sussex, UK
Hi all,

I was replacing the main power switch (a combo LED/latching push switch) on an old mic amp I have a few weeks ago, and realised that the "power-on" LED was powered by the same 15V rail the rest of the LED circuitry used.

For me it doesn't make sense that the mains-on LED indication isn't "pre-power supply", if you know what I mean. I'd assumed it'd be fed from a half rectified, post power transformer point.. Because it is after all indicating whether power is being supplied to the power supply, not whether one rail of the supply is working.. What's the normal way to power something like this? Or is this normal?!

Cheers!

R
It can be either way in my experience.
 

JohnRoberts

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Nov 30, 2006
Messages
21,162
Location
Hickory, MS
it depends on how important that information is how much cost/complexity you are willing to spend.

I tried to get clever with a big console power supply using bi-color LEDs on each rail voltage. Green for rail is working and up, red for rail is up but fuse is blown so output is down, and dark for rail is not up at all.

An LED on a power switch is kind of superfluous IMO, but YMMV. Simple products need at least a one active LED, complex products with rich front panel displays not so much.

JR

PS: back last century while thinking outside the box I considered the possibility of driving the power on LED from a microprocessor port incorporating technology to blink out digital data when first powered up. This digital data could include model name, manufacturing date, serial number, troubleshooting status, etc. This product was ahead of its time but now we could probably write a smart phone app to decode the data. This could be pretty useful for warranty confirmation and field service.
 

Redtns

Member
Joined
Apr 11, 2017
Messages
20
Thanks all, fair enough.. Not really what I expected! I imagined there would be some sort of rule for this.
 

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