6.4 Volts?

[spisi]

So, I’m trying to upgrade my marquee lighting to led. Currently there are a bunch of little incandescent bulbs. My multimeter is reading 6.4 volts. Is that normal? Can I connect leds to these wires?

[RandyT]

You can connect LEDs to any DC source (above the turn-on voltage), so long as you condition the incoming power to the specifications of the LEDs.

This entails using current limiting resistors, or in some cases running them in series/series-parallel circuits.

But if you try using LEDs directly which are not designed for the specific voltage you have, they will probably die immediately.  In your case, no, even an LED assembly rated for 6v would not last long with that extra .4v on the line, without some means to lower it to 6v.

[PL1]

So, I’m trying to upgrade my marquee lighting to led. Currently there are a bunch of little incandescent bulbs. My multimeter is reading 6.4 volts. Is that normal? Can I connect leds to these wires?

Are the bulbs wedge-base or bayonet base?
Spacing between bulbs?
Distance from the sockets to the marquee?
Is this a commercial cab with possible collector value or a home-built cab?

You can run 12v LEDs on 6.4v no problem.
- I run 12v wedge-base button LEDs on 5v and they work fine.  They have the current limiting resistor hidden in the housing.



You might run into a problem with the angle and spacing of the LEDs because they are far more directional than incandescent bulbs.
- You may need to add a diffuser layer to avoid bright spots.



Another approach that might work is to use LED strips with close spacing. (more LEDs per meter)
- You may need to add a diffuser layer to avoid bright spots.


Scott

[spisi]

Thanks for the info! I'll report back soon.

[RandyT]

You can run 12v LEDs on 6.4v no problem.
- I run 12v wedge-base button LEDs on 5v and they work fine.  They have the current limiting resistor hidden in the housing.

You can do that, but there are caveats.  The main one being that those LED/resistor combos are usually rated for a bit over 12v, but in the best case scenario, running a 12v configured LED at 6.4v will sacrifice about 40% of the luminous output, making them just over half as bright as they could be, and most of those LEDs aren't all that bright to begin with.  When coupled with the directional nature of the LED, I would expect that to be a poor substitute for the more omni-directional incandescents, even with diffusion.   But there is an upshot to under-driving LEDs...if the result is bright enough for the application, they will run cooler and likely last much longer than they otherwise would.

[PL1]

Very true.   

There are also LED replacements for 6.3v #44/#47 bulbs (bayonet base) or 6.3v #555 bulbs (wedge base) that would be a better option than the cheap button LEDs.

https://www.cometpinball.com/pages/the-art-of-pinball-leds

A frosted lens provides better diffusion than no lens or a clear one.

https://www.cometpinball.com/collections/retro - 1.0x as bright as the original bulbs.
https://www.cometpinball.com/products/1smd-non-ghosting - 1.7x as bright as the original bulbs.
https://www.cometpinball.com/products/2smd-bulbs - 2.5x as bright as the original bulbs.


Scott