need help to find blue led bulb

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dacflyer
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need help to find blue led bulb

Post by dacflyer » Tue Nov 27, 2018 12:09 pm

need help to find led bulb
120vac operation , blue, DC Bayonet base , something bright.
haven't had much luck, found plenty of white leds, but they look like crap with blue lenz cover.
makes them look very faded.

dyarker
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Re: need help to find blue led bulb

Post by dyarker » Tue Nov 27, 2018 12:59 pm

... makes them look very faded.
Because they are! A white "LED" is really a blue LED with fluorescent elements. Some blue light causes some green fluorescence. Some blue light causes some red fluorescence. Some blue light leaks out. The combination makes white.

A blue filter absorbs 2/3s of the light, so "faded".

What size bayonet socket? By "DC" you mean "double contact"?
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Externet
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Re: need help to find blue led bulb

Post by Externet » Tue Nov 27, 2018 4:33 pm

Perhaps
----> https://in.rsdelivers.com/product/schne ... ip/3404736

----> https://www.amazon.com/Blue-BA15S-120VA ... B00SVHBJHW

----> https://www.aliexpress.com/item/FILN-FL ... 1f254fjysz

Or, solder its wires to the inside of a beheaded bulb with the bayonet size of choice:
----> https://www.delcity.net/store/Incandesc ... gJyUvD_BwE

I believe they are not made/marketed because when inserting/replacing such bayonet bulb, the outer case terminal is exposing 120VAC to fingers. Not the case for automotive type on 12VDC.

And what kind of bayonet? ----> https://www.superbrightleds.com/cat/bayonet-bulbs/
- Abolish the deciBel ! -

dyarker
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Re: need help to find blue led bulb

Post by dyarker » Tue Nov 27, 2018 5:54 pm

I believe they are not made/marketed because when inserting/replacing such bayonet bulb, the outer case terminal is exposing 120VAC to fingers.
???Neutral to shell, switched hot to contact.
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Re: need help to find blue led bulb

Post by dacflyer » Thu Nov 29, 2018 11:21 am

Externet >> the leds i looked at are not bright enough for outdoor use..

dyarker >> the shell of the socket is no connection,, the bulb is a dual contact ( DC )
as for the faded look, the white leds cause the len scap to loose it's color richness , makes it look bleached out.
the lights are being used as replacements for the police call stations in a parking deck garage.
the CITY deemed it too expensive to replace them with the originals.

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Externet
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Re: need help to find blue led bulb

Post by Externet » Thu Nov 29, 2018 12:42 pm

I would replace the sockets and get rid of the planned overpriced replacement design.
Like printers cheaper than their ink... forcing to spend abuse prices for ink.
- Abolish the deciBel ! -

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Re: need help to find blue led bulb

Post by dyarker » Thu Nov 29, 2018 1:28 pm

Dacflyer,

Then how would the shell get 120VAC on it like Externet suggested.

In vehicles dual contact bulbs are sometimes used for brake and turn signal. The bulbs have two elements, one contact to each ans the shell is common return. So not using shell at all for electrical contact doubles the no problem with 120VAC.

I asked you if DC mean duel contact, (you did not answer)

If you want to jump on someone, jump on Externet. Now he's comparing a socket to printer ink ?????????
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Re: need help to find blue led bulb

Post by haklesup » Thu Nov 29, 2018 4:45 pm

you can use an LED for 120VAC, all you need is a sufficient dropping resistor, it's not as safe as 12V though, Blue LED in T1 package or various COB formats are available and pretty bright. I'm still unclear on the actual bulb base you are looking for. What is the bulb number of the original? is it the BA15D base?

https://www.topbulb.com/light-bulb-bases

Maybe if you have enough dead bulbs you can hollow out the bases and mount a COB LED (pulled from a T10 wedge bulb format) with dropping R epoxied in (search ebay for examples T10 blue LED)

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Re: need help to find blue led bulb

Post by dyarker » Fri Nov 30, 2018 4:32 am

A dropping resistor for 120VAC would be a huge beast. A dropping capacitor wastes a LOT less power.

And because it is for AC a rectifier is also needed.

Cheers,
Dale Y

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Re: need help to find blue led bulb

Post by dacflyer » Fri Nov 30, 2018 5:20 am

dyarker >> the dual contact base, uses the contacts for power,, nothing on the shell. some Dodge vehicles in the 70's used a 12v dual contact bulb for power interior lighting ( dome light ) only power went into the dual contacts. nothing on the shell ( example 1004 lamp )
the base is said to be a BA15D

the original lamp had no info on it, except for it being a china made bulb, and a sticker for the voltage 100v - 120v
the lamp sort of looks like this.. https://www.interlight.biz/light-bulb/L ... 1SWW-BA15D
i just can't find them in blue color..

and i wasn't jumping on anyone ....
but as for the bulb, when i said dual contact, i didn't mean for you to confuse it with a dual filament type lamp like a 1157 bulb ( brake/turn signal or parking light )

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Re: need help to find blue led bulb

Post by dyarker » Fri Nov 30, 2018 7:53 am

I never said your dual contact socket had power on the shell. I was answering Externet who said a bayonet would expose 120VAC. Even if shell were used, properly connected it would be safe. Repeat, I DID NOT (NOT) say your setup used the shell for power.

From the page you linked, it seems it contains 21 LEDs. Since blue and white LEDs both drop 3.8V forward, the series forward voltage would be 80V (the waveform won't be sine any more, but this is rough calculation) 120V - 80V = 40V

The page says the bulb is 1.5W. 1.5W / 80V = 0.01875A. If you used a dropping resistor it would be:
40V / 0.019A = 2105 Ohms (round to 2.2K) and power:
40V * 0.019A = .75W (round to 2W rating because a 1W would overheat being enclosed) This is why I suggested a dropping capacitor in the AC part of the circuit. The current and voltage are out of phase, so power is dramatically redused.

****************************************************************************************
Dacflyer,

I know that you want to buy. I did not find anything either, sorry. The above is to other comments made.

CUL
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haklesup
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Re: need help to find blue led bulb

Post by haklesup » Fri Nov 30, 2018 10:55 am

Well an LED is a diode so it in itself is a rectifier. Assuming you want to bias at 5mA (adjust accordingly maybe that's a bit low for this application) then 120V/.005 =24k resistor, .005^2*24000= 0.6Watts I would assume the incandescent bulb was more than that at least 6W, the base should be able to handle the heat.

Diode bias calculations should be done using the load current, the voltage drop across a diode can be a rule of thumb but unless you have a curve trace knowing the exact voltage drop at a given current is a bit of a guess. Not only that but it may not be immediately clear what series parallel connections may exist in a multi LED COB module.

The safety issue is that if the LED goes open circuit, you would have the full 120VAC exposed at the terminals on the COB. Only with current flowing through the LED would the voltage across it be low.

I understand you probably don't want to alter the lamp supply inside the base unit but that's another approach which leads to simpler low voltage bulb selection. here is a 14V (AC or DC) one https://www.interlight.biz/light-bulb/68-14B-LED

This seems to be what you are looking for
https://www.interlight.biz/light-bulb/LED-SMB21DC-120V

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Re: need help to find blue led bulb

Post by dyarker » Fri Nov 30, 2018 12:53 pm

You did not look at the page at the link Dacflyer gave. The calculations were for a bulb like that, not a single indicator LED.

An LED is a diode, but the PIV is like 5V. For use in a 120VAC circuit another diode (or bridge) with a PIV of at least 200V is needed.

With all components in the bulb, The hot terminal will have 120VAC on it whether LED is blown or not. The neutral terminal will have neutral (almost zero) on it whether the LED is blown or not.

((deleted before I hit "Submit"))
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Re: need help to find blue led bulb

Post by dyarker » Fri Nov 30, 2018 1:18 pm

Additional-
A resistor's power rating is based on it's max power in free air which is at 25°C.

Your calculation for 5mA was still 0.6W. Inside the base and bulb is not free air, it is not 25°C, and the resistor is not alone. So with thermal conductive epoxy (to move heat to metal shell) it might get by as a 1W.
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Re: need help to find blue led bulb

Post by haklesup » Fri Nov 30, 2018 3:39 pm

I did reconsider the LED breakdown voltage after I posted, it would be better than 5V but probably insufficient for 120V. Adding another rectifier in series would work but in any case it does appear there are bulbs of this type on the market though not cheap. Not sure how $20 compares to "originals" but at least you shouldn't ever have to replace them again. BTW, I found that one pretty quick with an image search.

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