Component questions

Ian0

Joined Aug 7, 2020
13,131
I didn't read all the responses but you don't really need a separate PS at all for LEDs. Just a 22K, 1/2 watt carbon film resistor in series with a standard 'modern' LED (older LEDs go POP) will light an LED just fine. That's for green and the resistor can be adjusted for other colors. No reverse diode needed, for green anyway. I'm looking at 6 of them glowing, wired up that way right now in a many year old power distribution center. Dunno about the flicker you need though. Trying to think of an AC circuit with a triac, a pair of N-Chan FETs driving it and a dual RC timer circuit. All 120 volt operation so the need to for an extra PS goes away.

Also, there are Tea Lights available for a few cents that have the LED flicker built in, so they look like a flickering candle...but they use 1.5 volt button batts. Could be jury rigged for your purposes to operate on 120 Vac though.

Just spit balling here.
Perfectly fine to drive an LED with a resistor straight off the mains, but watch out for the creepage and clearance distances. LEDs are not really designed as a mains indicator so providing enough insulation is the job of the designer.
(You can use a capacitor to avoid the heat generation of the resistor, which would be a much bigger problem for a 230V supply)

You can make a simple flickering circuit using a CD4006 shift register, a 4070 exclusive OR gate, a triac, three resistors, a diode, a zener and a capacitor. I'll draw it if you're interested.
 

Jim@HiTek

Joined Jul 30, 2017
60
Here's those Tea Lamps. Get 110 of them or so (need to do the math), put them all in series, add a diode to mains, and a 100uF filter cap and ya got yer flickering lights with hardly any work. Than take the entire setup to a machine shop and have them use their 20 ton press to smooch everything into the bulb you were thinking of using.

Oh, wait a second. That might not work so good. Okay, scratch that. :D

If you only need one tea light, pull the guts out of the case with the tiny circuit board, measure the operational current and the battery voltage, then calculate the needed resistor and wattage needed to drop the voltage to the battery voltage from mains through a diode. Use a tiny electrolytic across the tea light (not the resistor). Resistor wattage won't be very much, likely a 1/2 watt carbon film would fit the bill. Hang onto the frosted lamp cover. That frosting is needed for realism.

Come back and show us the results!
 

Thread Starter

DWiseguy

Joined Nov 7, 2020
17
I thank the last four responses, but you are talking WAY over my level. Read my very first post.
Why can't I just use something 'like' Anytiti LED driver? On amazon. I prefer that the wires coming out plug into the convertor with a four to six foot lead so the box is not on a table in plain sight. Such a convertor must exist, I know I could put a fm plug on the factory lead and a m plug on the wires from the lamp but it seems tacky to say the least.
What about the resistor heating issue mentioned in my previous post?
 

MisterBill2

Joined Jan 23, 2018
27,506
For the "resistor heating" part of the concern, the power wasted in the resistor that turns into heat is not very much. If the LED is a current really bright one and the forward current is 100 milliamps, (0.100 amps, and the forward voltage is 4.00 volts, , and the supply voltage is 12.0 volts, then the power turned to heat is 8 volts x 0.01 amps=0.080 watts, 80 milliwatts. the smallest common resistor would be rated to handle 1/4 watt-250 milliwatts. so there would be an adequate margin of safety.
 
Last edited:

MisterBill2

Joined Jan 23, 2018
27,506
OOPS!! Right! OK, 800 milliwatts! so use two LEDs in series and cut the power in half. And now I see it was not a math error, it was a typo-error. Thanks for catching that.
 

Thread Starter

DWiseguy

Joined Nov 7, 2020
17
Thanks for the info about the hot resistors. It is possible that the one with that experience had a malfunction or sensitive fingers. Regardless, my question has been answered.
Now to my unanswered question. To run a few constant LED's and a few flicker LED's hooked to a three position switch then to a power supply / convertor. Basically all I need is the LED's, resistors, hooked up properly of course, a switch and power supply / convertor, right?
I do not have the knowledge to design my own circuit boards. Plus I want this to be as simple as possible
Thanks
 

MisterBill2

Joined Jan 23, 2018
27,506
It appears to be that all you need is indeed a switch to select which LED strings you want to light. And each string will need to include the LEDs and a suitable current limiting resistor. The power supply will need to supply a single, fairly constant, DC voltage that you have chosen for that application. Often that will be 12 volts, both because those supplies are common and because 12 volts is easy to work with and not any shock hazard. Using a current limiting resistor is not the most efficient possible arrangement, but it IS simple and effective and certainly adequate for these applications.
 

Thread Starter

DWiseguy

Joined Nov 7, 2020
17
Let's assume I have three constant bulbs and three flicker bulbs hooked to a three position switch, would you recommend one resistor for all six? Or one resistor for the constants and another for the flickers? Or a resistor for each bulb, which is most appealing for me because sooner or later a bulb or resistor will die and that is the only one that would need to be replaced. I am trying to keep this as simple as possible.
 

MisterBill2

Joined Jan 23, 2018
27,506
Given that eack string is different, each string will require a resistor calculated fot that string. It may also be that each string would have a different number of LEDs. This is the least complex arrangement that I can come up with.
 

Thread Starter

DWiseguy

Joined Nov 7, 2020
17
Thanks to all of you I think I have enough information to get started on the electrical aspect of my idea. Now I 'just' need to figure out how to put it into my envisioned idea.
 

Thread Starter

DWiseguy

Joined Nov 7, 2020
17
I'm back ! I purchased 2V, .25W, 470OHM LED's. It is not going to work. It would take MANY LED.s to equal the brightness of a 3W, 120V incandescent flicker bulb. I haven't found a low voltage flicker LED that is equal to the incandescent.
So now I'm thinking use a 120V for the flicker under the insulator and batteries for the LED's. Just need to engineer a hidden, accessible battery pack. Different for each lamp.
Thanks for any assistance.
 

Ian0

Joined Aug 7, 2020
13,131
Luminous efficacy of a filament lamp is about 15 lumens/Watt. For a good white LED it's >100lm/W, so, to replace a 3W filament lamp, you will need 0.45W of LED - that's a single white LED run at 150mA, or ten run at 15.mA.
A single one run at 150mA would need a heatsink, but at 15mA they wouldn't.

PS. I don't know what you mean by "2V, .25W, 470OHM LEDs"..
 

Thread Starter

DWiseguy

Joined Nov 7, 2020
17
2V. ,25W, 4700HM LED is the specifications printed on the package of LED's that I bought.
Is there such thing as a flicker bulb rated at 150mA ?
Thanks
 

Thread Starter

DWiseguy

Joined Nov 7, 2020
17
I'm surprised no one has answered the last question.
I soldered some bulbs and resistors together and my first attempt worked! How ever. I can see that I will never duplicate the candle like flicker that a incandescent bulb produces. The small bulbs are just not going to do it. For now I will continue with the 120V incandescent flicker and some how fit in a battery pack for the LED's
 

MisterBill2

Joined Jan 23, 2018
27,506
I'm surprised no one has answered the last question.
I soldered some bulbs and resistors together and my first attempt worked! How ever. I can see that I will never duplicate the candle like flicker that a incandescent bulb produces. The small bulbs are just not going to do it. For now I will continue with the 120V incandescent flicker and some how fit in a battery pack for the LED's
Please be sure to use the adequate electrical insulation on all of the main powered segments of the product. Mains power can get really ugly very fast.
 
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