Thread: What capacitance to filter out LED nightlight 60 Hz flicker for grandmother clock?

1. What capacitance to filter out LED nightlight 60 Hz flicker for grandmother clock?

This Walmart nightlight has two flat LEDs shining up into its clear plastic diffuser.
The diffuser easily slips off and the 2700 K light is nice for shining down onto the clock's chains, weights and pendulum.
But there is flicker!!
Any idea of capacitance to add to filter out the flicker?

Thank you.
Robert

2. Re: What capacitance to filter out LED nightlight 60 Hz flicker for grandmother clock

This Walmart nightlight has two flat LEDs shining up into its clear plastic diffuser.
The diffuser easily slips off and the 2700 K light is nice for shining down onto the clock's chains, weights and pendulum.
But there is flicker!!
Any idea of capacitance to add to filter out the flicker?

Thank you.
Robert
Are you operating it on a dimmer switch circuit? LEDs not labeled as dimable will flicker, or the one you have may be defective.

RC

3. Re: What capacitance to filter out LED nightlight 60 Hz flicker for grandmother clock

This Walmart nightlight has two flat LEDs shining up into its clear plastic diffuser.
The diffuser easily slips off and the 2700 K light is nice for shining down onto the clock's chains, weights and pendulum.
But there is flicker!!
Any idea of capacitance to add to filter out the flicker?

Thank you.
Robert
Hi Robert,

I am not familiar to the LED flicker. Since LED is diode, which rectifier half wave. So every half wave it shine. If you reverse one of the LED polarity so each LED shine each half wave (one positive half and the other negative half wave). It will not have the flicker. What I mean is you parallel two LEDs with one LED's Anode connected to another LED's Cathode. So two LEDs are oriented in opposite direction connected in parallel. Hope this solve the flickering problem. You need to make sure both LEDs are working first. If one of the LED is not working, you only have one LED shining 50% of time.
Ming

4. Re: What capacitance to filter out LED nightlight 60 Hz flicker for grandmother clock

I think I understand, for the pendulum it is like
a strobe with 120Hz flashes.
One would have to significantly change the circuit.
The circuit is designed to use and take advantage
of 60Hz source. You'd need to replace the dropping
circuit with a pure DC supply.
If the diodes are laid out as Ming says, a capacitor would
not be useful.
I suspect they use a capacitor to drop the voltage of the
AC to power the LEDs.
Tinker Dwight

5. Re: What capacitance to filter out LED nightlight 60 Hz flicker for grandmother clock

Sometimes these lights have a diode in the circuit ahead of the LEDs, some do not. If there is a diode ahead of the LEDs then reversing one will not work since 1/2 of the wave is already blocked before it gets to the LEDs. A lot of these LEDs are not designed to use 120 volts, so a bit of circuitry is included to drop the voltage. That circuitry usually includes a diode. There are LED lights where the circuitry is designed with a pass through and an inverter to provide continuous DC. It would probably be best to get one of those, although they do cost more.

https://www.cnet.com/how-to/how-to-b...icker-or-buzz/

Originally Posted by marylander
Hi Robert,

I am not familiar to the LED flicker. Since LED is diode, which rectifier half wave. So every half wave it shine. If you reverse one of the LED polarity so each LED shine each half wave (one positive half and the other negative half wave). It will not have the flicker. What I mean is you parallel two LEDs with one LED's Anode connected to another LED's Cathode. So two LEDs are oriented in opposite direction connected in parallel. Hope this solve the flickering problem. You need to make sure both LEDs are working first. If one of the LED is not working, you only have one LED shining 50% of time.
Ming

6. Re: What capacitance to filter out LED nightlight 60 Hz flicker for grandmother clock

I'm suspecting the two diode strips are place in parallel
with the directions reversed. A capacitor is then in series
as a voltage dropping and current limiter.
It then only need the three parts ( cheap ).
Tinker Dwight

7. Re: What capacitance to filter out LED nightlight 60 Hz flicker for grandmother clock

If this is true, then what is causing the flicker? Is it the capacitor?

Originally Posted by Tinker Dwight
I'm suspecting the two diode strips are place in parallel
with the directions reversed. A capacitor is then in series
as a voltage dropping and current limiter.
It then only need the three parts ( cheap ).
Tinker Dwight

8. Re: What capacitance to filter out LED nightlight 60 Hz flicker for grandmother clock

The capacitor is just passing AC.
The LEDs are each flickering at 60Hz with
a combined 120Hz flicker.
It would be clear on a moving pendulum.
If it has a flicker that you can see just
stationary looking at the light, it must
have a poorly working regulator circuit.
Tinker Dwight

9. Re: What capacitance to filter out LED nightlight 60 Hz flicker for grandmother clock

Maybe just convert whatever diode configuration it's using with a bridge array?

10. Re: What capacitance to filter out LED nightlight 60 Hz flicker for grandmother clock

Martin, you beat me to it. If they use a single diode in the circuit before the LED's, a bridge rectifier replacement will give them 120hz driving the LEDS.

Ralph

11. Re: What capacitance to filter out LED nightlight 60 Hz flicker for grandmother clock

I think we need to see how it is currently wired.
If it is using a capacitor as a drop and current limiter,
putting the bridge on the line will just make the
light flash once when plugged in.
Tinker Dwight

12. Re: What capacitance to filter out LED nightlight 60 Hz flicker for grandmother clock

Robert buy another one and take it apart so we can see it. If they are using the reactance of a series capacitor as the voltage dropping element with now smoothing then you will have a strobe effect.

David

13. Re: What capacitance to filter out LED nightlight 60 Hz flicker for grandmother clock

Isn't it easier just to buy a short length of self adhesive LED strip and use a wall wart transformer to drive it? Presumably those are already smoothed so you won't get this problem?

Is the problem occuring because the way the supply is rectified is giving you a 60 hz flicker instead of a 120 hz flicker you get in your normal house lighting?

14. Presumably the two LEDs are connected in opposite polarity

Thank you, All.
Presumably the two LEDs are connected in opposite polarity. (That is the way I would do it.)
During positive half of the AC sine wave, left LED is illuminated while right, off. During negative half of the sine wave right LED is on while left is off.
Otherwise BOTH are ON 1/120th second and BOTH OFF for the next 1/120th second.
I would want the capacitor to discharge in the areas of zero voltage.

(If I could, I'd have all of our house lights be LED operating from a constantly-charging storage battery.
Zero flicker and light during power outages. Bottom outlet receptacles and kitchen outlets would remain 120 VAC.)

If no simple solution, I'll just leave the 5-Watt incandescent nightlight bulb in place.

15. Re: Presumably the two LEDs are connected in opposite polarity

Google "flicker free screw in LED" - there are many available for different base sizes and watts made by more than one manufacturer and different color tints. I find a slightly bluish tint makes shiny brass weights and pendulums look very nice.

Thank you, All.
Presumably the two LEDs are connected in opposite polarity. (That is the way I would do it.)
During positive half of the AC sine wave, left LED is illuminated while right, off. During negative half of the sine wave right LED is on while left is off.
Otherwise BOTH are ON 1/120th second and BOTH OFF for the next 1/120th second.
I would want the capacitor to discharge in the areas of zero voltage.

(If I could, I'd have all of our house lights be LED operating from a constantly-charging storage battery.
Zero flicker and light during power outages. Bottom outlet receptacles and kitchen outlets would remain 120 VAC.)

If no simple solution, I'll just leave the 5-Watt incandescent nightlight bulb in place.

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