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Mains operated LED night lamp

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raja1

New Member
Description.

Here is a simple and powerful LED based night lamp circuit that can be operated directly from the 230V mains supply. The are total 24 white LEDs used and the lamp produces an output of around 15W.The resistance R1 and capacitor C1 provides necessary current limiting. The circuit is sufficiently immune against voltage spikes and surges.

Circuit diagram with Parts list.



Notes.

* Assemble the circuit on a general purpose PCB.
* The capacitor C1 can be polyester type.
* White LEDs are preferred in this circuit.
 

Sceadwian

Banned
I would strongly recommend that you rectify the mains power and use a filter capacitor, the flicker when powering an LED array like that is quiet intolerable to most people.
 

RODALCO

Well-Known Member
Good idea, I second Sceadwian 's comment to rectify it and reduce flicker of the LED's.

Most LED lamps I built, have not a capacitor but a resistive voltage divider, for more long term reliability and reducing the chance of the LED's to fail, when the capacitor has a bad day at switch on and overload the 1k resistor.
 

crutschow

Well-Known Member
Most Helpful Member
If the lamps are close together than the combined flicker is at 100Hz (or 120Hz for 60Hz mains) which is usually not that noticeable to most people.
 

Diver300

Well-Known Member
Most Helpful Member
If the lamps are close together than the combined flicker is at 100Hz (or 120Hz for 60Hz mains) which is usually not that noticeable to most people.
I beg to differ.

Although I can't see 100 Hz flicker when I look directly at a lamp, I can detect flicker up to at least 1 kHz in the right (wrong?) conditions.

If there is high contrast, both between the light and its surroundings, and between the on and off phases of the light, it is quite easy to see 100 Hz flicker I move my eyes past the light.

The off period is more important than the frequency. Lights lit from UK mains at 100 Hz usually have off periods of about 5 ms and aren't as bad as the tail lights of some cars that are 1 ms on and 9 ms off. I can see that they are flashing at any distance from about 5 metres to a couple of km.

Some car tail lights are now lit at about 400 Hz, which is still visible but isn't nearly as distracting. I haven't had a chance to get a 'scope on one of them to measure for sure.

Also, it doesn't really matter that only a few percent people find 100 / 120 Hz lighting intolerable, you shouldn't be subjecting them to lighting like that, any more than you should put door lintels 1.8m off the ground and only 5% of visitors knock themselves out.
 

Hero999

Banned
Scotopic vision is more sensitive to flicker than photopic vision so you'll notice flicker more under low light conditions if the source is in your peripheral field of vision.
 

Diver300

Well-Known Member
Most Helpful Member
Scotopic vision is more sensitive to flicker than photopic vision so you'll notice flicker more under low light conditions if the source is in your peripheral field of vision.
True, but you can detect flicker at still higher frequencies if you move your eyes, especially at night. The movement of the eye causes a light to leave a trail, which one comes to expect. Flashing lights leave a broken trail, which isn't expected, so becomes distracting.

A similar effect has been found with florescent lighting. When high-speed recordings are made of eye movements when people look from one object to another, in 100Hz lighting the eyes often overshoot the target, if it happens to be dark at that moment.

We have florescent lights at work, but they are all inverter driven at 30 kHz, so there is no problem.
 

Hero999

Banned
I sometimes notice the stroboscopic effect created by sodium lights when driving past a fence at night or on the wheels of other vecicles but it normally doesn't bother me too much.
 
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