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  1. #16
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    Default Re: Presumably the two LEDs are connected in opposite polarity (By: THTanner)

    Thank you.
    In the house we like the warm color. The yellow in the warm color brings out the brass color.

    It is unfortunate that Walmart accepted this lightnight with flicker. We already have too many things which flicker.

    (Some of our LED Christmas lights appear to be half wave emitters strobing at 60 times a second.
    I am planning to build full-wave bridge rectifiers which produce filtered DC for the outdoor and indoor lights.
    Will probably have to change some wires in the strings so sections of the strings will not be dark.)
    Confucius say: "Man own clock know time. Own two, never sure."

  2. #17
    Registered user. MartinM's Avatar
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    Default Re: Presumably the two LEDs are connected in opposite polarity (By: Robert Gift)

    I must not be understanding your intent with the capacitor. This isn't half or full wave rectified DC you're looking to smooth. It's AC.
    So, (given your assumption about the current circuit, I could see you improving the dwell of one LED, but not both (with a single capacitor).
    Living life at eight beats per minute.

  3. #18
    Registered user. kinsler33's Avatar
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    Default Re: Presumably the two LEDs are connected in opposite polarity (By: MartinM)

    Historical note: The AC frequency of 60 Hz was chosen as the lowest frequency which would not cause visible flicker in an incandescent lamp. (In Europe, they lowered this to 50 Hz, which gave less voltage drop on long lines.) But I've been told that there are people who perceive 60 Hz or even 120 Hz flicker from an LED or fluorescent lamp. Dual fluorescent fixtures are arranged so that one lamp is phased 90 degrees (1/4 cycle) from the other one, which minimizes strobe effects near rotating machinery.

    If you check the label on old vacuum cleaners you'll find that they're rated for use from 25 Hz to 60 Hz. 25 Hz was used in New York City for a time, and in Niagara Falls for the first hydro-electric installations. With 25 Hz, the flicker in an incandescent is clearly visible to everyone.

    M Kinsler
    512 East Mulberry Street; Lancaster, Ohio USA 740-503-1973; kinsler33@gmail.com
    http://www.lancastereaglegazette.com/search/kinsler/

  4. #19
    Registered user. THTanner's Avatar
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    Default Re: Presumably the two LEDs are connected in opposite polarity (By: kinsler33)

    In the 70s and 80s when the first computer screens began to be used widely, there were people who would have real problems with some of the slower fly back frequencies. Some would get nasty migraines after a short time and the flicker would even trigger epileptic like seizures in others. I have a renter in one of my houses who is especially sensitive to any flicker from about 50 to 100 Hz so all fluorescent and led lights are impossible and she has to use computer screens with really high refresh cycles.

    Quote Originally Posted by kinsler33 View Post
    Historical note: The AC frequency of 60 Hz was chosen as the lowest frequency which would not cause visible flicker in an incandescent lamp. (In Europe, they lowered this to 50 Hz, which gave less voltage drop on long lines.) But I've been told that there are people who perceive 60 Hz or even 120 Hz flicker from an LED or fluorescent lamp. Dual fluorescent fixtures are arranged so that one lamp is phased 90 degrees (1/4 cycle) from the other one, which minimizes strobe effects near rotating machinery.

    If you check the label on old vacuum cleaners you'll find that they're rated for use from 25 Hz to 60 Hz. 25 Hz was used in New York City for a time, and in Niagara Falls for the first hydro-electric installations. With 25 Hz, the flicker in an incandescent is clearly visible to everyone.

    M Kinsler
    You miss 100% of the shots you don't take. - The Great One

  5. #20
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    Default Re: Presumably the two LEDs are connected in opposite polarity

    How interesting!, Webster's pedestal.
    Some parts of NYC, I recall, were on DC up to the 1960s!

    In London, in my peripheral vision I could detect the 50 Hz both in Hg-vapor lamps (or were they high pressure Na?) and their TVs.

    To minimize strobing making spinning machinery wheels appear still, were fluorescent lamps in factories wired 120-degrees out-of-phase from three-phase power?

    How terrible if the 25 Hz. flicker was visible even in.candescent lamps.
    Can instruments detect any flicker from 60 Hz. AC in lower-wattage lamps? I assume the.rmal mass of heavier higher wattage filaments would reduce or prevent flicker.

    Fortunately, in our cheap Walmart "60-Watt" lamps, I cannot detect any flicker!
    On some of the bulbs I cut off the plastic top. The 9 "pin-point" LEDs are ideal for revealing detail in clock movements!
    Confucius say: "Man own clock know time. Own two, never sure."

  6. #21

    Default Re: Presumably the two LEDs are connected in opposite polarity (By: Robert Gift)

    It isn't a 50hz or 60 hz flicker in AC lamps, it is 100Hz or 120Hz. Incandescent's flicker less because they don't get a chance to cool down, however machine tools are fitted with DC lamps so that they never appear stationary to an operator through the strobe effect. The problem with LEDs is that being diodes they only react to the electron flow in one direction so it will depend on the rectification if they have a flicker.

    I demonstrate the flicker of fluorescent lights to students using the receiver of a modulated light demo, the receiver gives out a 100hz hum.
    Nick, lots to learn, late starter.

  7. #22
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    Default Re: Presumably the two LEDs are connected in opposite polarity (By: novicetimekeeper)

    Interesting about pure DC for machine tools! I suspect our "strobing" LED strings have only LEDs with no other circuitry.
    Scanning eyesight across them yields - - - - - - - - - - - indicating OFF for half each cycle = 60 illuminations/second.
    That is why I want to build a full-wave rectifier with capacitors to fill in the two zero-voltage areas each cycle.

    The Walmart nightlight is not that bad. I suspect its two LEDs are opposite polarity = but its 120 illuminations/second flicker is still noticeable
    in peripheral vision
    .
    Confucius say: "Man own clock know time. Own two, never sure."

  8. #23
    Registered user. THTanner's Avatar
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    Default Re: Presumably the two LEDs are connected in opposite polarity (By: Robert Gift)

    You could also rewire the duplex that you use for the lights in the clock so that each of the receptacles is powered by a different leg of the mains, then put in two lights, one plugged into each of the receptacles. (check local building codes)

    Quote Originally Posted by Robert Gift View Post
    Interesting about pure DC for machine tools! I suspect our "strobing" LED strings have only LEDs with no other circuitry.
    Scanning eyesight across them yields - - - - - - - - - - - indicating OFF for half each cycle = 60 illuminations/second.
    That is why I want to build a full-wave rectifier with capacitors to fill in the two zero-voltage areas each cycle.

    The Walmart nightlight is not that bad. I suspect its two LEDs are opposite polarity = but its 120 illuminations/second flicker is still noticeable
    in peripheral vision
    .
    You miss 100% of the shots you don't take. - The Great One

  9. #24
    Registered user. kinsler33's Avatar
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    Default Re: Presumably the two LEDs are connected in opposite polarity (By: THTanner)

    One aspect of flicker on led or arc (fluorescent or vapor) lamps is that their minimum voltage can't be maintained over the entire ac half-cycle. Both have
    significant firing and extinguishing voltages, and so even two led's connected in anti-parallel will both be off for a significant portion of the entire ac cycle. More sophisticated circuits have a bridge rectifier plus a filter capacitor to maintain a nice dc, and there are other ways of dealing with flicker.

    M Kinsler
    512 East Mulberry Street; Lancaster, Ohio USA 740-503-1973; kinsler33@gmail.com
    http://www.lancastereaglegazette.com/search/kinsler/

  10. #25
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    Default Walmart night light ONE [O] LED!

    I have been considering making the top outlet 12VDC from a automobile battery so all lights (which I will have to alter) will be on pure DC.
    Will also operate during power outages.
    But have found no way to get cable run to the 2nd floor attic and down to the outlets. Running cables up from the unfinished basement has been easy.

    Even more fun would be to attach a coil under each end table to induce power into a coil in the base of each table lamp to charge batteries in the lamp.
    Then no wires from the lamps!

    Walmart night light circuit:
    Left plug prong - [diode] - [1/4-Watt 10,000 ohm 5% resistor] - LED[o] - switch - right prong.
    How so little flicker if half-cycle OFF period? The LED has 3 leads on each side!
    Is the solid round [o] material a phosphorescent material excited by UV from LEDs beneath?

    Last edited by Robert Gift; 04-21-2017 at 02:13 PM.
    Confucius say: "Man own clock know time. Own two, never sure."

  11. #26
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    Default Re: Walmart night light ONE [O] LED! (By: Robert Gift)

    Sheet-rock is temporary.
    Tinker Dwight

  12. #27
    Registered user. kinsler33's Avatar
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    Default Re: Walmart night light ONE [O] LED! (By: Robert Gift)

    Quote Originally Posted by Robert Gift View Post
    I have been considering making the top outlet 12VDC from a automobile battery so all lights (which I will have to alter) will be on pure DC.
    Will also operate during power outages.
    But have found no way to get cable run to the 2nd floor attic and down to the outlets. Running cables up from the unfinished basement has been easy.

    Even more fun would be to attach a coil under each end table to induce power into a coil in the base of each table lamp to charge batteries in the lamp.
    Then no wires from the lamps!

    Walmart night light circuit:
    Left plug prong - [diode] - [1/4-Watt 10,000 ohm 5% resistor] - LED[o] - switch - right prong.
    How so little flicker if half-cycle OFF period? The LED has 3 leads on each side!
    Is the solid round [o] material a phosphorescent material excited by UV from LEDs beneath?

    That LED package likely contains a good deal of active circuit wizardry integrated right onto the chip. They may have figured out how to pulse the LED such that the flicker is minimized, though I can't think just how they'd do that.

    Yes, white LED's get their light from a dot or ring of fluorescent material that's excited by a high-power ultra-violet LED. The chip material is likely silicon carbide, a particularly sturdy semiconductor that also has the virtue of yielding high-frequency (visible blue to UV) with a minimum of trickery.

    You can certainly wire the house with 12VDC--some motor homes and boats have that arrangement, and so you'd look into those areas to find ideas and equipment. However, you might just want to install a number of stand-alone, continuously-charging emergency lights like they have in restaurants and other public venues. These could be modified/disguised/hacked to supply things like your clock lights.

    M Kinsler
    512 East Mulberry Street; Lancaster, Ohio USA 740-503-1973; kinsler33@gmail.com
    http://www.lancastereaglegazette.com/search/kinsler/

  13. #28
    Forums Administrator harold bain's Avatar
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    Default Re: Walmart night light ONE [O] LED! (By: Tinker Dwight)

    Quote Originally Posted by Tinker Dwight View Post
    Sheet-rock is temporary.
    Tinker Dwight
    But real rocks are permanent
    harold bain, Member ch 33
    "If it won't "tick",
    let me "tock" to it"

  14. #29
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    Default Re: Walmart night light ONE [O] LED! (By: Robert Gift)

    I am not clear on your set up. But why not get some USB powered leds and power them from cheap usb chargers? Everything will be DC, low voltage and safe.

    David
    David S

  15. #30
    Registered user. THTanner's Avatar
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    Default Re: Walmart night light ONE [O] LED! (By: Robert Gift)

    Have you looked at the duplexes that have built in 5 VDC USB chargers? I am not sure how that 5 VDC is setup - it may be pulsed or continuous- but might be worth a look.

    Quote Originally Posted by Robert Gift View Post
    I have been considering making the top outlet 12VDC from a automobile battery so all lights (which I will have to alter) will be on pure DC.
    Will also operate during power outages.
    But have found no way to get cable run to the 2nd floor attic and down to the outlets. Running cables up from the unfinished basement has been easy.

    Even more fun would be to attach a coil under each end table to induce power into a coil in the base of each table lamp to charge batteries in the lamp.
    Then no wires from the lamps!

    Walmart night light circuit:
    Left plug prong - [diode] - [1/4-Watt 10,000 ohm 5% resistor] - LED[o] - switch - right prong.
    How so little flicker if half-cycle OFF period? The LED has 3 leads on each side!
    Is the solid round [o] material a phosphorescent material excited by UV from LEDs beneath?

    You miss 100% of the shots you don't take. - The Great One

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