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Thread: Over-the-Stove Microwave Range Hood Light

  1. #1
    Unenlightened
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    Default Over-the-Stove Microwave Range Hood Light

    I’m new to the forum—and VERY new to LED circuits. I am, however, a well-seasoned computer support technician. That means I’m technical enough to understand the old saying: “You can never give an engineer too much information”—which is why this post is rather lengthy. I’ m also experienced enough to be quite leery of unexpected but spectacular olfactory, aural, or visual displays or special effects from overloaded circuits or over-driving electronic components. Some of that knowledge was deservedly, though ignorantly earned from shall we say, “hands-on” tutoring. (Isn’t it odd how the smell can linger for days in an office setting?) Humor aside, I probably have a good, layman’s knowledge of circuitry and simple schematics—though I’ll never claim to be an electrical engineer or an electrician. This is why I’m asking for help today. Please feel free to critique or ask questions.

    I’m installing LEDs in my new, over-the-stove microwave’s “range hood light” light cavity. I’m trying to save the four or more bulbs per year at $4.00 a pop plus the electricity for 5-6 hours nightlight-like usage—never mind the full-power cooking time. I’m considering two fairly simple circuits:

    Option 1


    1. Power supply (120 or 240VAC in/12 or 24VDC out)
    2. Switch (rocker or rotary) 12/24VDC, using the proper amperage [leaning towards rotary]


    1. off, low, high or
    2. off, low, medium, high


    1. Two or three high power but lower-lumen LEDs (100-300 lumens, warm white)
    2. One, high-power, higher lumen LED (700-750 lumen, daylight white
    3. Miscellaneous heat/water resistant wires and connection insulators.
    4. Resistors soldered to each LED.

    With the switch at the low setting, both lower lumen LEDs would be powered. At the medium setting, if used, the high lumen LED alone would be powered. The high setting would drive all LEDs. (The mix of warm white and daylight seems more subjectively natural to my eyes.)

    Option 2


    1. Power supply (120 or 240VAC in/12 or 24VDC out)
    2. Toggle switch (off, on)
    3. Dimmer
    4. Two or three high-lumen LEDs
    5. Miscellaneous heat/water resistant wires and connection insulators.
    6. Resistors soldered to each LED.


    Option 1 is preferred. My wife will be using the installation and is very unimpressed with anything she considers needless complex or technical. (“Really, a dimmer, dear! Why would I use a dimmer? Keep it simple”) J

    I've drawn a very rough schematic but can't seem to insert it into the post.



    It’s probably a very good thing to avoid any whiff of an ancient, pagan-style burnt offering so I think I must applying resistance to each LED by stepping down the power supply’s output voltage to match what the LED expects. What I don’t understand is which value in the LED specs is used in an online resistance calculator. Just in case I leave out something crucial from the specs below, I’ll post the URLs to the items.

    Low Lumen LED

    Continuous Forward Current 750 Forward Voltage 3.6V
    LED Brand Vollong LED Package 14.5 mm x 7.5 mm
    Lumen 200 Lumen Maximum Forward Voltage 4V
    Maximum LED Junction Temperature 120 Operating Temperature -35~+50 °C
    Peak Forward Current 1000mA Power Dissapation 3W
    Reverse Current 10µA Reverse Voltage 5V
    Storage Temperature -40~+100 °C Total Power Consumption 3 Watt
    Viewing Angle 120 degree



    High Lumen LED

    Color Cool White Color Temperature 5500 K
    Continuous Forward Current 500 Forward Voltage 15.5V
    LED Brand Vollong LED Package COB
    Lumen 750 Lumen Maximum Forward Voltage 24V
    Maximum LED Junction Temperature 105 Millicandela 131000mcd
    Operating Temperature -20~+80 °C Peak Forward Current 600mA
    Power Dissapation 10W Reverse Current 100mA
    Reverse Voltage 5V Storage Temperature -30~+100 °C
    Total Power Consumption 10 Watts Viewing Angle 170 degree

    URLs
    Low lumen
    http://www.superbrightleds.com/morei...ower-leds/898/

    High lumen
    http://www.superbrightleds.com/morei...-led/979/2386/

    Thank you in advance. I may be asking about the switch wiring in a future post if I can’t figure it out.

  2. #2
    Flashaholic wws944's Avatar
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    Default Re: Over-the-Stove Microwave Range Hood Light

    What size incandescent bulbs does the hood normally take? A15? An off-the-shelf LED replacement would be a lot easier than rolling your own. However either way, I would worry about heat from the cooktop affecting the lifespan of the LEDs and/or their driver circuitry.
    "Your light emits unnecessary heat" - Zar

  3. #3
    Flashaholic Marcturus's Avatar
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    Default Re: Over-the-Stove Microwave Range Hood Light


    Imitation and study first, mastery later.

    And I noticed you're intending to operate 60-CRI light in spousal territory?
    Anyone else tried that recently? Still married?

  4. #4

    Default Re: Over-the-Stove Microwave Range Hood Light

    I second this, LOL. My range has a single A19 bulb in it. First tried a Philips alien-head LED bulb, but it didn't last long enclosed. I've now had a Cree 60W equivalent in there and it's been on daily as part of the kitchen lighting scheme since the Cree bulbs became available. Works fine with the two position hi-Lo switch in the vent hood.

    Good luck, though!

  5. #5
    Flashaholic* LEDninja's Avatar
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    Default Re: Over-the-Stove Microwave Range Hood Light

    Quote Originally Posted by wws944 View Post
    I would worry about heat from the cooktop affecting the lifespan of the LEDs and/or their driver circuitry.
    LEDs (commercially available bulb) normally run at 85°C.
    Capacitors in the power supply need to be around 60°C for long life similar to an LED. At 85°C they can be dead in as few as 5000 hours.
    A DIY allows the power supply to be in a cooler area. I am leery of DIY where part of the circuit is at grid voltage though.
    -
    Do not forget the heat sinks!!!
    Picture of the low power LED shows it on a star. Makes it easy to bolt on a bigger sheet of metal. Stars were designed to handle a 1 watt Luxeon a decade ago. You are running 5 watts.
    Pictures of the high power LED just show the LED. I do not think the heat sink as shown in the last picture is included. You may have to buy that separately. Plus thermal paste/thermal epoxy.

    Quote Originally Posted by bbaskin View Post
    My range has a single A19 bulb in it. First tried a Philips alien-head LED bulb, but it didn't last long enclosed. I've now had a Cree 60W equivalent in there and it's been on daily as part of the kitchen lighting scheme since the Cree bulbs became available. Works fine with the two position hi-Lo switch in the vent hood.
    !
    Xledia went to great lengths to keep the LED generated heat away from the electronics. Claim to be for enclosed fixtures. Available from Earthled or Amazon.

    Quote Originally Posted by PNman View Post
    the electricity for 5-6 hours nightlight-like usage.
    Why not buy a dedicated night light for that?
    Stay away from the dollar stores - Their LED nite lites dim to useless in a month.
    Buy a night light with an on-off switch and candelabra base. HD sells a 2 pack of Philips 0.6W LED night light bulbs. Warm white. Good enough for not bumping into furniture.
    As you are already on superbrightleds they also have a 2 watt 21 LED bulb that fits night lights.
    Fits short wide night light.

    Fits tall narrow night light.

    Comparison with a regular LED night light. The bulb in the hall is a 2 watt from Eliteled. I used to use that as my apartment night light.
    Last edited by LEDninja; 10-21-2013 at 02:21 AM.

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