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Thread: Dimmed T5 fixture

  1. #1
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    Dimmed T5 fixture

    I tried searching for this but couldn't find it so forgive me if this is a redundant question.
    I recently changed out new (installed a few months ago) dimming 4 lamp 120v 0 - 10 t5 high bays with prismatic lens for LEDs of the same spec in a gymnasium.
    I got to take two of the t5 fixtures and put them in my garage. They seem dim in my garage. I capped the 0 - 10 leads.
    I think that we had the fixtures dimmed before we killed power and DEMOd them.
    Is it possible that they stayed at 65%? I always though the ballast operated at 100% with the control leads caped.
    Is there a way to check this without buying a 50 dollar switch?

  2. #2
    Join Date
    May 2005
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    Richmond, Virginia
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    Try a 9v battery (if DC) or a small transformer (if AC) on the control leads. Sorry I'm not familiar with them to know which.
    Code references based on 2005 NEC
    Larry B. Fine
    Master Electrician
    Electrical Contractor
    Richmond, VA

  3. #3
    Join Date
    Apr 2008
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    Ann Arbor, Michigan
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    180428-2159 EDT

    82angelfan:

    A fluorescent or LED ballast (power supply) with with a 0-10 V DC input control is really an analog type of control of dimming. It won't have any memory of its last dimmer setting.

    I have never worked with one, but my understanding is as follows relative to the control circuit:

    1. Internal to the dimmer is a DC voltage source with current limiting. Possibly a large enough DC voltage, a current limiting resistor, and a 10 V clamp (Zener diode) across the 0-10 V input leads.

    2. A sufficiently low impedance external DC voltage source can override the internal current source.

    3. With no external voltage source a variable resistance across the 0-10 input terminals can adjust the 0-10 V value.


    I expect that a high impedance meter across the control terminals will read about 10 V DC. If you change to a low resistance across the terminals, like 10 ohms, I expect the voltage will drop to less than 1 V. I don't like going to current mode on the meter until I know what actual current I may be looking at. 1000 ohms is 1 mA/V.

    If the unloaded input terminals read 10 V, then you should be at full brightness. Otherwise apply 10 V and see what happens.

    .

  4. #4
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    Quote Originally Posted by gar View Post
    180428-2159 EDT

    82angelfan:

    A fluorescent or LED ballast (power supply) with with a 0-10 V DC input control is really an analog type of control of dimming. It won't have any memory of its last dimmer setting.

    I have never worked with one, but my understanding is as follows relative to the control circuit:

    1. Internal to the dimmer is a DC voltage source with current limiting. Possibly a large enough DC voltage, a current limiting resistor, and a 10 V clamp (Zener diode) across the 0-10 V input leads.

    2. A sufficiently low impedance external DC voltage source can override the internal current source.

    3. With no external voltage source a variable resistance across the 0-10 input terminals can adjust the 0-10 V value.


    I expect that a high impedance meter across the control terminals will read about 10 V DC. If you change to a low resistance across the terminals, like 10 ohms, I expect the voltage will drop to less than 1 V. I don't like going to current mode on the meter until I know what actual current I may be looking at. 1000 ohms is 1 mA/V.

    If the unloaded input terminals read 10 V, then you should be at full brightness. Otherwise apply 10 V and see what happens.

    .
    I'll try reading the voltage on the 0 - 10 leads. I have a lot of resisters so I can probably use two resisters in series to create 9 - 10 volt drop across the leads. It would be a fun experiment in the least.

  5. #5
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    So my suggestion of a 9v battery should set the dimmer to 90%?
    Code references based on 2005 NEC
    Larry B. Fine
    Master Electrician
    Electrical Contractor
    Richmond, VA

  6. #6
    Join Date
    Apr 2008
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    180429-1302 EDT

    LarryFine:

    Correct, or thereabouts 90%.

    Or an adjustable power supply. A 12 V battery with a 1 k pot would work for adjustment over the entire range. Connect a 2 W AB 1 k pot in series with a 180 ohm resistor in series with the pot. One end of the pot goes to battery minus, and the 180 ohm resistor to battery plus.

    Determine which of the two dimmer input wires is negative and connect this to the battery minus. The pot slider goes to the other dimmer input control wire.

    The values above will get you close to a 0 to 10 V range.

    It is my guess that 0 input voltage from an adequately low impedance source produces about 0 light output, and 10 V or nothing (a high impedance) connected to the input leads produces maximum light output.

    .

  7. #7
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    Quote Originally Posted by gar View Post
    180429-1302 EDT

    LarryFine:

    Correct, or thereabouts 90%.

    Or an adjustable power supply. A 12 V battery with a 1 k pot would work for adjustment over the entire range. Connect a 2 W AB 1 k pot in series with a 180 ohm resistor in series with the pot. One end of the pot goes to battery minus, and the 180 ohm resistor to battery plus.

    Determine which of the two dimmer input wires is negative and connect this to the battery minus. The pot slider goes to the other dimmer input control wire.

    The values above will get you close to a 0 to 10 V range.

    It is my guess that 0 input voltage from an adequately low impedance source produces about 0 light output, and 10 V or nothing (a high impedance) connected to the input leads produces maximum light output.

    .
    Larry was right Woop woop woop woop woo! (sorry, Curly for your Larry Fine)
    The fixture has a 2 Phillips advance ballasts, inside lamps and outside lamps. It does not generate the control voltage. My guess is the switch or a control system does it.
    I used an electronic signal generator, the ground connection to the grey and the adjustable + voltage to the purple of the outside ballast.
    At 10 volts the lamps were at full bright, as were the capped ballast lamps (static setting). At 0 volts the lamps dimmed to what I am guessing is about 10%.
    I don't know why they seem dim to me but maybe it is proximity to the fixtures, 8' ceiling vs 30' ceiling or 2 fixtures vs 36 fixtures. or I am having a stroke and don't know it yet.
    Anyway, thanks everyone, I'll just shut up and be happy with my FREE light fixtures.

  8. #8
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    180429-1516 EDT

    82angelfan:

    So the the two outside bulbs are supplied from one ballast, and the two inside from a different ballast. This would imply you have two control wires (a + and a -) for each ballast, and these control wires are not connected together unless you do so.

    What voltage, with a high impedance meter, did you read between the control wires of one ballast?

    What is an electronic signal generator? Usually this implies some form of AC source. I believe you used an adjustable DC power supply.

    What are "
    as were the capped ballast lamps"? I assume this means the 0-10 control wires with no connection. If so, then with no connection to these wires the voltage between them should be around 10 V if the associated pair of bulbs is at or near full brightness.

    .



  9. #9
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    180429-1601 EDT

    I took a look at the Phillips website and found mostly useless information on how the control function for their 10 V dimmer worked. I found 10 V and 0.5 mA, but that alone does not mean much.

    .

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