How many lamps in a 0-10V circuit?

Discussion in 'C-Bus Wired Hardware' started by 2SC, Jul 4, 2008.

  1. 2SC

    2SC

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    I was asked to use a Four Channel Analogue Output Unit for controlling 4 circuits of cold cathode lamps.
    The project has:
    Four Channel Analogue Output Unit 1 piece
    Four Relay unit with power supply 1 piece
    Bus coupler 3 pieces

    1. We used a PAC for the communication with the PC. The system worked fine as far as the PAC was connected. When it was disconnected the system crashed although the PAC was not used for keeping scenarios or anything. Any ideas why?

    2. How can we calculate how many ballasts or lamps can we use in a sole
    circuit? Below are the electrical specifications but I don't know what to check ...

    Output Voltage Range 0 (?0.5) to 10 (?0.5) VDC
    Output Rating - Sourcing 2.5mA (i.e. minimum of 4kΩ)
    Output Rating - Sinking 15mA at Vout = 0V
    8mA at Vout = 10V i.e. I = 15-(0.7*Vout)mA
     
    2SC, Jul 4, 2008
    #1
  2. 2SC

    NickD Moderator

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    You need to know the characteristics of whatever you are controlling with the analog output unit.

    I assume the cold cathode lamps have some kind of controller or electronic ballast? There should be some kind of spec on the input impedance of its 0-10V input.

    Each channel of the analog output unit can source 2.5mA, meaning it can drive a 4kΩ load at 10V (V=I*R). If your ballast has an input impedance higher than this, then it will draw less current, which is fine.

    Does this help?

    Nick
     
    NickD, Jul 7, 2008
    #2
  3. 2SC

    Matthew

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    Hi 2SC
    Re question 1, did you check the basics such as burden enabled on the relay?
    Re Q2, from memory, rough rule of thumb about 8 of 0-10V ballasts per channel, but as Nick indicates there is an appropriate formula to work it out!:rolleyes:
    Matthew
     
    Matthew, Jul 8, 2008
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