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Electronic Theatre Controls Inc

ELV Modules and Test Mode in Sensor CEM, CEM3, DRd

This information is accurate as of 7/29/11.

Going back to the first release of Sensor/Unison ELV modules, there has been a lot of discussion about their function with a rack in test mode.  After some investigation, here are the facts as we currently know them:


The ELV module circuit must be powered (with the breaker on) before getting a control signal in order for the module to output.


The processor in the ELV module needs to see a zero on the pwm line before it is ready to output. With CEM+/3, test mode supplies a constant +5V signal starting before the module boots so the ELV never starts outputting.


In a Sensor+/3 rack in test mode, it is possible for a working ELV module to have signal LEDs illuminated with no fault indication and still not output.

  • Breaker trip/reset on a previously working circuit in test mode
    • Rack running in test mode
      • ELV module signal LEDs on and output circuit on.
    • Turn module breaker off
      • Signal LEDs stay on, output circuit off.
    • Turn module breaker back on
      • Signal LEDs stay on, output circuit stays off.
Note-Icon.png Note: This will only occur in test mode. In normal or set levels operation, the pwm signal will be turned off for zero cross blanking time during every half-cycle and the ELV will output after its breaker is reset.
  • Rack power applied with test mode active (a.k.a. How an EC may turn on lights during installation)
    • Power on rack with CEM+/3 installed in test mode
      • ELV signal LEDs on, output circuit off.
    • Loosen the CEM+/3 from the backplane and reseat.
      • ELV signal LEDS on, output circuit on.
Caution-Icon.png Caution: Do not remove the CEM+/3 from the rack. To maintain arc flash protection, keep the module within the rack -- only unseat/reseat it from/into the backplane.


DRd uses zero cross blanking time even in test mode. Consequently, an ELV should turn on even after a breaker trip/reset. However, there is a software bug that may inhibit test mode function in some versions of DRd code.

  • In DRd dimming engine versions 1.0.2 and below and 1.2.0 and above, a slot configured for an ELV module will turn on in test mode.
    • Affected
      • PACP 2.0.1+; 1.0.0-1.1.2 (but not 1.1.2b)
      • SACP 1.2.0+; 1.0.0-1.0.1
  • In DRd dimming engine versions after 1.0.2
    • A slot configured for an ELV will not turn on in test mode.
    • An ELV module in a slot inaccurately configured as a standard (Dxx) dimmer module will turn on in test mode.
    • Affected
      • PACP 1.1.2b-1.2.2
      • SACP 1.1.0-1.1.4

    In Brief: The ELV will fire with CEM+/CEM3 test mode IF these steps are followed:

    1. Insert the dimmer into the rack and turn on the dimmer circuit breakers.
    2. Put the CEM+/3 into test mode.
    3. Insert the CEM+/3 in the rack and/or energize the rack.

    Basically, if you provide power to the ELV10 before the CEM+/3, the ELV10 will not fire.

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