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Thread: Data General Nova 1220 Light Question

  1. #1

    Default Data General Nova 1220 Light Question

    So I have a Nova 1220 front panel (circa 1973) and am trying to figure out how to make it live again by connecting it to an Arduino board. However, being a software guy not a hardware guy, I am having a problem figuring out how to drive the lights. It is not clear to me they are actually LEDs, as they look like miniature light bulbs. And I do not think they are 5v DC, as I only get a very dim flicker at 5v off my Arduino. So rather than risk damaging them (there are a couple broken already) I figured I would ask if anyone knew what type of bulb they are and what correct voltage is ?

    I think I have figured out how to wire them up and use the Arduino to control them, as well as use some of the switches to control power on/off and also changes to the sequencing. I am trying to NOT replace them all with new LEDs, as it would look more realistic if I could make them work.
    Thanks

    Jack Morrison
    Small Business System development 1978-82
    Comprehensive Electronic Office support 1991-92

  2. #2

    Default

    They are incandescent lamps. LEDs didn't really exist in 1973 (or if they did, they were red only and very expensive). They didn't come into general use until later.

    Anyway, the lamp voltage is nominally +15VDC. Here's a link to the Nova 1220 Technical Manual: https://archive.org/download/bitsave...Tech_Mar73.pdf.

  3. #3

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    Thank You for the information and link. I think I could use a couple of 15v 8 channel demultiplexers to do what I want, but I noticed in the manual that there was 10ma always on the bulb. That I am not sure how to handle that, as I am not sure how that signal would interact with the demultiplexer. Guess I should have listened better in those Electronics 101 classes. Maybe I'll just buy an demultiplexer IC and play around. Have nothing else better to do.
    Thanks Again,
    Jack

  4. #4
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    The 10mA kept the bulbs warm so the thermal cycling from turning them on and off didn't lead to an early failure.
    Could you short the demux with a high value resistor so that the bulb always sees 10mA, and lots more when the mux turns on?
    Member of the Rhode Island Computer Museum
    http://www.ricomputermuseum.org

  5. #5

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    If the demultiplexers sink current (and can handle the current of a bulb when it's on), then there should be no problem with connecting them across the resistor thaht provides the idle current.

    Attempting ASCII art:

    +15V --- LAMP -+- RESISTOR --- GND

    If you connect a transistor from the point marked + to GND then it will essentially bypass the resistor when it is on, and light the lamp. You may be able to use the output of your device directly, or you may have your device drive a separate transistor.

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