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How too Drive j111 from a PCF8574 — Parallax Forums

How too Drive j111 from a PCF8574

Rick_HRick_H Posts: 116
edited 2011-11-01 23:01 in General Discussion
I am doing a lot of audio Switching with J111's and would like to control them with my prop chip. I plan on using the I2C IO expander chip PCF8574. is there an array I could use to drive -15V to turn off the J111's from the PCF8574? or what would be the most economical/smallest package I could use for this? I am currently driving 24 j111's with push buttons but I would like to add lots more.

Comments

  • BitsBits Posts: 414
    edited 2011-11-01 16:43
    May I ask what a J111 is? The PCF8574 seems like a great value and without a lot of extra passive components, makes it that much more desirable to me. I will see about purchasing one of these.
  • LeonLeon Posts: 7,620
    edited 2011-11-01 16:46
    It's a JFET.
  • Ron CzapalaRon Czapala Posts: 2,418
    edited 2011-11-01 17:48
    Bits wrote: »
    May I ask what a J111 is? The PCF8574 seems like a great value and without a lot of extra passive components, makes it that much more desirable to me. I will see about purchasing one of these.

    Bits, if you are looking for an I/O expander, you might want to look at a MCP23017...

    - Ron
  • Rick_HRick_H Posts: 116
    edited 2011-11-01 23:01
    A j111, j112 and j113 are JFET depletion mode switches, their commonly used for bipolar analog switching like audio signals. Specifically they need a negative voltage to turn them completely off. All my old projects contain min 10 j111's in them and I thought it would be cool to automate some of them with my extra prop I have on my bench. The MCP23017 is twice as much I/O for 20 cents less, its hands down a better deal but I have like 20 PCF8574 just taking up space at the moment and they work just fine. Basically I need something cheap and condensed that can take the 3.2V output from the PCF8574 to send -15V to the J111. Possibly an opto-coupler in as big an array as possible
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