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I need to switch a 0.5V to 0.5 to 5.5V seamlessly

  1. Jun 5, 2010 #1
    I'm working on a circuit to manipulate an existing signal for an automotive hydraulic hybrid product.

    I need to pass on a 0.46 to 0.55V signal to the ECU during accelereration to keep the engine from revving and restore the original signal (0.55 to 5.5V) when the engine takes over.

    This would be easy but I only have one position on my connector left.

    Basically I need to make the ECU think that the truck is idling while accellerating and then take over and function normally.

    Maybe I'm being a bonehead, but it seems this should be possible.

    I won't complicate this more with the other accellerator input.
  2. jcsd
  3. Jun 6, 2010 #2


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    Look up analog switch / analog multiplexer.
  4. Jun 6, 2010 #3
    That is the kind of thing I need. Just trying to get it done by Monday with the parts we have laying around: Op-Amps, FET's, etc. New customers are coming this week so I need to get something working.

    Thanks for the reply.
  5. Jun 7, 2010 #4


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    Science Advisor

    I'd hit the phones and call up the Radioshacks (a few may still carry components), components places, and friends who are electronics hobbyists around you locally. That or bite the bullet and pay for same-day shipping from DigiKey or Mouser.

    I'd also go armed with a part number, for instance, CD4051:
    http://www.fairchildsemi.com/ds/CD%2FCD4051BC.pdf [Broken]

    Good luck!

    EDIT: Note that many analog switches are made from FETs in linear mode:

    However, you may have to fiddle with the circuit so that it works properly...

    Alternately, you might consider an SPDT relay, however, you might end up with a split second of glitching (if that's a significant issue) when the relay is switching from one contact to the other, and no connection exists.
    Last edited by a moderator: May 4, 2017
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