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EB500 connection status question — Parallax Forums

EB500 connection status question

LLordLLord Posts: 9
edited 2005-03-08 01:03 in Robotics
Hi all

I need to know what is the best way to check the connection status of pin 8 of the eb500.

the users manual ·states that it is a ttl output how ever all 12 of my·eb500's ·put out a 2.75v signal for high· and the pic i am using is not seeing that as high.

Lee

Comments

  • LLordLLord Posts: 9
    edited 2005-03-04 19:20
    how about this

    is there a chip that converts 3.3v logic to 5v ttl and back.

    i need 5 lines
  • Paul BakerPaul Baker Posts: 6,351
    edited 2005-03-04 22:08
    the CD40109B is a 4 channel level shifter, they're $.80 apeice @ digikey, youd need 4, 2 for each way, if the lines are bidirectional you can theoretically cascade them using the enable to achieve bidirectionality. They were designed for 5,10,15V shifting but the spec says that 3V is the minimum, so you may still be able to use it. One final note, it is CMOS levels.

    A quick search of interfacebus.com shows the following recomended interface: http://www.interfacebus.com/Design_Translation.html#i
    its an octal transceiver for $.90 @ digikey in 24 soic and 24 ssop packages, goto www.sparkfun.com breakout board section to get an SOIC or SSOP to DIP adapter board for under $3 if you need dip format to prototype it, just get the 28 pin version and leave the other 4 pins unused

    Post Edited (Paul Baker) : 3/4/2005 10:13:58 PM GMT
  • Paul BakerPaul Baker Posts: 6,351
    edited 2005-03-04 23:14
    look at http://www.interfacebus.com/voltage_threshold.html·the 2.75V should still be picked up as voltage level high.

    I am concerned that you may be suffering from voltage sag, your not trying to operate 12 eb500s off the stamp regulator are you? They will absolutely require thier own power. Thier total power requirement is 420mA. Since you posted in the robotics forum, are you running them off a battery? If so, check the voltage before the regulator (straight across the batteries) If this value is much lower than the batteries rated voltage, your drawing too much current from them.
  • RickBRickB Posts: 395
    edited 2005-03-05 19:15
    The eb500 docs state that it is appmod compatible, i.e. works with the stamp. Sounds like you may have another problem unrelated to logic levels.

    Rick
  • LLordLLord Posts: 9
    edited 2005-03-08 01:03
    answers to Paul's questions.

    the battery source is 48v 50A using a dc to dc converter for each pic , offering it 9 v at 1000 ma power source

    thank you for the reply.
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