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2 For One I/O — Parallax Forums

2 For One I/O

EverQuriousEverQurious Posts: 48
edited 2009-10-23 05:47 in Robotics
Am I'm currently working with my young grandson on a Bot which at first was a multisensor bot that did a fine job of roaming the house avoiding collisions with inanimate objects and moving objects. My grandson wanted to add an arm ( I had an OWI OO7 arm trainer which I quickly modified for our use) so we bolted it on and all was well and he was delighted with out FRANKENBOT.
Now to my problem. Since the drive motors tie up 4 I/O lines the arm 8 lines and 3 are used for PING sensors. This leaves only one line open and we had to sacrifice some sensors to control the arm. I am thinking I might be able to use this open line to connect the I/O lines to the arm controller when the BOT is stationary and the switch them to the sensors when the robot is mobile.
I could do it with a relay board but I'm sure there is probably a chip out there that would do the job. Can anyone tell me where to find a solution for this. Any help would be a Godsend.

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EverQurious

Try not to fret and worry bout the things that you have not...
Just remember to be thankful for the things you've got !!!

Comments

  • EverQuriousEverQurious Posts: 48
    edited 2009-10-17 05:33
    Oh !!! forgot to mention am using a standard BS-2 MP.

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    EverQurious

    Try not to fret and worry bout the things that you have not...
    Just remember to be thankful for the things you've got !!!
  • Mike GreenMike Green Posts: 23,101
    edited 2009-10-17 05:58
    How about some details on the various sensors and motors (other than the PINGs). If most of the lines are servo motor control lines, you probably need an external servo controller. It's kind of hard to get the relatively precise pulse timing for servo control when you're using an I/O expander of some sort. Similarly, the PINGs really can't be handled through an I/O expander without losing some accuracy of the timing.

    The Propeller Servo Controller would be a good way to handle this (if you are talking about lots of servos). It can be used with a BS2 and can handle up to 16 servos. The interface to the BS2 is just a pair of serial lines (Tx and Rx).
  • EverQuriousEverQurious Posts: 48
    edited 2009-10-18 21:40
    I originally had PIR sensors, tactile sensors and an accelerometer on the bot. These just added additional object avoidance capabilities. The PINGS are on dedicated lines so they are not a concern. I would simply like to switch the 8 Arm lines depending on if the bot is mobile or not. Some type of solid state 8 pole double throw chip that could be switched with the single free I/O line is what I was hoping for. If you know of something like this or have a different route to go I could use any help you could offer.
    As I said I could do it with SPDT relays but this is a rather awkward way to go. freaked.gif
    Thanks Mike for replying.

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    EverQurious

    Try not to fret and worry bout the things that you have not...
    Just remember to be thankful for the things you've got !!!
  • Mike GreenMike Green Posts: 23,101
    edited 2009-10-18 22:10
    The CD4066B is a quad bilateral switch. They're SPST switches, so you'd need an inverter to switch one bank. You'd effectively get a DPDT switch out of each device. The inverter could be used for all four devices (for 8 x 2 lines). For outputs (from the Stamp) you'd need a pulldown or pullup resistor to set the default state since an "off" switch would let the signal line float.

    NXP makes a 4PDT analog switch: www.standardics.nxp.com/products/nx/datasheet/nx5dv330.pdf
    It only comes in a surface mount package.
  • EverQuriousEverQurious Posts: 48
    edited 2009-10-18 23:51
    Thanks again Mike. I will see if I can find a spec sheet on the quad chip.
    I may bug ya again but this will give me something to work on.

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    EverQurious

    Try not to fret and worry bout the things that you have not...
    Just remember to be thankful for the things you've got !!!
  • EverQuriousEverQurious Posts: 48
    edited 2009-10-21 06:47
    I downloaded data sheets on both the CD4066B and NX5DV330 and the later seems like the ticket. Problems is I can find the 4066 plenty of places but I can't find a vendor for the NX5DV330 unless I want to but 2500 at a time. Any suggestions?

    Thanks in advance.

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    EverQurious

    Try not to fret and worry bout the things that you have not...
    Just remember to be thankful for the things you've got !!!
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2009-10-21 07:11
    Also, take a look at the 74HC4051 (or CD4051), '52, and '53.

    -Phil
  • Mike GreenMike Green Posts: 23,101
    edited 2009-10-21 15:37
    See if you can get them as samples from NXP or one of their distributors.
  • EverQuriousEverQurious Posts: 48
    edited 2009-10-23 05:38
    Being no electronics genius I have a question about if using the NX5DV330 I figure I will need 2 to switch 8 lines. After looking over the data sheet as I understand it will switch 4 inputs ( 4 BS2 lines ) from, in my case, from input sensors to output devices by making a single select line ( another BS2 line) . What I don't understand is the ENABLE line. Can it be left tied to ground and still have the switching function work just by switching the S line hi or lo. If E too has to be toggled that will take one BS2 line more than I have and defeats my whole concept. Before I order and sit down to actually design the support circuit I need to know if I can control the switching with only one line. Like I said at the start I'm no electronics so if you could let me know I would be obliged.

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    EverQurious

    Try not to fret and worry bout the things that you have not...
    Just remember to be thankful for the things you've got !!!
  • Mike GreenMike Green Posts: 23,101
    edited 2009-10-23 05:47
    Yes, the not-Enable line can be tied to ground.
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