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Propeller Robot Control Board — Parallax Forums

Propeller Robot Control Board

RambomanRamboman Posts: 101
edited 2010-07-11 16:48 in Propeller 1
Hello,
I am building a r/c hexapod with 18 leg servos, 1 head servo, 1 ping input and 4 rx input.
I tested the rx program with my education kit, it works nice with my spektrum DX5e radio.
When I load the program on the robot control board, it does not work anymore...
Does anybody have a suggestion about the cause ?
Thanks

Comments

  • hover1hover1 Posts: 1,929
    edited 2010-07-11 13:29
    You need to be a little more descriptive on you problem. Your post reads like "My car won't run, how do I fix it"

    What kind of problems? Power, servo, receiver?

    Jim
    Ramboman said...
    Hello,
    I am building a r/c hexapod with 18 leg servos, 1 head servo, 1 ping input and 4 rx input.

    I tested the rx program with my education kit, it works nice with my spektrum DX5e radio.

    When I load the program on the robot control board, it does not work anymore...

    Does anybody have a suggestion about the cause ?

    Thanks
  • RambomanRamboman Posts: 101
    edited 2010-07-11 13:59
    Sorry...
    The RX actvates the servo that are dirctly connected...
    but the robot control board does not recognize the pulses coming from the RX...
    When connected directly to the pins (true a resistance) of the propeller (education kit) it works...
    I guess this may be a question of voltage level of the pulses...
    The propeller recognize "on" above 1.65V and "low" below...
    I have no indication about the treshold level of I/O translators...
  • RambomanRamboman Posts: 101
    edited 2010-07-11 13:59
    Sorry...
    The RX actvates the servo that are dirctly connected...
    but the robot control board does not recognize the pulses coming from the RX...
    When connected directly to the pins (true a resistance) of the propeller (education kit) it works...
    I guess this may be a question of voltage level of the pulses...
    The propeller recognize "on" above 1.65V and "low" below...
    I have no indication about the treshold level of I/O translators...
  • RambomanRamboman Posts: 101
    edited 2010-07-11 14:41
    After further investigation, I discovered the following:
    - the i/o translator, at 5V input, recognize "on" over 3.25V and "off" below 1.75V...
    - the pulses of the RX are between 2.7V and 3.0V...
    So, the propeller recognize the pulses (at 1.65V) when the RX is directly connected, but NOT thru the i/o translator ;-(
    A solution would be to bypass the i/o translator, but then I would loose a bank of 8 servos; that's not appropiate for my project (I need 18+1)...
    Conclusion: the Robot Control Board is not appropriate for my hexapod robot... I go back to my basic education kit ;-(
  • hover1hover1 Posts: 1,929
    edited 2010-07-11 14:56
    The data sheet I read: http://focus.ti.com.cn/cn/lit/ds/symlink/txb0108.pdf , if I'm reading it correctly, says 1.65V threshold.

    You will not loose the servos by disabling the translator. You would just run your servo signal line from the pads before the translator, with the inline resistor you were using on the Education kit, ( if you were using a resistor.) I know it's a little more wiring, but it can be done.

    Jim
    Ramboman said...
    After further investigation, I discovered the following:
    - the i/o translator, at 5V input, recognize "on" over 3.25V and "off" below 1.75V...
    - the pulses of the RX are between 2.7V and 3.0V...
    So, the propeller recognize the pulses (at 1.65V) when the RX is directly connected, but NOT thru the i/o translator ;-(
    A solution would be to bypass the i/o translator, but then I would loose a bank of 8 servos; that's not appropiate for my project (I need 18+1)...
    Conclusion: the Robot Control Board is not appropriate for my hexapod robot... I go back to my basic education kit ;-(
  • RambomanRamboman Posts: 101
    edited 2010-07-11 15:21
    Hi Jim
    I read 65% of 5V...
    Back to my education kit and resistors... that works!
    txb1080.JPG
    1196 x 462 - 122K
  • hover1hover1 Posts: 1,929
    edited 2010-07-11 15:33
    Gotcha, I read too quickly.

    Jim
    Ramboman said...
    Hi Jim

    I read 65% of 5V...

    Back to my education kit and resistors... that works!
  • RambomanRamboman Posts: 101
    edited 2010-07-11 16:31
    Hi Jim,
    look at this...
    Keep It Simple and Stupid ;-)
    using the USB propeller, a piece of veroboard and some resistors...
    Thanks
    prop.jpg
    640 x 480 - 169K
    prop.jpg 169.3K
  • hover1hover1 Posts: 1,929
    edited 2010-07-11 16:38
    Very Nice! MSR1 Rev B. Didn't know you had a PropStick. Perfect!

    Ramboman said...
    Hi Jim,
    look at this...

    Keep It Simple and Stupid wink.gif

    using the USB propeller, a piece of veroboard and some resistors...

    Thanks
  • RambomanRamboman Posts: 101
    edited 2010-07-11 16:48
    from the education kit wink.gif
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