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multiple RC servos, & DC motor speed control — Parallax Forums

multiple RC servos, & DC motor speed control

ArchiverArchiver Posts: 46,084
edited 2000-07-21 01:09 in General Discussion
I am doing a uav project along the same lines

I first measure the pulse width for that particular channel - calculate and
scale position as as a number 0 to 255 - and then send to a serial servo
controller chip - I am using Scott Edward's ssc

I am only using 5 channels but there is room for 8

richard


Original Message
From: "Nic Nicholson" <nicnicholson@p...>
To: "Basic Stamps" <basicstamps@egroups.com>
Sent: Thursday, July 20, 2000 5:54 PM
Subject: [noparse][[/noparse]basicstamps] multiple RC servos, & DC motor speed control


> I know this subject must have come up many times, but I haven't been able
to
> find a satisfactory solution in any of the archives...
>
> I would like to be able to put the BS2 in between an RC receiver and the
> servos it controls, probably three of them, and also control a DC motor at
> the same time. It's the output part of this that's causing me problems.
>
> My intended solution is to make a circuit which takes 0-5V analog in (from
> the PWM of BS2) and will continue to put out a corresponding RC pulse
until
> the the BS2 next updates the analog voltage--sort of a "fire and forget"
> approach. A possible solution that occurred to me was to use a 20mS
astable
> in conjunction with a votage controlled monostable, but I'm not familiar
> enough with what's out there to know which chips to use...I guess the hard
> part of this for me is the voltage-controlled monostable: 0 to 5V in, 1mS
> to 2 mS output. Anyone know how to implement this? I've not decided on
> multivibrators, I'd just like to be able to control a servo with the PWM
> analog output of the BS2.
>
> The second part of this is to control a DC motor using the same analog-out
> technique. I've been looking at the MC33030 chip. Has anyone tried using
a
> motor tach as the feedback on this chip? Does anyone know any reasons why
> this chip can't be controlled with a 0 to 5V input? (I would, of course,
> scale this up to 0 to Vcc with a transistor to the reference input)
>
> Also, I have a couple of LM18200T's on the shelf, so if anyone knows how
to
> go from BS2 analog-out to PWM. I'd love to know the name of a good chip
> here too.
>
>
> The main type of information I'm looking for here is suggestions of chips
to
> look at...anyone?
>
> Thanks,
>
> Nic
>
>
>
>
>
>

Comments

  • ArchiverArchiver Posts: 46,084
    edited 2000-07-20 23:54
    I know this subject must have come up many times, but I haven't been able to
    find a satisfactory solution in any of the archives...

    I would like to be able to put the BS2 in between an RC receiver and the
    servos it controls, probably three of them, and also control a DC motor at
    the same time. It's the output part of this that's causing me problems.

    My intended solution is to make a circuit which takes 0-5V analog in (from
    the PWM of BS2) and will continue to put out a corresponding RC pulse until
    the the BS2 next updates the analog voltage--sort of a "fire and forget"
    approach. A possible solution that occurred to me was to use a 20mS astable
    in conjunction with a votage controlled monostable, but I'm not familiar
    enough with what's out there to know which chips to use...I guess the hard
    part of this for me is the voltage-controlled monostable: 0 to 5V in, 1mS
    to 2 mS output. Anyone know how to implement this? I've not decided on
    multivibrators, I'd just like to be able to control a servo with the PWM
    analog output of the BS2.

    The second part of this is to control a DC motor using the same analog-out
    technique. I've been looking at the MC33030 chip. Has anyone tried using a
    motor tach as the feedback on this chip? Does anyone know any reasons why
    this chip can't be controlled with a 0 to 5V input? (I would, of course,
    scale this up to 0 to Vcc with a transistor to the reference input)

    Also, I have a couple of LM18200T's on the shelf, so if anyone knows how to
    go from BS2 analog-out to PWM. I'd love to know the name of a good chip
    here too.


    The main type of information I'm looking for here is suggestions of chips to
    look at...anyone?

    Thanks,

    Nic
  • ArchiverArchiver Posts: 46,084
    edited 2000-07-21 00:53
    Nic,

    Check out my page at http://members.tripod.com/~divelec/r3rcjs01.html
    This setup has worked well for me for a couple of years. There is a schematic
    and a downloadable
    program. You may be able to use it with minor modifications for your project.

    Carl


    Original Message
    From: Nic Nicholson <nicnicholson@p...>
    To: Basic Stamps <basicstamps@egroups.com>
    Sent: Thursday, July 20, 2000 6:54 PM
    Subject: [noparse][[/noparse]basicstamps] multiple RC servos, & DC motor speed control


    > I know this subject must have come up many times, but I haven't been able to
    > find a satisfactory solution in any of the archives...
    >
    > I would like to be able to put the BS2 in between an RC receiver and the
    > servos it controls, probably three of them, and also control a DC motor at
    > the same time. It's the output part of this that's causing me problems.
    >
    > My intended solution is to make a circuit which takes 0-5V analog in (from
    > the PWM of BS2) and will continue to put out a corresponding RC pulse until
    > the the BS2 next updates the analog voltage--sort of a "fire and forget"
    > approach. A possible solution that occurred to me was to use a 20mS astable
    > in conjunction with a votage controlled monostable, but I'm not familiar
    > enough with what's out there to know which chips to use...I guess the hard
    > part of this for me is the voltage-controlled monostable: 0 to 5V in, 1mS
    > to 2 mS output. Anyone know how to implement this? I've not decided on
    > multivibrators, I'd just like to be able to control a servo with the PWM
    > analog output of the BS2.
    >
    > The second part of this is to control a DC motor using the same analog-out
    > technique. I've been looking at the MC33030 chip. Has anyone tried using a
    > motor tach as the feedback on this chip? Does anyone know any reasons why
    > this chip can't be controlled with a 0 to 5V input? (I would, of course,
    > scale this up to 0 to Vcc with a transistor to the reference input)
    >
    > Also, I have a couple of LM18200T's on the shelf, so if anyone knows how to
    > go from BS2 analog-out to PWM. I'd love to know the name of a good chip
    > here too.
    >
    >
    > The main type of information I'm looking for here is suggestions of chips to
    > look at...anyone?
    >
    > Thanks,
    >
    > Nic
    >
    >
    >
    >
  • ArchiverArchiver Posts: 46,084
    edited 2000-07-21 01:09
    > My intended solution is to make a circuit which takes 0-5V analog in (from
    > the PWM of BS2) and will continue to put out a corresponding RC
    > pulse until
    You can use a PAK-VIII and bypass the PWM altogether. Just send the PAK the
    "on" time and the "off" time and it will keep going. 8 channels in all.



    Regards,

    Al Williams
    AWC
    *Microcontroller Projects with Basic Stamps at
    http://www.al-williams.com/awce/sbook.htm
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