Subject:
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Re: controlling an opto isolated motor
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Newsgroups:
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lugnet.robotics.handyboard
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Date:
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Mon, 17 Mar 1997 18:06:06 GMT
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Original-From:
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Chuck McManis <cmcmanis@netcom.=avoidspam=com>
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Reply-To:
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cmcmanis@netcomSTOPSPAM.com
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Viewed:
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1581 times
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Phil wrote:
> Hello. Does anyone hve any info. on how to control the direction of
> a motor while having it seperated from the H.B. by an optoisolator?
> (the motors run at 3.0- volts) I figured out how-to, if I use 2
> motor ports per motor.
I've got a MOSFET h-bridge I built that uses an opto isolator and it
talks to the Handyboard, I don't know if it will solve your problem but
I'll tell you what I did with it.
I've designed in a "Handyboard" mode. In this mode you can connect
it to any Martin/Sargent 68HC11 board (Miniboard, Rugwarrior, 6.270,
or Handyboard). It uses only the two pins that normally connect to
the motor to connect to the bridge. It works as follows;
Imagine that the four transistors in the H-bridge were identified
as :
UL UR
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+---- MOTOR ----+
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LL LR
Where UL is 'upper left' and LR is 'lower right', etc.
I have a four channel optoisolator (PS2501-4 from NEC) with each
output transistor controlling one of the four bridge transistors.
If we call these four optoisolators A, B, C, and D. Then I have
A controlling UL, B controlling UR, C controlling LL, and D controlling
LR.
To turn on the bridge in the 'forward' direction I need to apply
current to A, D. To reverse it I apply current to B, C. Since the
opto-isolator uses diodes (LEDs) in its implementation, I've wired
it up like so:
Motor Motor
Pin 1 Pin 2
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| (A) (RP-a) |
+------+---|>|---\/\/\/----+-----+
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| (D) (RP-b) |
+---|>|---\/\/\/----+
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| (RP-c)b (B) |
+--\/\/\/---|<|-----+
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| (RP-d) (C) |
+--\/\/\/---|<|-----+
(Forgive the ascii graphics, you'll need a fixed width font to view
this correctly)
The way this works, when the motor is going 'forward' then Pin 1 is
positive with respect to Pin 2. (this would normally be attached to
the motor and drive it forward) In this circuit the LEDs in A, D
illuminate (the optoisolator drives two transistors) because those
diodes are foward biased. The other two inputs (B, C) do not illumniate
because the LEDs inside of them are reverse biased in this situation.
When the motor is 'reversed', the opposite is true, B and C are on
when A and D are off.
The value of the resistors is selected to insure about 10mA flow
through the LEDs, so for a handyboard with its 9.6v NiCd battery
a resistor pack with 680 - 1K resistors would be fine. For a miniboard
with four C cells, a 470 - 680 ohm pack would be best.
> Also, has anyone ever used muscle wires with the H.B.? Results? Just
> wondering! ;-}
I've not used muscle wire (Nitonal) with the HB but it sounds
interesting. The motor ports should be able to support it.
--Chuck
--
cmcmanis@netcom.com http://www.professionals.com/~cmcmanis
All opinions in the non-included text above are the sole opinions of
the author.
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Message is in Reply To:
 | | (no subject)
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| Hello, All! Long time listener, first time caller. Hello. Does anyone hve any info. on how to control the direction of a motor while having it seperated from the H.B. by an optoisolator? (the motors run at 3.0- volts) I figured out how-to, if I use (...) (28 years ago, 15-Mar-97, to lugnet.robotics.handyboard)
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