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[DPRG] RE: Re: Motor Control and parts shopping

Subject: [DPRG] RE: Re: Motor Control and parts shopping
From: Jose I Quinones jiq at avayan.com
Date: Fri Aug 28 15:14:44 CDT 2009

You would think it is like a Servo controller, but that is in fact a miss
conception. I am writing a tutorial depicting the differences between RC PWM
and Speed Control PWM.


But basically, RC PWM encodes the position information on  a pulse that is
1.0 ms to 2.0 ms wide with 1.5 ms encoding dead center (if properly


With Speed Control PWM, there is no information encoded. What you are doing
is segmenting the available energy into percentages. Per example, if you
have a 12V battery, a PWM on the ENABLE or the PHASE pin translate into how
much time the motor is ON and how much it is OFF, which is equivalent to a
fraction of the 12V. Hence, a 50% duty cycle PWM with a 12V battery is
analogous to a 6V battery. That is why you can use this to control motor
speed. Because speed is directionally proportional to applied voltage. You
can see this better on a video I released last week. I expect to present
more videos in the upcoming weeks, in case you are interested in motion
control basics.






From: Jose I Quinones [mailto:jiq at avayan.com] 
Sent: Friday, August 28, 2009 1:27 PM
To: 'dprglist at dprg.org'
Subject: Re: Motor Control and parts shopping


Hi guys!


Allow me to recommend something totally different and to my understanding
considerably easier to use, better deal, and better performance. Maybe it is
"less fun" but I believe it can still be an enjoyable experience.


TI has a new device called the DRV8800PWP. It is a 2.8A H Bridge. The cool
thing about is that all you need to supply is ENABLE and PHASE. So you do
not have to worry about all the IN1/IN2 combinations, decay modes and stuff.
Just to add to the coolness, it is protected against output shorts, thermal
overrun and demonic possessions. This thing is practically immortal! The
only thing that it will not survive is voltage inversion or over voltage but
I have hardly heard of an H Bridge that contains those features. I believe
we are supposed to be minded enough to not let something as simple to


That being said, you can PWM either the ENABLE or the PHASE and you get
speed control on both situations. You may be saying "WHAT THE HECK??? PWM
THE PHASE?" If you have never heard of this, it allows you to control both
direction and speed with a single PWM timer. Per example, if PWM duty cycle
(DC%) is less than 50%, then the motor moves Counterclockwise (CCW). The
closer the DC% is to 0%, the faster the motor moves. But if DC% is above 50%
then the motor moves clockwise (CW). In this case, the closer the DC% is to
100%, the faster the motor moves. This is of course only possible when
ENABLE is asserted.


I have a design on my Open Source Design web page around this chip and am
working some new versions. Feel free to take a look and copy whatever you
want. It is as free as free gets. I also have some bare boards to sell in
case you want to build your own. They are sold at whatever cost me, so in
other words as cheap as I can afford.


BTW if you need superbly high currents (which does not seem to be the case
for those considering to use a 600 mA device), then there is another larger
design here:


Thanks and best regards,




Feel free to visit some of my pages at:

http://www.avayan.com <http://www.avayan.com/> 

http://avayanings.blogspot.com <http://avayanings.blogspot.com/> 

http://www.comicups.com <http://www.comicups.com/> 


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