[Robotgroup] MOTORtHrEAD

Fri May 2 16:48:17 PDT 2008

Ok Robert,
  I'm not an engineer but I know a couple of these and since I have the maturity of a 9 year old here goes:

PWM I know is PULSE WIDTH MODULATION ,meaning, in the R/C world, a transmitter sends out a pulse stream around 60hz with the servo information being the width of the pulses, the servo measures these widths and positions the servo to match. There is some multiplexing involved for muti channels at some point in the transmit/receive of the radio part but the basic PWM is what the servo is looking at.

Transient current (joke answer) The stream that comes from under the cardboard box where several people would passout drunk in the alley behind the cafe on 6th street where I used to work. 
  But really guys ...I have heard people talk about kickback or flyback, and I'm thinking kickback is what I have experienced when useing PWM as a speed control for DC motors which will work but in some cases the frequency of the pulses match the frequency of the pulse that you get when the motors fields colapse and send a reverse charge back down the same wires like an echo. We had that problem with my first TaiChi arms, although some disspute that, the motors would run all day on my variable voltage power supply but on the PWM version they would burn out in minutes.

OverClock...I'll get back with you on joke for that one.

Locked motor amps... I'm guessing it would be the current draw from a motor that is not turning. My tablesaw will run all day long under light load but when the blade binds up I have about 3 seconds to free it up or its off to the breaker box to reset.

-----Original Message-----
>From: Robert Carter <rcarter at ischool.utexas.edu>
>Sent: May 2, 2008 7:02 PM
>To: The Robot Group Mailing List <robotgroup at puremagic.com>
>Subject: Re: [Robotgroup] MOTORtHrEAD
>
>Hey y'all--
>
>I feel kinda proud of myself that I was able to follow most of the  
>thread on RC motor controllers without being completely lost. While  
>reading, I started keeping a list of terms/phrases I didn't  
>understand. Here's the list; if anyone would like to fill in some of  
>the blanks for me, that'd be great.
>
>·      PWM (example: "… but you can drive 5A with PWM 80% duty cycle…")
>·      Transient currents
>·      Overclock ("…you can run it at 6V and run it faster and  
>overclock it as well.")
>·      Locked rotor amp ("…you pretty much need to have a motor  
>controller rated for the locked motor amps of the motor you are going  
>to use." )
>
>That last one, I think I understand what it means from the context,  
>but when I tried to put it in my own words I couldn't come up with  
>anything that makes sense, so I'm curious to hear how someone might  
>explain it to an inquisitive 9-year old.
>
>I've got more questions specific to what I'm trying to do with my  
>project, but let's start with these. BTW, has there ever been talk  
>about creating a glossary page on the wiki for stuff like this? Or  
>are there already a lot of good ones out there, that I just don't  
>know about?
>
>Thanks--
>
>Robert
>
>
>On May 2, 2008, at 2:04 PM, brooksdesign wrote:
>
>>
>>  Allthough I think there are programs out there that I've heard of  
>> you just made public one of the parts of a new video game I've be  
>> contemplating. And in saying that and letting that cat out of the  
>> bag, any of you game programmer guys want to come out and talk  
>> about how to turn my scripts, cad files and ideas into something  
>> real that I won't leave sitting on the shelf because I can't get  
>> around to learning to write code? This project is waay more than a  
>> game.
>> -brooks
>> -----Original Message-----
>>> From: Robert Carter <rcarter at ischool.utexas.edu>
>>> Sent: May 2, 2008 2:24 PM
>>> To: The Robot Group Mailing List <robotgroup at puremagic.com>
>>> Subject: [Robotgroup] MOTORtHrEAD
>>>
>>> <clip>
>>> The nice thing about electronics is that physics is the final  
>>> judge of
>>> your choices.
>>>
>>> You can get people to "vote" for various approaches, but even if  
>>> all of
>>> us voted for item "A" (placing a fuse in parallel with the motor
>>> controller) that wouldn't make one whit of difference to the circuit.
>>> </clip>
>>>
>>> Hell yeah, that's my way of learning: forge ahead with crazy ideas,
>>> and learn from the consequences. If nothing else, you'll get some
>>> good stories. Like when my brother and his best friends discovered
>>> the formula for gunpowder and started a fireworks shop in the attic
>>> over our garage. But, when it comes to electronics, I have to admit,
>>> it gets expensive and time-consuming to have to keep running back to
>>> the store or to the internet for replacement parts when something
>>> explodes/melts/starts to smoke.
>>>
>>> I keep hoping that someone will invent an interactive website for
>>> designing circuits, aimed for grade school students and/or middle-
>>> aged project addicts with more enthusiasm than sense (like yours
>>> truly). You could drag and drop motors of various amperage, LEDs,
>>> transistors, capacitors, etc. onto a virtual breadboard to create a
>>> circuit. If it works, you get the results in animation form: the
>>> motor spins, the lights blink, etc. Or conversely, if you design it
>>> badly, you can show the sparks and smoke as your components burn to a
>>> crisp. Fun, inexpensive, and no one gets hurt.
>>>
>>> Usually when I think of something and it seems like a really good
>>> idea, something like it already exists. Does anyone know?
>>>
>>>
>>>
>>> Robert Carter
>>> Visual Resources Collection
>>> School of Architecture
>>> The University of Texas at Austin
>>> rcarter at ischool.utexas.edu
>>>
>>>
>>>
>>> _______________________________________________
>>> Robotgroup mailing list
>>> Robotgroup at puremagic.com
>>> http://lists.puremagic.com/cgi-bin/mailman/listinfo/robotgroup
>>
>>
>> ________________________________________
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>
>Robert Carter
>Visual Resources Collection
>School of Architecture
>The University of Texas at Austin
>rcarter at ischool.utexas.edu
>
>
>
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