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Gadget Freak Case #226: Speed Regulator for Rotary Tool
9/20/2012

Andrew Morris' microcontroller-based DC motor speed regulator brings control for delicate work.
Andrew Morris' microcontroller-based DC motor speed regulator brings control for delicate work.

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mrdon
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Re: Speed control for rotary tool
mrdon   9/23/2012 9:07:09 PM
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William K, It would be interesting to see the circuit schematic diagram of your design. Sounds like a possible Gadget Freak article to me!

William K.
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Platinum
Speed control for rotary tool
William K.   9/23/2012 5:51:58 PM
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In 1979 I designed an inexpensive PWM speed controller for use with a 12 volt DC motor. The control kept the torque at maximum because of not having a voltage drop, other than the Vce of the switching transistor. And the design was not patentable, so I was home-free there as well. It use a 556 dual timer chip with one section as an oscillato9r and the other section as a comparator for the ramp waveform and the setpoint voltage. One intermediate transistor buffer stage and it drove a 100 volt 5 amp switching transistor, which I don't recall the number. The BOM cost, except for the control pot, was just under $5. Probably all of the parts are still available, and there is probably a much better output transistor available today. Possibly even a FET of some type.

armorris
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Re: Handy project!
armorris   9/21/2012 3:12:35 PM
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I just visited the PICLIST for the first time in about 2 years. I can't find any sign of somebody asking money for help. I see that it is under new managment from when I last visited it. I don't know where I got that idea. It must have been for some big-name consultants like (but not necessarily) Myke Predko. I guess the big-name consultants probably have to ask a fee to prevent being swamped with questions.  I'm sure that there are plenty of lesser known wizards that are willing to help. I'll be less reluctant to go to the PICLIST for help next time I need it. Maybe I'll even try to help someone else, since I have acquired a fair amount of experience with PICs over the years. I do not consider myself an expert, however.

mrdon
User Rank
Gold
Re: Handy project!
mrdon   9/21/2012 2:01:15 PM
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Hi Nancy, Your quite welcome. I agree, Microchip does have awesome documentation and their forums provide a wealth of technical support and solutions  to some tricky design application problems.

Rob Spiegel
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Blogger
Re: Handy project!
Rob Spiegel   9/21/2012 1:00:21 PM
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That makes sense, Nancy. And chances are, you'll never run into trouble. And if someone wants it -- as has been pointed out in these comments -- that person can make a small change. 

armorris
User Rank
Platinum
Re: Handy project!
armorris   9/21/2012 12:59:16 PM
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Yes, Rob. You're absolutely right, but the patent work I did was almost 10 years ago. Also, far more money is involved in the smartphone business.

Rob Spiegel
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Blogger
Re: Handy project!
Rob Spiegel   9/21/2012 12:50:05 PM
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Andy, the small changes you describe to get around patents doesn't seem to work in the world of smartphones. There is a great number of patent suits in that world. Some of the suits are quite successful at banning companies from selling their products in a number of countries.

Nancy Golden
User Rank
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Re: Handy project!
Nancy Golden   9/21/2012 12:37:22 PM
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For a fee????  Times have changed...but I am willing to bet there are still plenty of folks who love what they are doing and love sharing their knowledge with others. I needed some help with my last project and had four different people offering very intelligent suggestions that helped me resolve the issue I was having - and they never asked for compensation.

armorris
User Rank
Platinum
Re: Handy project!
armorris   9/21/2012 12:27:48 PM
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Thanks, Nancy. I'll take your advice next time I need help. When I needed help, I didn't actually ask for it. I tried to find the answer from comments that were already posted, but the archive is just so huge, and I do not know how to sort through them in any useful way.

I saw plenty of people willing to give advice for a fee.

Nancy Golden
User Rank
Platinum
Re: Handy project!
Nancy Golden   9/21/2012 12:16:28 PM
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Sorry to hear that armorris - that has not been my experience. I am not saying you did this, but what I did find is that there is little patience on the forum for questions that are just thrown out there without evidence of the person trying to solve the problem themselves first. I did notice that when I went into detail as to what I had already tried and where I was stuck with code examples - plenty of folks jumped in with some great suggestions. There are also different areas that help localize where you should post to get the best chance of receiving knowledgeable help. You might want to give it another try - or maybe jump on it to help someone else out ;)

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