Comments for Random Thinker http://www.randomthinker.org Some thoughts, some string, and some sticky tape! Mon, 09 Jul 2012 12:17:26 +0000 hourly 1 https://wordpress.org/?v=5.0.8 Comment on Linear Bipolar Stepper Controller … early thoughts by Alina http://www.randomthinker.org/?p=75#comment-121 Mon, 09 Jul 2012 12:17:26 +0000 http://www.randomthinker.org/?p=75#comment-121 You can calculate the cut-off fnrcueeqy (fc) of the filter (the fnrcueeqy at which the power halves or the voltage is reduced to about 70%) fromfc =1/(2PI*R*C) (where PI is 3.14)The higher fnrcueeqy will be rolled off at 6dB/octave Every time you double the fnrcueeqy, the power will be attenuated by a factor of four or the voltage attenuated by a factor of two.If you pick a value of C , and you transpose the formula , you can work out RR = 1/(2PI*C*fc)To get better attenuation of noise & harmonics you can go for a Sallen-Key low pass filter, which uses two caps , two resistors & an OP AMPand an attenuation of 12 dB/octaveLee

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Comment on Linear Bipolar Stepper Controller … early thoughts by Bill Dreschel http://www.randomthinker.org/?p=75#comment-107 Wed, 06 Jun 2012 15:44:39 +0000 http://www.randomthinker.org/?p=75#comment-107 Interesting! I have heard that the tracking telescope guys will often use linear stepper drivers to reduce jitter noise on their scopes. Also any REALLY low electrical noise applications require them. The German company Phytron sells one:
ftp://ftp.phytron.de/manuals/power_stages/sincos-gb.pdf

Most of these designs use a linear power amp, like the OPA54x, MSK541 series which will require you to use a dual supply… or perhaps you could single supply the power op amp and use an external power switch to reverse the current thru the motor coils.

Here is a posted design for a single driver (you would need two for a bipolar stepper:
http://jammnelectronics.com/h-bridge-circuit/#more-58

The other thought would be to use PWM but then filter the output before the motor, so you end up with a linear signal driving the motor. See:
http://electronicdesign.com/article/analog-and-mixed-signal/improve-emc-in-class-d-amplifier-applications12004

I am interested in this. If you would like to discuss this off line, feel free to email me.

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Comment on Linear Bipolar Stepper Controller … early thoughts by Chris http://www.randomthinker.org/?p=75#comment-43 Tue, 01 Nov 2011 04:15:30 +0000 http://www.randomthinker.org/?p=75#comment-43 Not sure if you are still interested in the filtered PWM but I have VHDL code for a delta sigma DAC for an FPGA, I posted it at: http://talsmasfpgas.blogspot.com, the post is called FPGA “DAC” Trick. I implemented it on a project I was doing to create arbitrary waveforms, a sort of signal generator. Check it out, see what you think…. CT

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Comment on Well it’s not really software … by Gadget Factory - What makes FPGA’s special from the perspective of a newcomer. http://www.randomthinker.org/?p=102#comment-31 Wed, 12 Oct 2011 17:01:34 +0000 http://www.randomthinker.org/?p=102#comment-31 […] Random Thinker blog has a nice post that articulates what is so exciting about FPGA’s for the […]

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Comment on Linear Bipolar Stepper Controller … early thoughts by rt http://www.randomthinker.org/?p=75#comment-6 Thu, 14 Jul 2011 12:57:06 +0000 http://www.randomthinker.org/?p=75#comment-6 These drivers look really nice, I love the way they fit into an attachment that goes right on the stepper.

Unfortunately though, these are still PWM chopper drivers, which although probably fine, is not the goal of this little experiment.

I’m making progress on the linear driver, onto the second version of the board, another blog will follow.

RT.

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Comment on Linear Bipolar Stepper Controller … early thoughts by Miniature Stepper Driver http://www.randomthinker.org/?p=75#comment-5 Thu, 14 Jul 2011 09:50:11 +0000 http://www.randomthinker.org/?p=75#comment-5 Miniature stepper driver from UIROBOT

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Comment on Linear Bipolar Stepper Controller … early thoughts by Integrated Stepper Motor http://www.randomthinker.org/?p=75#comment-4 Thu, 14 Jul 2011 09:49:31 +0000 http://www.randomthinker.org/?p=75#comment-4 Integrated Stepper Motor with Drives from UIROBOT

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Comment on Linear Bipolar Stepper Controller … early thoughts by CNCzone.com-The Largest Machinist Community on the net! http://www.randomthinker.org/?p=75#comment-3 Tue, 05 Jul 2011 07:24:17 +0000 http://www.randomthinker.org/?p=75#comment-3 Home build linear bipolar driver card!…

Thanks for the comments so far, especially H500 … I did suspect there was a flaw in my plan, it all seemed a little too easy. I had intended using 5v to avoid the heat problems, I did wonder whet……

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