Rotary encoder - Revision history

ChuckH: /* Rotary capacitance encoder ("Capacitive resolver") */

2012-01-09T06:12:53Z

Rotary capacitance encoder ("Capacitive resolver")

← Older revision		Revision as of 06:12, 9 January 2012
Line 43:		Line 43:

	The design includes 4 stationary outer electrode rings, offset 1/4 of a tooth pitch, driven by 2-phase square waves A+ A- B+ B-. One rotating inner electrode. All electrodes are splined (e.e. toothed). Buffer the hi-z rotating electrode signal, filter with tuned circuit, and measure its phase to interpolate within 1 spline tooth pitch. (This has been called the "phase analog technique" when used with resolvers. [http://www.analog.com/static/imported-files/application_notes/394309286AN263.pdf]) Electronics can be arduino, development code at [[File:Cap_encoder.ino \|Cap_encoder.ino]]		The design includes 4 stationary outer electrode rings, offset 1/4 of a tooth pitch, driven by 2-phase square waves A+ A- B+ B-. One rotating inner electrode. All electrodes are splined (e.e. toothed). Buffer the hi-z rotating electrode signal, filter with tuned circuit, and measure its phase to interpolate within 1 spline tooth pitch. (This has been called the "phase analog technique" when used with resolvers. [http://www.analog.com/static/imported-files/application_notes/394309286AN263.pdf]) Electronics can be arduino, development code at [[File:Cap_encoder.ino \|Cap_encoder.ino]]
	. Special electronic parts: 1 FET(buffer), inductor, capacitor. Expected carrier freq: 1-10kHz. Use arduino capture/compare function to measure time of zero crossings. [[CapEncoderSpiceModel]]		. Special electronic parts: 1 [http://www.mouser.com/Search/ProductDetail.aspx?R=2N7000virtualkey51210000virtualkey512-2N7000 FET](buffer), [http://www.mouser.com/Search/ProductDetail.aspx?R=RLB0812-103KLvirtualkey65210000virtualkey652-RLB0812-103KL inductor], [http://www.mouser.com/Search/ProductDetail.aspx?R=ECQ-V1H273JL2virtualkey66720000virtualkey667-ECQ-V1H273JL2 capacitor]. Expected carrier freq: 10kHz. Use arduino capture/compare function to measure time of zero crossings. [[CapEncoderSpiceModel]]

	[[Image:CapEncoderModel.png\|thumbnail\|Electrical Simulation Model]]		[[Image:CapEncoderModel.png\|thumbnail\|Electrical Simulation Model]]

ChuckH: /* Rotary capacitance encoder ("Capacitive resolver") */

2012-01-09T04:54:16Z

Rotary capacitance encoder ("Capacitive resolver")

← Older revision		Revision as of 04:54, 9 January 2012
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	[[Image:CapEncoderSchem.png\|thumbnail\|Simplified Schematic]]		[[Image:CapEncoderSchem.png\|thumbnail\|Simplified Schematic]]

	The design includes 4 stationary outer electrode rings, offset 1/4 of a tooth pitch, driven by 2-phase square waves A+ A- B+ B-. One rotating inner electrode. All electrodes are splined (e.e. toothed). Buffer the hi-z rotating electrode signal, filter with tuned circuit, and measure its phase to interpolate within 1 spline tooth pitch. (This has been called the "phase analog technique" when used with resolvers. [http://www.analog.com/static/imported-files/application_notes/394309286AN263.pdf]) Electronics can be arduino, development code at ~~http~~:~~//opensourceecology~~.~~org/wiki/File:~~Cap_encoder.ino		The design includes 4 stationary outer electrode rings, offset 1/4 of a tooth pitch, driven by 2-phase square waves A+ A- B+ B-. One rotating inner electrode. All electrodes are splined (e.e. toothed). Buffer the hi-z rotating electrode signal, filter with tuned circuit, and measure its phase to interpolate within 1 spline tooth pitch. (This has been called the "phase analog technique" when used with resolvers. [http://www.analog.com/static/imported-files/application_notes/394309286AN263.pdf]) Electronics can be arduino, development code at [[File:Cap_encoder.ino \|Cap_encoder.ino]]
	. Special electronic parts: 1 FET(buffer), inductor, capacitor. Expected carrier freq: 1-10kHz. Use arduino capture/compare function to measure time of zero crossings. [[CapEncoderSpiceModel]]		. Special electronic parts: 1 FET(buffer), inductor, capacitor. Expected carrier freq: 1-10kHz. Use arduino capture/compare function to measure time of zero crossings. [[CapEncoderSpiceModel]]

ChuckH: /* Rotary capacitance encoder ("Capacitive resolver") */

2012-01-09T04:33:09Z

Rotary capacitance encoder ("Capacitive resolver")

← Older revision		Revision as of 04:33, 9 January 2012
Line 42:		Line 42:
	[[Image:CapEncoderSchem.png\|thumbnail\|Simplified Schematic]]		[[Image:CapEncoderSchem.png\|thumbnail\|Simplified Schematic]]

	The design includes 4 stationary outer electrode rings, offset 1/4 of a tooth pitch, driven by 2-phase square waves A+ A- B+ B-. One rotating inner electrode. All electrodes are splined (e.e. toothed). Buffer the hi-z rotating electrode signal, filter with tuned circuit, and measure its phase to interpolate within 1 spline tooth pitch. (This has been called the "phase analog technique" when used with resolvers. [http://www.analog.com/static/imported-files/application_notes/394309286AN263.pdf]) Electronics can be arduino. ~~Multiple encoders can share drive waveform~~. Special electronic parts: 1 FET(buffer), inductor, capacitor. Expected carrier freq: 1-10kHz. Use arduino capture/compare function to measure time of zero crossings. [[CapEncoderSpiceModel]]		The design includes 4 stationary outer electrode rings, offset 1/4 of a tooth pitch, driven by 2-phase square waves A+ A- B+ B-. One rotating inner electrode. All electrodes are splined (e.e. toothed). Buffer the hi-z rotating electrode signal, filter with tuned circuit, and measure its phase to interpolate within 1 spline tooth pitch. (This has been called the "phase analog technique" when used with resolvers. [http://www.analog.com/static/imported-files/application_notes/394309286AN263.pdf]) Electronics can be arduino, development code at http://opensourceecology.org/wiki/File:Cap_encoder.ino
			. Special electronic parts: 1 FET(buffer), inductor, capacitor. Expected carrier freq: 1-10kHz. Use arduino capture/compare function to measure time of zero crossings. [[CapEncoderSpiceModel]]

	[[Image:CapEncoderModel.png\|thumbnail\|Electrical Simulation Model]]		[[Image:CapEncoderModel.png\|thumbnail\|Electrical Simulation Model]]

ChuckH: /* Rotary Encoders and Linear Motion */

2012-01-04T08:55:30Z

Rotary Encoders and Linear Motion

← Older revision		Revision as of 08:55, 4 January 2012
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	* '''Encoded pickoff'''. In this case, the rotary measurement device is separate from the drive system. Rack-and-pinion is a common technique; toothed-belt and coarse-thread leadscrews (often with 2 or four "starts" on a high-helix thread) are also used.		* '''Encoded pickoff'''. In this case, the rotary measurement device is separate from the drive system. Rack-and-pinion is a common technique; toothed-belt and coarse-thread leadscrews (often with 2 or four "starts" on a high-helix thread) are also used.

	Variants of the rack-and-pinion that have some attractive features are the [http://www.southwesternindustries.com/swi/prod_measurement1.shtml Trav-a-dial] and random grit wheel. Unlike most encoded pickoffs, they do not rely on the precision of a long rack, belt, or screw. The rotating wheel has a random pattern of small but hard protrusions which effectively form a mating "rack" when the wheel is first assembled and run against its companion mild steel rail, which needs only be initially smooth and straight. The steel wheel might receive its surface texture with a knurl -- or by hand with a rasp-stitching chisel (a lovely video of rasp-making [http://www.youtube.com/watch?feature=player_embedded&v=_pzK2Ei19t4 here]) -- then be case-hardened.		Variants of the rack-and-pinion that have some attractive features are the [http://www.southwesternindustries.com/swi/prod_measurement1.shtml Trav-a-dial] and random grit wheel. Unlike most encoded pickoffs, they do not rely on the precision of a long rack, belt, or screw. The rotating wheel has a random pattern of small but hard protrusions which effectively form a mating "rack" when the wheel is first assembled and run against its companion mild steel rail, which needs only be initially smooth and straight. The steel wheel might receive its surface texture with a knurl -- or by hand with a tiny rasp-stitching chisel (a lovely video of rasp-making [http://www.youtube.com/watch?feature=player_embedded&v=_pzK2Ei19t4 here]) -- then be case-hardened.

	==See Also==		==See Also==
	*[[Stepper Motor]]		*[[Stepper Motor]]
	*[[Electric Motor]]		*[[Electric Motor]]

ChuckH: /* Rotary Encoders and Linear Motion */

2012-01-04T08:55:09Z

Rotary Encoders and Linear Motion

← Older revision		Revision as of 08:55, 4 January 2012
Line 59:		Line 59:
	* '''Encoded pickoff'''. In this case, the rotary measurement device is separate from the drive system. Rack-and-pinion is a common technique; toothed-belt and coarse-thread leadscrews (often with 2 or four "starts" on a high-helix thread) are also used.		* '''Encoded pickoff'''. In this case, the rotary measurement device is separate from the drive system. Rack-and-pinion is a common technique; toothed-belt and coarse-thread leadscrews (often with 2 or four "starts" on a high-helix thread) are also used.

	Variants of the rack-and-pinion that have some attractive features are the [http://www.southwesternindustries.com/swi/prod_measurement1.shtml Trav-a-dial] and random grit wheel. Unlike most encoded pickoffs, they do not rely on the precision of a long rack, belt, or screw. The rotating wheel has a random pattern of small but hard protrusions which effectively form a mating "rack" when the wheel is first assembled and run against its companion mild steel rail, which needs only be initially smooth and straight. The steel wheel might receive its surface texture with a knurl -- or by hand with a rasp-stitching chisel -- then be case-hardened.		Variants of the rack-and-pinion that have some attractive features are the [http://www.southwesternindustries.com/swi/prod_measurement1.shtml Trav-a-dial] and random grit wheel. Unlike most encoded pickoffs, they do not rely on the precision of a long rack, belt, or screw. The rotating wheel has a random pattern of small but hard protrusions which effectively form a mating "rack" when the wheel is first assembled and run against its companion mild steel rail, which needs only be initially smooth and straight. The steel wheel might receive its surface texture with a knurl -- or by hand with a rasp-stitching chisel (a lovely video of rasp-making [http://www.youtube.com/watch?feature=player_embedded&v=_pzK2Ei19t4 here]) -- then be case-hardened.

	==See Also==		==See Also==
	*[[Stepper Motor]]		*[[Stepper Motor]]
	*[[Electric Motor]]		*[[Electric Motor]]

ChuckH: /* Rotary Encoders and Linear Motion */

2012-01-04T08:07:01Z

Rotary Encoders and Linear Motion

← Older revision		Revision as of 08:07, 4 January 2012
Line 59:		Line 59:
	* '''Encoded pickoff'''. In this case, the rotary measurement device is separate from the drive system. Rack-and-pinion is a common technique; toothed-belt and coarse-thread leadscrews (often with 2 or four "starts" on a high-helix thread) are also used.		* '''Encoded pickoff'''. In this case, the rotary measurement device is separate from the drive system. Rack-and-pinion is a common technique; toothed-belt and coarse-thread leadscrews (often with 2 or four "starts" on a high-helix thread) are also used.

	Variants of the rack-and-pinion that have some attractive features are the Trav-a-dial and random grit wheel. Unlike most encoded pickoffs, they do not rely on the precision of a long rack, belt, or screw. The rotating wheel has a random pattern of small but hard protrusions which effectively form a mating "rack" when the wheel is first assembled and run against its companion mild steel rail, which needs only be initially smooth and straight. The steel wheel might ~~be textured~~ with a knurl -- or by hand with a rasp-stitching chisel -- then case-hardened.		Variants of the rack-and-pinion that have some attractive features are the [http://www.southwesternindustries.com/swi/prod_measurement1.shtml Trav-a-dial] and random grit wheel. Unlike most encoded pickoffs, they do not rely on the precision of a long rack, belt, or screw. The rotating wheel has a random pattern of small but hard protrusions which effectively form a mating "rack" when the wheel is first assembled and run against its companion mild steel rail, which needs only be initially smooth and straight. The steel wheel might receive its surface texture with a knurl -- or by hand with a rasp-stitching chisel -- then be case-hardened.

	==See Also==		==See Also==
	*[[Stepper Motor]]		*[[Stepper Motor]]
	*[[Electric Motor]]		*[[Electric Motor]]

ChuckH at 08:04, 4 January 2012

2012-01-04T08:04:34Z

← Older revision		Revision as of 08:04, 4 January 2012
Line 53:		Line 53:

	Accuracy refinement: Lay out so stator tooth crest is inside bolt circle dia, making slight hourglass tooth profile. Consider this as an internal gear. Make another gear with fewer teeth, ''relatively prime'' to stator tooth count, that will mesh inside. Running these two gears in mesh with lapping compound should bring teeth into precisely uniform spacing. After lapping, clean 4 stators and assemble them as above.		Accuracy refinement: Lay out so stator tooth crest is inside bolt circle dia, making slight hourglass tooth profile. Consider this as an internal gear. Make another gear with fewer teeth, ''relatively prime'' to stator tooth count, that will mesh inside. Running these two gears in mesh with lapping compound should bring teeth into precisely uniform spacing. After lapping, clean 4 stators and assemble them as above.

			==Rotary Encoders and Linear Motion==
			Although precise linear encoders are available, many times a rotary encoder is used to measure linear travel of a machine tool table or other mechanism. The principal methods are ''encoded drive'' and ''encoded pickoff''.
			* '''Encoded drive'''. Often the rotation of a motor is converted to linear travel by a leadscrew or toothed-belt drive. A rotary encoder on the motor shaft indirectly measures the linear movement. For good accuracy, there should be very little looseness or "windup" in the drive train.
			* '''Encoded pickoff'''. In this case, the rotary measurement device is separate from the drive system. Rack-and-pinion is a common technique; toothed-belt and coarse-thread leadscrews (often with 2 or four "starts" on a high-helix thread) are also used.

			Variants of the rack-and-pinion that have some attractive features are the Trav-a-dial and random grit wheel. Unlike most encoded pickoffs, they do not rely on the precision of a long rack, belt, or screw. The rotating wheel has a random pattern of small but hard protrusions which effectively form a mating "rack" when the wheel is first assembled and run against its companion mild steel rail, which needs only be initially smooth and straight. The steel wheel might be textured with a knurl -- or by hand with a rasp-stitching chisel -- then case-hardened.

	==See Also==		==See Also==
	*[[Stepper Motor]]		*[[Stepper Motor]]
	*[[Electric Motor]]		*[[Electric Motor]]

ChuckH at 17:41, 1 October 2011

2011-10-01T17:41:35Z

← Older revision		Revision as of 17:41, 1 October 2011
Line 32:		Line 32:

	''note: this page was started because I wanted a place to document some brainstorming I had done on the rotary capacitance encoder design. Please add other conventional and/or unconventional concepts as appropriate -- ChuckH''		''note: this page was started because I wanted a place to document some brainstorming I had done on the rotary capacitance encoder design. Please add other conventional and/or unconventional concepts as appropriate -- ChuckH''
			<div id="CapEncoder"></div>

	====Rotary capacitance encoder ("Capacitive resolver")====		====Rotary capacitance encoder ("Capacitive resolver")====
	~~<div id="CapEncoder"></div>~~
	This idea addresses a goal to design a high-resolution, fairly accurate encoder that can be made with a minimum of precision equipment (e.g. manual layout, simple lathe work) and minimum purchased electronics outside the "OSE standard" Arduino platform. This design has a base resolution of 48 cycles per revolution and should support ~100x electronic interpolation for a resolution of 1/4800 rev (0.075 degree).		This idea addresses a goal to design a high-resolution, fairly accurate encoder that can be made with a minimum of precision equipment (e.g. manual layout, simple lathe work) and minimum purchased electronics outside the "OSE standard" Arduino platform. This design has a base resolution of 48 cycles per revolution and should support ~100x electronic interpolation for a resolution of 1/4800 rev (0.075 degree).

ChuckH at 17:40, 1 October 2011

2011-10-01T17:40:08Z

← Older revision		Revision as of 17:40, 1 October 2011
Line 19:		Line 19:
	* power requirements		* power requirements

	~~TBD:~~ links to existing commercial products		links to existing commercial products
	[http://www.usdigital.com/products/encoders US Digital] (an encoder vendor).		* [http://www.usdigital.com/products/encoders US Digital] (an encoder vendor).

	=== GVCS applications ===		=== GVCS applications ===
Line 34:		Line 34:

	====Rotary capacitance encoder ("Capacitive resolver")====		====Rotary capacitance encoder ("Capacitive resolver")====
			<div id="CapEncoder"></div>
	This idea addresses a goal to design a high-resolution, fairly accurate encoder that can be made with a minimum of precision equipment (e.g. manual layout, simple lathe work) and minimum purchased electronics outside the "OSE standard" Arduino platform. This design has a base resolution of 48 cycles per revolution and should support ~100x electronic interpolation for a resolution of 1/4800 rev (0.075 degree).		This idea addresses a goal to design a high-resolution, fairly accurate encoder that can be made with a minimum of precision equipment (e.g. manual layout, simple lathe work) and minimum purchased electronics outside the "OSE standard" Arduino platform. This design has a base resolution of 48 cycles per revolution and should support ~100x electronic interpolation for a resolution of 1/4800 rev (0.075 degree).

ChuckH at 17:25, 1 October 2011

2011-10-01T17:25:42Z

← Older revision		Revision as of 17:25, 1 October 2011
Line 40:		Line 40:
	[[Image:CapEncoderSchem.png\|thumbnail\|Simplified Schematic]]		[[Image:CapEncoderSchem.png\|thumbnail\|Simplified Schematic]]

	The design includes 4 stationary outer electrode rings, offset 1/4 of a tooth pitch, driven by 2-phase square waves A+ A- B+ B-. One rotating inner electrode. All electrodes are splined (e.e. toothed). Buffer the hi-z rotating electrode signal, filter with tuned circuit, and measure its phase to interpolate within 1 spline tooth pitch. (This has been called the "phase analog technique" when used with resolvers. [http://www.analog.com/static/imported-files/application_notes/394309286AN263.pdf]) Electronics can be arduino. Multiple encoders can share drive waveform. Special electronic parts: 1 FET(buffer), inductor, capacitor. Expected carrier freq: 1-10kHz. Use arduino capture/compare function to measure time of zero crossings.		The design includes 4 stationary outer electrode rings, offset 1/4 of a tooth pitch, driven by 2-phase square waves A+ A- B+ B-. One rotating inner electrode. All electrodes are splined (e.e. toothed). Buffer the hi-z rotating electrode signal, filter with tuned circuit, and measure its phase to interpolate within 1 spline tooth pitch. (This has been called the "phase analog technique" when used with resolvers. [http://www.analog.com/static/imported-files/application_notes/394309286AN263.pdf]) Electronics can be arduino. Multiple encoders can share drive waveform. Special electronic parts: 1 FET(buffer), inductor, capacitor. Expected carrier freq: 1-10kHz. Use arduino capture/compare function to measure time of zero crossings. [[CapEncoderSpiceModel]]

	[[Image:CapEncoderModel.png\|thumbnail\|Electrical Simulation Model]]		[[Image:CapEncoderModel.png\|thumbnail\|Electrical Simulation Model]]