features ? small size ? multiple mounting options ? linear and rotary options available ? no signal adjustment required ? insensitive to radial and axial play ? -40 c to +85 c operating temperature ? two channel quadrature output heds-978x series ? ttl compatible or 5.0 v cmos compatible ? single 5 v supply ? wave solderable description the heds-978x series is a high performance, low cost, optical incremental encoder module. when operated in conjunction small optical encoder modules technical data esd warning: normal handling precautions should be taken to avoid static discharge. package dimensions mounting option #50 - standard (baseplane mounting) contact factory for detailed package dimensions
2 with either a codewheel or codestrip, this module detects rotary or linear position. the module consists of a lensed led source and a detector ic enclosed in a small c-shaped plastic pack- age. due to a highly collimated light source and a unique photo- detector array, the module is extremely tolerant to mounting misalignment. the two channel digital outputs and 5 v supply input are accessed through four solder-plated leads located on 2.54 mm (0.1 inch) centers. the standard heds-978x is designed for use with an 11 mm optical radius codewheel, or linear codestrip. other options are available. please contact factory for more information. applications the heds-978x provides sophisticated motion detection at a low cost, making closed-loop control very cost-competitive! typical applications include printers, plotters, copiers, and office automation equipment. note: agilent technologies encoders are not recommended for use in safety critical applications. eg. abs braking systems, power steering, life support systems and critical care medical equipment. please contact sales representative if more clarification is needed. theory of operation the heds-978x is a c-shaped emitter/detector module. coupled with a codewheel, it translates rotary motion into a two-channel digital output. coupled with a codestrip, it translates linear motion into a digital output. as seen in the block diagram, the module contains a single light emitting diode (led) as its light source. the light is collimated into a parallel beam by means of a single lens located directly over the led. opposite the emitter is the integrated detector circuit. this ic consists of multiple sets of photodetectors and the signal processing circuitry necessary to produce the digital waveforms. the codewheel/codestrip moves between the emitter and detector, causing the light beam to be inter- rupted by the pattern of spaces and bars on the codewheel/code- strip. the photodiodes which detect these interruptions are arranged in a pattern that corre- sponds to the radius and count density of the codewheel/code- strip. these detectors are also spaced such that a light period on one pair of detectors corresponds to a dark period on the adjacent pair of detectors. the photodiode outputs are fed through the signal processing circuitry. two com- parators receive these signals and produce the final outputs for channels a and b. due to this integrated phasing technique, the digital output of channel a is in quadrature with channel b (90 degrees out of phase). block diagram
3 phase ( f ): the number of electrical degrees between the center of the high state of channel a and the center of the high state of channel b. this value is nominally 90 e for quadrature output. phase error ( df ): the deviation of the phase from its ideal value of 90 e. direction of rotation: when the codewheel rotates counterclock- wise, as viewed looking down on the module (so the marking is visible), channel a will lead channel b. if the codewheel rotates in the opposite direction, channel b will lead channel a. optical radius (rop): the distance from the codewheels center of rotation to the optical center (o.c.) of the encoder module. angular misalignment error (e a ): angular misalignment of the sensor in relation to the tangential direction. this applies for both rotary and linear motion. mounting position (r m ): distance from motor shaft center of rotation to center of alignment tab receiving hole. output waveforms definitions count (n) = the number of bar and window pairs or counts per revolution (cpr) of the codewheel, or the number of lines per inch of the codestrip (lpi). 1 shaft rotation = 360 mechanical degrees = n cycles 1 cycle (c) = 360 electrical degrees ( e) = 1 bar and window pair pulse width (p): the number of electrical degrees that an output is high during one cycle. this value is nominally 180 e or 1/2 cycle. pulse width error ( d p): the deviation, in electrical degrees, of the pulse width from its ideal value of 180 e. state width (s): the number of electrical degrees between a transition in the output of channel a and the neighboring transition in the output of channel b. there are 4 states per cycle, each nominally 90 e. state width error ( d s): the deviation, in electrical degrees, of each state width from its ideal value of 90 e.
4 recommended operating conditions parameter symbol min. typ. max. units notes temperature t s -40 85 c supply voltage v cc 4.5 5.0 5.5 v ripple < 100 mv p-p load capacitance c l 100 pf 3.2 k w pull-up count frequency 80 khz (velocity (rpm) x n)/60 angular misalignment e a -2.0 0.0 +2.0 deg. mounting considerations mounting position r m r op -0.14 mm (in. (r op -0.006) absolute maximum ratings parameter symbol min. max. units notes storage temperature t s -40 85 c operating temperature t a -40 85 c supply voltage v cc -0.5 7 v output voltage v o -0.5 v cc v output current per i o -1.0 5 ma channel soldering temperature 260 ct 5 sec. electrical characteristics electrical characteristics over recommended operating range, typical at 25 c. parameter symbol min. typ. max. units notes supply current i cc 17 40 ma high level output voltage v oh 2.4 v i oh = -200 m a low level output voltage v ol 0.4 v i ol = 3.2 ma rise time t r 180 ns c l = 25 pf, fall time t f 40 ns r l = 3.2 k w pull-up c l shaft 0.13 mm (0.005) see mounting considerations mm (inch)
5 recommended codewheel and codestrip characteristics parameter symbol min. max. units notes window/bar ratio ww/wb 0.7 1.4 window length (rotary) lw 1.80 2.30 mm (0.071) (0.091) (inch) absolute maximum codewheel rc rop + 3.40 mm includes eccenC radius (rotary) (rop + 0.134) (inch) tricity errors center of post to inside w1 1.04 mm edge of window (0.041) (inch) center of post to outside w2 0.76 mm edge of window (0.030) (inch) center of post to inside edge l 3.60 mm of codestrip (0.142) (inch) encoding characteristics encoding characteristics over recommended operating condition and recommended mounting tolerances. these characteristics do not include codewheel/codestrip contribution. the typical values are averages over the full rotation of the codewheel. parameter symbol typical maximum units pulse width error d p547 e logic state width error d s347 e phase error df 217 e note: 3.2 k w pull-up resistors used on all encoder module outputs.
6 note: these dimensions include shaft end play and codewheel warp. for both rotary and linear motion, angular misalignment, e a , must be 2 degrees to achieve encoding characteristics. all dimensions for mounting the module and codewheel/codestrip should be measured with respect to the two mounting posts, shown above. mounting considerations recommended screw size: m2.5 x 0.45 or 2-56 e a alignment tab receiving hole 4.44 0.13 0.175 0.005 image side of codewheel/codestrip a 0.13 mm (0.005") center of rotation motor shaft center ?a rm optional packages available mounting option #54 C tabless (baseplane mounting)
7 typical interface host processor ch b ch a hedsC978x hctl-2016/2020 quadrature decoder/ counter heds-978 option ordering information lead bend 0 C straight leads 1 C bent leads resolution options a C 500 cpr g C 360 cpr h C 400 cpr mounting options 50 C standard 54 C tabless note: please contact factory for codewheel and codestrip information. recommended wave solder conditions flux C rma water soluble (per mil-f-14256d) process parameters 1. flux 2. pre-heat 60 seconds total nominal preheat temp: 90 c min: 85 c max: 110 c 3. solder pot zone nominal dip in time: 2.5 - 4.5 seconds min: 2.5 seconds max: 5 seconds pcb top side: 140 -160 c pcb bottom side: 240 - 260 c 4. wave solder 255 c, 1.2 meters/minute line speed 5. hot water wash 1st: 30 c 45 seconds 2nd: 70 c 90 seconds 6. rinse 1st: 23 c 45 seconds 2nd: 23 c 45 seconds 7. dry 1st: 80 c 105 seconds 2nd: 95 c 105 seconds
50 51 52 53 54 55 HEDS-9780 a * g* * h* heds-9781 h * www.agilent.com/semiconductors for product information and a complete list of distributors, please go to our web site. for technical assistance call: americas/canada: +1 (800) 235-0312 or (408) 654-8675 europe: +49 (0) 6441 92460 china: 10800 650 0017 hong kong: (+65) 6271 2451 india, australia, new zealand: (+65) 6271 2394 japan: (+81 3) 3335-8152(domestic/interna- tional), or 0120-61-1280(domestic only) korea: (+65) 6271 2194 malaysia, singapore: (+65) 6271 2054 taiwan: (+65) 6271 2654 data subject to change. copyright ? 2002 agilent technologies, inc. obsoletes 5988-5605en october 2, 2002 5988-8043en
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