Users Guide

GettingStarted
WhatisaServo?
WhatisOpenSource?
Beforeweillustratehowtousetheservocontrollerweneedtoexplainwhataservois,
anddefinethecontrolmethodology.
Pulse-proportionalservosaredesignedforuseinradio-controlled(R/C)cars,boatsand
planes.Theyprovideprecisecontrolforsteering,throttle,rudder,etc.usingasignalthat
iseasytotransmitandreceive.Thesignalconsistsofpositivegoingpulsesrangingfrom
0.9to2.1mS(milliseconds)long,repeated50timesasecond(every20mS).Theservo
positionsitsoutputshaftinproportiontothewidthofthepulse,asshownbelow.
Inradio-controlapplications,aservoneedsnomorethana90°rangeofmotion,sinceit
isusuallydrivingacrankmechanismthatcan'tmovemorethan90°.Sowhenyousend
pulseswithinthemanufacturer-specifiedrangeof0.9to2.1mS,yougetaround90°
rangeofmotion.
Mostservoshavemorethan90°ofmechanicalrange.Infact,mostservoscanmoveup
to180°ofrotation.However,someservoscanbedamagedwhencommandedpasttheir
mechanicallimitations.TheSSC-32letsyouusethisextrarange.Apositionvalueof500
correspondsto0.50mSpulse,andapositionvalueof2500correspondstoa2.50mS
pulse.Aoneunitchangeinpositionvalueproducesa1uS(microsecond)changein
pulsewidth.Thepositioningresolutionis0.09°/unit(180°/2000).Fromhereon,theterm
pulsewidthandpositionarethesame.
Rememberthatsomeservosmaynotbeabletomovetheentire180°range.Usecare
whentestingservos.Movetotheextremeleftorrightslowly,lookingforapointwhen
additionalpositioningvaluesnolongerresultinadditionalservooutputshaftmovement.
Whenthisvalueisfound,putitasalimitinyourprogramtopreventdamagingthe
servo.Generally,microservosarenotabletomovetheentire180° range.
Itsimplymeanswearedistributingthesourcecodeforthebootloaderandfirmware.
Thegoalistohaveanaffordableplatformthatmanypeoplewillprovidefirmwarefor.It
shouldalsohelpmanyaspiringprogrammerslearnsometricks.Anyonecanusethe
sourcecodetowritespecializedfirmware,providingyouallowLynxmotion,Inc.to
publishitforotherstoenjoy.Thesourcecodecannotbeusedinacommercialproduct.
Asitis,thisservocontrollerwilloutperformcontrollerscostingtwotothreetimesas
much.Havingseveral"flavors"ofthefirmwarewillmakethisanevenbettervalue.
HS-422HS-422
HS-422HS-422
HS-422HS-422
0.9mS
1.5mS
Servo
Centered
Servo
Centered
Servo
-45°
NormalRange ExtendedRange
Servo
-90°
Servo
+45°
Servo
+90°
2.1mS
0.50mS
1.5mS
2.50mS