Eloy Marez SERVOS discussion last time left hope youwith some curiosity about decided take closer look some currently available discovered some interesting things Surface Mount Technology SMT latest electronic assembly methodology includes unique components assembly methods responsible extremely small lightweight very reliable inexpensive electronics out RC now available us Older assembly technology now referred through-hole used comparatively large wire-lead-mounted components leads inserted holes printed circuit PC board part upright soldered opposite side Under vibration prone break solder joints crash heavy shock inertia would often pull out soldered connection Such equipment hand-soldered always professionals Actually much came cottage labor Dropouts new equipment numerous new items failed early earlier times often said troubleprone system must have built Monday morning Friday afternoon Along came SMT PC boards no longer have holes components supported flat legs mate soldered wide areas PC board known lands components considerably smaller since standing up skinny legs far less prone effects vibration shock assemblies made completely automatic equipment parts being placed soldered proper position being touched human hands placement perfect soldering perfect some cases fully automatic burning testing done before assembly wired final product Refer photo complete PC board actually receiver chose because large high component count can see results better Note precision parts mounted uniformity soldering Now take look rest SMT components Note great difference resistor sizeand examples shown part story case size item bears 90 Model Aviation old-technology servo amplifier board assembled using older much-larger through-hole pans Properly done Surface Mount Technology SMT electronic NC Electronics PT1OS digital optical tachometer guaranteed assembly Note uniformity parts locations soldering one-rpm accuracy lOs lOOs number such 0805 1206 resistors indicate actual size hundredths inch An 0805 resistor 08 inch long 05 inch wide 1206 12 long 06 wide think small Chip resistors called now available 0402 case size can own calculations hundredths inch other SMT components similarly shrunk size example receiver board middle two larger components two integrated circuits ICs Dont love abbreviations acronyms Significant size reductions have taken place ICs though actually active element inside seldom 1Ao package size has encased larger ease handling can soldered circuit discovered some interesting things mostly case aftermarket cheaper servos available companies other major RC system manufacturers should news such servos regardless what label package says come same manufacturer Grand Wing Servo-tech Co Taiwan Often difference wiring sometimes color necessarily bad some excellent electronic products now coming Taiwan also discovered couple unpleasant things Some SMT servos made automatic equipment obviously put together hand desirable couple reasons just plain neatness components just dont line up neatly machineassembled units soldering nowhere nearly uniform either major problem Like electronic components Surface Mount Components SMCs rated soldering temperature time can applied overdone component values its expected life can affected soldering SMCs handheld irons instead automated equipment chances overheating extremely high Such equipment will meet high tolerances its life will probably shortened Another disturbing thing discovered some servos advertised being SMT construction old-fashioned wire-lead type Actually such servos work OKafter flew yearsthough makes wonder can say cannot expect same kind performance reliability $10 servo can $50 servo flying expensive airplanes have actually built big time investment can accept using cheapies throttle other minor functions saving money using main flight controls can turn out false economy get what pay Actually same applies radio equipment Another point look quality connectors Some use plain silvercolored parts others goldplated latter have less contact resistance less likely corrode thus preferred Getting what pay applies everything purchase Price makes difference example tachometers first tachometer appear intended primarily modeler Heath Thumb Tach now-disappeared Heathkit Company loved despite fact read 0-25000 rpm analog scale about 1 inches wide sun just right get good reading Other analog instruments appeared no doubt best Royal Products ProTach used expanded-scale techniques allow much smaller accurate readings digital readouts related circuitry appeared obvious would find way modelers tachometers did As case servos have place Thumb Tach better no tach serious about operation engine However serious moreinvolved flier better way skin particular cat digital optical tachometer TNC Electronics 2 Whites Ln Woodstock NY 12498 Tel [914] 679-8549 different versions first bit about optical tachs Optical tachometers react light reflections prop blades reflections picked up photoresistor phototransistor generates electrical pulses step reflected light phototransistor expensive preferred method pulses generated processed routed counting circuits drive display Thumb Tach used photoresistor aided magnifying lens six transistors perform its now-crude counting functions TNC PT1OS have evaluated use includes phototransistor eleven ICs can contain hundreds transistors very sophisticated very advanced piece equipment Calibration tachometer can have great deal its accuracy common calibrate instruments aiming light bulb flickers 120 times per second tach reads 3600 rpm Thats fine 3600 rpm error circuitry calibrator multiplied higher readings 20000 rpm indication can grossly inaccurate tachs must calibrated higher rpm Being mind test claims whenever can trait referred friends nosy test PT1OS calibration first test rig simply electric motor powered variable power supply could adjust speed black plastic disc painted white stripes provided necessary reflections rpm read circuit described July issue driving frequency counter particular motor tended drift speed high rpm adding second set stripes wheel double apparent rpm did give positive repeatable results needed better motor Knowing things can improved electronics decided different approach breadboarded rather simple crystalcontrolled oscillator circuit pulse LED high frequencies accuracy such circuit determined crystal Probably best crystal readily available used television color circuitry AC-powered clocks cut extremely low 005% tolerancequite adequate application consideration necessary electronic trickery produces some uneven values 6555 13107 26215 simulated rpm numbers would better such crystal being available Radio Shack less two bucks can live odd values frequency counter used check above figures slightly off because crystal tolerance close enough practical purposes important thing PT 105 matched indicated values its 10- 100-rpm resolution settings four versions TNC tachs PT1OS 100 rpm resolution 150K 10 rpm resolution 999K PT 100 rpm resolution 999K updateable PTIOS PF Prop/Fan external airplanemounted pickup 100 rpm resolution lOOK JT Turbine external plane mounted pickup 100 rpm resolution 200K claimed have rpm accuracy two- three-blade selection include nine-volt battery required can provide prop readings up three feet can modified TNC meet special requirements no longer excuse guess about performance fire-belcher yours Neither excuse guess about accuracy whatever tach may have LED calibrator circuit availablejust send SASE mber1999 91
Edition: Model Aviation - 1999/11
Page Numbers: 90, 91
Edition: Model Aviation - 1999/11
Page Numbers: 90, 91
Eloy Marez SERVOS discussion last time left hope youwith some curiosity about decided take closer look some currently available discovered some interesting things Surface Mount Technology SMT latest electronic assembly methodology includes unique components assembly methods responsible extremely small lightweight very reliable inexpensive electronics out RC now available us Older assembly technology now referred through-hole used comparatively large wire-lead-mounted components leads inserted holes printed circuit PC board part upright soldered opposite side Under vibration prone break solder joints crash heavy shock inertia would often pull out soldered connection Such equipment hand-soldered always professionals Actually much came cottage labor Dropouts new equipment numerous new items failed early earlier times often said troubleprone system must have built Monday morning Friday afternoon Along came SMT PC boards no longer have holes components supported flat legs mate soldered wide areas PC board known lands components considerably smaller since standing up skinny legs far less prone effects vibration shock assemblies made completely automatic equipment parts being placed soldered proper position being touched human hands placement perfect soldering perfect some cases fully automatic burning testing done before assembly wired final product Refer photo complete PC board actually receiver chose because large high component count can see results better Note precision parts mounted uniformity soldering Now take look rest SMT components Note great difference resistor sizeand examples shown part story case size item bears 90 Model Aviation old-technology servo amplifier board assembled using older much-larger through-hole pans Properly done Surface Mount Technology SMT electronic NC Electronics PT1OS digital optical tachometer guaranteed assembly Note uniformity parts locations soldering one-rpm accuracy lOs lOOs number such 0805 1206 resistors indicate actual size hundredths inch An 0805 resistor 08 inch long 05 inch wide 1206 12 long 06 wide think small Chip resistors called now available 0402 case size can own calculations hundredths inch other SMT components similarly shrunk size example receiver board middle two larger components two integrated circuits ICs Dont love abbreviations acronyms Significant size reductions have taken place ICs though actually active element inside seldom 1Ao package size has encased larger ease handling can soldered circuit discovered some interesting things mostly case aftermarket cheaper servos available companies other major RC system manufacturers should news such servos regardless what label package says come same manufacturer Grand Wing Servo-tech Co Taiwan Often difference wiring sometimes color necessarily bad some excellent electronic products now coming Taiwan also discovered couple unpleasant things Some SMT servos made automatic equipment obviously put together hand desirable couple reasons just plain neatness components just dont line up neatly machineassembled units soldering nowhere nearly uniform either major problem Like electronic components Surface Mount Components SMCs rated soldering temperature time can applied overdone component values its expected life can affected soldering SMCs handheld irons instead automated equipment chances overheating extremely high Such equipment will meet high tolerances its life will probably shortened Another disturbing thing discovered some servos advertised being SMT construction old-fashioned wire-lead type Actually such servos work OKafter flew yearsthough makes wonder can say cannot expect same kind performance reliability $10 servo can $50 servo flying expensive airplanes have actually built big time investment can accept using cheapies throttle other minor functions saving money using main flight controls can turn out false economy get what pay Actually same applies radio equipment Another point look quality connectors Some use plain silvercolored parts others goldplated latter have less contact resistance less likely corrode thus preferred Getting what pay applies everything purchase Price makes difference example tachometers first tachometer appear intended primarily modeler Heath Thumb Tach now-disappeared Heathkit Company loved despite fact read 0-25000 rpm analog scale about 1 inches wide sun just right get good reading Other analog instruments appeared no doubt best Royal Products ProTach used expanded-scale techniques allow much smaller accurate readings digital readouts related circuitry appeared obvious would find way modelers tachometers did As case servos have place Thumb Tach better no tach serious about operation engine However serious moreinvolved flier better way skin particular cat digital optical tachometer TNC Electronics 2 Whites Ln Woodstock NY 12498 Tel [914] 679-8549 different versions first bit about optical tachs Optical tachometers react light reflections prop blades reflections picked up photoresistor phototransistor generates electrical pulses step reflected light phototransistor expensive preferred method pulses generated processed routed counting circuits drive display Thumb Tach used photoresistor aided magnifying lens six transistors perform its now-crude counting functions TNC PT1OS have evaluated use includes phototransistor eleven ICs can contain hundreds transistors very sophisticated very advanced piece equipment Calibration tachometer can have great deal its accuracy common calibrate instruments aiming light bulb flickers 120 times per second tach reads 3600 rpm Thats fine 3600 rpm error circuitry calibrator multiplied higher readings 20000 rpm indication can grossly inaccurate tachs must calibrated higher rpm Being mind test claims whenever can trait referred friends nosy test PT1OS calibration first test rig simply electric motor powered variable power supply could adjust speed black plastic disc painted white stripes provided necessary reflections rpm read circuit described July issue driving frequency counter particular motor tended drift speed high rpm adding second set stripes wheel double apparent rpm did give positive repeatable results needed better motor Knowing things can improved electronics decided different approach breadboarded rather simple crystalcontrolled oscillator circuit pulse LED high frequencies accuracy such circuit determined crystal Probably best crystal readily available used television color circuitry AC-powered clocks cut extremely low 005% tolerancequite adequate application consideration necessary electronic trickery produces some uneven values 6555 13107 26215 simulated rpm numbers would better such crystal being available Radio Shack less two bucks can live odd values frequency counter used check above figures slightly off because crystal tolerance close enough practical purposes important thing PT 105 matched indicated values its 10- 100-rpm resolution settings four versions TNC tachs PT1OS 100 rpm resolution 150K 10 rpm resolution 999K PT 100 rpm resolution 999K updateable PTIOS PF Prop/Fan external airplanemounted pickup 100 rpm resolution lOOK JT Turbine external plane mounted pickup 100 rpm resolution 200K claimed have rpm accuracy two- three-blade selection include nine-volt battery required can provide prop readings up three feet can modified TNC meet special requirements no longer excuse guess about performance fire-belcher yours Neither excuse guess about accuracy whatever tach may have LED calibrator circuit availablejust send SASE mber1999 91
