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An insight into Servos
How Do
They Work
Servos are
controlled by sending them a pulse of variable width. The control wire is used
to send this pulse. The parameters for this pulse are that it has a minimum
pulse, a maximum pulse, and a repetition rate. Given the rotation constraints of
the servo, neutral is defined to be the position where the servo has exactly the
same amount of potential rotation in the clockwise direction as it does in the
counter clockwise direction. It is important to note that different servos will
have different constraints on their rotation but they all have a neutral
position, and that position is always around 1.5 milliseconds (ms)
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The angle is determined by the
duration of a pulse that is applied to the control wire. This is called Pulse
width Modulation. The servo expects to see a pulse every 20 ms. The length of
the pulse will determine how far the motor turns. For example, a 1.5 ms pulse
will make the motor turn to the 90 degree position (neutral position).
When these servos are commanded to move they will move to the position and
hold that position. If an external force pushes against the servo while the
servo is holding a position, the servo will resist from moving out of that
position. The maximum amount of force the servo can exert is the torque rating
of the servo. Servos will not hold their position forever though; the position
pulse must be repeated to instruct the servo to stay in position.
When a pulse is sent to a servo that is less than 1.5 ms the servo rotates
to a position and holds its output shaft some number of degrees counter
clockwise from the neutral point. When the pulse is wider than 1.5 ms the
opposite occurs. The minimal width and the maximum width of pulse that will
command the servo to turn to a valid position are functions of each servo.
Different brands, and even different servos of the same brand, will have
different maximum and minimums. Generally the minimum pulse will be about 1 ms
wide and the maximum pulse will be 2 ms wide.
Another parameter that
varies from servo to servo is the turn rate. This is the time it takes from the
servo to change from one position to another. The worst case turning time is
when the servo is holding at the minimum rotation and it is commanded to go to
maximum rotation. This can take several seconds on very high torque servos.
Looking for servo bearings ??
TONEGAWA SEIKO
Corporate Profile
Synopsis
of Achievements
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1962 -- Tonegawa
Seiko created a vane pump for R/C fuel supply and for a time obtains
50% of the world share of RC fuel pump products.
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1962 -- This micro
pump fuel technology was bought and becomes "LON-Friend" Showa
Electric Corporation precision pump for dispersing agricultural
chemicals. Approximately 30,000 units have been produced over
10-years.
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1967 - Production
of chemical-resistant PVC for fixed volume detergents pump has been
started for Sony Trading.
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1969 - Received
orders from overseas to develop high power RC servos. However, the
servos were in conflict with existing regulations concerning the
Japanese export of weapons law. So, it was first developed for sale
as a domestic general-purpose RC servo.
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1975 - Received
request from Komatsu ZENOA co. to develop the current SSPS-105. Aim
was focused on mass production to keep prices down. Initially, this
product was mainly used for the United States market where it was
widely used for special effects in Hollywood movies, such as 007 and
RC robots which has been used in commercial films.
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1980 - Following
the tragedy of the challenger space shuttle, the SSPS-105 was used
in NASA. This model is still in NASA show room.
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The company has
also designed and produced special servos for use in such areas as
wind tunnels, pan-and-tilt moving mechanisms for underwater robotic
cameras and automatic photography equipment for NHK.
It was also successful in providing the free travel of the world's
first super-conductive magnet coil powered RC model ship. As well as
the design and manufacture of the mask controller for the main
characters in the Walt Disney musical "The Lion King." Other
successes include arranging six of one kW DC brusheless motors in
parallel to create 6 kW engine for airship
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PS050 Large servo
for R/C model
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PS050 control speed and maximum torque depend on
power input voltage.
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 690 oz in stall
torque @ 8.4 VDC
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580 oz in stall
torque @ 7.2 VDC
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480 oz in stall
torque @ 6 VDC
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350 oz in stall
torque @ 4.8 VDC
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The operating speed and hold torque power concern with input power.
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0.3 sec > 60 deg
@ 6 VDC
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PS050 This is the line-up that fills in the product
specs between our flagship model and general servos.
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May be mounted on over 2-meters class wingspan plane.
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2.98×1.75×3.16",10
oz
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The output shaft is supported by two large-diameter
ball bearings.
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JR connector is used. This can be connected to FUTABA
receiver, also.
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Component parts click In PDF File
Dimensions Click In PDF File
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