HITEC General Servo - Manual

This document contains general servo information and frequently asked questions regar-
ding the use and care of Hitec servos. Please note that modifying your servo will void the
warranty.
Pulse Data
All Hitec servos require 3-5V peak to peak square wave pulse. Pulse duration is from
0.9mS to 2.1mS with 1.5mS as center. The pulse refreshes at 50Hz (20mS).
Voltage Range
All Hitec Servos can be operated within a 4.8V-6V. range.
Only the HS-50 operates exclusively with 4 Nicad cells ( 4.8 volt ).
Wire Color Meanings
On all Hitec servos the Black wire is 'ground', the Red wire ( center ) is 'power' and the
third wire is 'signal'.
Direction of Rotation
All Hitec servos turn Clockwise direction ( CW ).
1. Servos are rated for Speed and Torque. In many cases, Hitec will create one servo
and then gear it for speed and sacrifice torque, then create its twin, geared for torque
at the sacrifice of speed, i.e. 525/545, 625/645, 925/945.
2. If you are not sure, it is better to have more torque than you need, as torque is your
friend.
3. When in doubt ask your peers about servo application questions. Look at what others
are using in comparable applications. Usually the kit manufacturer will suggest a servo
of a certain physical size and torque value specification in the aircraft, car or boat
plans. It is wise to follow their guidelines.
4. Even though micro servos like the HS-81 may offer 38oz/in of torque, they are not
appropriate for larger powered aircraft due to the flight loads placed on the control
surfaces during flight. The geartrain can fail under excessive flight loads.
Smaller servos have thinner gears that are inherently more fragile than those of
"standard" sized servos.
1. Instantaneous Response
The digital micro processor sends out signals five times faster than analog servos.
This results in much quicker response.
2. Precision Resolution
There are many more steps in the digital format compared to the conventional analog
version. This means the servo is capable of finer adjustments.
3. Enormous Standing Torque
The standing torque of the digital servos is 3 times that of the analog counterpart.
Check it out, try moving the transmitter stick or wheel and at the same time hold the
servo horn to keep it from twisting.
You will not be able to prevent the horn from turning. Muy fuerte mi amigo!
4. Metal Servo Arm
Hitec is the first servo manufacturer to include metal horns as a standard accessory
for our digital servo line. Not just any metal horn but our own design super horn.
Hitec engineers were not satisfied with the traditional plastic or composite servo arms
as they would flex and fail long before the servo reaches its maximum torque capa-
bility. Just another very unique feature of Hitec digital servos.
Changing Gears
Hitec offers gear sets for all our servos and these are available from your local hobby
shop or from a mail order retailer. To replace the gears on any servo, carefully lay out the
new gears on a clean work surface to have them available for re-assembly. You will also
need a supply of servo gear lubricant. We suggest the Hitec lube part # 58450.
Loosen or remove the screws located on the bottom of the servo case enough to pop the
upper case off and expose the gears. If any gears or shafts are stuck in the upper case,
remove them and plug them back into position on the lower case. Now carefully remove
the gears while placing them in approximate order on your work surface in front of you.
One of the most frequently asked questions is "What servo should I use for ..".
While there have been many magazine articles that attempted to provide a general rule
of thumb to answer these questions, we offer you the following suggestions.
In addition to our full line of analog servos, Hitec produces several digital servo products.
These powerful servos offer programmable features such as, direction of rotation, center
point, end points, failsafe option, speed and dead bandwidth adjustment using Hitec's
proprietary programmer and servo tester device.(Model HFP-10).
What are the advantages of digital servos ?
The Appropriate Servo for Your Application
Digital Servo Information
Servo Maintenance
General Servo Information General Servo Information
Special Warning for Digital servos !!!
(1) If you accidentally plug in the Hitec "S" type digital servo into the old Airtronics(Sanwa)
receiver, this will blow up the servo circuits so please take special care.
(2) Digital servos consume tremendous amount of power, so dry batteries cannot be used
at all. Use large capacity Nicd batteries or better yet NiMH batteries.
(3) Do not use BEC system built in most 2 channel receivers.
Make sure you bypass the BEC for stable operation.
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