PULSE PROPORTIONAL RADIO REMOTE CONTROL SYSTEM
I have read many descriptions of this system and today I feel that it was either that the technology was too young then and explanations lengthy or that it was intended to make it look so difficult at that time by manufacturers. I discussed the system with some friends into RC electronics and I came to the conclusion that many of us CONFUSED THE PULSES SENT BY THE TX AND THE COMMAND PULSES FED TO THE SERVOS. The problem I think was the description the command pulse was being sent from the TX which has a variable width from 1 MS to 2MS(1MS=1/1000 second). Actually, the TX sends short pulses with a duration of only .25MS to define the START and END of a command pulses created at the decoder. In modern days digital language, the TX sends clock pulses serially. It send a set of clock pulses, pause, then repeats. The number of clocks is always number of channels plus 1. Each clock is both the end and the start of the command pulse created at the decoder except for the first and last clocks. Had authors used "clocks" and not pulse in describing tansmissions, confusion would have been less. In fact, what the oscilloscope displayed as coming from the TX were small bars looking like matchsticks.For a 2 channel system, there were 3 bars and no command pulses. The duration from the first bar, to the second, then to the third is what will create command pulses in the decoder. When one stick is moved, he last two bars move to the right. When the other stick is moved, the last bar moves to the right. These bars can also be transmitted to a TV and can be seen as horizontal bars.Thus:
THE TRANSMITTER SENDS CLOCKS OF.25MS DURATION WHICH IS RECEIVED BY THE RX WHICH WILL CLOCK A SHIFT REGISTER DECODER WHICH WILL CREATE THE COMMAND PULSES FOR THE SERVOS.
THE SERVO
The servo is probaby the most ingenious system developed in the fifties. Before today's servo developed, there were crude predecessors. Immediately before it was the analog servo which had tendencies to delay and to overshoot in its response. Before analog servos were the various geared motors which did not have feedbacks to position the servo arm. ON/OFF pulses oscillated the motor at a given position.
The Mather/Spreng servo today is still the same servo in principle developed by thse two Americans in the fifties
AN INCOMING PULSE FROM THE DECODER IS SUMMED UP WITH A LOCALLLY GENERATED PULSE OF THE OPPOSITE POLARITY. WHEN THEY ARE OF THE SAME DURATION, THEY CANCEL EACH OTHER. THE RESIDUAL OF THE LONGER PULSE DRIVES EITHER OF TWO AMPLIFIER TRANSISTORS. A POSITIVE RESIDUAL PULSE DRIVES ONE AMP,A NEGATIVE RESIDUAL PULSE DRIVES THE OTHER AMP. THESE AMPS IN TURN DRIVES A BRIDGE TO TURN THE MOTOR CW OR CCW. THE FINAL OUTPUT SHAFT OF THE SERVO TURNS A POT WHICH WILL ADJUST THE LOCALLY GENERATED PULSE TO MATCH THE INCOMING PULSE TO STOP THE MOTOR. BY THEN,IT HAS TAKEN UP A NEW POSITION. THE PULSE KEEPSON REPEATING ON AVERAGE AT 6O TIMES PER SECOND.
THE DECODER
The decoder does two things: it creates the command pulses and separates them into channel ports. The first incoming clock from the RX turns CH1 port ON, the second clock OFF and turns the next CH2 port ON, third clock turns CH2 port OFF. A PAUSE is introduced before the clock frame repeats. This pause is detected and resets the decoder to begin on CH1 port again on the next clock.
MODULATION
Modulation has something to do on how the clocks are sent. In Amplitude Modulation, the amplitude of the carrier wave is varied. In RC, the CW is shut off to represent a clock. In Frequency Modulation, the frequency is shifted slightly to represent a clock. These modulations are detected in the receiver. It's amplified, filtered, shaped and sent to the decoder as clocks.
Saturday, August 7, 2010
PULSE PROPORTIONA RADIO SYSTEM
PULSE PROPORTIONAL RADIO REMOTE CONTROL SYSTEM
I have read many descriptions of this system and today I feel that it was either that the technology was too young then and explanations lengthy or that it was intended to make it look so difficult at that time by manufacturers. I discussed the system with some friends into RC electronics and I came to the conclusion that many of us CONFUSED THE PULSES SENT BY THE TX AND THE COMMAND PULSES FED TO THE SERVOS. The problem I think was the description the command pulse was being sent from the TX which has a variable width from 1 MS to 2MS(1MS=1/1000 second). Actually, the TX sends short pulses with a duration of only .25MS to define the START and END of a command pulses created at the decoder. In modern days digital language, the TX sends clock pulses serially. It send a set of clock pulses, pause, then repeats. The number of clocks is always number of channels plus 1. Each clock is both the end and the start of the command pulse created at the decoder except for the first and last clocks. Had authors used "clocks" and not pulse in describing tansmissions, confusion would have been less. In fact, what the oscilloscope displayed as coming from the TX were small bars looking like matchsticks.For a 2 channel system, there were 3 bars and no command pulses. The duration from the first bar, to the second, then to the third is what will create command pulses in the decoder. When one stick is moved, he last two bars move to the right. When the other stick is moved, the last bar moves to the right. These bars can also be transmitted to a TV and can be seen as horizontal bars.Thus:
THE TRANSMITTER SENDS CLOCKS OF.25MS DURATION WHICH IS RECEIVED BY THE RX WHICH WILL CLOCK A SHIFT REGISTER DECODER WHICH WILL CREATE THE COMMAND PULSES FOR THE SERVOS.
THE SERVO
The servo is probaby the most ingenious system developed in the fifties. Before today's servo developed, there were crude predecessors. Immediately before it was the analog servo which had tendencies to delay and to overshoot in its response. Before analog servos were the various geared motors which did not have feedbacks to position the servo arm. ON/OFF pulses oscillated the motor at a given position.
The Mather/Spreng servo today is still the same servo in principle developed by thse two Americans in the fifties
AN INCOMING PULSE FROM THE DECODER IS SUMMED UP WITH A LOCALLLY GENERATED PULSE OF THE OPPOSITE POLARITY. WHEN THEY ARE OF THE SAME DURATION, THEY CANCEL EACH OTHER. THE RESIDUAL OF THE LONGER PULSE DRIVES EITHER OF TWO AMPLIFIER TRANSISTORS. A POSITIVE RESIDUAL PULSE DRIVES ONE AMP,A NEGATIVE RESIDUAL PULSE DRIVES THE OTHER AMP. THESE AMPS IN TURN DRIVES A BRIDGE TO TURN THE MOTOR CW OR CCW. THE FINAL OUTPUT SHAFT OF THE SERVO TURNS A POT WHICH WILL ADJUST THE LOCALLY GENERATED PULSE TO MATCH THE INCOMING PULSE TO STOP THE MOTOR. BY THEN,IT HAS TAKEN UP A NEW POSITION. THE PULSE KEEPSON REPEATING ON AVERAGE AT 6O TIMES PER SECOND.
THE DECODER
The decoder does two things: it creates the command pulses and separates them into channel ports. The first incoming clock from the RX turns CH1 port ON, the second clock OFF and turns the next CH2 port ON, third clock turns CH2 port OFF. A PAUSE is introduced before the clock frame repeats. This pause is detected and resets the decoder to begin on CH1 port again on the next clock.
MODULATION
Modulation has something to do on how the clocks are sent. In Amplitude Modulation, the amplitude of the carrier wave is varied. In RC, the CW is shut off to represent a clock. In Frequency Modulation, the frequency is shifted slightly to represent a clock. These modulations are detected in the receiver. It's amplified, filtered, shaped and sent to the decoder as clocks.
I have read many descriptions of this system and today I feel that it was either that the technology was too young then and explanations lengthy or that it was intended to make it look so difficult at that time by manufacturers. I discussed the system with some friends into RC electronics and I came to the conclusion that many of us CONFUSED THE PULSES SENT BY THE TX AND THE COMMAND PULSES FED TO THE SERVOS. The problem I think was the description the command pulse was being sent from the TX which has a variable width from 1 MS to 2MS(1MS=1/1000 second). Actually, the TX sends short pulses with a duration of only .25MS to define the START and END of a command pulses created at the decoder. In modern days digital language, the TX sends clock pulses serially. It send a set of clock pulses, pause, then repeats. The number of clocks is always number of channels plus 1. Each clock is both the end and the start of the command pulse created at the decoder except for the first and last clocks. Had authors used "clocks" and not pulse in describing tansmissions, confusion would have been less. In fact, what the oscilloscope displayed as coming from the TX were small bars looking like matchsticks.For a 2 channel system, there were 3 bars and no command pulses. The duration from the first bar, to the second, then to the third is what will create command pulses in the decoder. When one stick is moved, he last two bars move to the right. When the other stick is moved, the last bar moves to the right. These bars can also be transmitted to a TV and can be seen as horizontal bars.Thus:
THE TRANSMITTER SENDS CLOCKS OF.25MS DURATION WHICH IS RECEIVED BY THE RX WHICH WILL CLOCK A SHIFT REGISTER DECODER WHICH WILL CREATE THE COMMAND PULSES FOR THE SERVOS.
THE SERVO
The servo is probaby the most ingenious system developed in the fifties. Before today's servo developed, there were crude predecessors. Immediately before it was the analog servo which had tendencies to delay and to overshoot in its response. Before analog servos were the various geared motors which did not have feedbacks to position the servo arm. ON/OFF pulses oscillated the motor at a given position.
The Mather/Spreng servo today is still the same servo in principle developed by thse two Americans in the fifties
AN INCOMING PULSE FROM THE DECODER IS SUMMED UP WITH A LOCALLLY GENERATED PULSE OF THE OPPOSITE POLARITY. WHEN THEY ARE OF THE SAME DURATION, THEY CANCEL EACH OTHER. THE RESIDUAL OF THE LONGER PULSE DRIVES EITHER OF TWO AMPLIFIER TRANSISTORS. A POSITIVE RESIDUAL PULSE DRIVES ONE AMP,A NEGATIVE RESIDUAL PULSE DRIVES THE OTHER AMP. THESE AMPS IN TURN DRIVES A BRIDGE TO TURN THE MOTOR CW OR CCW. THE FINAL OUTPUT SHAFT OF THE SERVO TURNS A POT WHICH WILL ADJUST THE LOCALLY GENERATED PULSE TO MATCH THE INCOMING PULSE TO STOP THE MOTOR. BY THEN,IT HAS TAKEN UP A NEW POSITION. THE PULSE KEEPSON REPEATING ON AVERAGE AT 6O TIMES PER SECOND.
THE DECODER
The decoder does two things: it creates the command pulses and separates them into channel ports. The first incoming clock from the RX turns CH1 port ON, the second clock OFF and turns the next CH2 port ON, third clock turns CH2 port OFF. A PAUSE is introduced before the clock frame repeats. This pause is detected and resets the decoder to begin on CH1 port again on the next clock.
MODULATION
Modulation has something to do on how the clocks are sent. In Amplitude Modulation, the amplitude of the carrier wave is varied. In RC, the CW is shut off to represent a clock. In Frequency Modulation, the frequency is shifted slightly to represent a clock. These modulations are detected in the receiver. It's amplified, filtered, shaped and sent to the decoder as clocks.
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