joliebrise
New Member
My black box servo tester was used to see how an 08m would handle inputs from 0 to 2.4ms.
Would you be surpresed if I told you I got 9 turns from a Hitec sail drum servo. The box says 3.5
My article gives full details.
Tony
9. Input by r/c receiver
Marine R/C users will want to control their Picaxe microprocessor with their Transmitter/Receiver. Let’s look at the signal coming from the Receiver.
Manufacturers don’t seem to want to disclose this information; there are no standards. All I have found out is what signal is required by analogue Servos. Who knows what is the Digital signal?
Servo PWM specification
Hitec 0.9 to 2.1ms — 1.5ms mid-point
Futaba 1.1 to 1.9ms — 1.52ms mid-point
3 — 5v peak to peak square wave pulse
Peak refresh rate 50Hz (20ms)
Dead band 20 — 40 micros
Rx input to Picaxe
The white/orange signal wire is connected to pin3.
The red +ve power feed from the Rx can be connected if the Picaxe is used to supply power to the Rx. It may be advisable to separate the power sources as this avoids any electrical noise reaching Picaxe from the servo motor.
The black/brown earth connection must be used as it is the signal’s ground.
Picaxe reads Rx signal
Manual 2 page 155
The Rx signal is automatically multiplied by 100 as Picaxe only uses positive whole numbers ie 1.1ms = 110
Pulsin 3,1,w1
Reads the signal on ‘pin3’ and puts its value in the variable ‘w1’
‘w1’ is a word variable as it accepts values upto 1024. (Byte values upto 255) If you are using “Byte b0 and Word w3” variables in the same code be careful of the numbers. b1 and w1 are not alllowed. Read Manual 2 page 10
‘1’ starts the timing when the pulse goes from low to high.
Test
Connect up circuit and see where the joystick is positioned to make the leds light up. Try going max, min and central joystick positions to establish your Rx characteristics. Use these figures for your coding.
Results
Most Transmitters have a switch to alter the direction of servo travel and a lever to make small adjustments to the central point. Minimum — Mid point — maximum stick position.
Normal 40Hz min 100 — 146 — 185 max values of w1. Joystick adjuster +/- 8
Reverse 40Hz min 190 — 146 — 100 max.
Normal 2.4GHz min 118 — 146 — 180 max.
Testing Servos
When testing servos over a year ago I built two ‘Servo Tester’ black boxes to save time getting out the transmitter & receiver. It was also possible to add a scale in msec. You can find details and illuminating results. Look at the Arm and Drum servo tests.
Tester results 0 to 2.4ms min 280 — 120 — 15 max values of w1.
What is a Servo
The Hitec sail winch HS785-HB will make 9 turns from 0.5 to 2.05ms. The box says 3 to 4. Above and below these values, it will run continuously. “Not a lot of people know that”
Would you be surpresed if I told you I got 9 turns from a Hitec sail drum servo. The box says 3.5
My article gives full details.
Tony
9. Input by r/c receiver
Marine R/C users will want to control their Picaxe microprocessor with their Transmitter/Receiver. Let’s look at the signal coming from the Receiver.
Manufacturers don’t seem to want to disclose this information; there are no standards. All I have found out is what signal is required by analogue Servos. Who knows what is the Digital signal?
Servo PWM specification
Hitec 0.9 to 2.1ms — 1.5ms mid-point
Futaba 1.1 to 1.9ms — 1.52ms mid-point
3 — 5v peak to peak square wave pulse
Peak refresh rate 50Hz (20ms)
Dead band 20 — 40 micros
Rx input to Picaxe
The white/orange signal wire is connected to pin3.
The red +ve power feed from the Rx can be connected if the Picaxe is used to supply power to the Rx. It may be advisable to separate the power sources as this avoids any electrical noise reaching Picaxe from the servo motor.
The black/brown earth connection must be used as it is the signal’s ground.
Picaxe reads Rx signal
Manual 2 page 155
The Rx signal is automatically multiplied by 100 as Picaxe only uses positive whole numbers ie 1.1ms = 110
Pulsin 3,1,w1
Reads the signal on ‘pin3’ and puts its value in the variable ‘w1’
‘w1’ is a word variable as it accepts values upto 1024. (Byte values upto 255) If you are using “Byte b0 and Word w3” variables in the same code be careful of the numbers. b1 and w1 are not alllowed. Read Manual 2 page 10
‘1’ starts the timing when the pulse goes from low to high.
Code:
Init:
w1 = 0
main:
pulsin 3,1,w1 ; code to finding central point
if w1= 144 then high 1 ; light on and remains on at 144
elseif w1 = 146 then low 1 ; light off at 146
endif
goto mainConnect up circuit and see where the joystick is positioned to make the leds light up. Try going max, min and central joystick positions to establish your Rx characteristics. Use these figures for your coding.
Results
Most Transmitters have a switch to alter the direction of servo travel and a lever to make small adjustments to the central point. Minimum — Mid point — maximum stick position.
Normal 40Hz min 100 — 146 — 185 max values of w1. Joystick adjuster +/- 8
Reverse 40Hz min 190 — 146 — 100 max.
Normal 2.4GHz min 118 — 146 — 180 max.
Testing Servos
When testing servos over a year ago I built two ‘Servo Tester’ black boxes to save time getting out the transmitter & receiver. It was also possible to add a scale in msec. You can find details and illuminating results. Look at the Arm and Drum servo tests.
Tester results 0 to 2.4ms min 280 — 120 — 15 max values of w1.
What is a Servo
The Hitec sail winch HS785-HB will make 9 turns from 0.5 to 2.05ms. The box says 3 to 4. Above and below these values, it will run continuously. “Not a lot of people know that”
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