The device was designed as a commercially available model servos tester. This is the first step to control/drive model servos and the subsequent device design of a test robotic arm.
The base part of the device is mikroprocesor PIC16F628 which provides displaying servo rotation (range 0-100%) via IO 4511 (binary signal decoder 7 segment) and three NPN transistors.
Then there is microprocessor reset button and 4 buttons for mode select. Fuse is F1 for securing the power supply of the servo. The circuit is powered via terminal X1 by 5VDC.
It is necessary to monitor the connection polarity and the size of the voltage including an external securing. This part has been omitted because of the simplicity of the device and also this device is only for a first tests.
JP1 switch selects cycle speed - closed slow / opened fast . Servo connector on the left side has pins values from up to down - GND / + 5VDC / signal.
Installation and commissioning are carried out in a standard way. First make PCB interconnections if you do not use two side PCB. 7-segment display units can be used with only 3 digits too, but must be preserved
logic of the replacement pins. Crystal oscilator 20MHz has to be followed, because rplacement with 8MHz or 10MHz part will be slowing the device. This will be shown at first glance by flickering displays and also on incorrect servos behavior.
After the the whole completation and with programmed processor, you can just simply connect voltage 5VDC ( double check correct of the voltage polarity before you connect it to the device ). Booted test of display as a deduction 9-0. Next, you will see 000 and now you are in manual mode. You can use drive the tester by a buttons now - see more on video . Materials for creating PCB, file with code for programming mikroprocesor and parts list you can find here .
Updated on Oct.4th 2016 - Modifications for servos with a range of 180 degrees.
For the project of robotic manipulator will be used a servo HJS3315D with a range of 180 degrees. When this servo was connected to the tester, servo works only within 90 degrees, therefore it was necessary to adjust the control pulse ranges in SW. Here is a modified HEX . New driving ranges for this scope is 38,5Hz operating frequency and it is equivalent to 26ms. The minimum pulse length, 0% is 0.8ms, 50% corresponds to 2ms and therefore the maximum length 100% is 2.6ms. It follows that the minimum pulse remained, but the length of the control pulse rose from 1ms to 1.8ms.
Servo-tester ver.1
The device was designed as a commercially available model servos tester. This is the first step to control/drive model servos and the subsequent device design of a test robotic arm.
In the beginning some usefull information. Modeller's servo operates at a frequency between 50 HZ and 60 Hz. Servo is based on the minimum pulse length 0,8ms. The regulation range of servo itself is then 1mS thus corresponds to 1% 10us.
Duty cycle at 60Hz is therefore 4.8% to 10.8%.
The base part of the device is mikroprocesor PIC16F628 which provides displaying servo rotation (range 0-100%) via IO 4511 (binary signal decoder 7 segment) and three NPN transistors.
Then there is microprocessor reset button and 4 buttons for mode select. Fuse is F1 for securing the power supply of the servo. The circuit is powered via terminal X1 by 5VDC.
It is necessary to monitor the connection polarity and the size of the voltage including an external securing. This part has been omitted because of the simplicity of the device and also this device is only for a first tests.
JP1 switch selects cycle speed - closed slow / opened fast . Servo connector on the left side has pins values from up to down - GND / + 5VDC / signal.
Pressing the button will automatically switch mode.
Buttons:
Buttons:
- Cycle - cycle between 0 and 100% up and down
- 3S - jump change of 3 predefined positions - 0% 50% 100%
- (+) - increase 1
- (-) - decrease 1
Installation and commissioning are carried out in a standard way. First make PCB interconnections if you do not use two side PCB. 7-segment display units can be used with only 3 digits too, but must be preserved
logic of the replacement pins. Crystal oscilator 20MHz has to be followed, because rplacement with 8MHz or 10MHz part will be slowing the device. This will be shown at first glance by flickering displays and also on incorrect servos behavior. After the the whole completation and with programmed processor, you can just simply connect voltage 5VDC ( double check correct of the voltage polarity before you connect it to the device ). Booted test of display as a deduction 9-0. Next, you will see 000 and now you are in manual mode. You can use drive the tester by a buttons now - see more on video . Materials for creating PCB, file with code for programming mikroprocesor and parts list you can find here .
The device is not intended to unprofessional public, and its publication does not transfer copyrights. Construction can be used for private testing only and any commercial use is prohibited.
The author reject any responsibility for any damage that might arise during construction, commissioning and operation of this device. By downloading a file with documents acknowledge familiarity and acceptance of these terms.
Updated on Oct.4th 2016 - Modifications for servos with a range of 180 degrees. For the project of robotic manipulator will be used a servo HJS3315D with a range of 180 degrees. When this servo was connected to the tester, servo works only within 90 degrees, therefore it was necessary to adjust the control pulse ranges in SW. Here is a modified HEX . New driving ranges for this scope is 38,5Hz operating frequency and it is equivalent to 26ms. The minimum pulse length, 0% is 0.8ms, 50% corresponds to 2ms and therefore the maximum length 100% is 2.6ms. It follows that the minimum pulse remained, but the length of the control pulse rose from 1ms to 1.8ms.
