RC Wheelchair 2 - Revision history

Alnwlsn: /* Version 2 */

2019-08-08T16:08:15Z

Version 2

← Older revision		Revision as of 12:08, 8 August 2019
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	===Version 2===		===Version 2===
	Not long after the initial version, I decided to slightly alter the setup ~~so that both radio modules run the exact same sketch, making them more universal~~. This is now listed on its own project page [[gLora module]].		Not long after the initial version, I decided to slightly alter the setup. This is now listed on its own project page [[gLora module]].

			Now, both remote control and h-bridge board use the same radio module, and handle the client/server architecture on their own time. Each device is informed when a new message comes in, and can transmit out messages. Buffer size is now increased to 32 bytes.

	==5 - Remote Control==		==5 - Remote Control==

Alnwlsn: /* 4 - LoRa radio modules (v1) */

2019-08-07T04:16:14Z

4 - LoRa radio modules (v1)

← Older revision		Revision as of 00:16, 7 August 2019
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	First, I hooked up two pairs of IR leds and matching photodiodes. Then, I designed a rotor and housing to attach to the motor axle and the back housing of the motor. One interesting thing I learned when making these is that the ABS plastic I was using is somewhat transparent to IR light, but the parts were thick enough for this to not matter so much. The pairs of sensors are placed 90 degrees out of phase of each other, ie, when one sensor is in the center of a rotor vane, the other is at the edge of the rotor vane. When the rotor rotates and we observe the signals coming off of the sensors, we can figure out the direction and speed of the motor. Imagine drumming your fingers on a table; you can easily tell if the motion is left to right or right to left, as well as how fast you are doing it - this is the mechanical/electrical equivalent. Two digital signals are sent to Atmega interrupt pins (pin change interrupts, which there are a lot of), for processing as a quadrature encoder. By observing which signal changes first, we can figure out what direction the motor is turning, and by counting changes and dividing by time, we can calculate speed.		First, I hooked up two pairs of IR leds and matching photodiodes. Then, I designed a rotor and housing to attach to the motor axle and the back housing of the motor. One interesting thing I learned when making these is that the ABS plastic I was using is somewhat transparent to IR light, but the parts were thick enough for this to not matter so much. The pairs of sensors are placed 90 degrees out of phase of each other, ie, when one sensor is in the center of a rotor vane, the other is at the edge of the rotor vane. When the rotor rotates and we observe the signals coming off of the sensors, we can figure out the direction and speed of the motor. Imagine drumming your fingers on a table; you can easily tell if the motion is left to right or right to left, as well as how fast you are doing it - this is the mechanical/electrical equivalent. Two digital signals are sent to Atmega interrupt pins (pin change interrupts, which there are a lot of), for processing as a quadrature encoder. By observing which signal changes first, we can figure out what direction the motor is turning, and by counting changes and dividing by time, we can calculate speed.

	==4 - LoRa radio modules ~~(v1)~~==		==4 - LoRa radio modules==
	[[File:Wch2-lora-v1.jpg\|thumb\|A lora-promini module, encased in Kapton tape for insulation. ]]		[[File:Wch2-lora-v1.jpg\|thumb\|A lora-promini module, encased in Kapton tape for insulation. ]]
	I originally used nrf24l01 modules for the radio communications between robot and remote control. These don't have the best range, and after reading about the impressive range from LoRa radio modules, I decided I would try these instead. Since I might want to experiment with different radios in the future, I decided I would also make the radios into an independent module, which operate the radio separately from the h-bridge and remote control microcontrollers. That way, I could also avoid any nonsense with different radios requiring different pins, different power supplies, and different signal voltages.		I originally used nrf24l01 modules for the radio communications between robot and remote control. These don't have the best range, and after reading about the impressive range from LoRa radio modules, I decided I would try these instead. Since I might want to experiment with different radios in the future, I decided I would also make the radios into an independent module, which operate the radio separately from the h-bridge and remote control microcontrollers. That way, I could also avoid any nonsense with different radios requiring different pins, different power supplies, and different signal voltages.
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	Files are at the end of this article.		Files are at the end of this article.
	Relevant files are rf95-client-i2c and rf95-server-i2c, which are the actual sketches loaded on the LoRa radio modules.		Relevant files are rf95-client-i2c and rf95-server-i2c, which are the actual sketches loaded on the LoRa radio modules.

			===Version 2===
			Not long after the initial version, I decided to slightly alter the setup so that both radio modules run the exact same sketch, making them more universal. This is now listed on its own project page [[gLora module]].

	==5 - Remote Control==		==5 - Remote Control==

Alnwlsn: /* Files */

2019-08-04T23:09:00Z

Files

← Older revision		Revision as of 19:09, 4 August 2019
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	Eagle files for this H-bridge board can be found here: [[File:Wchmotor2-eagle.zip]]		Eagle files for this H-bridge board can be found here: [[File:Wchmotor2-eagle.zip]]

	A dump of my Arduino sketch folder contains all the revisions for my radio modules, and the sketches running on the robot and remote control. Be careful, earlier versions sometimes use different hardware!		A dump of my Arduino sketch folder contains all the revisions for my radio modules, and the sketches running on the robot and remote control. Be careful, earlier versions sometimes use different hardware! - [[File:Wch2-arduino-v3.zip]]

Alnwlsn at 23:07, 4 August 2019

2019-08-04T23:07:43Z

← Older revision		Revision as of 19:07, 4 August 2019
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	The resulting board works fine, although there could be some improvements to improve the board layout (this is only the second board I have designed, ever). Additionally, the board lacks seperation for the logic power and motor power, forcing me to add it in later when I realized I still needed the board powered even when I wasn't using the motors.		The resulting board works fine, although there could be some improvements to improve the board layout (this is only the second board I have designed, ever). Additionally, the board lacks seperation for the logic power and motor power, forcing me to add it in later when I realized I still needed the board powered even when I wasn't using the motors.

	~~Eagle files for this board can be found here: [[File:Wchmotor2-eagle.zip]]~~

	==2 - DC motor controller (Supporting components and processor)==		==2 - DC motor controller (Supporting components and processor)==
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	It's not perfect, but does work. The main limitation is the speed at which I can draw things on the screen, so the radio messages get sent out a little less often than I would like. This can probably be optimized, but I'll leave that for the future.		It's not perfect, but does work. The main limitation is the speed at which I can draw things on the screen, so the radio messages get sent out a little less often than I would like. This can probably be optimized, but I'll leave that for the future.

			==Files==
			None of the below files are organized well for a "release", but they are here anyways for your own research purposes.

			Eagle files for this H-bridge board can be found here: [[File:Wchmotor2-eagle.zip]]

			A dump of my Arduino sketch folder contains all the revisions for my radio modules, and the sketches running on the robot and remote control. Be careful, earlier versions sometimes use different hardware!

Alnwlsn: /* 4 - LoRa radio modules (v1) */

2019-08-04T22:06:14Z

4 - LoRa radio modules (v1)

← Older revision		Revision as of 18:06, 4 August 2019
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	Again, not perfect, and not the most efficient, but again, does work. The size of 30 bytes was chosen because the size the Arduino I2C commands can work with at a time is apparently 32 bytes. Of note is that the server/client architecture is probably not needed within the modules themselves; it would probably be preferred that I add some extra flag wires and let the remote control and h-bridge controller handle it themselves. This would make both radio modules identical, and get rid of a little bit of delay - as it stands now, the server radio module sends out its transmit buffer immediately instead of waiting for new, current data to be copied in.		Again, not perfect, and not the most efficient, but again, does work. The size of 30 bytes was chosen because the size the Arduino I2C commands can work with at a time is apparently 32 bytes. Of note is that the server/client architecture is probably not needed within the modules themselves; it would probably be preferred that I add some extra flag wires and let the remote control and h-bridge controller handle it themselves. This would make both radio modules identical, and get rid of a little bit of delay - as it stands now, the server radio module sends out its transmit buffer immediately instead of waiting for new, current data to be copied in.

	~~Arduino sketch for~~ this ~~version is here:~~		Files are at the end of this article.
	Relevant files are rf95-client-i2c and rf95-server-i2c, which are the actual sketches loaded on the LoRa radio modules.		Relevant files are rf95-client-i2c and rf95-server-i2c, which are the actual sketches loaded on the LoRa radio modules.

Alnwlsn: /* Aug 2019 version */

2019-08-04T22:04:03Z

Aug 2019 version

← Older revision		Revision as of 18:04, 4 August 2019
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	===Aug 2019 version===		===Aug 2019 version===
			I took an 3.3v Arduino Pro mini and attached a RFM95 Lora module. I used the RadioHead library for controlling the radio. Finally, I added a logic level converter which provides the Arduino I2C pins and the UART pins, either of which could also be used for general purpose IO, and interface the whole module to a 5v system or whatever.

	To make a long story short, the radio modules appear as I2C slave devices. Taking after the RadioHead radio library examples, there are 2 versions of the module programming, a server module which rides on the robot, and a client module which the remote controls use.		To make a long story short, the radio modules appear as I2C slave devices. Taking after the RadioHead radio library examples, there are 2 versions of the module programming, a server module which rides on the robot, and a client module which the remote controls use.

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	Again, not perfect, and not the most efficient, but again, does work. The size of 30 bytes was chosen because the size the Arduino I2C commands can work with at a time is apparently 32 bytes. Of note is that the server/client architecture is probably not needed within the modules themselves; it would probably be preferred that I add some extra flag wires and let the remote control and h-bridge controller handle it themselves. This would make both radio modules identical, and get rid of a little bit of delay - as it stands now, the server radio module sends out its transmit buffer immediately instead of waiting for new, current data to be copied in.		Again, not perfect, and not the most efficient, but again, does work. The size of 30 bytes was chosen because the size the Arduino I2C commands can work with at a time is apparently 32 bytes. Of note is that the server/client architecture is probably not needed within the modules themselves; it would probably be preferred that I add some extra flag wires and let the remote control and h-bridge controller handle it themselves. This would make both radio modules identical, and get rid of a little bit of delay - as it stands now, the server radio module sends out its transmit buffer immediately instead of waiting for new, current data to be copied in.

			Arduino sketch for this version is here:
			Relevant files are rf95-client-i2c and rf95-server-i2c, which are the actual sketches loaded on the LoRa radio modules.

	==5 - Remote Control==		==5 - Remote Control==

Alnwlsn at 21:56, 4 August 2019

2019-08-04T21:56:35Z

@@ Line 35: / Line 35: @@
 [[File:Wh2-encoder-asm.png|thumb|Cad assembly of the encoder, showing how the placement of the sensors (holes in red blocks) creates a 90 degree phase offset.]]
 First, I hooked up two pairs of IR leds and matching photodiodes. Then, I designed a rotor and housing to attach to the motor axle and the back housing of the motor. One interesting thing I learned when making these is that the ABS plastic I was using is somewhat transparent to IR light, but the parts were thick enough for this to not matter so much. The pairs of sensors are placed 90 degrees out of phase of each other, ie, when one sensor is in the center of a rotor vane, the other is at the edge of the rotor vane. When the rotor rotates and we observe the signals coming off of the sensors, we can figure out the direction and speed of the motor. Imagine drumming your fingers on a table; you can easily tell if the motion is left to right or right to left, as well as how fast you are doing it - this is the mechanical/electrical equivalent. Two digital signals are sent to Atmega interrupt pins (pin change interrupts, which there are a lot of), for processing as a quadrature encoder. By observing which signal changes first, we can figure out what direction the motor is turning, and by counting changes and dividing by time, we can calculate speed.
 ==5 - Remote Control==

Alnwlsn at 21:27, 4 August 2019

2019-08-04T21:27:50Z

← Older revision		Revision as of 17:27, 4 August 2019
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	[[File:Wh2-encoder-asm.png\|thumb\|Cad assembly of the encoder, showing how the placement of the sensors (holes in red blocks) creates a 90 degree phase offset.]]		[[File:Wh2-encoder-asm.png\|thumb\|Cad assembly of the encoder, showing how the placement of the sensors (holes in red blocks) creates a 90 degree phase offset.]]
	First, I hooked up two pairs of IR leds and matching photodiodes. Then, I designed a rotor and housing to attach to the motor axle and the back housing of the motor. One interesting thing I learned when making these is that the ABS plastic I was using is somewhat transparent to IR light, but the parts were thick enough for this to not matter so much. The pairs of sensors are placed 90 degrees out of phase of each other, ie, when one sensor is in the center of a rotor vane, the other is at the edge of the rotor vane. When the rotor rotates and we observe the signals coming off of the sensors, we can figure out the direction and speed of the motor. Imagine drumming your fingers on a table; you can easily tell if the motion is left to right or right to left, as well as how fast you are doing it - this is the mechanical/electrical equivalent. Two digital signals are sent to Atmega interrupt pins (pin change interrupts, which there are a lot of), for processing as a quadrature encoder. By observing which signal changes first, we can figure out what direction the motor is turning, and by counting changes and dividing by time, we can calculate speed.		First, I hooked up two pairs of IR leds and matching photodiodes. Then, I designed a rotor and housing to attach to the motor axle and the back housing of the motor. One interesting thing I learned when making these is that the ABS plastic I was using is somewhat transparent to IR light, but the parts were thick enough for this to not matter so much. The pairs of sensors are placed 90 degrees out of phase of each other, ie, when one sensor is in the center of a rotor vane, the other is at the edge of the rotor vane. When the rotor rotates and we observe the signals coming off of the sensors, we can figure out the direction and speed of the motor. Imagine drumming your fingers on a table; you can easily tell if the motion is left to right or right to left, as well as how fast you are doing it - this is the mechanical/electrical equivalent. Two digital signals are sent to Atmega interrupt pins (pin change interrupts, which there are a lot of), for processing as a quadrature encoder. By observing which signal changes first, we can figure out what direction the motor is turning, and by counting changes and dividing by time, we can calculate speed.

			==5 - Remote Control==
			[[File:Wch2-remote-control.jpg\|thumb\|The remote control unit of the system, made from the old hand control of the wheelchair, because I wanted to reuse the original joystick.]]
			The entirety of the original controller was contained inside the joystick handle. The original joystick is a quite good one, so I decided to gut the unusable electronics and reuse the case. There's plenty of space inside to fit lots of switches, a battery, and microcontroller. The only issue is that the base of this case is aluminum, so I had to place the radio module on the outside (for now).

			The design of the remote control is really pretty simple. Switches and buttons are hooked up to digital inputs on an Arduino Pro mini, and potentiometers and the joystick are attached to the analog inputs. An 18650 battery and boost converter provides 5 volts to the system. The tiny OLED screen is an I2C device, as is the LoRa radio module I made.
			In software, I smooth the joystick inputs, and compute what the target speeds of the left and right wheels are given the position of the joystick. This gets sent out over the radio, and the h-bridge box returns with some telemetry information, which gets displayed on the screen.

			It's not perfect, but does work. The main limitation is the speed at which I can draw things on the screen, so the radio messages get sent out a little less often than I would like. This can probably be optimized, but I'll leave that for the future.

Alnwlsn at 21:11, 4 August 2019

2019-08-04T21:11:39Z

← Older revision		Revision as of 17:11, 4 August 2019
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	[[File:Wchmc2-v3-hbridge.jpg\|thumb\|The current (Aug 2019) incarnation of the project, showing the inside of the H-bridge module (the main electronics that ride on the robot platform). Messy, but does work quite well. From left, the H bridge PCB, main power relay, and LoRa radio module, with the Atmega1284 controller board at the bottom.]]		[[File:Wchmc2-v3-hbridge.jpg\|thumb\|The current (Aug 2019) incarnation of the project, showing the inside of the H-bridge module (the main electronics that ride on the robot platform). Messy, but does work quite well. From left, the H bridge PCB, main power relay, and LoRa radio module, with the Atmega1284 controller board at the bottom. The brown stain visible inside the lid is magic smoke residue from a wiring error :).]]
	After my attempts to modify the settings of the existing wheelchair controller I accidentally erased all the board settings and was left with an inoperable board. Since it is almost impossible to locate the correct file for my particular controller, I decided to construct a new motor controller. This would give me the added advantage of full control over each wheel motor, and I could write all my own control algorithms (though these do not necessarily come easily). I eventually extended this to support rotary encoders on each wheel, a custom radio control setup, and a robotic arm, turning an old electric wheelchair into a powerful general robot platform.		After my attempts to modify the settings of the existing wheelchair controller I accidentally erased all the board settings and was left with an inoperable board. Since it is almost impossible to locate the correct file for my particular controller, I decided to construct a new motor controller. This would give me the added advantage of full control over each wheel motor, and I could write all my own control algorithms (though these do not necessarily come easily). I eventually extended this to support rotary encoders on each wheel, a custom radio control setup, and a robotic arm, turning an old electric wheelchair into a powerful general robot platform.

Alnwlsn at 21:10, 4 August 2019

2019-08-04T21:10:13Z

← Older revision		Revision as of 17:10, 4 August 2019
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	After my attempts to modify the settings of the existing wheelchair controller I accidentally ~~erases~~ all the board settings and was left with an inoperable board. Since it is almost impossible to locate the correct file for my particular controller, I decided to construct a new motor controller. This would give me the added advantage of full control over each wheel motor, and I could write all my own control algorithms (though these do not necessarily come easily).		[[File:Wchmc2-v3-hbridge.jpg\|thumb\|The current (Aug 2019) incarnation of the project, showing the inside of the H-bridge module (the main electronics that ride on the robot platform). Messy, but does work quite well. From left, the H bridge PCB, main power relay, and LoRa radio module, with the Atmega1284 controller board at the bottom.]]
			After my attempts to modify the settings of the existing wheelchair controller I accidentally erased all the board settings and was left with an inoperable board. Since it is almost impossible to locate the correct file for my particular controller, I decided to construct a new motor controller. This would give me the added advantage of full control over each wheel motor, and I could write all my own control algorithms (though these do not necessarily come easily). I eventually extended this to support rotary encoders on each wheel, a custom radio control setup, and a robotic arm, turning an old electric wheelchair into a powerful general robot platform.

			This project is ongoing, and as it stands today, was completed over a series of many months, and I didn't document most of it at the time. The following is, in general, the process I went through to develop this system.

	==1 - DC motor controller (H-bridge)==		==1 - DC motor controller (H-bridge)==