ActuatorPage - Revision history

Elcanoadmin: /* Steering System */

2026-06-12T23:01:13Z

‎Steering System

Elcanoadmin: /* Steering System */

2026-06-12T22:46:37Z

‎Steering System

Elcanoadmin: /* Rotary servos */

2026-06-12T22:38:30Z

‎Rotary servos

Elcanoadmin: /* WARNING: Servo Problems */

2026-06-12T22:36:07Z

‎WARNING: Servo Problems

Elcanoadmin: /* Drive System */

2026-06-12T22:27:46Z

‎Drive System

ZeroTrunks: /* WARNING: Servo Problems */

2021-08-18T23:39:36Z

‎WARNING: Servo Problems

ZeroTrunks: /* Linear servos */

2021-08-18T23:39:08Z

‎Linear servos

ZeroTrunks: /* Servo Problems */

2021-08-18T23:37:23Z

‎Servo Problems

Tfolsom: /* Rotary servos */

2019-07-10T16:04:49Z

‎Rotary servos

Tfolsom: /* Drive System */

2019-07-10T15:53:00Z

‎Drive System

@@ Line 36: / Line 36: @@
 == Steering System ==
 There are two main steering signals:
@@ Line 41: / Line 44: @@
 . Signal In is a 5 V analog feedback signal that gives the pointing angle of the wheel. There is one such signal for each of the two front wheels. More details on [[SteeringSensor]].
 The linear steering servo on the Catrikes https://www.servocity.com/hdls-6-2-12v  has 25 lb. thrust with  6" throw. In the past we have used 4" throw. A more suitable part may be https://www.servocity.com/motors-actuators/linear-actuators/heavy-duty-linear-actuators. The servo is powered by a pulse signal.
@@ Line 55: / Line 56: @@
 Students built an H-bridge circuit board to swap positive and negative voltages, but it never quite worked. We then discovered that the Arduino Motor Control shield can control the actuator when powered from its own 12V supply. This is the preferred design as of 2026.
 == Braking System ==

@@ Line 44: / Line 44: @@
 === Linear servos ===
-The linear steering servo on the Catrikes https://www.servocity.com/hdls-6-2-12v  has 25 lb. thrust with  6" throw. In the past we have used 4" throw. A more suitable part may be https://www.servocity.com/motors-actuators/linear-actuators/heavy-duty-linear-actuators. The servo is powered by a pulse signal. The actuator would be powered by a relay to give it either +12V or -12V and use angle feedback to stop motion. Using the actuator requires hardware and software changes.
+The linear steering servo on the Catrikes https://www.servocity.com/hdls-6-2-12v  has 25 lb. thrust with  6" throw. In the past we have used 4" throw. A more suitable part may be https://www.servocity.com/motors-actuators/linear-actuators/heavy-duty-linear-actuators. The servo is powered by a pulse signal.
 The steering servo or actuator is powered by 12V DC. It produces 5V DC which can be used by other equipment. Steering is controlled by sending a pulse to the actuator. A pulse width of approximately 1 ms will cause the actuator to fully extend (right turn on Catrike). A pulse of about 2 ms will fully retract the actuator. A pulse of 1.5 ms will keep the vehicle pointed straight ahead. There is some variation in these voltages; thus the Catrikes have a mechanical adjustment for fine-tuning the position for going straight. Typically there are about 30 pulses per second; the exact rate does not matter. At 12V, servo operating speed is 56mm/s with no load or 35 mm/s at maximum load.
 The actuator interfaces to the Arduino over a three wire servo connector that is standard for RC planes and cars. The three wires are Signal Out, Ground, and Power. The power wire is not used since both the actuator and Arduino have their own sources of power. The actuator is fused for 5 Amps and has blown fuses. Be careful not to drive it beyond physical limits.
 == Braking System ==

← Older revision		Revision as of 22:38, 12 June 2026
Line 49:		Line 49:

	The actuator interfaces to the Arduino over a three wire servo connector that is standard for RC planes and cars. The three wires are Signal Out, Ground, and Power. The power wire is not used since both the actuator and Arduino have their own sources of power. The actuator is fused for 5 Amps and has blown fuses. Be careful not to drive it beyond physical limits.		The actuator interfaces to the Arduino over a three wire servo connector that is standard for RC planes and cars. The three wires are Signal Out, Ground, and Power. The power wire is not used since both the actuator and Arduino have their own sources of power. The actuator is fused for 5 Amps and has blown fuses. Be careful not to drive it beyond physical limits.
−
−	~~=== Rotary servos ===~~
−
−	~~The ELF uses a i00600 Torxis rotary servo.~~
−
−	~~https://www.pololu.com/product/1390~~

	== Braking System ==		== Braking System ==

← Older revision		Revision as of 22:36, 12 June 2026
Line 49:		Line 49:

	The actuator interfaces to the Arduino over a three wire servo connector that is standard for RC planes and cars. The three wires are Signal Out, Ground, and Power. The power wire is not used since both the actuator and Arduino have their own sources of power. The actuator is fused for 5 Amps and has blown fuses. Be careful not to drive it beyond physical limits.		The actuator interfaces to the Arduino over a three wire servo connector that is standard for RC planes and cars. The three wires are Signal Out, Ground, and Power. The power wire is not used since both the actuator and Arduino have their own sources of power. The actuator is fused for 5 Amps and has blown fuses. Be careful not to drive it beyond physical limits.
−
−	~~===<pre style="color: red">WARNING: Servo Problems</pre>===~~
−
−	It is important to note that under certain circumstances the servo can critically damage itself. It is a $300 part and we have had ten of them fail. Most of the failed servos were used for braking; this poor performance was the motivation for changing to the solenoid braking system. It appears that the servo needs its power turned on only AFTER providing it a PWM signal. Further, providing it a signal corresponding to its current position will prevent it from trying to move during startup. The low-level firmware (early 2019) has been adapted to perform this, with an optional external relay board.
−
−	<blockquote>So, worth noting that the linear actuators claim a duty cycle of 25%. I’ve just identified the driver chip, which has a duty cycle of 20% at 2A — with no thermal shutdown or safety. If you use the actuator continuously, it will just die. The driver is the Toshiba TB6612FNG, available from digikey.com TB6612FNG, C,8, EL Toshiba Semiconductor and Storage \| Integrated Circuits (ICs) \| DigiKeyMotor Driver Power MOSFET Parallel 24-SSOP}}
−
−	Thinking about this some more; once we’re using a PID we can use the deltas — cap them to prevent long-distance moves, and add them to an accumulator to keep track of total distance commanded. If the accumulator fills, we enter an error state and can’t steer. Then reduce the accumulator at a fixed rate, so that steering availability returns over time … or, probably easier… we could just use a different motor driver. Wire the driver to the DC motor in the servo that failed, and use the external feedback instead of the potentiometer inside the actuator.
−	~~- Ben Rockhold (December 2018)</blockquote>~~

	=== Rotary servos ===		=== Rotary servos ===

@@ Line 23: / Line 23: @@
 The ELF has two chains. One is driven by pedaling and the other by an electric motor. Both chains have freewheels, so they do not interfere with each other.
-The electric motor is powered by an e-bike controller. The ELF uses a Kelly controller. The Catrikes are scheduled to be upgraded to the same controller:  https://www.kellycontroller.com/shop/kbs-e/
+The electric motor is powered by an e-bike controller. The trikes use a Kelly controller. https://www.kellycontroller.com/shop/kbs-e/
 The e-bike controller converts the main voltage (36 or 48V) from DC to three phase to power the motor. The power can draw 25 or 30 Amp and is potentially lethal. Interface to the e-bike controller is an analog signal from the low-level board that gives the throttle.

@@ Line 50: / Line 50: @@
 The actuator interfaces to the Arduino over a three wire servo connector that is standard for RC planes and cars. The three wires are Signal Out, Ground, and Power. The power wire is not used since both the actuator and Arduino have their own sources of power. The actuator is fused for 5 Amps and has blown fuses. Be careful not to drive it beyond physical limits.
-==='''<pre style="color: red">WARNING: Servo Problems</pre>'''===
+===<pre style="color: red">WARNING: Servo Problems</pre>===
 It is important to note that under certain circumstances the servo can critically damage itself. It is a $300 part and we have had ten of them fail. Most of the failed servos were used for braking; this poor performance was the motivation for changing to the solenoid braking system. It appears that the servo needs its power turned on only AFTER providing it a PWM signal. Further, providing it a signal corresponding to its current position will prevent it from trying to move during startup. The low-level firmware (early 2019) has been adapted to perform this, with an optional external relay board.

@@ Line 50: / Line 50: @@
 The actuator interfaces to the Arduino over a three wire servo connector that is standard for RC planes and cars. The three wires are Signal Out, Ground, and Power. The power wire is not used since both the actuator and Arduino have their own sources of power. The actuator is fused for 5 Amps and has blown fuses. Be careful not to drive it beyond physical limits.
-=== Servo Problems ===
+<pre style="color: red">=== WARNING: Servo Problems ===</pre>
 It is important to note that under certain circumstances the servo can critically damage itself. It is a $300 part and we have had ten of them fail. Most of the failed servos were used for braking; this poor performance was the motivation for changing to the solenoid braking system. It appears that the servo needs its power turned on only AFTER providing it a PWM signal. Further, providing it a signal corresponding to its current position will prevent it from trying to move during startup. The low-level firmware (early 2019) has been adapted to perform this, with an optional external relay board.
-Ben Rockhold (December 2018) wrote:
+<blockquote>So, worth noting that the linear actuators claim a duty cycle of 25%. I’ve just identified the driver chip, which has a duty cycle of 20% at 2A — with no thermal shutdown or safety. If you use the actuator continuously, it will just die. The driver is the Toshiba TB6612FNG, available from digikey.com TB6612FNG, C,8, EL Toshiba Semiconductor and Storage | Integrated Circuits (ICs) | DigiKeyMotor Driver Power MOSFET Parallel 24-SSOP}}
-So, worth noting that the linear actuators claim a duty cycle of 25%. I’ve just identified the driver chip, which has a duty cycle of 20% at 2A — with no thermal shutdown or safety. If you use the actuator continuously, it will just die. The driver is the Toshiba TB6612FNG, available from digikey.com TB6612FNG,C,8,EL Toshiba Semiconductor and Storage | Integrated Circuits (ICs) | DigiKeyMotor Driver Power MOSFET Parallel 24-SSOP
+Thinking about this some more; once we’re using a PID we can use the deltas — cap them to prevent long-distance moves, and add them to an accumulator to keep track of total distance commanded. If the accumulator fills, we enter an error state and can’t steer. Then reduce the accumulator at a fixed rate, so that steering availability returns over time … or, probably easier… we could just use a different motor driver. Wire the driver to the DC motor in the servo that failed, and use the external feedback instead of the potentiometer inside the actuator.
+ - Ben Rockhold (December 2018)</blockquote>
 === Rotary servos ===

@@ Line 62: / Line 62: @@
 === Rotary servos ===
-The ELF uses a rotary actuator.
+The ELF uses a i00600 Torxis rotary servo.
 == Braking System ==