Control Outputs

The DS models have two digital or analog control outputs. These outputs allow control of, among other things:

• Fan speed controller
• Eddy current dynamometer
• Hydraulic dynamometer valve
• Throttle

The outputs have several working modes according to what you want to control.

Digital Mode

In digital mode, you get a voltage output from 0 to 5 volts. It can only have two states: off (0V) and on (5V). It can be used to control devices on/off. For example, to turn on a fan when the roller reaches a certain speed.

Output Power

The outputs have low current capacity. In all cases, it is necessary to use some type of amplification, such as a relay or an optocoupler.

Analog/PWM Mode

In analog mode, a variable voltage between 0 and 5 volts is generated. In PWM mode, a pulse width modulation (PWM) signal is also generated variably. In this case, the voltage ranges from 0 to 5 volts as a digital square signal, but what is controlled is the pulse width or duty cycle, between 0% and 100%.

Select the type of signal according to the device you want to control. The most common use is for controlling "eddy" type dynamometers.

Dynamometer Control

Eddy dynamometers typically require a DC voltage between 0 and 192V. The output voltage or current will be proportional to the control signal. This type of controller requires high working power, as dynamometer current usually ranges between 20 and 40 amperes. Dynamometer manufacturers usually offer controllers with phase angle control through thyristors/triacs. In the output stage of these controllers, it will always be necessary to have a rectifier bridge with the appropriate current and some type of protection.

Stepper Motor Mode

In stepper motor mode, both outputs are used to generate control signals to manipulate a stepper motor through a stepper motor driver. The two signals are "PULSE" and "DIRECTION". The Accudyno system is responsible for managing the count of the necessary pulses for the stepper motor movement.

The number of travel pulses defines the total angle that the stepper motor is capable of rotating. This is defined in the software by a single working range number. To calculate this value, you can use the following formula:

Total Number of Pulses = Motor Steps per Revolution x Number of Turns x Number of Microsteps

For example, for a typical 200 pulse per revolution motor that needs to manipulate a valve with 2.5 turns of travel, working with 2 microsteps:

Total Pulses = 200 x 2.5 x 2 = 1000 total pulses

In the software, we will configure the maximum travel value of the controller at 1000.

Zero Adjustment

For simplification purposes of the valve mechanics, we will not include a zero indicator switch for the motor. Due to the way stepper motors work (open loop), the Accudyno system does not know the actual position of the motor, but rather assumes the position based on the movement that was generated. For this reason, it is important that when the interface is turned on, the motor is in its initial position (valve closed). In this way, upon startup, the interface will assume that the motor is in the zero position.

Similarly, if the motor lacks the strength to move the valve, or in case of a power outage, the interface is likely to lose track of the actual position of the valve.

Servo Mode

Servo mode generates a low frequency PWM signal with a variable pulse between 1ms and 2ms. This signal is suitable for controlling servomotors, such as the micro servos used in aeromodeling.

Servo Power Supply

Although the Accudyno system has a 5V output, it is recommended that the servo be powered by an external power supply to avoid generating interference in the internal measurement circuits of the Accudyno interface.

Connection

Number	Function	Range
1	OUT1 Signal	Configurable output: Digital Analog PWM Servo STEP/PUL in Stepper Motor mode
2	OUT2 Signal	Configurable output: Digital Analog PWM Servo DIR in Stepper Motor mode
3	GND	0V