Analogue Inputs

Analogue Inputs and +5V External Supply

This is the Analogue commanding port of SOLO, through these inputs/outputs, you can control the Speed or Torque of your motors by sending analogic commands using PWM pulses with any frequency above 5kHz or sending direct analogue voltages rated from 0V to 5V, you can also use them to limit the current fed into your Motor in a completely Analogue Mode (see the Minimum Required Wirings Section)


This part is composed of 5 pins as can be seen below:

Analogue Inputs 1

1. “GND” PIN: This is the Ground or in another word the 0V reference of SOLO, so if you want to send an analogue commands to SOLO, you need to make sure the Ground of the commanding unit ( Arduino, Raspberry Pi , … ) is shared and connected with SOLO at this point..

2. “+5V” PIN: This is a 5V/1A output to supply external peripherals or controllers, remember that this output is fused, and if you drain more than 1A, the fuse will be blown ( internally ) and this output will become dysfunctional for safety reasons..

3. “DIR” PIN: This is the Direction control pin which is a digital pin, accepting voltage levels of 0V or 3.3V, so by giving each of these values, the connected Motor to SOLO, will either rotate in C.W. direction or C.C.W. direction.


Remember that DIR pin is NOT 5V tolerant and if you like to connect it to a 5V source, you must use a resistor of a value between 1kΩ to 2.2kΩ (the exact value doesn’t matter, it just must be in this range)

4. “P/F” PIN: This is a pin with three main different functionalities depending on the control Mode and the type of the motor you select as below:

In Open Loop mode of 3 phase motors : It will act as increasing or decreasing the injected power into the Motor, so by applying 0V of analogue voltage or 0% duty cycle of PWM, there will be no power injected inside the Motor, and at 5V or 100% duty cycle of PWM, it will apply the maximum deliverable power into the Motor.

In Closed-Loop mode of DC, BLDC and PMSM motors: It will act as the current Limit, so if the voltage applied to this pin is 5V, it will stop the current floating to the motor ( current Limit at zero), and if this pin is left open it will allow up to 32A floating into your Motor, so any value between these will define the value of the current limit. You can calculate the current limit value based on the following formulas:

In case of using PWM:

The current Limit value = ((100 – duty cycle percentage of PWM at P/F input)/100) * 32.0

In case of using Analogue Voltages:

The current Limit value = ((5.0 – the voltage at P/F input)/5.0) * 32.0

In Closed-loop mode of AC Induction Motors:
it will act as the reference for magnetizing current reference known as “Id” which is in charge of generation of stator flux. The maximum amount of current that can be injected into the motor using this pin is 10Amps. So in order to calculate the amount of magnetizing current you can use the following formulas:

In case of using PWM:

The Magnetizing current value = ((100 – duty cycle of PWM at P/F input)/100) * 10.0

In case of using Analogue Voltages:

The Magnetizing current value = ((5.0 – the voltage at P/F input)/5.0) * 10.0


5. S/T: This is the input for controlling the Speed or Torque of the Motor connected to SOLO. in each of these Modes it will act like:

In Torque mode: if you apply 100% duty cycle to this pin, without having a current limit, will try to inject 32A of current inside your motor , and knowing that the amount of Torque has direct relationship with the injected current as :

Applied Motor Torque = Current inside of the Motor* Torque Constant.

In Brushless motors the Current causing the torque generation is known as Quadrature Current.

In Speed mode: if you apply 0V or 0% duty cycle to this pin, it will keep your motor’s speed at 0 RPM, and at the same time by applying 100% duty cycle it will force your motor to go to the maximum speed considered based on the Motor type as below, of course your motor should be able to reach to maximum speed, otherwise it will stay at it’s nominal speed even if you keep increasing the duty cycle. (look at the piano switch settings)

Analogue Inputs 2