![]() The variable test weight is an accumulation of M10 galvanised washers – I had a heap of these left over from a decking project. The pulley is connected to the ‘load’ container using fishing line. The washers in the plastic container are used to weigh the apparatus down onto the bench. The pulley and blocks were 3D printed and connected to the edge of a 3mm MDF scrap so that the pulley could overhang the edge of a bench. The motor support block was described in this previous post. The pulley wheel has a diameter of 40mm and was designed in Fusion360. The test setup is shown in the photos below. ![]() In the rest of the analysis, each is referenced by its Test ID. Tests 1, 2 and 3 were conducted using the same motor, tests 4 and 5 each use different motors – a total of three motors.Ī summary of the motors used is given in the table below. This is an easy modification – a description of what needs to be done is found here. ![]() The unipolar/bipolar conversion (test 3) eliminates one of the wires (the red center tap) and allows the motor to be safely driven with doubled voltage. Standard 12V stepper driven by a ULN2003 driver board using a half wave step pattern.5V stepper modified to bipolar configuration driven by L298 half bridge using a half wave step pattern.Standard 5V stepper driven by a ULN2003 driver board in a half wave pattern but at 50% motor overvoltage.Standard 5V stepper driven by a ULN2003 driver board using a half wave step pattern.Standard 5V stepper driven by a ULN2003 driver board using a full wave step pattern.My testing trying to determine which motors, and what configuration, would suit my robotics project, so I tested five different configurations of motor/motor driver: The motor datasheet gives the following specifications: These stepper motor with integrated gearbox are extremely popular with makers due to their really low cost and hacking potential. They are manufactured in large quantities for the HVAC industry, where they are used as actuators for airflow control in ducts and vanes. This 28BYJ-48 is a 5V unipolar geared stepper motor. This will be an average value, given that the current will vary up and down when each stepper coil is energised. The input power is the voltage supplied times the current drawn (VI) to run the motor, measured in Watts (W). In SI units this is often given as Nm (Newton metres), but any ‘force’ and ‘distance’ dot product could be used (eg, lb⋅ft). It is measured as the cross product between the distance vector (the distance from the pivot point to the point where force is applied) and the force vector. Torque is a measure of how much a force acting on an object causes that object to rotate. So in this application I want to get the most output motor torque for the power input (voltage and current) for different motor variations. However, I really wanted to dig down to understand what I could do to optimize the output of these motors.Īs the electrical power in the bot comes from a battery pack it is important to get the best out of this limited resource. I wanted to replace the DC motors in my SmartCar bot (see this previous post) with stepper motors to get more precise control. ![]() So what are the parameters for these motors and how hard can we push them? Why Test? They usually come with a ULN2003 based driver board, making them super easy to use, and they have been used in countless hobby applications. Stepper motors are great motors for position control and one of the least expensive options for makers to use is the 28BYJ series of motors.
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