We're doing an electromechanical trebuchet that can control it's shooting distance. Our total budget is around 600 usd.
We've been thinking a lot about what kind of stepper motor, what kind of driver and how to implement the release function of the motor (to launch the trebuchet).
Our current idea is to use a stepper motor connected to an Arduino Uno Rev3 with a microprocessor and a stepper motor shield. Does it sound like a good idea?
The class Adafruit_StepperMotor (represents a stepper motor attached to the shield) has the function
"void release(void);". What bothers me is that I'm not sure if the "released" motor will induce a momentum in the opposite direction due to Lenz Law as it spins. Or is the circuit disconnected making it impossible for induction?
Any tips and recommendations are most welcome and appreciated.
If the motor is driving the arm directly then reverse the motor at the desired release point. That will flick the rope off the hook.
I would not pick a stepper for this. A DC motor and encoder will be much more efficient. The acceleration profile of the arm cannot be estimated in advance so the stepper will always be too fast or too slow. Too fast = missed steps and a crash. Too slow = less power and less range.
If you are not driving the arm directly then you need to tell us more about the project.
Can you post/attach a diagram of how you are going to configure your trebuchet?
Is the motor releasing the arm?
OR
Is the motor powering the arm?
If the latter, first calculate the amount of torque you are going to need.
You can bring a stepper to a stop by powering both/all the windings together.
BUT
It would be hard to say if you could stop it quick enough to give a predictable launch arm angle.
If you keep the arm low mass then the stopping effort will be low compared to the launching effort needed to get your load up to speed.
So before getting any steppers or drivers, calculate, the energy you are going to need to drive the trebuchet and load.
This will also dictate the power supply voltage and current you will need.
We're doing an electromechanical trebuchet that can control it's shooting distance. Our total budget is around 600 usd.
We've been thinking a lot about what kind of stepper motor, what kind of driver and how to implement the release function of the motor (to launch the trebuchet).
Our current idea is to use a stepper motor connected to an Arduino Uno Rev3 with a microprocessor and a stepper motor shield. Does it sound like a good idea?
The class Adafruit_StepperMotor (represents a stepper motor attached to the shield) has the function
"void release(void);". What bothers me is that I'm not sure if the "released" motor will induce a momentum in the opposite direction due to Lenz Law as it spins. Or is the circuit disconnected making it impossible for induction?
Any tips and recommendations are most welcome and appreciated.
//Simon
So you are cranking back the arm using a motor, then want to release by removing motor power?
An undriven stepper has significant residual cogging torque, and if over-spun will totally fry your stepper
driver (or even explode). This is not the way to do things.
The motor should not spin on release, a separate release mechanism is the way to do this.
Steppers are not efficient, consider a DC gear motor and an encoder to detect arm angle.
