Hello,
I have an experimental setup where I use two mirrors (one from each side of the surface, facing each other) to reflect light from an above source onto a surface where I view my samples. I want to be able to change the angle/rotation of the mirror using a controller, so that I can control the angle of light hitting my samples. Depending on the price, the resolution should be 1 degree or better. Each mirror is currently 1" x 6" x 1/8" pieces of mirror-polished aluminum.
I am unfamiliar with general robot parts. Should I use a stepper motor, brushed DC motor, or servo motor to achieve my goal? I would also need the corresponding motor controller, I suppose. And any suggestions on how to couple the motor to the mirror? I thought about creating a custom metal sleeve, and tap-welding it to the back of aluminum mirror. We have a fairly large machine shop available at my university, so it may be possible.
To interface the motor controller, I was planning to use a program such as NI LabVIEW. I have analog outputs of 0-10 V and 4-20mA current output modules that I could use, if needed. I also have digital outputs but I am unfamiliar with how to use them, but I could if needed–it would just require me asking more people for assistance.
Anyway, thanks for reading and taking the time to assist me.
Thanks for your help! It looks like a pan/tilt kit was not exactly what I was looking for, but it may work. I was hoping to be able to rotate the mirror in place from one end, so that the center of the mirror is always in the same location. However, It is no problem to provide constant power to the servos. I was hoping to find something that just rotates the mirror without leaving that cylindrical volume. Any recommendations for servo controllers? I will need 2 pan/tilt kits so a total of at least 8 servos.
Thanks for the information. I found a product on here that gave me some hope that I may be able to rotate my mirror about its center of mass. Could this be used? robotshop.com/productinfo.aspx?pc=RB-Lyn-48&lang=en-US The description states that its wrist rotates approximately 180 degrees. I would also need the grip to close completely and fairly tightly. Are there other grips that may work better?
Thanks. So I decided I actually want this motor: servocity.com/html/20_rpm_precision_gear_motor.html since I don’t need an encoder, and I only need a small 20 RPM motor. This motor’s stats:
Operating Voltage: 6-12V
No load current: 80 mA
Based on the tutorial, I need a motor controller that operates motors between 6-12V and then oversize the controller with respect to current, since I don’t know the current required under load. From this it looks like a lot of these low power brushed DC motor controllers on this page will work: robotshop.com/low-power-motor-controllers.html.
However, I still don’t quite understand how to connect the motor controller “between” the servo controller and the motor. How do they interface? I am planning to use the Phidgets servo controller specifically for PC interface via LabVIEW.
Also, I was originally planning to use an electronic speed controller between the servo controller and the motor. Such as servocity.com/html/precision_digital_speed_contro.html. Would this take the place of a motor controller?
Hello, could someone help me finalize this setup with figuring out the controllers for my motors/actuators? If I want to control 2 DC gear motors very similar to this one below except lower RPM (the ones I have are from the same manufacturer but are 10rpm and 20rpm and have a no load current of 80mA):
Also can anyone suggest an appropriate R/C controller from the link above to use with such motors?
I want to control everything through LabVIEW. I have an I/O board for LabVIEW with various analog and digital inputs and outputs (4-20mA, 0-10V, etc.). I know I can control the Phidgets servo controller through LabVIEW, but I’m not sure about the motor controllers. Do they need to be connected to the Phidgets board or can they connect directly to my NI/LabVIEW board?
CBenson, thanks for your response. I will look for a DC motor controller that accepts R/C input to control the 2 DC motors.
This is not for a mobile robot, it will always be connected to a computer for LabVIEW control. A reason the Phidgets board was attractive to me is that Phidgets already offers example LabVIEW code for servo control (phidgets.com/programming_resources.php). I also wanted to check if the Phidgets board was capable of controlling the gearmotors directly or if the separate DC motor controller was needed. I may ask Phidgets tech support, since there is some example code for “Motor Control”.
On your last point, I don’t know if we are confusing the terminology. I was asking about connecting the DC gearmotors not the Hitec servos. I know that the Hitec servos are compatible and can be controlled directly using the Phidgets board. I guess I was just not sure how to control the gearmotors. Fortunately, your comments just helped me out quite a bit! Thanks again.
Most hobby pan/tilt systems are servo based. In your situation, a worm-gear based system would be ideal because it does not move when the power is cut off, though we don’t have any available. The Lynxmotion Pan/Tilt Kit is reliable and is easy to use. However, it needs to be kept powered at all times in order to retain an angle. You may also want to add a counterweight to reduce vibration. You can control this with any servo controller (you would need at least a four servo controller, though most can operate many more than that). Resolution is a theoretical 180 degrees /2000 pulses = 0.09 degrees (in practice it is a lot more though).
Being able to rotate an object about its center of mass is not easy since manufacturers would need to somehow predict the size of the object, or make the frame variable. If you want to control it with LabView, consider the Phidgets Advanced Servo 8-Motor since there’s already code available.
The gear motor you chose also has a built-in encoder. A servo controller cannot directly operate a DC gear motor; if you don’t plan on using the encoder, all you need is an RC motor controller between the servo controller and the motor. This tutorial on choosing a motor controller should help.
Looking at the specs, it is unfortunate they don’t list the current under load. You can either contact them to see what it is or assume it is ~5 times the no load current.
You seem to have chosen the Phidgets servo controller. Note that the Phidgets servo controller you chose needs to be connected to a computer at all times - it cannot operate on its own. If you are making a mobile robot, you might choose a microcontroller or servo controller with onboard microcontroller.
You need to check the specs of the board to see if it can directly control servo motors; in theory it can, but double check to be certain.
