My challenge is to create a “tool” controlled by a tethered laptop operating windows xp pro. The laptop would control a continuous rotating DC motor driving a toothed belt around pulleys. The belt speed would be programmable from 0.5 mm a second to 5.0 mm a second and a belt clamp needs to travel 360mm (14”). Two separate drive units would be operating at the same time with each traveling a different belt speed and a different overall distance. It would require software…like the ServoCity 8- SCB program…to allow motor direction, belt speed, belt travel distance and return to home commands to be created and stored. Unfortunately, I do not have any programming experience.
My preference is to operate DC geared motors at 12V nominal creating 75-125 ounces of torque. If RC servos would be better for simplicity I could manage less torque with 50 ounces minimum.
I need to hit a home run on this the first time; there is no time for R&D. So, I ask for your help to recommend specific 12V brushed geared motors, brushed motor controllers, PC interface, and driving software. Feel free to ask any questions.
Thank you Coleman. I greatly appreciate your customer service…very helpful.
Can you please expand on how belt speed is calculated regarding pulley diameter? Is there a calculator or Excel spread sheet avaiable? Since the motor RPM is variable, pulley diameters are selected so the maximum motor RPM gives you just a little more belt speed than you require?
Is geared DC motor RPM accurate at low speeds? Is there a minimum RPM to maintain accuracy…such as don’t go below “X” RPM?
Please recommend the most “elementary user friendly” control software that will allow me to create and save programs, establish “home” position, establish a “stage” position, establish distance by time movement, pauses, and return to “home”.
For computer control of a DC motor, we suggest a serially controlled DC motor controller. Since you plan to operate two, you can choose a dual motor controller or two single motor controllers. You should find the pulley system to you know the outer diameter of the drive pulley so you can get an idea of the motor’s RPM. If you need the system to move at exactly the correct speed, you’ll need a gear motor with an encoder and a motor controller which can take encoder input (or digital inputs).
You can calculate the speed of the belt using the formula v=ω*r where ω= angular velocity in radians per second. The units will be in whatever units your radius is in (cm, mm, inches etc.). Convert revolutions per minute (rpm) to radians per second use 1rpm = 0.1047 rad/s.
Using a motor controller it should be relatively accurate. You would greatly increase accuracy using an encoder.
Not really. Inexpensive motors have greater internal resistance and friction (it’s really hard to quantify) and as the RPM gets really low, the power is consumed simply to overcome internal friction etc. This may cause more “slip” as static (stationary) friction becomes kinetic (moving) friction.
“Please recommend the most “elementary user friendly” control software that will allow me to create and save programs, establish “home” position, establish a “stage” position, establish distance by time movement, pauses, and return to “home”.”
Easier said than done. It’s a very specific application, so no manufacturer has developed exactly that software. Phidgets has a lot of sample code in a variety of languages, so it’s a good place to start.
