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1  Using Arduino / Motors, Mechanics, and Power / Re: Control of 6 12VDC linear actuators with Arduino Mega on: February 25, 2013, 01:12:14 am
I'll check into that, thanks for the response.  I'm relatively new to the whole Arduino world so I'm not as familiar with all the add-ons and options that are available to do this.  The other option I considered was just building a circuit with all the necessary transistors and H-bridges but I would rather avoid that if possible.
2  Using Arduino / Motors, Mechanics, and Power / Control of 6 12VDC linear actuators with Arduino Mega on: February 24, 2013, 08:19:41 pm
I'm currently working on a project that needs independent operation of 6 linear actuators.  I was planning on using an Arduino Mega with three motor shields but after looking around I can't say for sure if its possible to have three motor shields coupled with the Mega.  I just want to make sure that it is possible before purchasing the shields.  I have seen independent operation of 4 motors using 2 shields with some pin trimming.

The project is just extending one of the actuators after sensing a corresponding input and then retracting.  So I need 6 pins available for inputs as well.

The current draw of each actuator is 2A and they are 12V.  Only one actuator will be moving at any given time and I don't need to use PWM as they will be used full speed each direction.

Thanks
3  Using Arduino / Project Guidance / Re: Use of Arduino In Custom Vending Machine on: January 20, 2013, 03:23:17 pm
So if you push out the bottom package from the bottom of a stack of packages,   all the rest of the packages
in the stack are going to fall on top of your pushing device.

We have a "pushing block" in the design that takes the place of the package that is being dispensed so the stack remains at the same height until the actuator is fully retracted.
4  Using Arduino / Project Guidance / Re: Use of Arduino In Custom Vending Machine on: January 20, 2013, 04:14:44 am
I found the datasheet for that actuator at http://progressiveautomations.com/download.php?download_file=PA-15_Tubular_High-Speed_Linear_Actuator.pdf. It takes from 2A at no load to 9A at full load and max speed. If the load is expected to be light then MC33926-based H-bridges such as http://www.pololu.com/catalog/product/1213 should be suitable.

The homing sensor is likely to be an optical pickup that provides a signal once per revolution of the screw so that revolutions can be counted. Once you know its details, you can easily simulate that with an Arduino.

Thanks for your help, I appreciate it. The homing function I was originally referring to is done at the machine start up.  The VMC re-homes each motor at start up, if a motor takes too long to respond then a motor error is reported and that motor is shut down until the error is resolved.  You may have described another potential scenario with the feedback that we will need to simulate.
5  Using Arduino / Project Guidance / Re: Use of Arduino In Custom Vending Machine on: January 20, 2013, 04:02:32 am
How much force is required and what is the push distance? Servos like below or smaller (even some in the $7 range) might make a less expensive alternative motive source to a linear actuator.

http://www.hobbyking.com/hobbyking/store/__18743__Vigor_VSD_11YMB_MG_HV_Extra_Large_360_Degree_Winch_Servo_0_75sec_40kg_150g.html




14" push distance and the force just needs to be above 10lbs.  We considered using servo with a rack and pinion or a belt to do the moving, but I didn't realize they were that cheap.  I'll look around at some of them.
6  Using Arduino / Project Guidance / Re: Use of Arduino In Custom Vending Machine on: January 20, 2013, 02:44:09 am
Thanks for the responses.
To help clear things up we are using a linear actuator to essentially push the bottom package from a stack of packages into another section of the vending machine. After the package is dispensed, the actuator retracts to its original position.

liudr, that was our intention to essentially to send the power signal sent from the VMC to an Arduino and then operate the actuators through the arduino.  We just had the issue with the homing signal(the position feedback associated with the screw motor) sent from the VMC.  I'm currently checking if the homing function can just ignored or overridden through the VMC interface. If it can not be ignored, then we will figure it out with an oscilloscope. Thanks for the suggestion.

The selection of the linear actuators was just based on the force and speed it offered, we didn't anticipate the homing issue originally.
Here's a link for it:
http://progressiveautomations.com/tubular-high-speed-linear-actuator-tubular-high-speed-linear-actuator-stroke-size-force-lbs-speed-551sec-p-127.html


7  Using Arduino / Project Guidance / Re: Use of Arduino In Custom Vending Machine on: January 17, 2013, 10:21:00 pm
I don't know exactly what amperage the actuators require because it is not listed on the spec sheet, but I do know that they are DC. In a demonstration video on the actuator site they have one hooked up to a lab-type power supply (the kind with the red and black alligator clips), and on the display of that power supply it read 0.00 on whatever range of amps it was set on.  So I'm assuming it was low, unless it was set on kilo amps or something. I could contact the manufacturer for a precise range need be it.  Thank you for the help
8  Using Arduino / Project Guidance / Use of Arduino In Custom Vending Machine on: January 17, 2013, 05:51:57 pm
I am currently involved in designing and manufacturing a custom vending machine as part of a final year project for college.  My group consists of all mechanical engineers so we have not been exposed to too much programming in our curriculum and I am posting this in hopes of some guidance or if our ideas will even work. 

We plan on using linear actuators to do the physical dispensing of the product as we can not use traditional screw motors that are seen in most snack machines due to the nature of the product we will be dispensing.  Traditional vending machine controllers (VMC's) are available and pre-programmed to operate these screw motors as well as the coin dispensers and ordering operations.  We want to use an off the shelf VMC to avoid the programming required to control all the money functions and such. Our problem is that we do not believe that the off the shelf VMC will be able to control the linear actuators because the screw motors have a position feedback that the linear actuators do not.  The linear actuators also need a polarity shift in the power supply to retract (to clarify: switching the power supply leads on the actuator would do the opposite action, either extend or retract).  The linear actuators require 12 volts for operation and they just have the two power supply wires, the speed and force are constant.

Here is where we need advice: our idea was that we could intercept the the signal from the VMC with an arduino board (possibly with a motor shield) and then use the arduino to control the linear actuators, in a way tricking the VMC into thinking that it is operating the screw motors that it usually does. Again, we have little programming knowledge so we were wondering if this was even possibility or even the right approach to take

Side note: we have contacted multiple VMC companies to determine if their controllers would have a shot of operating the actuators but everyone we spoke with did not have enough technical knowledge to answer our questions.

Thanks
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