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Thread: Scorpion Mini question(s)

  1. Scorpion Mini question(s)

    Hi, I'm relatively new to robotics and had a few questions about one device in particular.

    Here's a little background, just to give you an idea of my experience/knowledge. I've been interested in electronics and robotics for a while, I just haven't had much formal education in either subject. I've taken a robotics course in college which I thoroughly enjoyed, and I've played around with some of the Lego Mindstorms stuff a bit. I'm still learning about electronics in general, so please bear with me as I muddle through some of this.



    I've had plenty of ideas over the years, but only recently have been motivated enough to give some of them a try. One thing I'd like to attempt is to play around a bit with the idea of home automation/security. Someone suggested I check out Phidgets, so I did.

    I recently bought a Phidget LCD Interface Kit, along with a few assorted components to play with. These included some simple analog sensors (light and heat) as well as some digital inputs and outputs (switches and LEDs). I haven't programmed anything yet, I've mostly just played around with the sample code that allows a user to monitor the inputs and toggle the outputs. And, of course, I've tooled around with sending messages to the LCD display. Altogether, it looks to be a nice little system.

    Another component I got was a small DC motor (well, two of them) off the TrossenRobotics.com site (which I see has been updated since I ordered). These were for a project I have in mind and I'd like to give it a shot. They were small 574:1 16mm motors which may or may not (hopefully MAY) be of use in my project:

    http://www.trossenrobotics.com/store...or-FF-050.aspx



    Which brings me to my questions (sorry for taking so long to get to them). I wanted to use the 8/8/8 interface to be able to control these two motors. Nothing too complex, just turn them on and off from time to time (a pretty tame duty cycle), reverse direction, maybe control speed, etc. I picked such a low-speed gear ratio (574:1) because I wanted very fine control of the motors and what they would manipulate (think: telescope automation).

    I was wondering how to control these motors. At first, I thought I could use a regular ol' SPST relay for turning the motors on and off, while a DPDT relay could control the forward/reverse aspect. Then I got to talking to a co-worker who told me of the magic of transistors and how THEY could help me. To make it even cooler, he told me about how opto-isolators would let me do the same thing, without the risk of screwing up my interface kit.

    Eventually, he mentioned "motor controller" and I remembered something I saw on the site. The Scorpion Mini DC motor controller looked like what I needed. While it might be fun to build my own, I think I'd rather not reinvent the wheel and just use soemthing that is already well-established.

    http://www.trossenrobotics.com/store...pion-Mini.aspx



    So (finally), here are my questions in regards to the Scorpion Mini controller:

    1) CONNECTION
    What does the controller plug in to? It looks to have a three-wire lead to it, does it connect to an analog sensor port on the 8/8/8 interface kit? Or would I need some special device in order to control it using the same software that talks with my interface kit.

    2) ON/OFF
    This is probably an dumb question, but would the controller allow me to simply turn on and off a small DC motor?

    3) DIRECTION
    A slightly-less-dumb question: would I be able to use the controller to reverse the direction of the motor?

    4) SPEED
    Could I vary the speed of the motor? I don't know if this could be acheived by simply pulsing power to the motor or if there are fancier methods.

    5) POWER
    I'm assuming that I would use a separate power supply (a rechargable pack or 9-volt battery or something) to power the motor. Is this correct?

    6) RISK
    Is there any risk of damaging the interface kit through (mis)use of the controller? I wasn't sure if it used some kind of isolator or something.

    7) SOLENOID
    Could I use the controller to operate a solenoid instead of a motor? This might be a moot question, as I suppose I could just use a simple relay for that.

    8) DOCUMENTATION
    Is there a file I could download to read up more on the controller? I apologize if I missed a link to it on the site.



    Sorry if this post is a bit long-winded, but I tend to do that a lot. I figure I'd rather over-explain the situation (if resources permit) and give people too much information, than to be too vague and have to go back and forth on stuff.

    Anyway, I hope I haven't bored anyone, and I really hope to hear feedback from people. I like the Phidgets products so far, the site is pretty well-put-together, and it looks like you have a nice community here on these forums. Also, if I managed to post in the wrong section, please feel free to move this to a more appropriate place.

    Thanks in advace!

  2. Re: Scorpion Mini question(s)

    Quote Originally Posted by xyzzy1126 View Post
    http://www.trossenrobotics.com/store...pion-Mini.aspx

    So (finally), here are my questions in regards to the Scorpion Mini controller:

    1) CONNECTION
    What does the controller plug in to? It looks to have a three-wire lead to it, does it connect to an analog sensor port on the 8/8/8 interface kit? Or would I need some special device in order to control it using the same software that talks with my interface kit.
    The 8/8/8 is no good for motor control, both because of the current limitations of the outputs, and because you'd have no speed or direction control.

    The three-lead input found on most of the motor controllers we sell is an R/C control signal input. This signal is either generated by either a servo controller or an R/C receiver. To control motors via a PC, you would connect the PC to a servo controller (such as the PhidgetServo 4-Motor controller), and the servo controller to a motor controller.

    Like this!

    PC sends servo position command to the servo controller; servo controller generates R/C control signal; motor controller generates variable duty-cycle PWM signal to drive the motor.

    Quote Originally Posted by xyzzy1126 View Post
    2) ON/OFF
    This is probably an dumb question, but would the controller allow me to simply turn on and off a small DC motor?

    3) DIRECTION
    A slightly-less-dumb question: would I be able to use the controller to reverse the direction of the motor?

    4) SPEED
    Could I vary the speed of the motor? I don't know if this could be acheived by simply pulsing power to the motor or if there are fancier methods.

    5) POWER
    I'm assuming that I would use a separate power supply (a rechargable pack or 9-volt battery or something) to power the motor. Is this correct?
    Yes, yes, yes, and yes..

    Quote Originally Posted by xyzzy1126 View Post
    6) RISK
    Is there any risk of damaging the interface kit through (mis)use of the controller? I wasn't sure if it used some kind of isolator or something.

    7) SOLENOID
    Could I use the controller to operate a solenoid instead of a motor? This might be a moot question, as I suppose I could just use a simple relay for that.
    You want to avoid drawing more than 100 mA from a digital output on the 8/8/8. If your solenoid can be activated by 5V at a relatively low current, then you're ok. Otherwise, you'll want to power the solenoid externally and trigger it using a relay, which we can discuss further if you want more info.

    Quote Originally Posted by xyzzy1126 View Post
    8) DOCUMENTATION
    Is there a file I could download to read up more on the controller? I apologize if I missed a link to it on the site.
    There is no data sheet for that controller. All of the useful info is on the product page. If you have unanswered questions, I'll do my best to answer them.

    Quote Originally Posted by xyzzy1126 View Post
    Sorry if this post is a bit long-winded, but I tend to do that a lot.
    It's better than posting "I WANT TO DO PROJECT WITH MOTOR!"

  3. Re: Scorpion Mini question(s)

    Actually, you've got another option if you're using small motors like the 16mm BaneBots motors.

    PhidgetMotorControl LV
    http://www.trossenrobotics.com/store...ontrol-LV.aspx

    Connects to your computer via USB, and it can handle 1.5A per motor, which will suffice as long as you don't stall the motors with too much resistance.

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  5. Re: Scorpion Mini question(s)

    Before I continue, I'd just like to thank you for the quick reply. While I don't necessarily have a "deadline" for my pet project. it's definitely nice to get a reply so fast.


    The 8/8/8 is no good for motor control, both because of the current limitations of the outputs, and because you'd have no speed or direction control.
    Yeah, I wasn't sure if the 8/8/8 could be used for what I'm trying to in regards to controlling the motors. However, it will still have use in the overall project. Things such as envinronmental monitoring and triggering the aforementioned solenoid (via relay) can still be done with the 8/8/8.


    PC sends servo position command to the servo controller; servo controller generates R/C control signal; motor controller generates variable duty-cycle PWM signal to drive the motor.
    Wow, ok. That looks... complicated. Well, not all THAT complex, but it's probably more involved that what I need to turn/reverse a pair of motors.

    I think another thing I need to wrap my head around is the differences between a simple DC motor, a servo motor, and a stepper motor. I have a decent idea, but that might be a good subject for a separate thread.


    If your solenoid can be activated by 5V at a relatively low current, then you're ok. Otherwise, you'll want to power the solenoid externally and trigger it using a relay,
    Yeah, I'm not sure why I was thinking that a motor controller could perhaps control a solenoid. While I'm sure it COULD do it somehow, it's prbably a lot simpler and safer to just have the 8/8/8 use one of the digital-out ports
    to turn on and off a relay, which in turn would complete/break a circuit supplying power to the solenoid.

    But once again, this might be something I could ask about in a separate thread. Besides, my main concern here is to figure out a solution for controlling these two motors I have. Which brings me to my next quote...


    Actually, you've got another option if you're using small motors like the 16mm BaneBots motors.
    Yes, I think this is probably more of what i would need to turn on/off a pair of motors, reverse the direction, alter the speed through PWM, and have it run off an external power supply. Thank you very much for pointing me to this product.


    it can handle 1.5A per motor, which will suffice as long as you don't stall the motors with too much resistance.
    This is definitely a concern, as I would not want to damage the motors OR the controller device. Looking at the spec sheet for that particular motor, I see that it has a "stall current" of 1.8A. Which means that, in theory, I could fry the controller board if both motors happen to have enough load on them to stall them. This would be Badness.

    While I doubt that there'd be THAT much load on the motors, and while the motors I got have a pretty high gear ratio, I'd like to make sure i don't burn out any of my components. Besides, having safeties in place seems like "the right way to do things". So, I think I may have a solution. I'll pitch the idea and see if anyone can point out any flaws in my thinking.




    I have the two BaneBots 16mm 574:1 DC motors, each with a nominal operating voltage of 6V with a stall current of 1.8A.

    http://www.trossenrobotics.com/store...or-FF-050.aspx

    I would like to control them with a motor controller that can handle between 5V and 9V, at 1.5A per motor (nice that it is a controller for TWO motors).

    http://www.trossenrobotics.com/store...ontrol-LV.aspx

    In order to make sure I don't stall both motors simultaneously and damage the controller, (I think) I can use a 20-amp current sensor to monitor the load and kill power to the motors if it looks like I'm approaching that limit.

    http://www.trossenrobotics.com/store...sor-AC-DC.aspx

    To supply power to the motors, I can use a rechargable 6-volt battery pack:

    http://www.trossenrobotics.com/store...tery-Pack.aspx

    Which can be more easily plugged into the controller (or current sensor) via a connector cable:

    http://www.trossenrobotics.com/store...d-Female-.aspx

    And during down-time, I can recharge it with a charger:

    http://www.trossenrobotics.com/store...H-Charger.aspx



    Nice that I can get all this equipment through one source (which also happens to have good support in the form of an open forum). Now, the tricky question is.... "Will it work?" Well, more to the point, will the electronic side of things work (IE do what I want it to do and not damage the equipment). Whether or not the mechanics will operate correctly is something I'll find out later on.

    Once again, I have to apologize if it sounds like I'm rambling somewhat. It's a bit of a "thinking/typing out loud" kind of thing.


    It's better than posting "I WANT TO DO PROJECT WITH MOTOR!"
    Yeah, I kinda wanted to avoid something to the tune of "OMG HOW DO U MAEK TEH MOTORZ GO??? OK THX BYE!!!1oneone"


    However, I noticed the title of this particular forum, "Servos, Motors, and Linear Actuators", and am moved to ask: what is a linear actuator? Off the top of my head, I'd say that it's something that would let you... I dunno... move something along a linear path. Kind of like a hydraulic or pneumatic piston. Doing some quick google/wikipedia research, that's pretty much what I thought.

    I ask because it sounds a lot like what I'm trying to do with the motors. I want to move a platform with assorted equipment (optics, sensors, and other stuff). Basically, it's a pan/tilt set-up, but it's a bit too "heavy duty" to use a simple motor pairing to rotate/angle the platform.

    http://www.trossenrobotics.com/store...-and-Tilt.aspx

    Something like that, but able to move (about?) ten pounds of hardware, and able to move it in very fine degrees of motion.

    What I was thinking of doing, was to use one of the motors to turn a threaded shaft that would then shift the rear of the platform side-to-side (giving me control over right ascension), while another similar configuration (but in the vertical plane) would tilt the flatform up and down (giving me control over declination).

    So, while I like the idea of making my own actuators, I think I'd rather use something that is already pre-made, tested, and ready to use. Like I said before - no sense in reinventing the wheel.

  6. Re: Scorpion Mini question(s)

    Not to "answer my own post", but I just noticed something. In the specs sheet for the PhidgetMotorControl LV unit, it mentions "Overcurrent Protection". It says:

    When the current to a motor exceeds 1500 mA, an error is sent to the PC and the power to the motor is momentarily interrupted. The PC will then attempt to reestablish control of the motor.
    If I'm reading and understanding that that correctly, I would assume that there's no need for an external current monitor when using this device. It sounds like if there was too much load on a single motor, power would automatically be terminated so as to avoid damaging the hardware. Keen!

    I had gotten to thinking, "Do I need a single current sensor for the whole controller? Or do I need a separate sensor per motor..." But, I guess this clears it up quite nicely.

    Looking at the picture of the motor controller:

    http://www.trossenrobotics.com/store...0-DC-P1060.jpg

    and at a picture of the current sensor:

    http://www.trossenrobotics.com/store...S-50-P1119.jpg

    I wonder if the two medium-sized 8-pin chips on the controller are the same as one of the chips on the sensor.


    Anyway, feel free to either tell me I'm way off base in assuming I don't need an external current sensor, or if I'm right on the money.

  7. Re: Scorpion Mini question(s)

    Quote Originally Posted by xyzzy1126 View Post
    Wow, ok. That looks... complicated. Well, not all THAT complex, but it's probably more involved that what I need to turn/reverse a pair of motors.
    Don't panic. It looks a lot scarier than it is.

    Quote Originally Posted by xyzzy1126 View Post
    I think another thing I need to wrap my head around is the differences between a simple DC motor, a servo motor, and a stepper motor. I have a decent idea, but that might be a good subject for a separate thread.
    One of these day's we'll do a series of "What the heck is this thing and how does it work?" posts explaining the basics. Until then, Google and Wikipedia are your friends.

    Quote Originally Posted by xyzzy1126 View Post
    Yeah, I'm not sure why I was thinking that a motor controller could perhaps control a solenoid. While I'm sure it COULD do it somehow, it's prbably a lot simpler and safer to just have the 8/8/8 use one of the digital-out ports
    to turn on and off a relay, which in turn would complete/break a circuit supplying power to the solenoid.
    If you've already got an 8/8/8, then you could use the Dual relay board.


    Quote Originally Posted by xyzzy1126 View Post
    When the current to a motor exceeds 1500 mA, an error is sent to the PC and the power to the motor is momentarily interrupted. The PC will then attempt to reestablish control of the motor.
    If I'm reading and understanding that that correctly, I would assume that there's no need for an external current monitor when using this device. It sounds like if there was too much load on a single motor, power would automatically be terminated so as to avoid damaging the hardware. Keen!
    Correct. The Phidget motor controller has over-current protection built in. If you have problems with the controller shutting down from excessive current, using a 5V power source instead of 6V will alleviate, if not eliminate, the problem.

    Quote Originally Posted by xyzzy1126 View Post
    However, I noticed the title of this particular forum, "Servos, Motors, and Linear Actuators", and am moved to ask: what is a linear actuator?
    It behaves like a piston, but it has a motor to control the extension and retraction of the actuator arm.

    We don't currently stock any linear actuators, but we're evaluating a few of them and we hope to eventually add them to the catalog.

    Quote Originally Posted by xyzzy1126 View Post
    Basically, it's a pan/tilt set-up, but it's a bit too "heavy duty" to use a simple motor pairing to rotate/angle the platform.

    http://www.trossenrobotics.com/store...-and-Tilt.aspx

    Something like that, but able to move (about?) ten pounds of hardware, and able to move it in very fine degrees of motion.
    That's a bit more than our P/T kits will handle.

  8. Re: Scorpion Mini question(s)

    One of these day's we'll do a series of "What the heck is this thing and how does it work?" posts explaining the basics.
    That'd be great, I'd love to see something like that. While I'm not a complete newcomer, there's still a lot of stuff I don't know about these things. Google and Wikipedia are bountiful resources, but it'd also be nice to see an explanation of these components from the people who sell and use them. Kind of a "electronics/robotics primer by and for the people who use them".


    If you've already got an 8/8/8, then you could use the Dual relay board.
    That relay looks pretty heavy duty. I might be able to get away with something less fancy, although that particular dual relay certainly sparks ideas of home automation (cycling power to lamps, fans, monitors, coffee makers, etc).


    If you have problems with the controller shutting down from excessive current, using a 5V power source instead of 6V will alleviate, if not eliminate, the problem.
    Yeah, using a 5V power supply would work, since the motors would still operate at a less-than-nominal voltage. Also, if i wind up having stalling issues, I might need to come up with a better design for the mechanical side of the equation. But that's probably a subject for another day.


    We don't currently stock any linear actuators, but we're evaluating a few of them and we hope to eventually add them to the catalog.
    I think that'd be a pretty nifty addition to your catalog. I could see quite a few uses for such devices. I was poking around online and it looks like there are supliers for linear actuators. They seem to be a bit on the pricey side, though. For now, I think I'll try to rig up my own solution using the BaneBots motors, the controler, a battery pack, and the 8/8/8.


    That's a bit more than our P/T kits will handle.
    I'll have to take some weight measurements when I get home. The envisioned apparatus might not be as heavy as I'm imagining it might be, I've mostly been giving conservative guesses. Some minor engineering might go into adding counterbalances, shifting pivot points, etc.

    However, a COTS pan/tilt device would probably still not work for this project. With enough weight, I don't want the motors to bind, I need small adjustment increments (fractions of degrees), no wobble once the platform has come to the desired position, overall stability, and so on.

    I'm sure I can come up with SOME solution that gives me what I need. It'll probably involve motors and actuators or bolts with a shallow pitch or wormtooth gears or rails or tracks or pulleys or cams or SOMEthing.



    For now, I think I can go ahead and get that PhidgetMotorControl LV part (as well as batteries, et al) and work with the motors I already have. Thanks for the advice/suggestions! I'm sure I'll be back with more questions. And I'll try to keep people posted (if they're interested) on the progress (or lack thereof) on my project.

  9. Re: Scorpion Mini question(s)

    Right on. We love to see projects!

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