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Hi guys, let me start out that 1) I am a college student, 2) my major is biomedical engineering and not electrical or electronics engineering, and 3) no one on my team knows anything electrical or, in this case, robotics. However, we are doing a very important project to help the disability community and are, because of the previous information, more stuck than a shirt on the back of a sweaty man. We need two 12 volt motors that can be controlled with a simple joystick like the ones you see in arcades. We were told by a man that knew electronics and robots to buy the AndyMark "Add a Motor" set as it had all the parts for a simple motor and all we needed to do was add some batteries (currently trying to test full load current), a controller chip (we have a computer engineer helping us with that), and a joystick (she is helping with that as well). Problem is: we got the kits in today (we ordered two since we need two motors), looked at it, and realized that even the simple part of this plan is far over our heads. We have confirmed that the motor does work, and we are using an 8 volt battery (the Talon SR Speed Controller can handle 6 volts at the least) just to test with and will take full load current measurements when we test with a 12 volt battery. The main problem we are having is where and how to wire everything to the Talon SR Speed Controller. Oh, and also the placement of the breakers. Actually, pretty much how to wire that kit up in general... I have tried to look up guides online, but they are more for the robotics specifics kits like the "RobotOpen Arduino Controls Kit, everything for two motors" and we don't want anything near that complicated. Could someone help us? We are running out of time since getting funding took almost a year and now deadlines are coming up. Could you be as specific as possible? This will be like telling someone who speaks another language how to land a plane. Also, if you could show us picture as well or videos or even schematics of the motor system, I would be very grateful. Thanks in advance!  :)
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Really appreciate you reading and responding to my post!  The actuators are very basic, no positioning logic, no variable speeds.  I will try to take some voltage readings tonight.

The documentation just doesn't exist unfortunately and there is no tech support    :-\

I have run both actuators at the same time in my early testing and it wasn't a problem.

I should also note, I did this same install in 2 other cars and....over time, the same problems have surfaced with those cars. 

The ISIS system has an optional module (which I have installed) to monitor battery voltage.  When it drops below a certain level, (due to leaving the headlights or because of parasitic draw when the car sits for weeks), it shuts off the power.  So in theory, when you come back to the car, you hit the reset button and there is still enough juice to start the car.  I have reset buttons inside and outside the car.  I also have a (secret) option for opening the door from the outside or inside in the event I have some catastrophic problem with anything related to the door systems.

The doors cannot really be pushed out of position.  You can stop them anywhere along their travel and then restart and it isn't a problem.

I have looked far and wide for a better controller and not found anything yet that matches what I need it to do.
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Mechanics and Construction / Short Legs+Paw/feet help needed
« Last post by Aslyl on Yesterday at 01:27:37 PM »
I'm not an expert but I have some prior experience with robots. For one I am planning out, it would need two short legs with paw like feet. The design is already done, I just need to know what I need to build the legs and feet, how to control them with a remote controller, how to make them be able to jump, and where to buy all of these things. Like I said, not an expert. :)
Thank you!
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It sounds to me like the motor controller is either not running at 100% duty cycle (if it even uses PWM for variable speed, it wasnt clear to me if this is a capability)
Or there is a voltage drop across the controller (possibly due to the shunt resistor used in current measurement)

To test for either of these condtions you could measure the voltage at the input of the controler and the output while the actuator is moving, it would be a good idea to also measure the voltage of your power source without load as a refrence. If you cant figure it out post what your voltage readings are for these three locations and we will see if we can help.


Assuming one of the above condtions is the issue I have a few soutions:

Find a new contorller that can deilver full power to the motors
Get new actuators that will work with your existing system
increase the suply voltage (assuming you can do so safely without damaging your components)
use a spring to assist your actuators and reduce the load


One other possible source for the difference in opperation, when you tested the actuators connected directly to your power source did you run both at once?


Also, it moght help if you can post the documentation/datasheets for your components.


I hope you have thought about what happens when you leave the headlights on and the battery dies.
Also what happens if the door gets out of position, for example when it is openend it gets pushed open a little further...will it close all the way?
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Mechanics and Construction / Re: Looking to learn where to start
« Last post by bdeuell on July 29, 2014, 09:55:43 PM »
From my understanding of your mobility requirements it doesn't seem like treads are necessary, you could probably get away with some wheels, they would need to be large enough and have some traction. Of course tracked robots can be very cool and if that is what you want to build it isn't the wrong choice...wheels are just simpler. The most basic robot construction is probably two driven wheels and a caster.

For mounting wheels, I am not sure what you have in mind but when i think of lovejoy i think of the shaft couplers with a rubber spider in the middle. These would work to connect a motor to wheel but the wheel would need to be mounted to its own set of bearings. for this robot you can probably make it light enough and get away with using the bearings in the motor (assuming your motor has decently sized bearings). In this case the wheel would be directly mounted to the motor shaft, probably with use of a hub of some sort.

As for motors you will probably want something geared. While you can easily drive stepper motors slowly without a gearbox they would have to be larger in size to provide sufficient torque. Selecting a motor with a gearbox will allow you to pick one that weighs less and still meets your torque and speed requirements. Weight is important because for every pound you add to your robot it will require more batteries and structure to support the weight which will also add more weight and require stronger motors...this turns into a vicious cycle. In addition to getting a geared motor i would recommend a standard brushed DC motor as it will probably be the easiest to control, (there are plenty of stepper controllers out there tho if you go that route). Also because it will be under remote control you probably don't need to use encoders or rely on the open loop position control of stepper motors, i.e. your eyes will provide the feedback to make course corrections.

Just some thoughts and very much my opinion, others may have different ideas.
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Feetech 6 Degree Of Freedom NanoBiped Robot Combo
Please see the following video to learn more about our new smart control servo
FEETECH SCServo SCS15 Biped 6 Control by TTLinker mini Arduino part3
https://www.youtube.com/watch?v=-Pb8dm5RLU0

https://www.youtube.com/watch?v=Q7S8Mj9NgXc

https://www.youtube.com/watch?v=9CJTqoK9Kd
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Mechanics and Construction / Looking to learn where to start
« Last post by lippy on July 29, 2014, 06:41:05 PM »
Hello,

I've got a project I want to play with that will involve a robot that has a tray about 8x10" and can maneuver around the house via remote control.  Speed isn't a main concern, maximum load wouldn't be more than a few lb, and my maneuverability requirement is to easily go from hardwood to tile to carpet, maximum 3/4" transitions but nothing extreme, while maintaining the load relatively stable.

I do a good bit of playing around with micro-controllers and I have a 3D printer and access to a laser cutter.  In the past I've built a simple tank using a couple of continuous rotation sub-micro servos and a 3D printed chassis to chase my cats around, but that's about the limit of my robotics experience, so I wanted to ask for some advice here before I invest too much time/money in this project while going in the wrong direction. 

What I'm thinking at the moment is to use a Vex Robotics Tank Tread kit driven by a couple of stepper motors.  I have no idea about how to couple the steppers to the drive axle (is it acceptable/advisable to direct-couple this via a 'lovejoy' connector?) or if based on my requirements, is a tank just generally the wrong way to go and another form of robot would be better/cheaper to get off the ground?

Any advise/direction to documentation and resources would be greatly appreciated...Thanks for reading this far and I hope you're having a great day!

Cheers,

Roger
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Click on "Robot Tutorials" in the upper right corner of this web page and start reading. Then do google seaches and read more. Also just read through the many threads in the forums here.
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Mechanics and Construction / Help needed with a linear actuator motor controller
« Last post by PJV SL-C on July 28, 2014, 06:38:32 AM »
Hi,

  First time post - hoping I can find some help with a project I am working on.  Not exactly "robot" related, this is a custom car project and I am controlling the doors/front clip/rear clip with 12v linear actuators.

  I have an ISIS system controlling the car electronics, including 2 of their optional components that allow me to control items via an ISIS supplied RF transmitter as well as an android smartphone. 

  The actuators are controlled by an Autoloc motor controller.  You can program the run time for an actuator and when the motor controller sees a ground signal, it runs the actuator for the programmed time and then stops.  Next time the motor controller sees ground, it reverses the polarity and runs the actuator in the reverse direction for the same time.  If at any time during the up/down travel, it sees a ground signal, it stops the actuator.  When it sees ground again, it reverses the polarity and the actuator runs the same distance in the opposite direction.

The problem.

The motor controllers allow for a certain amount of adjustability for "sensitivity".  Even on the controllers highest setting, it is sometimes not enough to operate the doors.  There is no binding, the actuators have well over the weight rating needed and in fact work 100% of the time if I run power directly to the actuator motor.  When the doors are acting up/stalling on the open cycle, very slight one finger pressure assisting allows it to run the full travel without stopping.

I have searched for other motor controllers that might allow more adjustability of the force, but have not found anything with the features I need.  So I am left with trying to improve the ones I have.

Does anyone have any experience with these motor controllers or have any idea how I might modify them to do what I need?

Here is a link to see the actuators working:
https://www.youtube.com/watch?v=eHSa6tjS6PI

Also, I attached a picture of the different parts/how they work together.

Thanks!
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