motorised animal help required

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philspinks1
Posts: 2
Joined: Fri Jun 06, 2014 7:49 am

motorised animal help required

Post by philspinks1 » Fri Jun 06, 2014 7:53 am

Hi My name is Phil and I am new to this forum and to the whole robotics thing in general.

I have a project on the go and am in need of some assistance.

I am trying to do the following with either a servo or stepper in order to drive the tongue in and out of an ant eaters mouth. Here goes.

A, Start motor at a set place each time the unit is turned on to make sure gears are in correct position.
B, Drive motor CW for a set distance (130mm) and speed (half second) then have a slight delay
C, Drive motor CCW for a set distance (130mm) at a different speed (2 seconds) and have a slight delay.

I have tried to work with Accelstepper Random code as well as a host of others with no luck. I am now at a point where I need someone to help me out before I go crazy.

Hope you can help

regards

Phil

andrew
Site Admin
Posts: 1374
Joined: Sun Aug 05, 2012 4:15 pm

Re: motorised animal help required

Post by andrew » Sat Jun 07, 2014 1:08 pm

I assume this is not a real ant eater? ;)

How big is its tongue ? This would give us an idea of what sized servo/motor you would need.
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philspinks1
Posts: 2
Joined: Fri Jun 06, 2014 7:49 am

Re: motorised animal help required

Post by philspinks1 » Wed Jun 11, 2014 4:49 pm

Thanks for the reply and yes. You are correct. It's not a real Ant Eater.
I have what I hope is a big enough stepper motor in the (Mercury SM-42BYG011-25 56/2012)
The tongue is the moving part and it weighs approx .25kg
On power up, the motor needs to recognize where it is and go to a home position every time the power is turned on. (This is to prevent gear damage if the unit gets turned off mid cycle and restarts in the wrong place)
The tongue is on a linear gear system and it needs to travel in an upward direction for 150mm and take around 0.5secs (this will need to have a deceleration built in in order to prevent an immediate stop which could cause damage)
It then needs to retract the same distance and take around 2secs.

I am using an Arduino Uno with a Adafruit Motor shield.
https://learn.adafruit.com/adafruit-motor-shield

I have also trie the Arduino with a Big easy stepper drive
http://bildr.org/2012/11/big-easy-driver-arduino/

My problem is basic. I have no experience in programming and even though I follow the examples etc. I cant seem to get the stepper to do as it should.

Any help would be much appreciated as I am under massive pressure to get this done and am now panicking

andrew
Site Admin
Posts: 1374
Joined: Sun Aug 05, 2012 4:15 pm

Re: motorised animal help required

Post by andrew » Thu Jun 12, 2014 9:39 am

One useful thing about stepper motors is the are very precise type of motor. So with this type of motor a set number of steps will move the tong known distance and as you said you only need to initialise it with one know position. To do this I would suggest either one microswitch such as this item: http://hobbycomponents.com/index.php/v1 ... erbot.html

Or maybe something like this: http://hobbycomponents.com/index.php/ir ... odule.html which will trigger when the infrared beam is broken. both items can be wired directly to a spare pin on the Uno.

A quick look at your motor seems if anything, will be overkill and should defiantly be able to move a 1/4 Kg weight although I think you are going to have to gear up this motor as it may not spin fast enough to move the tongue 150mm in 0.5 seconds. The combination of the Uno and motor shield is probably the best way to go because the Adafruit library for this shield makes it much simpler to use. I assume you have looked at the stepper motor example in the Adafuit library? I understand that the software side of things is the barrier here but its a good first step to get that example working and see if you can make sense of what's going on in the sketch.
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