Society of Robots - Robot Forum

Electronics => Electronics => Topic started by: Magnus on August 18, 2009, 07:34:27 AM

Title: Auto center my robot torso.
Post by: Magnus on August 18, 2009, 07:34:27 AM

Hi,

I am using a clothes dryer drum as a torso for my robot. I will be using a DC gear motor to turn the torso back and forth. I will be using an ESC to control the speed of the torso motor to slow it down to about 4 RPM. After turning it left or right I would like to be able to push a button that will auto center it so the torso is oriented straight ahead. Anybody got any ideas or circuit examples on how to do this?

Thanks

Title: Re: Auto center my robot torso.
Post by: SmAsH on August 18, 2009, 03:43:11 PM

well, will you have any sensors on the robot so it can tell what angle the drum is at?

Title: Re: Auto center my robot torso.
Post by: Magnus on August 18, 2009, 07:21:19 PM

Hi,

Thanks for the reply. I was thinking about using IR sensors but do not have any experience using them. Any ideas? Also thought about using a potentiometer. Would these be better?
 ::)

Title: Re: Auto center my robot torso.
Post by: SmAsH on August 19, 2009, 12:32:52 AM

sure, if your rotation doesn't go past 180 degrees, a pot would be good...
you could try using an encoder type setup too?

Title: Re: Auto center my robot torso.
Post by: Magnus on August 19, 2009, 05:03:03 AM

Any ideas on where to find schematics that would help me understand how to hook up a circuit using a pot for feedback to cut off the torso motor at just the right spot?

Title: Re: Auto center my robot torso.
Post by: SmAsH on August 19, 2009, 05:05:58 AM

are you planning on using a microcontroller to run it?

Title: Re: Auto center my robot torso.
Post by: Conscripted on August 19, 2009, 05:52:05 AM

For a low tech solution you could try using limiting switches. It may do the job in a simple manner.

Conscripted

Title: Re: Auto center my robot torso.
Post by: Magnus on August 19, 2009, 08:21:12 AM

Yes. I was thinking of ordering the AXON. Do you think that all I would need to do is use the pot. to give me an anlog signal and feed it into the AXON then I could program the AXON to control the ESC (not exactly sure how to do this)? Then maybe I could turn the torso to several different points, including center position, record the analog values at these points then the AXON could position the torso until the anlog signal matches and stop rotation there. Does this sound feasible?

Thanks for responding......

Title: Re: Auto center my robot torso.
Post by: blackbeard on August 19, 2009, 08:32:07 AM

what if you used a neodymium magnet from a hard drive and an inductor? i'm just thinking but since the flat magnet from a hard drive has it's poles on either half you should be able to use that to detect when it's center when the inductor passes over it. you could use it with pretty much any microcontroler but from what i understand the axon is pretty much the king of the microcontroler world. if budget is tight you could always go with a $30 arduino.

Title: Re: Auto center my robot torso.
Post by: SmAsH on August 19, 2009, 03:59:10 PM

yeah, the axon could definitely do this! 40 times over!
the left leg of the pot is connected to +5V, the right leg is to ground and the middle goes to an analogue pin.
this will allow you to read the position of the pot.

Title: Re: Auto center my robot torso.
Post by: Magnus on August 19, 2009, 08:14:07 PM

Thanks to all who have responded. I will be ordering the AXON as soon as I save up some more "squirrel" money. BTW my robot will be called MAGNUS. MAGNUS will be aprox. 6ft tall and weigh in at around 300 lbs. He's a big boy! He will be similar in shape to the B9 Robot from the old LOST IN SPACE tv series from the 1960's. So far the hardest part has been engineering the arms. See my BLOG at www.r-gordon.blogspot.com.

 :D