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256  Forum 2005-2010 (read only) / Interfacing / Re: Encoder missing count on: October 30, 2010, 11:54:07 am
I'm a compete newbie at microprocessors but I do know a bit about stepper motors from building a CNC machine recently so here's my "dos centavos":
(I'm assuming you are using a stepper motor otherwise all of this is not true.) Steppers can easily lose steps. In other words the step pulses are generated but the motor doesn't move for a few steps. This usually happens when the load exceeds the torque of the motor. (and torque in a stepper drops off quickly at higher speeds). The same thing can happen if the motor accelerates too quickly. Using encoders and a PID loop to control steppers doesn't work well because the the motor will try to accelerate too fast lose steps and then compound it by accelerating even faster. So, usually a closed loop motor control uses a brushed motor or on larger machines an AC or brushless DC motor. It is possible to use the encoder count to compare to the steps and generate an error condition as a check however. I've considered using that method for my current project (unless I end up going with a closed loop servomotor setup)
Another thing to remember is if there is a load on the motor you need an acceleration ramp to avoid the problem of missed steps. If your going from 8k to 40k steps/sec in the space of 8000 steps you have a very high acceleration so I think that is why you lose the steps.
All of the above may be complete BS though  smiley-wink. I'm really just passing on what I've picked up from various CNC forums. You might want to check out http://CNCzone.com where you'll find a wealth of info on motor control and can get more knowledgeable advice than mine.

Good luck
Greg
257  Forum 2005-2010 (read only) / Interfacing / Re: i2c LCD Display on: November 24, 2010, 05:34:18 pm
I ordered one of the web4robot.com LCDs a couple of weeks ago and never recieved it. Only after several emails did I get a response and was told they were no longer offered for sale. Finally ended up getting a similar unit from moderndevice.com.
258  Forum 2005-2010 (read only) / Interfacing / Re: Arduino as an encoder pulse divider? on: November 02, 2010, 05:00:07 pm
Hmmmm... I just noticed all the posts by Richard disappeared. What's up with that?
259  Forum 2005-2010 (read only) / Interfacing / Re: Arduino as an encoder pulse divider? on: November 01, 2010, 08:56:30 pm
Steve-
I think this may be of use to you: http://emergent.unpythonic.net/projects/01149094674

Some people on this forum can be quite snarky in their replies. This is in marked contrast to other forums I've frequented such as CNCzone.com or the EMC2 forum where I've always found people to be extremely helpful without copping an attitude.
Hope that link helps you.

-Greg
260  Forum 2005-2010 (read only) / Interfacing / Re: How to display and input numberic caharcter? on: October 29, 2010, 09:00:30 pm
Hi there Teddy. I'm a beginner too working on a similar problem. So far I've gotten a keypad to do my bidding and as soon as I get my LCD I will integrate it with the display. You can see what I've come up with so far at: http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1287289086
261  Forum 2005-2010 (read only) / Frequently-Asked Questions / Re: Stepper motor using Arduino on: January 21, 2011, 11:57:03 am
Sure. That's what stepper motors are for smiley-wink
262  Forum 2005-2010 (read only) / Frequently-Asked Questions / Re: Stepper motor using Arduino on: January 21, 2011, 09:39:44 am
Both the Easydriver and Pololu boards are tiny, my Easydriver measures 20mm x 50 mm. A Nema 17 size stepper is only 42mm wide. Little Bird Electronics is an Australian source for everything you would need. http://www.littlebirdelectronics.com/
263  Forum 2005-2010 (read only) / Frequently-Asked Questions / Re: Stepper motor using Arduino on: January 20, 2011, 05:22:52 pm
I would suggest  the easiest and fastest route to your goal would be an Easydriver board board available from Sparkfun. It is for small motors (.75A per coil) but it is well documented on various sites. Sparkfun also sells a small motor that works well with it. A larger motor would require a driver with more capacity like some inexpensive ones by Pololu. The Playground section of this site has plenty of info to get you started.
264  Forum 2005-2010 (read only) / Frequently-Asked Questions / Re: Programming a 7-segment display w/ shift register on: January 11, 2011, 12:26:07 am
There's a good tutorial with code examples for the shift register here:http://arduino.cc/en/Tutorial/ShiftOut
265  Forum 2005-2010 (read only) / Frequently-Asked Questions / Re: Never programmed before. Can Arduino be a hobby? on: January 05, 2011, 03:26:34 pm
Welcome to the forum Pman! Yes, it can be a great hobby. I've had my Arduino for just a few months and came to it with practically no programming experience (just a little Basic back in the Commodore64 days). Just start with the easy blinking led stuff and work your way up. It can be a bit frustrating at first but once you're over the initial "hump" it starts making more sense and the learning comes more quickly. I got a lot from LadyAda's tutorials. To start I just got a breadboard some resistors and led's as well as a cheap multimeter and that kept me going for quite a while until I learned what else I needed. Good luck!
266  Forum 2005-2010 (read only) / Frequently-Asked Questions / Re: Personal jet device on: December 31, 2010, 04:28:51 pm
What exactly is a "personal jet device"?????
267  Forum 2005-2010 (read only) / Frequently-Asked Questions / Re: Hey im thinking of buying my first Arduino. on: December 22, 2010, 09:41:55 pm
Welcome Darrion! To get started you will need an Arduino board, a computer and lots of time and patience unless you already have a strong programming background. You will also need a prototyping board, a few electronic components such as resistors and LED's. Once you feel comfortable with the basics of flashing LED's etc. you will want to obtain a motor control board and motors if you want to control cars. I would reccomend Adafruit Industries http://www.adafruit.com/ or Sparkfun http://www.sparkfun.comas a good source both for hardware and tutorials. Read all you can and ask questions on the forums. Just be aware that all this takes time and effort and your goal of using a Wiimote to control a car will be some ways in the future. I got into using the Arduino about 3 months ago with the goal of creating a simple linear positioning system and I'm now only about halfway there but I've learned a great deal in the process. The learning curve can be frustrating at times but when you get something working it feels really great! Good luck to you.

268  Forum 2005-2010 (read only) / Frequently-Asked Questions / Re: Help sending digital outputs long distance. on: December 09, 2010, 05:23:44 pm
You should look at RS-485 for that distance. Here's one thread on the topic: http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1270227591
269  Forum 2005-2010 (read only) / Frequently-Asked Questions / Re: Assembling my project involving solenoids on: November 22, 2010, 03:41:03 pm
Actually, for safety's sake I would go with a 24 volt system. Relays and transformers for 24 V are readily available and not terribly expensive. 24 V systems are widely used in industry for control systems (motor contactors etc.).
270  Forum 2005-2010 (read only) / Frequently-Asked Questions / Re: Assembling my project involving solenoids on: November 21, 2010, 10:52:13 pm
Something like this should work fine:
http://www.mpja.com/prodinfo.asp?number=18194+RL
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