Automation: Need a point in the right direction

[Zeppelin1007]

Greetings everyone

First off, i love this software. Ever since i was a little kid i loved to tinker and i loved fiddling with 3D. Now that i decided to become an electrical engineering student, this project is just perfect. Great work guys

Anyways.

So i ordered and received the Logictech Quickcam 9000 (er whatever everyone's using) Scored a 10mw line laser with adjustable focus. Grabbed a battery holder for testing, but already am working on the 5v-3v circuit on a breadboard and in Multisim. Got everything here and installed, just gotta print the test patterns.

So in the next day or two here, i'll have a minute to do a test scan. But having both worked with 3D and electronics extensively, i'm already looking ahead to automate the process.

Now i'm somewhere between my second and 3rd year of my engineering degree, and sadly, i havent had the opportunity to take our robotics classes with the arduino/picaxe boards yet. But, after seeing tons of arduino code, and already knowing C/C++/Objective-C, Im not scared off at all. What i'd like to do, is have the laser automated, thats step one. Step 2 would be the turntabe, and step 3 would be automatic on/off of lights/laser.

But my question is this, which is more accurate and cheaper? Going with an arduino board or running off a COM Port so the entire thing is PC controlled? Im not afraid of either method, i'm completely confident i can handle each route, but a few things have confused me as i havent had the experience and need some direction and advice on parts. For one, if i have a driver board, can i drive both motors using one arduino? Can i do the same running off of the COM Port of a computer? Also, with an arduino, could i run off of one arduino board a: LCD, 2 stepper motors, lights (for texture capture) and laser on/off? How many of these could i control with the COMPort?

Also is there a reason you guys use a Serial to USB adaptor? I do have serial ports on my rig, dualcore 3.2ghz p4 and 3gigs of ram.

I figure since we have the developers here with the juicy foresight of whats coming in the future version, they might have some input on which they'd recommend.

I appreciate the advice guys! Keep up the good work.

[WalterMo]

Hi,
If you intend to completely automatize the scan process I would suggest to do it with a „bigger“ Arduino as the Duemilanove or the Arduino Uno. What about the Mega 2560?
http://www.watterott.com/index.php?page ... &info=1626
It has 53 IO pins and 16 Analog input ones.

As you can see here at the Arduino Duemilanove there are only two digital and one analog input free:
viewtopic.php?f=6&t=2421

(It's not allowed to use digital pin 0 and 1).

I wouldn't control motors, lamps, laser and so on by the serial ports. Arduino is a fine "intelligent" USB interface.

Walter

[Khalid Khattak]

Hi Walter;)
Why limit to Arduino Pins???... Use shift register for LCD with only two pins of Arduino... Also use multiple shift registers to get a lot of pins... see following:)
http://code.google.com/p/arduinoshiftreglcd/

you can add three shift registers (SIPO) 74LS164.so to get more than 20 output pins..
http://www.arduino.cc/en/Tutorial/ShiftOut

[MagWeb]

[WalterMo]

Hello Khalid,
„Normally“ the LCD display is connected to the Arduino by 6 parallel data lines. If they are reduced to two serial lines, the transmission rate must be three times higher to transfer the same information. This additional job would slow down the Arduino in general and of course also, e.g. the motor clock rate.

Walter

[Zeppelin1007]

hey guys,

well i did a scan by hand over the weekend and wow was i impressed. Though right off the bat, i noticed, i definently need to automate the laser coming down. Doing it by hand just takes too long and it leaves holes.

Now i've got some follow up questions on the advice you guys gave. For starters, whats the difference between the Arduino mega 1280 and 2560? Memory? i only ask because obviously i can get the 1280 for pretty cheap.

So as i said, my first interest is automate the laser. Would this motor be acceptable? :
http://cgi.ebay.com/CNC-stepper-motor-1 ... _500wt_922

The turntable here has perked my interest..
http://cgi.ebay.com/CNC-Rotary-Table-St ... _500wt_922

Im assuming, im better off going on sparkfun for the driver i take it?

I notice alot of ou guys use worm gears in your laser setup. How big of a difference does that make? I realize thats to make the steps finer/smoother, so is that recommended only with a certain gear ratio of motor?

So far though im loving this project. Thanks for all your help!

[milz]

hi zeppelin1007

the worm gear or gear box is to get more step out . 1,8 deg from the stepper are 200 steps at 360 deg.
thats to less for scanning.

for example
you like to scan are range of 25cm (calibration pattern size) with a camera resolution of 800x600
your laserline is 1 pixel strong so you need at least min 500 step (-50 top and above space) to scan all lines
with an angel range from 30-35 deg.
if you scan with higher resolutions or bigger calibration patterns you need more steps.
example with gearbox 200:1.
1,8deg per step
360deg / 1.8 deg * 100 (ratio from gearbox) = 20000 steps at 360 deg.
20000 steps / 360 deg * 30 deg (range you scan) = 1666 steps
the worm gear is good for backslash free smooth running but you cant
get big ratios. i think the most davidians switched over to planetary
gearboxes.
personal i use this gearbox
http://www.mercateo.com/p/live~s.100*10 ... 50_1_.html
a little bit cheaper then the planetary gearboxes but you get what you pay
more backslash not so smooth running
next i like to buy somethin like this
http://en.nanotec.com/planetary_gear_gple40.html

the motor you choose looks good. the turntable also but you can get a cheaper one.

the main differnent between the mega 128 and 256 is the memory 128/256kb
the arduino mega256 is the new version like the uno with 8u2 usb chip.
see here http://arduino.cc/en/Main/ArduinoBoardMega2560
i prefer the arduino uno with the ardafruit motorshield. easy to assambley.

mfg milz

[Zeppelin1007]

Millz thanks for the info man!

Im glad i took 4 years of german in highschool. Those pages actually made some sense.

Anyways. Alright. so a gearbox is another item. I figured 1.8 degree steps was far too large. Gotta find a gear box that doesnt cost too much for now

Also, most of the arduino stepper drivers i see only handle .6 amp, the motor i was looking at was .8. Any higher stepper drivers out there? Im sure there are, especially ones with dual motor control

lastlyk one thing ive been wondering. How the heck do you guys get the motor shaft attached to gearboxes/turntables etc?

[MagWeb]

[Zeppelin1007]

Hey guys. Appreciate all the help. Man those gearboxes are expensive. I have a question: microstepping. Im reading some drivers are 1/8 step modes. Would that mean a 1.8degree step motor could do .225 degree steps per step? Or am i misinterpreting? I assume a different motor is needed by that point?

[WalterMo]

Yes, each (micro)step is then 0.225 degree per step. Of course the motor driver board needs e.g. for one rotation eight times more impulses.
Micro stepping can be made with every „normal“ stepping motor. But up to now I have only heard of driver boards which can do it for bipolar stepping motors.

[Zeppelin1007]

Hmm now thats interesting. Can i use that in replacement(for now) than a gearbox? In the end i'll get one, but initially i was under the impression i was limited to the 1.8 degree steps, which even i thought was huge, but a .225 degree step (for now) doesnt seem so bad.

[WalterMo]

0.225° isn't sufficient. This angle corresponds to a laser line step of 2 mm at a distance of 0.5m or to 4 mm at 1m distance.
That means an additional gear is also necessary.

[milz]

mfg milz

[Zeppelin1007]

Alright guys Got it. Having a free day from classes ive been browsing the forums and researching. I figure, for now, i'll go with this stepper motor+gearbox.

http://www.phidgets.com/products.php?product_id=3313

I know its not the best, but its a bit more in my price-range and i see others using it. I see alot of guys using the easydriver with this for current protection, now, with this said, am i better off going with 2 easy drivers? Im using the Arduino Mega1280 by the way, hopefully be here soon. Or would i be better off with something like this?

http://cgi.ebay.com/Arduino-Special-Mot ... 886wt_1141

I figure with the motor i have listed above running at 2.5A, at 1.25Ohms = 3.125V. Hey just read the spec sheet, rated voltage at 3.1v. Ok, so if i want to play it safe with that second board, says drives up to .6A, 1.2 peaks, and run it at 0.5Amps, id require 0.625V!.....would that thing even turn at that low of a voltage?

I appreciate all the help guys. Also, based ont he stepper motor im looking at, it has an 8mm shaft. Where the heck can i find some mounts for it so i can safely and easily attach my laser? Ive found tons of 3mm-5mm mounting hubs, but cant seem to find a darn thing for 8mm.

Thanks in advance everyone.