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 826 Using Arduino / Motors, Mechanics, and Power / Re: Micro Stepping without a motor Driver on: February 04, 2013, 04:56:50 pm Micro-stepping is where you provide a sine-wave to each coil, 90 degrees out of phase with each other. The code presented is simulating the sine waves using PWM. Essentially, you need the beginning of one sinewave to start at the highest point of the first, etc.. etc..Eh... a picture does better:http://en.wikipedia.org/wiki/File:Drive.png
 827 Using Arduino / Motors, Mechanics, and Power / Re: Wishing my Tamiya Motors Had More Drive on: February 04, 2013, 04:35:21 pm Spinning one wheel faster than the other provides the turn motion. I will be the guy asking the really dumb question... the non-driven wheels. They are not connected to the same axle are they? They are independently free-running, right?Spinning in opposite directions provides rotation along the center of the axle. In your configuration, that won't work because you are trying to spin along the center of the rear axle and the other wheels will act as brakes trying to move sideways. Omniwheels would work like this, but not normal wheels. Having some swing (even it is not controlled) would allow the front wheels to change angle with the friction, which would help since they are not trying to move sideways) would probably work, but not optimal. This is what a caster does.Spinning one motor faster than the other puts the center of rotation on the center of the wheel spinning slower. Since the whole base continues to move forward while it does this, you are also causing the front wheels to spin at the same speed (assuming they are free-running). Now, your rotation is in an arc, with the center of rotation along one side of the base, instead of in the middle.With a four wheeled base like you have, this is the correct way to do it.Basically just image trying to turn a push-cart with wheels fixed in straight forward direction. You cant just pull one side back and push the other forward. You would have to push harder on one side. Of course, the turn radius is much larger. To decrease the turn radius, you use casters on the front wheels. This is why a car turns the front wheels to steer.(I'm sure I boggled up that explanation.)
 828 Using Arduino / Motors, Mechanics, and Power / Re: Motor Shield Capable of Driving 5 DC motors? on: February 04, 2013, 04:25:18 pm Using the SCARA motors, which have a 5.54A theoretical current draw at stall?That's the real kicker right there. A motor shield is really nothing more than an H-bridge and associated support components. If you are handy with perfboard, you could build one yourself. I tend to use TA7291S (in a freindyl SIP package), but these are rated at 1.2A max. Putting two in parallel would handle 2.4A, and so on (starting to get pricey though.)I would look for H-bridge ICs that can handle up to 6A. I have no idea how easily you would find one. The other option is to build 5 h-bridge circuits that can handle that load by hand or find a battlebot style board.I am suggesting this because I am not aware of an existing shield that meets your specifications. If you do find one that drive that current, but only has a few outputs, you can usually stack shields.Personally, I would just build my own. YMMV
 829 Using Arduino / Project Guidance / Re: best way to sense someone entering a room on: February 04, 2013, 04:07:47 pm Sounds like you need a little clarification of your goal. Do you want the sandpaper to actuate when someone enters the room (as in only once per person) or do you want it to actuate the entire time someone is standing in the room (meaning the film scratches to nothing the longer someone stays?)Monitoring just an entrace is the simplest way to count people. Depending on how you do that, it may have issues where it counts 2 people as one (though, if you put it at their legs, they would have to be walking perfectly in sync.) But how much does that really matter?Maybe defining the overall purpose/effect you are trying to get would help. I am envisioning that this is an interactive exhibit where you are trying to show the degradation of an image the more it is viewed. Clarify your parameters, and I think people can be of more help.BTW, a PIR sensor works by using two adjacent sensors angled slightly away from each other. Motion is detected by comparing the two sensors. The most you could determine from them (if you had a truly raw PIR sensor) is the direction of the movement. Most PIR modules have all the logic built in, which simply triggers if a sequential change between the two sensors is detected using comparators. *Technically* it can sense to some degree whether someone is continuing to stand in front of it, but again, you would need access to the raw sensors.Automatic doors at the store uses radar for this purpose (a special band that is absorped by the human body.) Sonar would provide a similiar effect. Though if your project is as I am envisioning, a simple break-beam detector circuit would really be enough.
 830 Using Arduino / Project Guidance / Re: Challenge: horizontally / inertially stabilize a pizza on motorcycle on: February 04, 2013, 03:55:19 pm I think the biggest destructive force is that a motorcycle leans in turns. This would essentially lift the pizza up (assuming the box is affixed to the bike), which reduces the friction and the pizza will basically continue trying to stay in place while the box is moving. For most other movements of the bike, the friction of the pizza is likely enough to keep it moving along with the box. The little plastic spacer they put in the middle of the pizza would help a little with keeping the pizza from lifting.
 831 Using Arduino / Project Guidance / Re: Connecting tft screen to arduino uno r3 on: February 04, 2013, 03:48:49 pm No. Latches, to expand an 8 bit data bus to a 16 bit data bus. You latch the upper byte.
 832 Using Arduino / Project Guidance / Re: Connecting tft screen to arduino uno r3 on: February 04, 2013, 03:12:13 pm It looks like the controller has an I2C and SPI interface mode, but that is not enabled on your LCD. However, there is an SPI interface to the SD card and Touchscreen as well as CS for the display being brought out. Would have been so much simpler if they had just made it a common SPI bus with individual CS lines for the display, SD, and touchscreen.The SPI mode of the controller is set by setting the IB pins high or low. I would investigate modifying the circuit if I were you. I couldn't advise you directly what to do because the pictures do not show what I would need to see, but first find if the IB pins are brought out somewhere so that you can change them to SPI mode, then look to see if the SCLK, DI, and DO lines are brought out somewhere (probably share a DB pin) Then connect them all together for a single SPI bus, and use the CS lines to pick which devices you are communicating with. 6 lines total would give you access to an SD card, LCD, and touchscreen.Otherwise, you are not going to have enough IO on the Uno to control that screen. Well, at least not without using latches.
 833 Using Arduino / Project Guidance / Re: Challenge: horizontally / inertially stabilize a pizza on motorcycle on: February 04, 2013, 03:00:24 pm I guess I am also one of those people that doesn't believe that a microcontroller is the solution for everything. Add me in for the gimball. A well balanced, bearinged and weighted gimball will react a million times faster than any closed loop micro/motor/sensor could ever respond.