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16  Using Arduino / Project Guidance / Re: RC plane project. on: September 06, 2014, 01:10:08 am
If you want an off-the-shelf transmitter/receiver try the Turnigy 9X (not 9XR). This uses the 2.4GHz range -- as most all RC radios use these days. See to understand how to interface with standard RC radios.

If you want to DIY your transmitter or you want two-way communication, look for "telemetry" radios based on the HM-TRP by HopeRF. These are 3.3V TTL serial available in 433MHz or 915MHz (unlicensed bands depending on what country you are in -- which you won't get an answer to since you haven't stated where you live in your profile). These are rated at ~1km range.

If you want to make the data transfer braindead easy try the EasyTransfer library.
17  Community / Bar Sport / Re: Reality check - when to stop adding features on: September 04, 2014, 06:10:29 pm
When I was writing my previous response I also tried finding a way to use a MySQL facility to do that type of quoting. I have plenty of experience with MySQL so I'm quite familiar with the documentation, but I can't find anything that would help you with your problem. I'm kinda surprised that there's nothing in the MySQL drivers/libraries for that.

I personally don't use those tickmarks at all. You definitely gave me some food for thought tho smiley

"Though a program be but three lines long, someday it will have to be maintained.''
18  Using Arduino / Motors, Mechanics, and Power / Re: Linear motion design on: September 04, 2014, 06:03:50 pm
In my experience it's difficult to get good speed with a leadscrew and stepper motors. When you go with a plan like that you typically find yourself using inexpensive threaded rod from the hardware store, and then the problem there is that the thread pitch of typical, coarse thread, metric or standard rod is still too fine to get the speed you'll want.

As an example, using 1/4", 20 TPI threaded rod and a stepper motor spinning at a well-performing 1500(*) RPM puts you at (1500RPM / 60seconds / 20TPI) 1.25" per second. That's over 12 seconds to move across a small, 16x16" chess board. If you don't want to start ordering stuff through the mail, and you're lucky, the most coarse, standard threaded rod you'll find is 1/2" ACME threaded rod which is 10 TPI, but that's still 6 seconds to traverse the board. If you do choose to mail order special rod like TR8x8 with 2 starts you're still at around 6 TPI and 4 seconds to cross the board. 4 seconds isn't too bad, but certainly tedious if you try to reset all 32 pieces at that speed.

(*) Probably not a practical expectation to reach 1500 RPM with an Arduino in a complex project like the one described.
19  Using Arduino / Project Guidance / Re: DIY 3D printer, your collective thoughts on: September 03, 2014, 10:06:31 pm
Try FreeCAD and Slic3r for software. If you're a student you can get good prices on commercial packages; Sketchup or Geomagic Design would be worth a shot there. But personally I think your time would be best invested in FreeCAD.

If you're going to visit a steel store, "Cold Roll" is the term used for the smooth, steel rod you would want, but it would not be appropriate for linear ball bearings. "1045 TGP" is for the high-tolerance dimension stuff.
20  Using Arduino / General Electronics / Re: Charge lipo battery on: September 03, 2014, 09:51:48 pm
You can find chips like the ISL94212 or BQ76PL536A to handle it; they use external mosfets so there's no particular charge current limit.
21  Using Arduino / Motors, Mechanics, and Power / Re: Linear motion design on: September 03, 2014, 09:32:54 pm
Belts or a rack and pinion will work fine. There are millions of 3D printers that use belts (like the Makerbot) to drive the extruder head and those are capable of reliable, sub-millimeter accuracy.
22  Using Arduino / Motors, Mechanics, and Power / Re: GWS S03TXF servo - how to get complete rotation on: September 03, 2014, 09:21:49 pm
This doesn't appear to be a multi-rotation servo. You could take it apart to be certain, but just turning it by hand should reveal that there are end stops to the rotation.

For servos that are capable of multiple rotations the Servo library will handle them fine. There's no difference in interfacing with them; you just get more rotational distance than usual.
23  Using Arduino / Interfacing w/ Software on the Computer / Re: Communicating with Computer on: September 03, 2014, 09:15:02 pm
You can connect your Arduino (Uno, Mega, etc.) via the USB port to a USB port on the Pi. "dmesg" output will show which USB device (/dev/usb0, etc.) the Arduino grabs. As you know, the Arduino emulates a serial device. From there it's just a matter of writing a program on the Pi that will communicate with a serial device -- perl Device::SerialPort, python pySerial, tail -f /dev/usb0, etc., and on the Arduino side it's just a matter of serial.print()ing whatever message you want to send.
24  Using Arduino / Motors, Mechanics, and Power / Re: Driver options for the Nema17 on: September 03, 2014, 01:47:39 pm
Check eBay for "A4988" drivers which are as low as $2 now. Your "Big Easy" driver is based on the A4983; slightly older version of the A4988. Couple those drivers with a RAMPS board and then you're just left with connecting the motors, limit switches, power, etc.

You don't need a separate power supply for each motor.
25  Using Arduino / Motors, Mechanics, and Power / Re: Brushless Gimbal Motor Battery on: September 03, 2014, 01:36:33 am
You can't use an ESC for a gimbal controller. ESCs are designed to spin motors at high speeds, switching each phase full-on or off, and you need to be able to control the motor slowly, on a phase-by-phase basis, and with a sinusoidal wave form.

I suppose an ESC does have all the circuitry you need, but you'd need to reprogram the micro on the ESC to control the gimbal properly. Not an introductory project any way you slice it.
26  Using Arduino / Motors, Mechanics, and Power / Re: Stepper motors - how do I find out which wire is which ? on: September 03, 2014, 01:12:42 am
The L298N (H bridge) would be used for bipolar motors. The ULN2003 would be used with unipolar motors.

Your motor has six solder connections on the motor itself but that is brought out to just five wires. In whatever device you removed it from it was assuredly driven as a unipolar motor -- and that's typical and probably advisable for small stepper motors -- but if you really wanted to you could drive it as a bipolar motor by identifying the common wire and leaving it unconnected.

If you google "28BYJ-48 wiring" (an extremely common, small, unipolar motor) you'll have the details you need to wire up your motor. Looking at your pictures and the soldered connection on the side of the motor it appears that the middle wire is the common wire.
27  Community / Bar Sport / Re: Reality check - when to stop adding features on: September 02, 2014, 04:56:12 pm
Finally, I thought... well, at least I get quoting for free.  I can programmatically add the `tick marks`, and even recognize table.column pairs and quote them separately (i.e., "table.column" becomes "`table`.`column`").  But, that's a weak argument in the cost-benefit analysis, and how do you even know what's a column name and what's a literal?  Or a function?  You pretty much have to write a basic SQL parser that is context-aware ... and even then, you can't reliably tell a text literal from a column name without knowledge of the schema.

One of the reasons you use the tick marks with MySQL queries is to protect yourself when you encounter reserved words. Assuming you've debugged your code and/or created a parser "today" to make sure you're protected, you still have no way of predicting what reserved words or new syntax will appear in future versions of MySQL. The only valid tick-mark-parser would need to be a facility included in the MySQL driver itself.

28  Using Arduino / Project Guidance / Re: Arduino CNC PCB Plotter (Need Ideas) on: September 02, 2014, 04:29:23 pm
There are a number of 3D printer controller boards that will work from G-Code stored on a SD card. The most known would be the RAMPS boards (google "SDRAMPS"). Appears that most sellers of the RAMPS boards on eBay don't include the little SD card add on module, but you'll find it if you look for it.
29  Using Arduino / Motors, Mechanics, and Power / Re: Looking for High Torque Servos. on: September 02, 2014, 12:58:25 am
You need something like a "crane" and not an "arm". One servo to raise/lower the boom and a second servo to pan the boom between tanks (where the tanks are arranged in a semicircle). Personally I'd just hang the board off a wire hook instead of trying to use a gripper, and if you want agitation you could put a continuous rotation servo on the end of the arm so that it raises/lowers the board as it spins.

You don't need much torque for the pan, and because you can counterbalance the boom you don't need much torque there either. Any standard size servo would handle it, but always a good idea to shop around and try to find ball bearing / metal gear servos. has plenty of generic servos that would meet those specs for not much dough (<$10).
30  Using Arduino / Sensors / Re: dirty earth - automotive / car application on: September 02, 2014, 12:47:18 am
It'd be worthwhile knowing what kind of car this is (modern car or older/classic) as well. Older cars don't have the protected electrical system that modern cars have.
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