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1306  Community / Bar Sport / Re: Cross-posting on: February 19, 2013, 01:01:29 am
Close but no cigar. Or was it something else he was holding onto  smiley-eek
Wasn't holding anything. Was just signing his chances of surviving the full length of the movie (youtube.com/watch?v=4sGR1-Wgo1M).

With respect to the forum tips, I'd suggest encouraging that users set their location in their profile. A lot of answers depend on it (mains voltages, suppliers, etc.).
1307  Community / Bar Sport / Re: Need help fixing my lenovo t61 MBR on: February 19, 2013, 12:56:50 am
You're using recovery CDs/DVDs, correct? They won't care about the MBR; they'll write it themselves. If these rescue CDs are worth a hoot then they should be capable of creating the partitions themselves (replacing the hard drive should be an anticipated scenario) and perhaps undoing any partitioning would be worth a try.

The MBR tells the BIOS were to go on the hard drive to boot the operating system installed there. If there's no OS installed then it doesn't make sense that you could create a MBR.
1308  Using Arduino / General Electronics / Re: Undisputed power to the Arduino on: February 19, 2013, 12:31:28 am
You should look at Tim Nolan's MPPT charger at http://www.timnolan.com/index.php?page=arduino-ppt-solar-charger. Not necessarily because you want to do MPPT but because it contains all the elements for controlling power from a solar panel and explains them pretty well. 

NiCD batteries should be charged to 1.45V per cell in the pack; 1.2V is only the nominal voltage. Typical charge rate is 1/10th the amp hour rating. For example, if the battery is 600mah then charge it at a rate of ~60ma.
1309  Using Arduino / Project Guidance / Re: BeBox style Blinkenlights on: February 19, 2013, 12:01:51 am
your bits are backwards. 00000001 is 1, 00000010 is 2....

If you're bad at bit math you might want to use the ShiftPWM library (http://www.elcojacobs.com/shiftpwm/)
1310  Using Arduino / Project Guidance / Re: BeBox style Blinkenlights on: February 18, 2013, 09:49:37 pm
Pretty straightforward to do. See: http://playground.arduino.cc/Main/InterfacingWithSoftware for examples of how to talk serial to the Arduino.

See http://arduino.cc/en/Tutorial/ShiftOut for how to control a row of LEDs from the Arduino.

1311  Using Arduino / Motors, Mechanics, and Power / Re: how to make 4 wires system of Unipolar Motor control into 2 wires on: February 17, 2013, 02:55:38 pm
You can try an Allegro UCN5804B. It's a pretty old chip; unipolar drivers just aren't very popular.
1312  Using Arduino / Motors, Mechanics, and Power / Re: Identify this linear actuator brand? on: February 17, 2013, 02:48:42 pm
It's an actuator for an electric door lock for a car. With some added plastic stuff on it. smiley
1313  Using Arduino / Project Guidance / Re: LED Lightbulb and Arduino Control on: February 17, 2013, 02:41:58 pm
You never want to control a LED with voltage only; once you reach the forward voltage of the LED (Vf) the current starts to ramp up very quickly with very small increments in voltage. A LED should always use a current controlled supply if you want reliability.

I'd suggest poking around on eBay for an AC LED driver; they're so cheap it's impossible to beat them with a DIY approach.
1314  Topics / Robotics / Re: Rotary encoder together with arduino for measuring angle on: February 17, 2013, 02:29:50 pm
http://www.mouser.com/ProductDetail/Bourns/EAW0J-B24-AE0128L/?qs=sGAEpiMZZMvy8cVzszrmR716n9pC3kk%2fKdD7OIhGwoE%3d

Absolute encoder with 128 positions. Under $7.
1315  Using Arduino / LEDs and Multiplexing / Re: Maths Guru ? or of course, a simpler approach in the first place ! on: February 16, 2013, 01:36:50 pm
Problem is, for a power level of 25 out of 50, I am actually sending 25 ONs, followed by 25 OFFs.
That delay (25 continuous OFFs), is now limiting how expandable the system will go.
e.g. if I want 100 power levels, or control other devices that require/benefit from more constant signals.
The ideal situation would to alternate, ON then OFF, 25 times.

This is the same kind of problem as drawing a straight line from (0,0) to (50,25) across a grid. The solution to that problem is the Bresenham algorithm; every time the line would increment up the Y axis you would turn the signal on, and every time you don't increment you would turn the signal off.

When you figure it out the code will be just ~10 lines. I can provide an example but I'm certain you won't understand it without first attempting to work it out yourself.
1316  Using Arduino / Project Guidance / Re: SX1509 16 Output I/O Expander Breakout on: February 16, 2013, 01:20:18 pm
You want either a shift register or a TLC5940. The chip you have linked really isn't designed for a lot of power.

"5.5V tolerant" means that its normal signaling voltage is only 3.3V but it will accept a 5.5V input.
1317  Using Arduino / General Electronics / Re: Current measurement on positive or negative side? on: February 15, 2013, 07:46:13 pm
Your motor rating is only 3kW (4HP) assuming 100% efficiency.  This seems far too small for a lawn tractor.

For a comparison you could look at the old GE "Elek-Trak" models -- the most popular model 12 was 1.5HP for the drive motor. They carried six batteries and ran at 36V.

The motors are replacing a 13hp ice motor (maybe the right term is ride-on lawnmower rather than tractor). So about 4 hp for drive, which I think is more than enough, and about 4 hp for the blades which might be too little, but if it works I’ll probably be happy to cut the grass before it gets to long. With this setup, I can also eliminate some pulleys and the clutch, which hopefully will reduce the power requirements a bit. I’m going to use four 85ah marine batteries, and I’m hoping to get a couple of hours juice for just driving, and maybe 40 minutes of grass cutting.

That sounds about right to me.

The Arduino will try do reduce power to 130 amps per motor, and will allow 150-200 amps for max 5 seconds, and will shut of power completely if consumption is more than 200 amps for one of the motors.

You should still use a breaker or fuse for overcurrent protection.
1318  Topics / Robotics / Re: Rotary encoder together with arduino for measuring angle on: February 15, 2013, 11:57:05 am
How much precision do you need?
1319  Using Arduino / General Electronics / Re: Transistors and Resistors on: February 15, 2013, 11:24:29 am

As an aside, 5mm LEDs with 100ma forward current (e.g. TSAL5100) are quite a bit cheaper than those larger, star emitter types. You shouldn't have any problem finding those from local distributors and won't feel as bad burning up a ~$.25 part as compared to a $5 part.

1320  Using Arduino / General Electronics / Re: Transistors and Resistors on: February 15, 2013, 06:38:10 am
There shouldn't be a need for a transistor for a camera button. Any switching requirement that required a high amount of current would be a very wasteful (battery wise) design. Unless you're trying to activate a mechanical apparatus (solenoid) to press the button there is assuredly a simpler way to do it.

To clarify what Mike said, base resistors are critical but the value usually isn't; always try to limit the current from your pins to 20ma.
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