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841  Using Arduino / Motors, Mechanics, and Power / Re: Servos write wrong value when using SD card on: March 12, 2012, 05:20:18 pm
How about printing out the number from the SD card file before multiplying? Are you sure the the negative number is not because of overflow in the multiplication?

Make sure you are reading the data correctly or getting the correct data first.
842  Using Arduino / Motors, Mechanics, and Power / Re: Controling Stepper with fuzzy logic and PID controller on: March 12, 2012, 05:15:08 pm
Is this a straight or tapered tube? YOu will have a lot of difficulty keeping the ball height stable in a straight tube. The only way I would know to control the height with a damper would be to drill holes up the tube so that air can leak out, and adjust the damper against the leaking air. Otherwise, enough air to lift the ball will blow the ball to the top of the tube.
843  Using Arduino / Programming Questions / Re: ISO C++ forbids comparison between pointer and integer on: March 12, 2012, 04:06:51 pm
Don't feel too bad.. Most of us have teeth marks in our butt from doing that at least once...
844  Using Arduino / Programming Questions / Re: Building Atmel programmer yourself? on: March 12, 2012, 04:04:38 pm
If you have an Arduino you already have the necesary hardware for a programmer. Would be real easy to get hold of a 328 and make a dedicated programmer. I built a small board that I hook to my Arduino and program 328 and tiny2313 chips using it.

There already exists the ArduinoISP sketch so it would just be a matter of figuring out whether you want a shield or a dedicated board to do the programming.
845  Community / Products and Services / Re: Very Inexpensive Rotary Encoder (2 Bit Gray Code) on: March 12, 2012, 12:41:14 pm
Digikey has some comparable units for less than US$5.  Made by CTS Electrocomponents.

I used some $2.58 16 posistion units on a welder control panel. All metal and very reliable.
846  Using Arduino / General Electronics / Re: Simple question about watts and amps on: March 08, 2012, 01:58:48 pm
Power supply Amps rating is like the water tower down the road. Just because it can supply the 10 inch pipe coming out the bottom doesn't mean that my 1/2 water line going to the outside faucet can carry the same capacity.
847  Using Arduino / General Electronics / Re: How can I go from using an Arduino Duemilanove board to just using the chip.? on: March 08, 2012, 01:55:12 pm
Look up Arduino Breadboard.

You will need a couple capacitors and whatever you want to use for the oscilator - crystal or resonator. 1 10K resistor for the reset pin.
848  Using Arduino / Programming Questions / Re: help with pwm on: March 08, 2012, 01:51:58 pm
It would appear that your circuit is working correctly. At analogWrite 1 the transistor is off so the SSR sees max voltage on its input.
849  Using Arduino / Project Guidance / Re: AccelStepper - do other tasks at the same time? on: March 08, 2012, 01:48:22 pm
The code to move a stepper is pretty involved. These little machines we call Arduino (and the underlying AVR) don't have a whole lot of excess resources...
850  Development / Other Hardware Development / Re: Removable programmer idea... where to post schematics, if there is interest on: March 06, 2012, 10:37:06 pm
Okay folks - If the idea were to never try anything that might already be available from somebody else then why do we have some many clones of the basic Arduino?

Post your Idea here and it might turn out that you have a different/cheaper/simpler/quirkier/more useful/less useful idea that others can look at, and make suggestions over so that you and others can have the chance to learn and develop the art of hardware and software.
851  Using Arduino / General Electronics / Re: Calculating amps!! on: March 06, 2012, 10:28:41 pm
Adding 4 batteries and making it 6v should work for 2500mA for 4 hours. So basically it depends on the load.. rite??

Not quite ... You are using the term battery to mean 2 different things.

A single "battery" is properly a CELL. Several cells in series of parallel is a BATTERY. Comes from the idea of artilery. 1 gun is just a gun, a group of guns is a battery.

Cells in series add their voltages so 4 cells in series for 6V is still only 2500mA for 1 hour. 4 cells in parallel would add their current capacity and provide you with 1.5V at 2500mA for 4 hours.
852  Using Arduino / General Electronics / Re: resistors change value with tension? on: March 06, 2012, 10:19:07 pm
Mecahincally stressed carbon resistors can change in resistance.

As a kid I had a slotcar set that compressed a carbon stack to vary the resistance to control the speed of the cars.
853  Using Arduino / Programming Questions / Re: how to handle multiple switches on: March 06, 2012, 10:12:05 pm
Look for debouncing a switch to begin with. Any switch is likeley to have the contacts close more that 1 time for and given closure and you need to "debounce" it so you only see it as one button press. I had one switch on the job that was capable of giving 15 bounces for 1 press.

854  Using Arduino / Programming Questions / Re: Running the sample "BLINK" program @ 16 MHz on: March 06, 2012, 01:15:18 pm
Underground - If you can get you program to execute 16 million times a second, YES, but what you need to understand is that the code to blink takes many instructions, ans thus there is no way you can get anywhere close.
If you write some really tight, dedicated code in assembly language you can get rid if all the extra instructions that are there from compiling the c code, then you can get the numbers higher for PWM frequency.

I took some stepper driver code from 1260 bytes to 88 bytes by coding in assembler.
855  Using Arduino / Project Guidance / Re: Invention Help. Need 8 hour delay off with 5 minutes on and then repeat on: March 05, 2012, 09:18:10 pm
How accurate does the timing need to be? 8 hours give or take 10 minutes?

How much air (volumn & pressure) do you need?

Under $20? that probably going to be a problem.

You need to define your specifications so you can then do some web searches and see what might be available.
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