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991  Using Arduino / Microcontrollers / Re: Question about driving LEDs with a LaunchPad MSP430 on: February 19, 2013, 07:24:43 pm
Unless you KNOW FOR SURE that there is some kind of CURRENT LIMITING PRESENT... it is a poor idea to connect an LED to ANY controller port. In 30 years I've destroyed a bunch too.

Bob
992  Using Arduino / General Electronics / Re: Feedback/Advice on MOSFET circuit on: February 19, 2013, 06:53:37 am
The easiest fix is to put a silicon diode in series with the battery that way there is a more limited discharge path for the battery...
993  Using Arduino / General Electronics / Re: Electromagnet on: February 19, 2013, 06:22:16 am
This project is do-able with an Arduino and a PID Loop I've seen several over the years. The problem is similar to keeping an object at a set temperature using several sensors.
THIS is NOT a trivial project. I would build the analog version and learn EXACTLY HOW IT WORKS FIRST.
Then start making a Digital version from the Analog version.
I would read the whole  article... These are the magnet construction details...
"Construction Details
The top detector is a reference detector and the bottom one senses when an object is in levitating position. The object detector must be level with the IR LED. The reference detector must see the IR diode at all times, even when levitating an object. The electromagnet should have maximum 15 ohms of resistance, any more and it will not be able to lift anything. Too little resistance and the transistor will have problems regulating electromagnet current and will also dissipate more heat. When constructing an electromagnet there are two things to remember. Magnetic force is proportional to the number of turns and current. So when using copper wire the magnetic force is roughly proportional to the square of the power dissipated in it, for all practical use. In my coil I used 70 meters of 0.45mm magnet wire. The coil can be wound on almost any ferrous metal rod if you're not concerned with efficiency. Remember that keeping the surface area of the face small will keep the object centered better. Constructing the circuit correctly is easiest if built in two parts; part 1 with the detectors and first op-amp to make sure the output swings when an object is put in the beam, and then part 2 with the rest. This way it will be much easier to troubleshoot when it is modified and all of the sensor information is valid and it will be useful for the Digital Version.
The author goes to great detail about sensor positioning and all the other details are either in pictures or in the text.
READ IT From Start to Completion There is a lot of information but mainly for the hard bits, the rest is in pictures and I found it quite interesting.. I would love to have one for my desk. Really impressive looking.
Especially with control from an Arduino... Could make a gravity meter with data from the correction current value, If it was air current and vibration protected... with some real care it could be made to look like the pendulum in an old fashioned clock... That however would be quite advanced

Bob
994  Using Arduino / Programming Questions / Re: COnvert const char to hex on: February 19, 2013, 05:52:27 am
I have the place where ALL the SECRET ANSWERS are...

And It's HERE  :   http://lmgtfy.com/...try it sometime when you are stuck... PW IS Tell Me...
995  Using Arduino / Programming Questions / Re: serial.print and printf on: February 19, 2013, 05:41:54 am
You should start here, I did.   http://www.cplusplus.com/reference/cstdio/sprintf/?kw=sprintf
                                         http://www.cplusplus.com/reference/cstdio/printf/?kw=printf
Read about "dtostrf()" in a thread here: "http://arduino.cc/forum/index.php/topic,37391.0.html"
And this from here :
char* dtostrf   (   double    __val,
signed char    __width,
unsigned char    __prec,
char *    __s
)      
The dtostrf() function converts the double value passed in val into an ASCII representation that will be stored under s. The caller is responsible for providing sufficient storage in s.

Conversion is done in the format "[-]d.ddd". The minimum field width of the output string (including the '.' and the possible sign for negative values) is given in width, and prec determines the number of digits after the decimal sign. width is signed value, negative for left adjustment.

The dtostrf() function returns the pointer to the converted string s.

From this reference:  http://www.nongnu.org/avr-libc/user-manual/group__avr__stdlib.html#g6c140bdd3b9bd740a1490137317caa44

Bob
996  Using Arduino / Programming Questions / Re: Reading and writing to a single digital pin on: February 18, 2013, 04:21:06 am
Perhaps out of line considering the previous discussion.. But OP did I think mention turning a LED on for a specific time on button stimulus Why not use PCF8574's?. IIC but easily chained, read the registers, write those that have changed state whether by input or timeout.

Bob
997  Using Arduino / Networking, Protocols, and Devices / Re: pass caps for the nRF24L01 on: February 18, 2013, 01:04:48 am
Basic electronics makes the point that it is a good idea to bypass any power used by a non trivial device with suitable components and in 50 or so years I have NEVER found the Opposite to be true. It was a suggestion not my own as a matter of fact but one I've seen before in reading about the nRF24Lxx trancievers in several threads and one very much common sense suggestion.

Bob
998  Using Arduino / Programming Questions / Re: Concatenate Float w/ a String on: February 18, 2013, 12:37:43 am
Personally I find no issue with using C style strings. I am a NEWBIE to C and C++ and although the Strings are handy (lazy?) when it comes to C or C++, learning how to deal with array's or C style strings is much more important than saving a line of typing to waste 1.5K of program memory. The function to deal with that bad old issue... could well be a macro saved in what I call a "Snippet Library" (I use a sketch and add code as I find it and prove it). Keeping it in a sketch works for me as a macro/code library.
I am NOT defending the POOR choice made by the Arduino development team, not by any means but with 2K of sram in an Uno you encourage people with less programming experience than you to make uninformed decisions that waste more time than simply learning how to deal with simple arrays and the rather simple Arduino Crutch that makes sprintf work...
Time spent by the person writing the sketch to as well as the people involved in debugging it. wasted.

Bob
999  Using Arduino / Programming Questions / Re: Determine device at build time? on: February 17, 2013, 11:43:49 pm
Off Topic...
Comment on krupski's tag line...
Quote
Wouldn't it be easier to make assault and murder illegal rather than trying to have a law against every and any type of weapon?
What a concept.. Think We can Sell it? God didn't... "Thou Shalt Not Kill" is present in one form or another in all the mainstream religions... Or So I've Been Told.

Robert Khayyam Johnson Sr.

My deep personal belief is that any references to guns is best left in forums devoted to that purpose, they serve little purpose in this forum. IMNSHO.
1000  Using Arduino / Networking, Protocols, and Devices / Re: NRF24L01+ Reliability with RF24 as a Gamepad on: February 17, 2013, 11:18:49 pm
@ OP I think you would do well to read ALL you can find in this forum about the RF24XX radio's. You might find your answer already.

1001  Using Arduino / Networking, Protocols, and Devices / Re: ARDUINO NETWORK TO SHARE THE WORKLOAD? on: February 17, 2013, 11:06:21 pm
@ Nick Gammon... We learned how to do that in Boy Scouts. The really advanced Merit badge was awarded for 3 in 3 month's... <BFG>

Bob
1002  Using Arduino / Networking, Protocols, and Devices / Re: Using nRF24L01+ on: February 17, 2013, 11:02:11 pm
@ OP. There are a large number of posts regarding the nRF24XX and nRF24LXX devices. My recommendation is to read them all. Search this website as well as Google nRF24L00''s for whatever you find. it's a bit of reading but in almost every post or article I've found more and useful data.
Maniacbug's library is well done and easy to use, I recommend it highly.

Bob
1003  Using Arduino / Networking, Protocols, and Devices / Re: pass caps for the nRF24L01 on: February 17, 2013, 10:54:29 pm
Put both capacitors on the VCC line as close to the radio as possible (the radio connector is good) The capacitors have little to do @ 2.4 GHz but a great deal to do with how clean the digital internals are and this is the real issue. I've never bothered to put an O'scope on it... I believe religiously that the parts are NECESSARY NOT OPTIONAL PLACES FOR EXTRA UNUSED CAPACITORS. I have in 50 years of "Messing" with this stuff proved often enough that By-pass capacitors a wise investment and a great time saver when trying to fix a new circuit. They are Never "Optional".

Bob
1004  Using Arduino / General Electronics / Re: Mixing and splitting signals: PWM RGB led on: February 17, 2013, 10:35:42 pm
I would personally use 3 linear drivers and sequentially strobe them. You have a linear voltage that must be by definition less than the maximum current of the LED's and a window in which to process it. So separate the two and do each in it's own time. Provide the amplitude modulated information to an LED driver and strobe/enable the driver in it's time (data position) slot.
trying to PWM data at that level of precision would be quite an undertaking both in generation and detection...   Assuming the modulation (voltage) is within the dynamic range of the LED. A 0 to 10 V signal would require "Some" processing first.

Bob
1005  Using Arduino / General Electronics / Re: What transistors have around a 2-3v turn on on: February 17, 2013, 10:20:24 pm
@ Lefty... That was covered in the NDA you signed.., You'll be hearing from the Secret Police.. Secret Division...

Bob
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