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16  Using Arduino / Programming Questions / Re: simple maths on: April 16, 2014, 06:41:45 am
Multiplication associates left-to-right, so w * w is done as a 16-bit operation and overflows.

        long w2 = 1L * w * w;
or
        long w2 = w * (w * 1L);
or
        long w2 = (long) w * w;

will fix it, the later being a cast to the long data type.

You may be aware, but the integer division (/ 490) will lose precision.

17  Community / Website and Forum / Re: Dealing with spam on: April 16, 2014, 06:20:43 am
An even simpler approach that would still catch a significant portion of the spam would just be to filter posts with the word "kitchen" in the subject line, haha!
"Looking for ideas for projects that let me use my Arduino in the kitchen..."
I'd hate to see that scrubbed as spam.

Of course. It was a tongue-in-cheek suggestion.
18  Topics / Robotics / Re: Arduino Uno R3 turns off when Arduino Motor Shield is attached on: April 15, 2014, 09:55:05 pm
I thought they could be deleted, I must be mistaken. Perhaps the moderators will take care of the duplicates. This is only one problem with cross-posting, creating work for the mods. Your answers are not all in one place, nor is the conversation. The answers you get will be better when everyone can see the conversation in one place, and duplicate effort can be avoided. Good luck with you issue and welcome to the forum.

19  Using Arduino / Project Guidance / Re: help please on: April 15, 2014, 06:01:23 pm
Couple questions. (1) What class is this for? (2) Have you read this?
20  Community / Bar Sport / Re: Adafruit's new website on: April 15, 2014, 05:58:41 pm
Gotta love the ten-foot UI.  Not.
21  Topics / Robotics / Re: Arduino Uno R3 turns off when Arduino Motor Shield is attached on: April 15, 2014, 05:51:24 pm
I am new to the forums.

No kidding. You should read the guidelines. One thing you don't want to do is cross-post, it's a great way to get off on the wrong foot.

If it were me, I'd go and delete all but one post.
22  Community / Website and Forum / Re: Dealing with spam on: April 15, 2014, 03:53:45 pm
An even simpler approach that would still catch a significant portion of the spam would just be to filter posts with the word "kitchen" in the subject line, haha!
23  Using Arduino / Networking, Protocols, and Devices / Re: "Tiny RTC I2C Module" issue on: April 15, 2014, 03:50:51 pm
Perfect. Just ordered one of yours. Thanks!

Thank you! Just dropped it off at the Post Office. Popular place, I forgot what day it was. I pulled in next to a lady that was filling out her tax return in the car!
24  Using Arduino / Networking, Protocols, and Devices / Re: "Tiny RTC I2C Module" issue on: April 15, 2014, 02:01:37 pm
I'm also having issues with this Tiny RTC module and after reading this thread, I get the feeling that it's not really worth my time to continue trying to get it to work.

Can anyone recommend an alternative module that "just works"?

If you want a DS1307, Adafruit's version is good.
The Chronodot is more accurate than a DS1307.
Heck, I'll even sell you one, link below (shameless plug).
25  Using Arduino / Programming Questions / Re: Arduino blocks i2c bus on: April 15, 2014, 11:26:25 am
The two Arduinos run identical code, except for their I2C address? Have you tried changing the addresses? Does the problem move with the address or stay with the board?
26  Using Arduino / LEDs and Multiplexing / Re: Maxim 7219 - Real and Fake compared on: April 15, 2014, 09:54:37 am
I've used MAX7219s from Tayda and while their appearance fits that of the fakes, they seem to work fine for me.

But recently I bought one of those 8-digit LED display modules on eBay, it had an SOIC MAX7219 on the back of the board. The thing worked, but drew about 300mA. The MAX7219 ran very hot to the touch. The LEDs themselves were OK, I removed them and it hardly changed the current usage. I breadboarded a similar circuit (with the Tayda part) and it uses less than one-tenth of the current.

Don't know if it was the MAX7219 itself or something else wrong with the board, but I demanded my money back. At first the guy wanted to give me a partial refund, saying "as our item is very low price ,it may be not as good as other ones that is more espensive  for this case ,can we partial refund to ease you ?"

Of course his web page said nothing about the product being "not as good" so I got pretty direct with him and he did give me a full refund.

Once every few years I have to buy something on eBay just to remind myself why I shouldn't.
27  Using Arduino / General Electronics / Re: somebody please explain this? sketch attached on: April 15, 2014, 06:50:03 am
the control is not specifically for ac fan, it can be any ac motor...

Well, no. There are different kinds of AC motors.

Induction motors (typically used in mains-powered fans) run at a speed determined by the mains frequency and the load on the motor, but their speed cannot vary by more than a few percent or they will stall. On/off control of an induction motor with a triac may be OK but don't expect to control speed very much.

Universal motors are found in things like power tools (drills, saws), kitchen appliances (blenders), etc. They can actually run on AC or DC. They are very noisy as compared to induction motors (so not usually used in fans) and have a relatively shorter life. Their speed can be controlled with a triac circuit.

There are other kinds of AC motors as well but those are the most common. Good luck. Be careful, keep your sneakers on and one hand in a pocket.
28  Community / Website and Forum / Re: Dealing with spam on: April 15, 2014, 06:30:25 am
How about a simple system that requires a newcomer with less than (say) 5 posts in other Threads to use the title "Hi, this is my first Thread" when s/he starts her/his first Thread.

Simple and clever!
29  Using Arduino / Programming Questions / Re: Arduino blocks i2c bus on: April 14, 2014, 10:07:32 pm
Is there a buffer used for I2C like a serial receive buffer ?

Yes, 32 bytes. I also note that the code below assumes that there are two bytes to read. Can't say for sure that it's causing a problem, but I'd at least test the value of bytes_read to ensure I'm getting what's expected. Overrun them buffers, next thing you know, someone will steal all your customers' credit card numbers smiley-wink

Code:
void rec_event(int bytes_recd){
  if(Wire.available() > 1){
    led_address = Wire.read();
    intensity = map(Wire.read(), 0, 255, 0, 4095);
    Tlc.set(led_address, intensity);
    recd = true;
  }
}
30  Using Arduino / Microcontrollers / Re: ATtiny84 with internal pull-ups on: April 14, 2014, 10:03:35 pm
And the current from each io pin to ground is 2.89mA, so I am not overloading the io pins

Agree with fungus, 2.89mA is definitely too high. How about a picture?
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