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1891  Using Arduino / LEDs and Multiplexing / Re: 38khz??????????? on: February 19, 2013, 10:56:50 am
Should be able to come pretty close by setting up one of the timers to output a fixed frequency. Lots of info at:
1892  Using Arduino / Project Guidance / Re: Alternative Blink without Delay on: February 19, 2013, 10:48:55 am
The single line of code in the loop below flashes a LED without use of delay().
Only issue I see is that pin 9 is being written to on every loop cycle.
Is this a bad thing to be doing ?

Not necessarily a bad thing, was there a specific concern you had in mind?
1893  Using Arduino / General Electronics / Re: High Side Switching on: February 18, 2013, 09:37:37 pm
I'd include the diodes, cheap insurance. The back-EMF is likely to be a relatively high voltage, so not something I'd want running around. Would hate to see hand-crafted beer ruined smiley-grin
1894  Community / Bar Sport / Re: Not quite available yet on: February 18, 2013, 09:27:29 pm
Yeah the free version is 128K, which as you say doesn't seem like much of a restriction. Then there are 256K and 512K versions, for $256 and $512 respectively. Cute. Obviously not a serious pricing policy, I wonder what they were thinking.
1895  Using Arduino / Programming Questions / Re: Trying to learn how to code Sketches on: February 18, 2013, 08:17:17 pm
Executable code must go in a function, e.g. the setup() function, the loop() function, or functions you write yourself. Global variables can be declared outside of functions, e.g. before setup().

1896  Community / Bar Sport / LPC81xM chips on: February 18, 2013, 08:06:01 pm
Looks like the LPC81xM chips are getting closer, Mouser now lists them as on order, although no delivery dates. Prices (single quantities) range from $0.78 for the LPC810 to $1.16 USD for the most expensive LPC812. Unfortunately the development board went up from $15.00 to $18.75 since I last checked. I may just order one up anyway. I also discovered that the free LPCXpresso IDE only does C, not C++. Major bummer.
1897  Using Arduino / Microcontrollers / Re: Programming standalone ATmega328p-pu, works but runs slow on: February 18, 2013, 06:56:24 pm
1898  Using Arduino / Microcontrollers / Re: Programming standalone ATmega328p-pu, works but runs slow on: February 18, 2013, 06:14:30 pm
From the factory, the ATmega328P comes with the system clock set to use the internal 8MHz RC oscillator divided by 8, in other words, the system clock is 1MHz, which as you observed, is 1/16 as fast as the Uno 16MHz clock.

Either do "burn bootloader" from the IDE, or use AVRDUDE to set the fuse bytes to use the external crystal rather than the internal oscillator.
1899  General Category / General Discussion / Re: Push Button Not Working on: February 18, 2013, 05:52:30 pm
Need to see your circuit. How is the button wired?

Edit: Easy enough to test a switch, use the circuit below.
1900  Using Arduino / Project Guidance / Re: NEED HELP WITH TIMER on: February 18, 2013, 05:15:02 pm
Here is a library I wrote to deal with buttons, it comes with example sketches to get you started.

Here is a project that uses the button library to set time and several other parameters.
1901  Using Arduino / LEDs and Multiplexing / Re: Newby Arduino UNO Blinking LED Issue on: February 18, 2013, 05:08:52 pm
Welcome to the forum, hope you have fun with Arduino!

For future reference, please see:,148850.0.html

Item #7 illustrates how to properly post code.
1902  Using Arduino / Project Guidance / Re: NEED HELP WITH TIMER on: February 18, 2013, 05:03:45 pm
so can anyone help with this at all? all these views so far and only one comment?

Define "help" ... if you want it written for you, post in the "Gigs and Collaborations" section. Looks to me like the hobbytronics link contains a big piece of what you want to do. CrossRoads' advice about the current-limiting resistors is well taken, though.

Usually when asking for "help", the expectation is that something has been tried and either needs to be built on or possibly some issue has presented itself, in which case there are good pointers as to how to proceed on the forum here:,148850.0.html (Item 11 in particular)
1903  Development / Other Hardware Development / Re: ICSP in 3v3 target (custom) board on: February 18, 2013, 09:16:23 am
I don't see any worries with your approach. A couple things to watch for (and these are really independent of whether the supply voltage is 5V or 3V3 or something else): If the target board has large loads connected to the µC SPI pins, those can interfere with programming. If it's just a logic-level SPI device, there should be no worries. Second, the SPI device will be exposed to the programming signals which may cause it some confusion, usually nothing that bouncing the power wouldn't fix if it ends up in some weird state, but if it tries to talk to the µC while programming is occurring, that would probably be an issue.
1904  Community / Gigs and Collaborations / Re: Need a small program written on: February 17, 2013, 11:19:42 am
As PaulS said, a 3V output is not the usual thing. If you can tell us what the 3V signal is used for, and how much current is required, then it may be possible to make some suggestions.
1905  Using Arduino / LEDs and Multiplexing / Re: Power supply questions for the Max7219 on: February 16, 2013, 04:13:13 pm
Alright, so the 5v can just be plugged into the Vin port on my arduino Uno? and the same line can also be plugged into the max7219's? then that makes sense. and the arduino will only draw as much current as it needs since I will be using a 5v 1.2 amp transformer. the Led's will draw as much current as they need and the current that is not used will dissipate as heat, in the wall wart? OR thereabouts. OK. the max7219 schematic says that I need two capacitors also, and the internet cant seem to tell me a specific type of capacitor to get. Do I need a specific type? Thanks again! and I moved last July, but I'll always remember the martians!

You've got it now, except that the wall wart will not dissipate "unused" current, it just doesn't supply it. A "5V 1.2A" wall wart is rated to supply 5v at up to 1.2A, or less, depending on the requirements of whatever it is powering. Plugging the wall wart into the wall then leaving the 5V output unconnected will cause the minimum amount of heat to be dissipated. Odds are it's a switch mode supply, so it shouldn't get real hot even under maximum load, but the general tendency will be to heat up more as it supplies more current.

Capacitors are as the datasheet says, a 10µF electrolytic, and a 100nF ceramic. These are exceedingly common, just as a couple examples of a million variations, here are some that I've used, although better prices can probably be found elsewhere:
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