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2026  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
2027  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.
2028  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().

2029  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.
2030  Using Arduino / Microcontrollers / Re: Programming standalone ATmega328p-pu, works but runs slow on: February 18, 2013, 06:56:24 pm
2031  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.
2032  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.
2033  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.
2034  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.
2035  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)
2036  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.
2037  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.
2038  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:
2039  Using Arduino / LEDs and Multiplexing / Re: Power supply questions for the Max7219 on: February 16, 2013, 03:57:20 pm
there is a 5v pin on the arduino between the GND and 3.3v pins, are you saying that I should connect the 5v pin on the max7219 to that pin? in that case , I would just need to supply all of my power through the arduino, correct? and am I also correct in assuming that I could use the power jack to provide 8v 1 amp of power to the arduino and it should all work? I am unaware of how many amps the 5v pin on the arduino can handle.

Here's the thing. The Arduino has a on-board voltage regulator whose input is connected to the power jack. It requires 7-12V as input, and reduces it to the 5V required by the board itself. The output of the regulator is connected to the 5V pin on the Arduino. (And the input from the power jack is connected to the Vin pin.)

BUT in doing its thing, the regulator dissipates (wastes) as heat the difference between 5V and the input voltage connected to the power jack. How hot it gets depends on (a) how large the voltage difference is, and (b) how much current is being drawn. The amount of power in watts that the regulator needs to dissipate is this voltage difference times the current. The regulator is small and does not have a large heat sink area. Trying to draw an amp through it with a differential of 3V means it will need to dissipate 3W, and that is going to make it very hot. It will likely shut itself down (most regulators have self-protection circuitry), or worst case it could be destroyed.

I thought you had a single 5V wall wart. In which case, as long as it is decently regulated, it can be fed in to the 5V pin, and the power jack left unconnected. And it can also power the 7219s (and hence the LEDs) simultaneously.

OTOH if you have two supplies, one which is 5V and one which is 8V, you could plug the 8V into the Arduino's power jack, and connect the 5v supply to the 7219s, just be sure to connect the grounds between the two. Earlier comment on bypassing still applies. This will require minimal current (~50mA) from the 8V supply, and the 5V supply will provide all the current for the LEDs.

Hope this helps.

OK, and if I split a 1 amp supply parrallely to two circuits, they won't each get .5 amps? because if the current just divides itself equally, I will provide too much current to the arduino. I would need .5 amps to the arduino and about 1 amp to the LEDs. On an unrelated note, I used to live in Goodrich, just south of Grand blanc! small world haha!

No, as CrossRoads said, each circuit will draw its required current. Current and voltage are not independent quantities, they are proportional to each other. The constant of proportionality is called resistance.

Goodrich! That makes you a Martian! Always loved that. When did you move away?
2040  Using Arduino / Project Guidance / Re: internet of things project on: February 16, 2013, 02:42:00 pm
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