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226  Using Arduino / Project Guidance / Re: What are the typical current drawn by these components? on: April 20, 2013, 03:42:13 am
Current for an LED can vary widely. Full current would usually be around 20mA but you don't always have to use full current, in fact lower current is usually perfectly adequate to suit the brightness you require.

Certainly more modern LEDe can give adequate brightness with quite low currents.

For example, I have a sentry gun controller board I made where I use Blue, Yellow and Red 3mm LEDs for the mode indicators (fire, comms and reload). With 5V I use 4k7 resistors, providing for around 0.4-0.5mA on the various colours (they have different Vfd's).

On the same board I have 5v and 9v outputs to servos, with power health indicator LEDs on he regulator outputs. I don't want these as bright, just enough to indicate they are on. With 5V year are on. 10k resistor. With 9V they are on a 22k resistor. This give about 0.25-0.3mA through 3mm Green diffused LEDs.

These give me the brightness I want and, as you can see, are well below the 20mA maximum the data sheets quote.

So, typical LED current for an SMD or 3mm or 5mm could be anything from about 0.25mA to 20mA.
227  Using Arduino / Microcontrollers / Re: ATMega1284P Issues on: April 14, 2013, 03:50:17 am
Tak - Refer to image. I simply used jumpers to connect the onboard 16Mhz resonator.

And a lot of great info. Ill surely look into that and post back. Much appreciated!
I can't follow the connections from the photo, there are just too many long looping jumpers everywhere.

You've got an Uno with no MCU and then two breadboards, one with a 328 and another with 1284.

Are you trying to share the Uno 16mhz crystal with both of these? If so then you can't just pick up both sides on the crystal to both XTAL pins on each chip. On one you drive the crystal normally and on the other just link the crystal output to XTAL in of 2nd chip I believe.

Also bear in mind that the XTAL pins are the opposite way round on 1284 vs 328. On the 328 it's the low impedance pin adjacent signal pin. On the 1284 it's the high impedance XTAL pin adjacent The RX0 signal pin. This is one reason we had issues with serial uploads on 1284 without adequate ground rings or full swing oscillator; the high z XTAL pin on 1284 seemed to susceptible to capacitively induced interference from the adjacent RX0 pin.
228  Using Arduino / Programming Questions / Re: can I use a momentary button on a analog pin? on: April 14, 2013, 03:32:39 am
Rather than use 50+ pins for individual LEDs you might also want to investigate LED drivers or shift registers to allow you to run all your LEDs with only a few Arduino pins.
229  Using Arduino / Microcontrollers / Re: ATMega1284P Issues on: April 13, 2013, 04:39:42 am
1st issue may well be out of sync due to wrong crystal.

Second issue; how exactly have you 'tapped into' the Uno onboard crystal.
230  Using Arduino / Microcontrollers / Re: installed new chip atmega168-20pu on: April 13, 2013, 04:36:06 am
Does your new chip have a bootloader on it so that new sketches can be  loaded on to it?

No I did not put new chip a bootloader on it.  I was using verion 1.0. Do you know where can I get more information how chip can install with a bootloader and able to burn bootloader.
231  Using Arduino / Microcontrollers / Re: Mega Junior,1284 on: April 04, 2013, 06:59:17 pm
I'm a big fan of the 1284 as I'm using it on a my custom boards for electronic props for compat games.

I like the idea of an Uno or Mega compatible footprint, although most people using 1284 are probably at a stage where they'd be designing a board, or using something like Crossroads Bobuino board. Still, it's a good idea as another option for people into this nice little MCU with the extra resources that will satisfy many larger projects.

I notice that SPI and UART are on incompatible pins than Uno. The Bobuino pinmapping makes these compatible, RXT/TXD on D0/D1 and SPI on D10-D13. You have SPI on D4-D7 and RX0/RX1 on D8/D9.

Surely a standard shield won't work with your pins as is? An SPI shield may do, if it uses the SPI header, rather than pins 10-13, although I believe the Ethernet shield uses Pin 10 for its SS, whereas you have SPI on D4-D7
232  Using Arduino / Project Guidance / Re: How do I make panel mount for display and keypad on: March 29, 2013, 01:58:17 pm
I had the same issue of getting a finish I was happy with and eventually came up with something I was happy with.

I made an Instructable on making your own LCD window/bezel that ends up as a kind of black glass iPhone'esque type look. You could probably make the same kind of surround for a normal keypad if you could actually cut out the inside part, or use the same trick with a membrane keypad on the surface to have the black surround.
233  Using Arduino / Project Guidance / Re: Help with 16x2 LCD and 595 shift register on: March 28, 2013, 06:56:51 pm
The easiest thing would be to look at fm's New LiquidCrystal Library, as it supports 585 shift register and the project page has example circuits fir 1 wire, 2 wire and 3 wire connection methods.
234  Using Arduino / General Electronics / Re: Basic Transistor Question? on: March 28, 2013, 03:15:27 pm
The point of the snubber diode is to contain that back EMF to a closed loop containing the coil and diode. It's not shunting anything to ground. The field collapses and generates a high negative spike, dependent on field strength and the speed it collapses. The diode contains this to that mini circuit and the energy is dissipated as the circulating current and respective magnetic field decays. The rest of the circuit is thus protected from that spike.
235  Using Arduino / Microcontrollers / Re: Atmega644P Second Serial port on: March 27, 2013, 07:27:14 pm
I thought I remember reading somewhere that the reference to no second serial port on the non-P 644 was an error and it does in fact have a second UART.

I keep meaning to get my 644P's and 644's bootloaded and actually prove it true or false, unless someone else can confirm.
236  Community / Products and Services / Re: Cheap Fusion PCB Service(Color Free) !! on: March 27, 2013, 04:28:03 pm
Elecrow. Tried to order boards from your service. The order was $58 and it adds $12 for shipping. In the first post, you mention that you offer free shipping on orders over $50...
Drop an email to and I'm sure they'll resolve it for you. They have been good in responding to me.
237  Community / Products and Services / Re: Panelised PCBs on: March 26, 2013, 03:42:33 pm
Interesting. Do you have any pictures of the grooved boards and did you do anything different when submitting that design?

I've used Elecrow a few times now and I'm very happy with the service but I've never had any panelised designs come back grooved.
238  Using Arduino / Programming Questions / Re: Programming with a Bluetooth Module on: March 26, 2013, 06:15:18 am
If you have an android mobile then you might want to take a look at the BTInterface app -

It's a great way to interface a phone to your Arduino sketch over bluetooth.
239  Using Arduino / General Electronics / Re: Ghostly push-button input on: March 26, 2013, 03:40:46 am
Floating Inputs

What do you imagine is the input on the Arduino pin when your finger is touching nothing?

The last part of Mike's response tells you how to resolve.
240  Using Arduino / Microcontrollers / Re: Using Arduino Uno instead of FTDI cable to program 1284p w/ Optiboot on: March 25, 2013, 07:45:52 pm
Changing the fuse to 0xf7 for Full Swing Oscillator solved the UART0 issue for most, me included.

The symptoms were being unable to upload anything other than small sketches via bootloader through UART0. The falure message was the pagef_write error. Uploading via ICSP worked fine. After changing the low fuse a full 128kb sketch can be uploaded vis UART0 without issue.
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