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856  Forum 2005-2010 (read only) / Frequently-Asked Questions / Re: eaaasy question.. on: March 27, 2008, 09:06:03 am
Hi,
I think I remember that Midi works with some optocouplers? Might be there to limit the current, or as a pull-up, I don't know. Any specific reason why you don't want that resistor to be around?

And .. errrr... what made you think that this is an easy question????

Eberhard
857  Forum 2005-2010 (read only) / Frequently-Asked Questions / Re: Arduino USB bus current draw on: March 27, 2008, 04:04:21 am
Three things I'd like to add:

Current drawn by the Arduino-board:
My NG burns only 60 mA running idle.

Max current drawn from USB:
As already mentioned the Arduino asks for 90 mA. If your circuit draws more than that, it's up to the Hub to decide what to do:
Usually the hub grants up to 500mA, but it is also possible that the hub decides to disable your device.
 
I remember a notebook (Acer?) that granted 500mA for  every device as long as it was powered from mains. But as soon as it ran on batteries it disabled all devices that consumed more current than they initally asked for.
So check with the computer (or UB-hub) you will be using in the end.
 
Power from external 5V source:
If you already use a regulated 5V power-supply you can power the board from the middle pin of the jumper that selects between USB and external Power.
(you remove the jumper and connect the middle pin to plus 5V).

If you get the Voltage wrong (>5V) this kills the board
If you get the polarity wrong this kills your board
If you use an unregulated power-supply the board might run unstable (or gets killed)

The traces should be fine for 800mA.
For safety you might want to add a fuse between the Powersupply and the board.

Check with the arduino schematic.

Eberhard
858  Forum 2005-2010 (read only) / Frequently-Asked Questions / Re: arduino button on: March 02, 2008, 05:10:56 am
Yes,
that is the way it's supposed to be
the software makes the Led blink...
then you reset the whole thing...
the arduino checks if there is new sketch to be uploaded, if not :
the software makes the Led blink...

Eberhard

859  Forum 2005-2010 (read only) / Frequently-Asked Questions / Re: What software do you use to draw circuit diagr on: February 04, 2008, 11:35:25 am
Hi,
I'm using this : http://www.abacom-online.de/uk/html/splan.html
examples drawn by myself are here : http://www.arduino.cc/playground/Main/MAX72XXHardware

It was very easy to get started but comes also with complete libraries. I use it for drawing Guitar-Tabs and Chords too. Very versatile...if they only had a linux version :-(

Eberhard

860  Forum 2005-2010 (read only) / Frequently-Asked Questions / Re: can arduino control 1000 leds on: January 12, 2008, 04:46:24 am
Hi,
yes it should be possible have a look at these tutorials
http://www.arduino.cc/playground/Main/LEDMatrix

Eberhard
861  Forum 2005-2010 (read only) / Frequently-Asked Questions / Re: Arduino digital delay? on: November 17, 2007, 03:36:46 pm
Hi,
simple answer, No!
...and if it were possible its would cost more than buying a digital delay at the store :-(
Sorry
 Eberhard
862  Forum 2005-2010 (read only) / Frequently-Asked Questions / Re: Sensor data aquisition on: December 12, 2007, 04:12:47 am
Hi,
Quote
I'll still need some on-board ram though since the sensor data will be coming very quickly.  I'll have to write to the usb in bursts from a ram cache.
What exactly is your datarate? There is an upper limit of the throughput of the USB-serial-connection too.
As far as I know the ftdi-chip on the Arduino uses a package-size of 64 bytes per transmission. If I understand that right nothing is gained in sending larger bursts.

Eberhard

863  Forum 2005-2010 (read only) / Frequently-Asked Questions / Re: Led as analog input on: December 12, 2007, 04:03:22 am
http://www.arduino.cc/playground/Learning/LEDSensor

easy to find with the new Playground hardware index at
http://www.arduino.cc/playground/Main/InterfacingWithHardware

Eberhard
864  Forum 2005-2010 (read only) / Frequently-Asked Questions / Re: Arduino to SMSBus & I²C bus on: December 11, 2007, 02:49:06 am
Hi,
I nerver heard of the SMS- bus, but there is plenty on I2C

here is one link
http://www.nearfuturelaboratory.com/2007/01/11/arduino-and-twi/

and google "arduino I2C" has a few thousand more

Eberhard
865  Forum 2005-2010 (read only) / Frequently-Asked Questions / Re: Batteries? on: November 23, 2007, 12:53:30 pm
Hi,
Quote
What about adding a sentence that says something like "If supplied with less than 7V, the board's power may fluctuate. ..."?
Quite a few people use the 5V from the Arduino to power their external hardware. For instance the MAX7221 is unforgiving when Vcc goes below 4.7 Volts. The Arduino-code on the AT is still running, but all Leds are off.

The KISS principle demands the sentence : ""If supplied with less than 7.5V, you are doomed!!!!",
(7.5V because its a common value you find at the wallwart powersupply store).

Eberhard

866  Forum 2005-2010 (read only) / Frequently-Asked Questions / Re: Visual Basic? on: November 17, 2007, 03:43:32 pm
Hi,
I have never tried it and I never used basic again since the Commodore64, but you can use every programming language to talk to an Arduino as long as it knows how to talk to a serial port. .NET2.0 has the SerialPort-class so VB should work.
(You don't want to write sketches for the Arduino using VB, do you? We are talking about exchanging data with a running Arduino-sketch don't we?)

Eberhard
867  Forum 2005-2010 (read only) / Frequently-Asked Questions / Re: driving LEDs on: October 15, 2007, 02:26:29 am
Hi, Cheater
Quote
Quote
But concering the maximum supply current it is important to understand, that at any given point in time a group of 8 Led's are switched on or off
Uuuh no. Only one LED is on at any one time with those chips.
Go read the datasheet.
I did when I wrote the LedControl-Lib, all of it!
You probably want to read the section Computing Power Dissipation on page 11 in the datasheet again.
The equation clearly shows that the number of lit segments (Leds) is relevant to the power-consumption (Factor N).
It also mentions the worst case scenario : 8 segments (Leds) lit.

If you need another proof, see the Electrical Charateristics Table on page 2.
In the third row Operating Supply Current there is a value given for the matrix when all 64 Leds(segments) are lit.
If the Led-(segment-) current is set to 40 mA (Resistor ISet) the resulting Current is given at 330 mA.
Thats 40 mA per Led (segment) plus some extra 10 for internal chip-logic.

Eberhard
868  Forum 2005-2010 (read only) / Frequently-Asked Questions / Re: driving LEDs on: October 13, 2007, 03:55:41 am
Hi,
Quote
No, it does a 8x8 array of LEDs. Also works well with 8 7 segment displays.
Yes, thats why its a 8x8 Matrix. But concering the maximum supply current it is important to understand,
that at any given point in time a group of 8 Led's are switched on or off, depending on the data sent to the device.
Since there is a chance that all Led's of the group are on at the same time, the maximum supply current to be expected is 8 times the current that was set on the hardware-side (Resistor ISet, see datasheet).

Eberhard

869  Forum 2005-2010 (read only) / Frequently-Asked Questions / Re: driving LEDs on: October 12, 2007, 06:35:10 am
Hi,
Quote
I'd use the MAX7921....
Its also rather light on the battery because only one LED is on at any time yet it still looks good.
If you meant MAX7221, not quite right, The MAX7221 always switches a group of 8 Led's on or off.
Still saves a lot of power though.

Eberhard


870  Forum 2005-2010 (read only) / Frequently-Asked Questions / Re: Tutorials on: September 16, 2007, 07:09:53 am
Hi,
moving the tutorials into the playground is a good idea, but I think the playgorund needs some kind of cleanup too.
Navigating among the different sections on the right panel gets more confusing all the time.
Like there is the entry "Standalone 3.3v 8Mhz" in the Tutorial section. What does someone new to the arduino expect to read here?
The distinction between CodeLibrary and ConnectingHardware is also not very clear.
I wrote a libray for controling a LedMatrix. Does that belong into the hardware-section, or the library-section?
For a start I suggest to implement a more tree-like navigation, with only a few links like tutorial/hardware/IDE/etc.
which links into another index of a subsection.
There is actually no need to have a direct link to the LedMatrix-Lib from the main page like it is now.

Another suggestion would be a playground-section in the forums.
There are sometimes articles I would like to comment on or discuss with others. (Actually there are some articles I would like to see beeing deleted, because there is no content at all):
Maybe this "playground-forum" would encourage people to ask questions, request changes etc. in a easy manner.

Eberhard
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