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Topic: Arduino Map (QUIZ) (Read 1 time) previous topic - next topic


Hi, this is  just a little quiz to create a map of every and each of the components that comes with the pre-built arduino board.

The idea is to use a blog for building it, then i will upload it somewhere in this forums so new people (like me) can understand better the electronics of the board.

Maybe i didnt saw it, thats the reason i uploaded a hi-res image of my arduino.

Please use the comments of the blog to add your descriptions to each of the marked (with letters as a recomendation from Ian) parts of the board in the hi-res image.



Feb 06, 2006, 05:15 am Last Edit: Feb 06, 2006, 05:18 am by admin Reason: 1
I've designed the board maybe I can answer :)

btw in order to understand what the components do,  you need to refer to the schematic diagram


a. power led, it lights up when the board is powered. Normally it's green. Some boards have a red led because of a mistake done by the assembly company.

b. ISP connector. ISP means "In System Programming" this connector allows programming the microcontroller directly. This is used to program the bootloader on the processor before the board can be used.

c. reset button

d. microcontroller

e. protection diode. prevents applying the power to the board with the wrong polarity (swapping + with - can damage the processor)

f. capacitor.  sometimes the circuit you attach to the board might have a sudden power surge that will drop the voltage and below a certain value the processor might reset. this capacitor kicks in a provides that extra bit of power to compensate for the fluctuactions.

g. RX TX leds. these light up when the board receives or  sends data from the USB. it's useful to debug issues with USB communication.

h. 16MHz quartz. this provides the clock signal to the processor.

i. 5v out. this provides a source for regulated 5V supply. where this come from is dependent on SV1 (letter o)

j. and k ground connection (the - on a battery). this is connected to the ground path on the board. why 2 ? because 2 is better than 1 (infact we have 3 since letter w is also ground)

l. 9V. this is the voltage that has been applied to the dc power plug (letter r) normally it's around 9v but it depends on the power supply you're using.

m. analogue inputs. see http://arduino.berlios.de/index.php/Tutorial/JoyStick for an example of use.

n. USB connector. It's an USB 2.0 (not high speed. 12 MBit max) connector that brings data into the board.

o. power selector jumper. this jumper decides where the power comes from. between pin 2 and 3 it takes the power from the USB bus while between pin 1 and 2  takes power from and external power supply.

p. ceramic resonator. this provides the 12 MHz clock to the usb interface chip.

q. power regulator. when the board is powered from the external power supply this makes sure that the voltage applied to the processor is always 5v

r. external power plug. this is where you plug an external power supply. the size is 2.1mm with the plus at the centre pin. power applied to this plug should go from 9 to 15 volts.

s. resistors. these are required to interface to the USB bus.

t. usb to serial interface chip. this chip allows the microcontroller to connect to the USB bus and use it to talk to the computer.

u. capacitors. these are used by the usb interface chip (letter t)

v. aref. this is a tough one... this pin is used to tweak the way the analogue pin translate voltage into numbers. it's used only by advanced user.

w. ground

x. digital pin number 13. the only difference from the others is that this one has an 1k resistor attached to it so that we can plug an LED directly from 13 to ground without burning it.

y. these are special pins controlled by the USB bus. they will be used in the future to automatically reset the board before exporting. this will save users from having to press the reset button all the time.

z. resistors. the one you are pointing at is used to limit the current that goes into the RX TX led.

hope this helps...
You'll learn more from the schematic when you know how to read it :)



Feb 07, 2006, 06:45 pm Last Edit: Feb 07, 2006, 06:52 pm by beltran Reason: 1
this post should be linked from the  "Familiarise with the Arduino Board" tutorial...

I'm curious to work on the aref...
can I just stick a pot in the aref and see what happens to another analog input (via serial feedback)?
is this enough or do I need more circuitry?
do I risk somenthing or once I remove the pot from the aref pin it will get back to behaving normally? (I mean playing with it won't "record" any preset in the atmega8, right?)

thanks in advance


The aref works like this...

When you do analogue to digital conversion the arduino board uses the 5V supply as a reference. this means that any voltage between 0 and 5v is represented as numbers between 0 and 1024. If the signal you are measuring never reaches 5V it is possible to change  the reference  to an internal 2.5 v source and this divides the space between 0 and 2.5v in 1024 steps effectively doubling the resolution. If this still doesn't work for you then you can ask the processor to use an external voltage applied to aref. if you find a super stable 1V refernce source this will give you 1milli volt resolution for the ADC. this is used only in special applications because at that resolution the noise becomes a big issue etc etc

switching reference voltage requires adding a few lines of C code to your arduino code.

Summarising : changing your aref is advised only if you have  good grasp of analogue electronics otherwise it's a mess.. :))



ok thanks for the reply,

maybe a day I'll try it out exactly because I don't have any grasp of analog electronics :)
hopefully in the process I'll get some more of that needed grasp



alex just told me over the #arduino channel that the Digital 0 and 1 allow communication with the computer. Sort of obvious (Rx, Tx) but is good to confirm with someone who has experience before connecting stuff.

just to add those 2 that had no letters assigned.


Aug 25, 2006, 10:42 pm Last Edit: Aug 25, 2006, 10:44 pm by armadillo Reason: 1
and just for the record im adding a comparison pic between the arduino board and the wiring board, i just got one, hopefully later i will be adding some notes on the diff. and advantages i find. /a

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