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Topic: my first post: arduino, clock, LEDs... (Read 829 times) previous topic - next topic

yves

Apr 10, 2008, 07:50 pm Last Edit: Apr 10, 2008, 07:52 pm by yves Reason: 1
hi there

this is my first post, so bear with me  ;) . I'm an architecture student and
for some time now, I'm planning a wrist watch that I initially sent into a
competition.

I would like to create this watch and develop it further by using the arduino
hardware.

I have ordered the arduino diecimilia kit and I'm just about to start learning elecronics.
I have had some contact with electronics (e.g. building a diy projector), but apart
from that, I'm quite a newb...

So here I have some questions:

- clock in general: how precise is the arduino board? do I need an extra quartz? And how would
I use it?

- how big is the arduino mini? I've read about width and lenght (3x1 cm), but I've seen nothing
about the height of the board...

- LEDs: I'll need to order a number of LEDs. What will I have to look at while ordering them?
Do they need to be 5V? Or could I also order 3V LEDs? And where can I find information which
LEDs need what kind or resistor?

- and finally: do you know of a super easy explanation of shift registers? I've read the tutorial
on this page, but I frankly don't quite get it. I'll certainly work it out for myself, but it would
be nice if there was an easy explanation of the concept behind it, somewhere...


sorry, I know, these are quite a lot of questions, I'm thanking
you in advance for any help you can give me!

best
yves

Oracle

#1
Apr 10, 2008, 08:15 pm Last Edit: Apr 10, 2008, 08:16 pm by Oracle Reason: 1
Quote

- clock in general: how precise is the arduino board? do I need an extra quartz? And how would
I use it?

- how big is the arduino mini? I've read about width and lenght (3x1 cm), but I've seen nothing
about the height of the board...

- LEDs: I'll need to order a number of LEDs. What will I have to look at while ordering them?
Do they need to be 5V? Or could I also order 3V LEDs? And where can I find information which
LEDs need what kind or resistor?

- and finally: do you know of a super easy explanation of shift registers? I've read the tutorial
on this page, but I frankly don't quite get it. I'll certainly work it out for myself, but it would
be nice if there was an easy explanation of the concept behind it, somewhere...


The Dieci has a quartz crystal on it.  It should be accurate within about 5 seconds a day.  That's comparable to a commercial quartz watch.  

The mini is in the form factor of a standard dip package.  Including pins it's maybe 7mm thick (that's my estimate).

The LED question is a lot more complicated than that because what people don't usually recognize is that they're current devices, not voltage.  Basically though, if you want 20mA, the resistor should be ([supply voltage] - [led voltage]) / 0.02.  Or 50*(supply voltage - led voltage).

Supper easy explaination of shift registers would be "serial in, parallel out"  or "parallel in, serial out"  depending on the model.


yves

hey thanks for your fast reply!
that helped alot. I'll probably have more questions
later on... cu then  8-)

greets
yves

dansku

Quote
Quote

- clock in general: how precise is the arduino board? do I need an extra quartz? And how would
I use it?

- how big is the arduino mini? I've read about width and lenght (3x1 cm), but I've seen nothing
about the height of the board...

- LEDs: I'll need to order a number of LEDs. What will I have to look at while ordering them?
Do they need to be 5V? Or could I also order 3V LEDs? And where can I find information which
LEDs need what kind or resistor?

- and finally: do you know of a super easy explanation of shift registers? I've read the tutorial
on this page, but I frankly don't quite get it. I'll certainly work it out for myself, but it would
be nice if there was an easy explanation of the concept behind it, somewhere...


The Dieci has a quartz crystal on it.  It should be accurate within about 5 seconds a day.  That's comparable to a commercial quartz watch.  

The mini is in the form factor of a standard dip package.  Including pins it's maybe 7mm thick (that's my estimate).

The LED question is a lot more complicated than that because what people don't usually recognize is that they're current devices, not voltage.  Basically though, if you want 20mA, the resistor should be ([supply voltage] - [led voltage]) / 0.02.  Or 50*(supply voltage - led voltage).

Supper easy explaination of shift registers would be "serial in, parallel out"  or "parallel in, serial out"  depending on the model.



So, if I want to use a bright let that uses 3v/20mA, I should use a 100ohm resistor instead of a 220ohms resistor to have a better light?
thanks

Adilson Akashi

Daniel,

to use a led you must know it's voltage and current.

In case of using it with Arduino pins (that works with 5v.), you must calculate the resistor value using the first Ohm Law:

R=U/I

where U is (5-led's voltage) in Volts, and I is the led's current in Amperes.
R value is in Ohm.
In your example, R=(5-3)/0,02A=2/0,02=100ohms.

I'm sure you can find this in your Electrical Engineering School Books...
PCB Designer

dansku

Quote
Daniel,

to use a led you must know it's voltage and current.

In case of using it with Arduino pins (that works with 5v.), you must calculate the resistor value using the first Ohm Law:

R=U/I

where U is (5-led's voltage) in Volts, and I is the led's current in Amperes.
R value is in Ohm.
In your example, R=(5-3)/0,02A=2/0,02=100ohms.

I'm sure you can find this in your Electrical Engineering School Books...


Yes, thanks! :) I wans't sure because everywhere I find examples using 220ohm resistor for leds.

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