Arduino Forum

Using Arduino => General Electronics => Topic started by: diggee17 on Feb 08, 2013, 11:20 pm

Title: need to know what resistor to use for my project
Post by: diggee17 on Feb 08, 2013, 11:20 pm
hello,
I'm a total newbie.  I just bought the Arduino Uno board and I bought Radio Shack's Sidekick Basic Kit for Arduino.    I'm trying to do a project I found in a book.  It calls for 100 ohm resistor.  I have 3 types of resistors marked 1)1k Ohm Resistor , 2)10K Ohm Resistors  and 3) 330 Ohm Resitors.  I think  I should us e the 330 Ohm but I'm not sure and I don't want to brake anything before I even get started!!!! 
TIA
Title: Re: need to know what resistor to use for my project
Post by: JChristensen on Feb 08, 2013, 11:28 pm
I might go back to RS and get some 100 ohm resistors.

My crystal ball is in the shop, so I can't comment on whether a 330 ohm resistor would work, without seeing the project (hint: got a link?)

If you have three 330-ohm resistors, put them in parallel, that will give 110 ohms.
Title: Re: need to know what resistor to use for my project
Post by: diggee17 on Feb 09, 2013, 01:58 am
Thanks.  (Can't go to RS now- a blizzard on US EAST COAST!)
  The project is a simple led flasher. From book "beginning arduino "
The hardware used in Project 1:

Breadboard

5mm LED

100 ohm Resistor*

Jumper Wires

* or whatever value appropriate for your LED

The code is:

Listing 2-1. Code for Project 1

// Project 1 - LED Flasher
int ledPin = 10;
void setup() {
         pinMode(ledPin, OUTPUT);
}
void loop() {
        digitalWrite(ledPin, HIGH);
        delay(1000);
        digitalWrite(ledPin, LOW);
        delay(1000);
}
Title: Re: need to know what resistor to use for my project
Post by: JChristensen on Feb 09, 2013, 02:03 am
Oh, OK, 330 will be fine. It's a current-limiting resistor for the LED. With 330 it might not be as bright, but actually 330 is sort of my "standard" resistor for most 5mm LEDs, many of them are quite bright with 330 ohms at 5V.

Good luck digging out. The storm has moved out here, it will be a cold and clear night with lows around 5°F. We had maybe 4" or 5" of snow, so nothing all that remarkable here.

Good weather to stay in and play with microcontrollers, enjoy!
Title: Re: need to know what resistor to use for my project
Post by: nickgammon on Feb 09, 2013, 02:32 am
As Jack said, 330 ohms would (probably) let 10 mA flow through your LED, which should be plenty to make it light up nicely. Have fun playing with it. :)
Title: Re: need to know what resistor to use for my project
Post by: CrossRoads on Feb 09, 2013, 04:27 am
Ah, blizzard, its just snow!
Greater hindrance is the governor banning all traffic on the roads with fines & jail time 8)
(except public safety kinds of vehicles - and the media!)
Title: Re: need to know what resistor to use for my project
Post by: JChristensen on Feb 09, 2013, 05:26 am

Ah, blizzard, its just snow!
Greater hindrance is the governor banning all traffic on the roads with fines & jail time 8)
(except public safety kinds of vehicles - and the media!)


Wow, that is serious.  Sure am glad the media can do their thing though :smiley-zipper:

How much snow?
Title: Re: need to know what resistor to use for my project
Post by: spcomputing on Feb 09, 2013, 08:45 am

Ah, blizzard, its just snow!
Greater hindrance is the governor banning all traffic on the roads with fines & jail time 8)
(except public safety kinds of vehicles - and the media!)


Good luck Crossroads, Mass. looks to be the winter wonderland of the week.
Title: Re: need to know what resistor to use for my project
Post by: fungus on Feb 09, 2013, 12:28 pm
Is this a good place for a joke about Global 'Warming'...? :)

Title: Re: need to know what resistor to use for my project
Post by: JimboZA on Feb 09, 2013, 12:48 pm
Here in Johannesburg it's 23 right now....

..... but then, we use Celsius. And also, being in the Southern Hemisphere it's summer  XD
Title: Re: need to know what resistor to use for my project
Post by: cjdelphi on Feb 09, 2013, 12:54 pm
Global Cooling...


To the original poster, if the resistor is a higher value than required, it will never hurt..... the most that could happen is that it simply fails to work (unless it's some kind of circuit which increases voltage depending on resistance)  or.... incase of the LED, not as bright.

BUT...

You could use PWM via the Arduino or even make your own resistor using nichrome or similar wire.

Title: Re: need to know what resistor to use for my project
Post by: A4kash on Feb 09, 2013, 04:00 pm
try resistors using ohms's law which states E=I*R,know the input voltage and the current that the device can handle ,such as for glowing the leds you should first know the max amount of current the leds can handle and the input voltage you are getting from the arduino pins and you can easily calculate the resistance.For more info
http://www.kpsec.freeuk.com/components/resist.htm
Title: Re: need to know what resistor to use for my project
Post by: CrossRoads on Feb 09, 2013, 04:11 pm
We got 20-24", heading out to clear the driveway in a few minutes.
End of the driveway is over 4' from the plows, right up to the bottom of the mailbox.
Title: Re: need to know what resistor to use for my project
Post by: JimboZA on Feb 09, 2013, 04:19 pm
Quote
know the input voltage and the current that the device can handle ,such as for glowing the leds you should first know the max amount of current the leds can handle and the input voltage you are getting from the arduino pins and you can easily calculate the resistance


Bzzzzzzt not quite  8) .... for LEDs you subtract the LED voltage from the supply voltage which gives the drop you need to cause over the resistor, and divide that by the current to get the resistance needed.
Title: Re: need to know what resistor to use for my project
Post by: JChristensen on Feb 09, 2013, 08:23 pm

We got 20-24", heading out to clear the driveway in a few minutes.
End of the driveway is over 4' from the plows, right up to the bottom of the mailbox.


Yikes! :smiley-eek:  Hope you have a snowblower. Either way, don't hurt yourself.
Title: Re: need to know what resistor to use for my project
Post by: CrossRoads on Feb 09, 2013, 10:16 pm
Yup, bought a snowblower when my son was born.
The year he was born, or maybe a year later, we had 106" of snow!
Ground was bare before this storm, looks nice & wintery now.