# Society of Robots - Robot Forum

## Electronics => Electronics => Topic started by: Crunchy Theory on July 15, 2010, 07:02:38 PM

Title: \$50 Robot tutorial - resistor values
Post by: Crunchy Theory on July 15, 2010, 07:02:38 PM
Hey Guys, I'm a bit confused on the \$50 Robot tutorial. I understand that though the parts list says to use 1.62Kohm resistors for the photoresistors, I should perform the calculation in the photoresistor tutorial to make sure and make changes if necessary.

The tutorial doesn't say which of the resistors I should use with the LED, though. The parts list has two values: 340ohm and 1.62Kohm - which one?

Title: Re: \$50 Robot tutorial - resistor values
Post by: Choco_liger on July 15, 2010, 07:54:27 PM
The 340ohm resistor is for the LED.
Title: Re: \$50 Robot tutorial - resistor values
Post by: Alfa_Zulu on July 16, 2010, 03:00:21 AM
the value of the resistor for the led depends on the led it self, it may draw anywhere from 10ma-50ma and the resistor is the keep this value low enough for that exact led so it doesn't burn out.

if you buy the led from an electronics shop just ask them "what resistor do i need to run this led on a 5v circuit" and they can tell you
Title: Re: \$50 Robot tutorial - resistor values
Post by: Soeren on July 16, 2010, 04:16:52 AM
Hi,

if you buy the led from an electronics shop just ask them "what resistor do i need to run this led on a 5v circuit" and they can tell you
Not many of that kind of shops left. Most desk jockeys wouldn't know an LED from a transformer these days, so if you want to get it right, know what you're shopping for.
Title: Re: \$50 Robot tutorial - resistor values
Post by: Alfa_Zulu on July 16, 2010, 04:58:53 AM
Hi,

if you buy the led from an electronics shop just ask them "what resistor do i need to run this led on a 5v circuit" and they can tell you
Not many of that kind of shops left. Most desk jockeys wouldn't know an LED from a transformer these days, so if you want to get it right, know what you're shopping for.

Really? we must just be lucky here, at my local electronics shop you have to have a fair knowledge of electronics to get a job there lol
Title: Re: \$50 Robot tutorial - resistor values
Post by: Razor Concepts on July 16, 2010, 05:24:18 AM
You actually have an electronics shop  :o

Most electronic shops in the U.S. would just be "uhh... would you like to buy an ipod?"
Title: Re: \$50 Robot tutorial - resistor values
Post by: Alfa_Zulu on July 16, 2010, 05:34:06 AM
lol, that sucks.

i thought radio shack was meant to be a proper electronics shop? lol

here in Aus we have Jaycar and their fairly decent for an elec shop
Title: Re: \$50 Robot tutorial - resistor values
Post by: Joker94 on July 16, 2010, 05:46:58 AM
here in Aus we have Jaycar and their fairly decent for an elec shop

yeah they are descent but they are over priced if your stocking up for your next robot or electronics project. 40cents for 10 resistors when i can get them 12 for 10 on line. i can get a 4 number led display for 44 cents online where i would pay \$7 for a single number 7 seg display from Jaycar. you get the idea.

it is well worth planing in advance and getting what you need online. you save yourself an arm and a leg.
Title: Re: \$50 Robot tutorial - resistor values
Post by: Conscripted on July 16, 2010, 06:26:20 AM

i thought radio shack was meant to be a proper electronics shop? lol

I went into a radio shack not to long ago and picked up a few things I needed for a sandwich robot "www.robotroom.com" and the guy that runs the place looked at my purchase and offered me a job. I had to turn him down. The military keeps me more then busy enough. It felt good though.

Conscripted
Title: Re: \$50 Robot tutorial - resistor values
Post by: Alfa_Zulu on July 16, 2010, 06:29:30 AM

yeah joker i get what you mean,

4 number led display for 44 cents online where i would pay \$7 for a single number 7 seg display from Jaycar. you get the idea.

please tell me where you can get 7 segment displays so cheap?
Title: Re: \$50 Robot tutorial - resistor values
Post by: Razor Concepts on July 16, 2010, 08:09:47 AM
http://mouser.com/ProductDetail/Lite-On/LSHD-A101/?qs=sGAEpiMZZMu0f%252bT2bkVfujrlA%252bqhCh1/ (http://mouser.com/ProductDetail/Lite-On/LSHD-A101/?qs=sGAEpiMZZMu0f%252bT2bkVfujrlA%252bqhCh1/)

Digikey and Mouser always have excellent prices
Title: Re: \$50 Robot tutorial - resistor values
Post by: SmAsH on July 16, 2010, 06:29:06 PM
Most bulk online stores should have decent prices, just try to stay away from the robotics specific stores, they're generally horrible.
Title: Re: \$50 Robot tutorial - resistor values
Post by: Alfa_Zulu on July 16, 2010, 06:31:22 PM
ah ok thanks