Hi all,

This is my first time here and I hope you guys can answer my question. I am trying to build a true bypass loopers using this schematic: http://i2.photobucket.com/albums/y50/PRSplaya/DIY/4-loop-MB.png

I'm trying to get the LEDs from ebay and the seller offer to include resistors when I purchase 10 LEDs. However, the description of the resistor choice is confusing me:

"We have 5V / 7.2V / 9V / 12V / 13.2V resistors for choose, please tell us which Value you want, otherwise we will send the default 12V resistors."

I know from the schematic I will be needing 4.7K resistors. And I also studied this diagram:
http://www.sentex.ca/~mec1995/gadgets/resistors/resistor.gif
which tells me that I need resistors that have Yellow, Violet, Red, and Gold. So which one from the voltage selections above is this? And will the fourth band (tolerance %) matter for this small project?

Thank you

 

This is a 9 volt circuit and the 4700 ohm resistors are supplying a rather low current (1.4 ma) to the LED because 9 volt batteries are rather weak in the current department. It is foolish to expect an LED seller to assume the 4700 ohm number because he is trying to show off how bright his LEDs are by giving the maximum amount of current they can use without smoking. Give up and buy the resistors seperately or just ask for 4700 ohm resistors. This is a bad case of miscommunication based on entirely different goals. In other words, you think you're barking at a cat, but it's really a fire hydrant.

 

Thanks for that advice #12

 

Also, will using 5mm LED require different resistor Ohm value than using 3mm?

 

No. The specs for LEDs are about allowable current and minimum voltage. Lots of 3mm and 5mm LEDs are rated for 20 ma max. The switching circuit uses small currents so the LEDs are just indicators, not room lighting.

 

Instead of buying CHEEP (cluck cluck) YingYang Chinese no-name-brand LEDs from e-bay without a detailed datasheet, why don't you buy REAL GOOD NAME-BRAND LEDs locally?
Their detailed datasheet is in your own language and the spec's are guaranteed.
They are much more reliable than the CHEEP CRAP!

The arithmatic to calculate the value of a current-limiting resistor is extremely simple.

 

I disagree. Get the stuff from eBay. You're just going to burn them all out anyway, experimenting. I bought some crap from the Chinese overlords off of eBay, and it turned out alright. Shipping takes awhile, though. Tell them you want some of each of the resistor values and I bet they'll do it for the sale. They don't care; they've got millions of 5 year olds making this stuff all day long. They might even include an order of egg rolls.

 

I have been in electronics all my career and I have NEVER burned out anything by experimenting because I read the datasheets FIRST.

I also have NEVER bought anything from E-Bay because the products are no-name-brand and do not have a datasheet.