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Author Topic: LEDs without the use of current limiting resistors  (Read 5311 times)
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Sparkfun did sell a no-resistor-multiplexed-led display,

How "misinformed" they are, smiley
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Where do you get resistors for less than one cent each? I get them cheap on the internet, and they are 2-5 cents each, in packs of 100 or more.

Pretty much anywhere. Here's some 10K resistors from DigiKey for 0.2 cents each at qty 100:

http://www.digikey.com/product-detail/en/1622826-4/A106045CT-ND/3477682

As an aside, this is easily my favorite thread of the new year.

Those are 1/16w 0402 smt parts, I actually have some of those, have you ever tried soldering them?

I should look over digikey and mouser more often, but I find them those sites a bit overwhelming.
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How about regular 1/4W carbon resistors then? $0.01 each for 10-lots.
http://www.taydaelectronics.com/resistors/1-4w-carbon-film-resistors/10-x-resistor-220-ohm-1-4w-5-carbon-film-pkg-of-10.html

I don't like what Tayda did to their website - the menu shows up on the left, while anything selected now shows up underneath it with a big empty space next to the menu.
My screen is set to 1280 x 800 - anyone else seeing the same?

Looks to be IE9 thing - don't see the layout issue with Google Chrome.
IE9 didn't used to do to that, this is fairly recent.
« Last Edit: January 08, 2013, 08:51:44 pm by CrossRoads » Logged

Designing & building electrical circuits for over 25 years. Check out the ATMega1284P based Bobuino and other '328P & '1284P creations & offerings at  www.crossroadsfencing.com/BobuinoRev17.
Arduino for Teens available at Amazon.com.

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works fine for me

edit: firefox
« Last Edit: January 08, 2013, 09:51:46 pm by Osgeld » Logged


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How about regular 1/4W carbon resistors then? $0.01 each for 10-lots.
http://www.taydaelectronics.com/resistors/1-4w-carbon-film-resistors/10-x-resistor-220-ohm-1-4w-5-carbon-film-pkg-of-10.html

I don't like what Tayda did to their website - the menu shows up on the left, while anything selected now shows up underneath it with a big empty space next to the menu.
My screen is set to 1280 x 800 - anyone else seeing the same?

Looks to be IE9 thing - don't see the layout issue with Google Chrome.
IE9 didn't used to do to that, this is fairly recent.

On IE 8 it works ok, with chrome when you mouse over a menu category on the left the submenu displayed is 95% hidden behind whatever picture is displayed in the middle of the screen, just that very edge of the submenu can be seem. I just sent them an email about it. I'm at 1280x960 display.

Lefty

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How about regular 1/4W carbon resistors then? $0.01 each for 10-lots.
http://www.taydaelectronics.com/resistors/1-4w-carbon-film-resistors/10-x-resistor-220-ohm-1-4w-5-carbon-film-pkg-of-10.html

I don't like what Tayda did to their website - the menu shows up on the left, while anything selected now shows up underneath it with a big empty space next to the menu.
My screen is set to 1280 x 800 - anyone else seeing the same?

Looks to be IE9 thing - don't see the layout issue with Google Chrome.
IE9 didn't used to do to that, this is fairly recent.

I think thats where i got the ones am currently using. after shipping their costs go up 2-5 times depending on your patience.
Standard 7 - 16 Days $1.08
Economic Express 6 - 9 Days $4.08
DHL Express 2 - 4 Days $16.00

I can also get them from thaishine, for a few bucks with 4 day shipping. Its much better than the local prices (about a quarter each), but its no 10 for a penny.
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I've only used the slow/cheap shipping. I stock up when I buy, $30-40 worth of stuff at a time, so shipping becomes a small part of the total price.
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Designing & building electrical circuits for over 25 years. Check out the ATMega1284P based Bobuino and other '328P & '1284P creations & offerings at  www.crossroadsfencing.com/BobuinoRev17.
Arduino for Teens available at Amazon.com.

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I should look over digikey and mouser more often, but I find them those sites a bit overwhelming.

I agree they can be daunting at first but they're manageable. I much prefer DigiKey's interface; I find it the easiest to use. Many times if I get something from Mouser, Newark, etc. I'll find it on DigiKey then cut & paste the part # at the other sites.

I start by searching for as close to what I need as possible, e.g. "atmega328p-au" or "1/4 watt 10k resistor". This generally does a good job of getting close.

Next I check the "In Stock", "Lead Free", and "RoHS Compliant" boxes and search again; there's usually no point in searching if they don't have it in stock and the other two seem to help whittle things down further.

Next I start going through the search boxes like "packaging" or "height", etc. for things I know I want, e.g. a specific size or footprint and click "apply filters" each time.

When the result list is a reasonable size I sort by "unit price" and buy the cheapest one (unless I know I'll eventually need a lot of the part, in which case I give "quantity available" some weight).

Having said all that, I try to do as CrossRoads says and batch up purchases at one of the Chinese companies; this is usually the overall least expensive option.
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mousers interface is down right frustrating to me, but its better than it was?

digikey is overwhelming until you get it, then once you do you can take an idea like "i need a shift register" and filter it down to the cheapest one in the quantity range you want, while meeting your requirements with two - three filter passes, its almost an art
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I don't buy Chinese or e-bay generally (WS2803 is one exception), except for iteadstudio.
dipmicro.com in Canada/Western NY, taydaelectronics in Thailand
and Digikey, Mouser, Avnet, Pololu.
Sometimes Newark. They have eagle symbols for some parts too.
Phoenixent.com for strip sockets & headers & wirewrap stuff.

I use these sources for their repeatability.

Digikey/Mouser both irritating digging down trying to find things like header strips.  I buy that kind of mechanical stuff from pololu and phoenixent instead.
For resistors, caps, transistors, diodes, surface mount, digikey is the best.
Mouser has best prices on Atmel parts.
Avnet for TPIC6x595 shift registers.
« Last Edit: January 09, 2013, 12:45:42 am by CrossRoads » Logged

Designing & building electrical circuits for over 25 years. Check out the ATMega1284P based Bobuino and other '328P & '1284P creations & offerings at  www.crossroadsfencing.com/BobuinoRev17.
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I usually stick to digikey and mouser for small quantities

I got to give props to arrow and avnet, they are 2 of our suppliers at work, and hey, they buy me nice lunches hehe, and both have good support even if they dont know who you are

DK on the other hand sent me 250 .1uF 805 caps, which were suposta be 5Amp rectifier diodes in a SMC package (for those not familiar with surface mount packages its a grain of rice vs a jellybean, never mind its totally the wrong component), and I got a deadline on (next)Tuesday ... I had to get bitchy with them and reorder somewhere else cause a couple weeks later and people still cant find info on the mix up is not cool, so they are a bit on my list right now
« Last Edit: January 09, 2013, 01:02:34 am by Osgeld » Logged


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they buy me nice lunches hehe

Someone at work got a drawer full of atmel's USBKEY, as  free samples. That would have been worth some serious money during the height of ps3 jailbreak.
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Just an analogy here,   my neighbour , when he decides to drive to the casino, never wears his seat belt.

Both of these choices are his ( although the seat belt is compulsory )  I am just trying to show his mentality here.

He has never been killed yet in 50 years of driving without a seat belt.  If asked about it he might well say " I heard of someone who had a crash and was thrown out of the burning car ,  and survived because he wasn't wearing a seat belt "  There are a few variations of this.

The point is,  if there was a forum for newcomers to learn about driving, should we be saying " don't worry about wearing a seat belt, I know someone who has got away with it for 50 years ! "  ?

Another point is, wouldnt at least one LED manufacturer jump on the bandwagon and say " you don't need a resistor with our LEDs " and sell more ?     Perhaps they know something, being manufacturers.

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With my mobile phone I can call people and talk to them -  how smart can you get ?

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wouldnt at least one LED manufacturer jump on the bandwagon and say " you don't need a resistor with our LEDs " and sell more ?     Perhaps they know something, being manufacturers.

They do, that's why you never hear an LEd manufacturer (reputable ones) who says "you have to use a resistor with LEDs".

Because both statements ("you have to use a resistor" and "you cannot use resistors") are wrong. Whether you should use a resistor or not is application specific and needs to be evaluated specifically.

Just common sense.
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wouldnt at least one LED manufacturer jump on the bandwagon and say " you don't need a resistor with our LEDs " and sell more ?     Perhaps they know something, being manufacturers.

They do, that's why you never hear an LEd manufacturer (reputable ones) who says "you have to use a resistor with LEDs".

Because both statements ("you have to use a resistor" and "you cannot use resistors") are wrong. Whether you should use a resistor or not is application specific and needs to be evaluated specifically.

Just common sense.


Wrong.

Manufacturers supply things called "datasheets" with their parts. In the datasheet there's always a section titled "Absolute Maximum Rating". The values in there are determined by people who know stuff about their product and know what power is likely to damage it.

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No, I don't answer questions sent in private messages (but I do accept thank-you notes...)

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