Asked — Edited

Way To Power An Led Rather Than Dig. Port

I'm really sort on digital ports on my rad project. I don't have any more digital ports left. I don't want to spend +$10 on a tip circuit because that wont allow me to turn individual leds on and off. Is there an alternate way I could power them?


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I2C Expander, but they wont be natively supported by ARC (i.e. the digital controls wont work). Second EZ-B. Multiplexer circuits.

A second EZ-B is the ideal choice. It's simple and supported by ARC's built in controls. I2C Expander is next best but you will need to use scripts and you will need to find an expander that is well documented with all of the I2C commands you'll need to use to enable outputs. Multiplexer is not really recommended, they cost a lot of ports to increase by few. They have been discussed and the conclusion was they are not really a good solution for increasing digital outputs.

Look around for parts for the TIP circuit too, $10 is a lot for the few items it needs. You should easily be able to pick up what you need to make one for $3 (plus any shipping if applicable).


If you wish to power them and not need to control them - use the +5 on the side expansion port of the EZ-B. If powering directly off the +5, I would recommend throwing a resistor inline.


again the "put 2 and 2 together" come to mind.

@rich, already out of money in my budget so a second ez-b is out of the question. i2c scares me. I've looked at the commands and examples and it seems overly complicated.

I guess i'll wait until I've got the rad torn apart until I ask the questions.

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Do you know how many LEDs you need and how you want them to work?

I2C is pretty simple once you get past the initial "wow, what in God's name do I do with this" part. I was planning to use I2C extenders on Melvin's eyes before his head change to power and sequence rows of LEDs to simulate eye lids opening/closing (I've since found out that Loki has something very similar).

Besides, even if I2C does scare you, there's a community here waiting to help if you need it.


Its OK I2C scared me too thunder buddy



Let us know what you had in mind.

I've doubled up LED's connected to the EZB just to keep simple, but it all depends on your plan.



I'm planning on testing the leds on a aa battery pack test like I do with all my leds to see if I can double up some. then ill start finding alternate ways. thanks for all the comments


visit this video sorry i don't know how to include a video

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How can you have more than 1 led in the matrix on at the same time though? Say you wanted all 9.


cycle through them fast if you watched all the tutorial it will explain everything i might make a tutorial post soon


@Technopro ....Certainly, there are ways to prioritize ports, multiplexing, charlieplexing for extra LED's but adding an extra EZ-B is the best way to go as explained previously. We are all painfully aware of budgets and I myself included. I have cut back on liquor consumption dramatically (which is a good thing anyways), dining out and like Rich said in an earlier thread put on extra sweaters and save on heating bills. You as a young person are in a different boat for sure. My suggestions are and if they apply to you....You might have 4 grandparents, they are usually willing to help out a focused grandchild! You might have a couple of favorite uncles who would like to see your cool project expand.....and of course your parents who want to keep you focused on future job prospects/interests.....10 dollars each and your there. Or like myself, always said to my two daughters , if the request was valid(in our opinion) to provide half of the financing and the young person provide the other half. That means finding 40 dollars from cutting grass or....raiding you Uncles empty bottle stash and returning them for deposit values.......Thats just a few creative financing ideas.:) Did I ask......when is your birthday coming up?:):)

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Sell some stuff. Work hard mowing lawns, delivering papers, washing cars. Throw a load of Wall-E videos on YouTube and turn on the adverts, get commission or even the possibility of funding for other projects. Email manufacturers, give them details of the projects, see if they will sponsor you by way of heavily discounted (or even free) items. Or just swat up on EZ-B related stuff and answer technical issues, you never know what might come to your door:) Or be patient and wait for Christmas, planning other projects, improving existing projects where possible.

@Kudo's method of multiplexing could work but it would be a lot of data being passed from PC to EZ-B. Considering you have a limit of how much you can send and receive in one second fast switching of ports to enable multiple LEDs would be a real strain on that and has a very high possibility of bottlenecking the communications (after all, a 5 x 5 matrix would have 25 very fast port switches required, best case scenario is 250ms timings which is 100 commands per second, benchmark shows it's capable of 40-50). As I said originally, multiplexing was mentioned before and concluded as being a bad idea. I may knock up a test at some point with a 3 x 3 matrix, 4 x 4 matrix and 5 x 5 matrix and test to see if it provides acceptable results - it's another thing added to the ever growing list:) As is an I2C expander for driving LEDs


Why don't you use the analog ports? You can even dim them, turn them off, or make them brighter with the analog port.


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Can you? I know you can take the 5V and Ground from the port but as far as I am aware you can't control the voltage on the signal pin of the ADC ports, the ADC ports read that pin voltage. PWM only allows Digital ports through both the control and script.


What is that plug with 6 pins on the middle left of the board beside the proccessor? theres power outputs there. And there's also that 2 pin plug above D14.

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Read my original reply in this thread


sorry about that. I missed it. so the expansion port is the one with 6 pins? if so, what about the 2 pin port above d14?


It's just a gnd and +5. Extended off the row of digital labelled pins.


that would work? it would turn on with the ez-b, right?

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As DJ has mentioned, if you want them to come on with the EZ-B and have no control over them then use the +5 and Ground on the side expansion port.

The +5 and Ground of the digital track should also work if you really wanted to use them.


side expansion port and 2 pin ports can both be used. ok. now I know what to do. thanks everyone!i!


I could have sworn that I used the variable on the Analog ports. But, you guys have a better memory than me. You have to take what I say with a grain of sand.