Help, with microcontroller, I'm confused, i thought both of

For Adafruit customers who seek help with microcontrollers

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gdgarced
 
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Help, with microcontroller, I'm confused, i thought both of

Post by gdgarced »

Hello, I'm using your bright white surfacemount LEDs 5050, I am working on a small matrix that I will attatch to a pet's outfit, so I need a small microcontroller, can you tell me which one can I use? I have 15 LEDs in the matrix, also will I need to add resisters if I use a conductive thread with low ohms per foot? I'm working with a fabric size of 3x4 and I am able to have 15 LEDs, I have my LEDs in 2 1/2 by 3 inchs of the 3x4 piece of fabric so that I have a tiny bit left to sew it to another piece of fabric. I have 2 of yr trinkets 3v and 5v. I also want to keep the power supply tiny as well, any advise on that too? Also what other small microcontroller do you carry that will work with my led projects that need to stay small since i design for pets but, i would like to be able to have lots of LEDs. I would like to have the microcontroller on the top of the matrix or i can try and put it in the back. Oh, i want to have a rain effect, a tiny diamond, and an x. I just finished a 9x9 matrix and i want to match the animation for that matrix to this tiny one. I did want to use the flora for that one, but its 3v and so i had to use the lilypad which is 5v. Thank you
Last edited by gdgarced on Tue Nov 26, 2013 1:01 am, edited 4 times in total.

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Franklin97355
 
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Re: Help picking the right microcontroler for my 3x5 matrix

Post by Franklin97355 »

If you could post the circuit perhaps we could help you better. The Flora might work with the right circuit and depending on what you want the LEDs to do.

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gdgarced
 
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Re: Help picking the right microcontroler for my 3x5 matrix

Post by gdgarced »

here is a pic of my prototyping, as i explained it is very small since it will be attached to a pet's outfit. I took a pic of the microcontrollers i have, i do have the flora but it's big. i have a 3v trinket too, so if that works with my matrix, that would be great also what conductive thread would be best? the little piece of fabric next to my matrix is what I'm working with. Thank You
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adafruit_support_mike
 
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Re: Help picking the right microcontroler for my 3x5 matrix

Post by adafruit_support_mike »

For the layout you're using, the controller at the top will probably be easiest to use.

Your matrix has 8 control lines, and you'll need need to control them in column/row pairs to control the LEDs. It's easiest to do that with a controller that has 8 IO pins, though you can use fewer pins if you're willing to make the code more complicated.

The pins of a microcontroller can usually handle 40mA of current at most, and the LEDs will want between 20mA and 60mA. If you're using a 5v supply, you'll need between 70 and 100 ohms of resistance between the controller's pins and the LEDs to make things work correctly. The conductive thread we sell has less than 2 ohms of resistance per inch, so you'll want a regular resistor on each of the three row lines. The standard values most likely to work for you are 56 ohms, 68 ohms, and 82 ohms.

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gdgarced
 
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Re: Help, my post was misread, don't have an 8x8

Post by gdgarced »

miscommunication, matrix is not 8x8, those lines on the sides are my rows, and the line on the right is to remind me to leave a space for sewing. I only have 5 columns and 3 rows, sorry if my pic confused you, but i am still prototyping so my circuit isn't done. This pic is just So can you can see how small my matrix is. Also, i have 5 different conductive threads with different ohms so, if you tell me which is best so that i don't have to use resisters that would be great, since I'm really working with a small piece of fabric. So, which one of the microcontrollers is better, now that you have the right info? By the way, those LEDs are from Adafruit,Vf: 3.0 - 3.2V Thank You again

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adafruit_support_mike
 
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Re: Help picking the right microcontroler for my 3x5 matrix

Post by adafruit_support_mike »

I didn't misread your post.

To make an LED matrix work, you need to control both the rows and the columns. If you don't, you can't turn one LED on while all the others in the same row and column remain off. 3 rows + 5 columns = 8 control lines.

The LEDs have a forward voltage of 3-3.2v, so if you use a 5v power supply there will be 1.8-2v between the LED's forward voltage and the supply voltage. The LEDs will want about 20mA of current, and Ohm's Law says it takes 90-100 ohms of resistance to make that happen.

As I said, the conductive thread we sell has 1-2 ohms of resistance per inch. To get 90-100 ohms, you'd need between 4 and 8 feet of thread. You'll need to measure the resistance of your own thread to see how much of that you'll need.

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gdgarced
 
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Re: Help picking the right microcontroler for my 3x5 matrix

Post by gdgarced »

I'm so sorry, I though you thought I had an 8x8 matrix. I just competed a 9x9 matrix, it was 25x44 inches using these same leds but, I used a lilypad because it is 5v but, since this matrix is small, I wanted a small microcontroller. Do I have to use the 5v one in the picture? I have a code for my large matrix which I hope to be able to use on this one. My code is very simple. I have conductive thread with 100 ohms per foot so, can I use that? I got it 3 years ago and haven't used it because of the high resistance. Thank you for the support help.

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adafruit_support_mike
 
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Re: Help, with microcontroller

Post by adafruit_support_mike »

You don't necessarily have to use a 5v device, but you do need some way to drive all 8 control lines. The easiest way to do that is to use a device that can use one GPIO pin for each signal.

There are ways to control LED displays with fewer pins than control lines, but the code is more complicated: http://en.wikipedia.org/wiki/Charlieplexing

If you use a 3.3v device, you'll need less resistance between the controller and the LEDs.. around 10-15 ohms. You can probably do that with regular conductive thread. If you choose a 5v device and have 100-ohm/foot thread, by all means use that.

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gdgarced
 
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Re: Help, with microcontroller, I'm confused, i thought both

Post by gdgarced »

i just realized that the large microcontroller is not a trinket, what is it? I got it but can't find the receipt for it. Can i use this one with my matrix and one of yr lion batteries? I have a few 3.7v batteries but with different mAh. From the picture i sent of my matrix, can i use the pins on one side of this microcontroller so that i can try and keep all of my sewing line going to one spot? which pins am i not suppose to use? This is new to me, so I'm sorry for all the questions. I calculated that i will need 20 to 22 inches of conductive thread, i have 28ohms per foot, i have 50ohms/meter, i have 100-150/inch or is the one you sell better, what are the ohms per foot of the ones you carry? I like to have different ones for different projects. I thought i had 100 ohms per foot but it's 1000ohms per foot. Thank You

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adafruit_support_mike
 
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Re: Help, with microcontroller, I'm confused, i thought both

Post by adafruit_support_mike »

The board at the top is an ATmega32u4 breakout: http://www.adafruit.com/products/296

We have a description for it here: http://ladyada.net/products/atmega32u4breakout/

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