Update2: I have been receiving feedback that I can use eBay suppliers to lower my price on the MAX7219. I had previously considered that option, but after some research I have found that a lot of people are receiving counterfeits on eBay. While some counterfeits may work, their reliability is questionable and that would make my product unreliable. I do not believe that it is “good business” to support businesses and companies which pirate technology and sell it as if it were legitimate. I sincerely hope everyone understands why I am skeptical about using an unknown suppler for parts. Here is a good forum post about coming across the fake variety: http://www.picaxeforum.co.uk/showthread.php?22481-Real-or-fake The more units I can sell initially will increase my per-part discount, which allow me to lower my selling price.
For example if you look at the first picture above, the line across the top is inline with pin 2. If you do a search on eBay or even Google image search you can see that they lines up with pin 3. Also mine has a notch and the eBay ones all have a dimple. Not to mention there is no way someone can go to Maxim and get a price much lower then their lowest price they have.
Last year I came across the MAZ7219\AS1107 LED Driver. This great little IC can drive a 7 segment display or an 8x8 matrix of LEDs. After some research, I noticed that most LED Matrices on the market are driven with simple shift registers which sole function is to reduce the GPIO pins used by a microcontroller. The AS1107 does this in addition to adding SPI control, daisy chaining capability, and single resistor brightness control. The AS1107 also takes care of refreshing the LEDs so the microcontroller isn’t burdened with this task as well. All this and there is a ready-made Arduino library for this IC.
This kit comes with everything you need to make and control an LED Matrix from your own microcontroller. It comes with all the SMD parts pre-soldered. All you need to do is solder the header pins and the LED Matrix to the board. This kit can also be a great way to practice through-hole soldering.
All documentation will be available at http://friedcircuits.us/docs/led-matrix-link/.
All design files will be posted on http://www.github.com/friedcircuits after the fundraiser.
A code example for scrolling text will be available on the website.
• Red 8x8 3mm LED Matrix • Runs on 2.7v to 5.5v with AS1107 from AMS • Ready to use Arduino Library: http://playground.arduino.cc/Main/LedControl • Easy to use • Daisy Chain up to 8 modules with no additional wiring or library modifications. o More than 8 modules may be daisy chained, however this isn't supported in the stock Arduino library. It has been done before and the Arduino forums should be helpful if this is what you are looking to do. Also the more modules affect performance. View my findings here: http://www.mobilewill.us/2013/04/led-matrix-wedding-and-twitter.html • The brightness can be adjusted in software and you can change the 33k resistor to set the max brightness. The current 33k Ohm resistor allows you run 3-4 from USB power. Using the USB Tester and OLED Backpack I measured 225mA for 2 displays fully on at max brightness. (I was actually able to do all 8 but it reduced the brightness a tad.)
• PCB with AS1107 • 8x8 LED Matrix • Right angle female header (unsoldered) • Right angle male header (unsoldered)
Note: You can buy the LED Matrix Master which is the same form factor as the LED Matrix. It has an Atmega328p microcontroller that attaches directly to the LED Matrix Link. https://www.tindie.com/products/FriedCircuits/led-matrix-master/
Follow us on twitter @friedcircuits.
May 6, 2013, midnight
Hi, did you sell only the board without the matrix? I have bought some common anode matrix and wanted to use your board with it.
June 24, 2013, midnight
The IC only supports common cathode, but I will be selling the PCB without the matrix soon.
The Link is now available without the LED Matrix for command cathode.
April 4, 2013, midnight
I'm curious about the mounting holes on the board: What type of screw is supposed to be used? When mounting two LED Matrix Link boards side by side, is there enough clearance for two screws to be next to each other? From the picture it looks like the heads of the screws might collide As the screws are under the LED matrix display, do they need to be attached before the LED matrix is soldered? How should the screws be tightened after the display is soldered? If screws are added, will the LED matrix display fit flush against the board, or will it be raised up off the board?
April 4, 2013, midnight
The idea was that not every matrix would need to be mounted or you could do opposite corners. I was trying to find some plastic standoffs that snap into the hole like the kind for motherboards. I have tried putting the screws in before soldering and it doesn't add much of a gap between the PCB and the LED Matrix. If you solder the PCB with some pressure against the LED Matrix it is enough friction to be able to tighten the nuts. The other option is to use a longer screw and tighten the nut before you solder and then use a second nut to tighten it down on the mounting surface. These are the screws I tested with: https://www.sparkfun.com/products/10453. They are 4-40's from Sparkfun. You could try a screw with a flat head and that would get rid of the slight gap. I figured someone could figure out a creative way of mounting them.
Can use "standard" Arduino LedControl lib for MAX7219 chips.
Areas for improvement: make them even more matcheable edge-to-edge: the links protude a bit (<1mm but enough to create a gap).
Feb. 12, 2014
Can you send me a picture of your setup? It should be flush, but maybe not all headers are the same? I will adjust it before my next run.
Feb. 12, 2014
I was able to build a clock for my mom really quickly, thanks to the clever, daisy-chain design of these modules. No hassle, no issues. The Arduino LedControl library makes it pretty easy to get these displays working. The boards are quality (oshpark it looks like) with good assembly quality. These are worth the price. I didn't get the Matrix Master but I should have. If you're looking for an LED matrix solution, look no further, buy these.
I suggest hookup documentation to make the experience even more awesome. A tip for aligning the pin headers: connect male and female, place on flat surface with legs pointing up, place two boards onto the pin headers. Now it's easy to align the two boards relative to each other while soldering in place.
Jan. 14, 2014
Feb. 26, 2014
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