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Author Topic: Scrolling LED matrix display - Parola for Arduino  (Read 48248 times)
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My results were a little different.  Pulling the +5V on the 20 module array didn't stop it - it just continued to run dimmer than before with the same aberrations.  So I kept the wires connected from the Uno to the 20th module and just disconnected it from all the others, causing them to black out (including module 16 with the problem).  I then reconnected the array and they stayed dark; pressed reset on the Arduino and the 20 module array was working perfectly without any corruptions showing.

It ran for about 20minutes just now without anything unwanted displaying.  I think we have a winner.  Thanks again Mel!  I'll make sure when this sign goes standalone to include that power cycle on startup.

Incidentally, why use the transistor with the IRF9540 since it would appear logic level will be enough to switch that MOSFET on its own?

Thanks
Geoff
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Some breaking news.

Tayda Electronics (http://www.taydaelectronics.com) are starting a kit section in additon to their component store and will be carrying instructions for Parola on their kits website http://www.taydakits.com/instructions/parola-for-arduino. They are now also stocking the LED matrix displays and right angle edge sockets, so you can buy all the parts from one source. I am hoping that they will eventually sell these as a kit, including the Parola PCB, which will make it more accessible to everyone.
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Congratulations Marco. You deserve some recognition for this project, it is a great piece of engineering  smiley-cool
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My results were a little different.  Pulling the +5V on the 20 module array didn't stop it - it just continued to run dimmer than before with the same aberrations.  So I kept the wires connected from the Uno to the 20th module and just disconnected it from all the others, causing them to black out (including module 16 with the problem).  I then reconnected the array and they stayed dark; pressed reset on the Arduino and the 20 module array was working perfectly without any corruptions showing.

It ran for about 20minutes just now without anything unwanted displaying.  I think we have a winner.  Thanks again Mel!  I'll make sure when this sign goes standalone to include that power cycle on startup.

Incidentally, why use the transistor with the IRF9540 since it would appear logic level will be enough to switch that MOSFET on its own?

Thanks
Geoff

The MOSFET is biased to keep it off when the Arduino cold starts so no power gets to the Parola boards. Normally the Arduino is in high impedance state during start up, so with a pull down resistor on the 3904 it keeps it off, and the positive bias on the MOSFET keeps it off.

Having said that, on a MEGA the circuit works exactly the way I expected it to. The power goes out, the MEGA resets, the power comes back on.

On some of the UNO's I have, not so much. I found my power LED indicator on the board flashes in sync with the D13 LED on the UNO. Which still seems to clear the artifacts from the displays with a warm reset, but obviously the UNO and MEGA reset is different.

I use an UNO for testing but normally almost everything here runs off MEGA 2560's.

I also found that you can pull the Vcc, then each of the three signal lines in any order and it's only when the last one is pulled that the display goes dark. I'm guessing that with these obvious clone chips, the logic levels from the Arduino are enough to keep the chip doing a bleed internally so all they do is dim. I also built 10 modules with 7221's in place of the 7219's and it makes no difference. Personally I think these are all the same chip and all they do is change the silk screening...

Mel
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Some breaking news.  Tayda Electronics (http://www.taydaelectronics.com) are starting a kit section in additon to their component store and will be carrying instructions for Parola on their kits website http://www.taydakits.com/instructions/parola-for-arduino.
Nice work Marco!  That certainly does make it more convenient to get some more modules made.  The kits I've bought there in the past used stripboard so it will be a welcome move if they start selling formed boards for these too.

Congrats - Geoff
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I finished putting together some more modules so I have a total of 24 running in the attached photo's. When you get this many modules, some of the entry and exit effects are pretty slow. The left side modules are using 7219's the right half using 7221's. Or perhaps I should say, the silk screen on the chips indicates either a 7219 or 7221. What's underneath the silk screen is any ones guess...

It's using my power board that I referenced in an earlier post and with that board I find that if I power down the Arduino, wait a few minutes, power it back up, I rarely get artifacts on those displays. If I cycle the power, I almost always get some on one or more displays but a warm reset always clears it.

In the photo you can see the UNO and power board on the right edge of the picture. When I power cycle the UNO or even upload a sketch to it, my power board cycles on/off twice and then stays off until the sketch starts. Even a warm reset will do this "double cycle". None of my MEGA's do this, so it's something unique to the UNO. Not that it matters a fig any way since the object is to clear all the junk from the displays.

Current draw, which is dependant on what's being displayed, for the second photo (Powered by) where almost every module has something on it, I registered 180ma and that includes the power the UNO uses. I'm using 68K resistors on the Parola PCB's mainly because I don't have any 62K.

I kind of wish I hadn't finished off the previous two projects because I'm curious to see what a 44 module string would look like (other than really long; the 24 modules take 30.5")...smiley

Mel


* 24_Modules.png (249.84 KB, 640x160 - viewed 191 times.)

* Powered_By.png (241.54 KB, 640x155 - viewed 178 times.)
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That is a very cool display. Very nice work and your wiring is so neat. My projects look like a spider orgy lol. smiley-red
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There are times when electronics projects are like Women. Just when you think everything is fine the blow up in your face :-0

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This is a great project. I'm building this with my 10 year old son. He is great at soldering.
In the Tayda site instructions there is a mention of a controle module being developed. (The one used in the video I guess?) Any news about that?

Thanks for the great woek and for sharing.
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I am guessing here that you are referring to the Parola modules and not Mel's clock project :-)

Not sure what you mean by the control module, and I can't see a reference to it on the Tayda site. The instructions are basically the same as the BoM PDF file on Google code site (link below).

The controller in the video is an Arduino Uno running one of the example sketches that come with the Parola library download. The switches and pots are just connected to a I/O shield, I just have pre-built switches, etc, on small PCBs with standard Ground Volt and Signal (GVS) headers that make hooking up things easier and faster. The details of the pins connected are in the sketches.

If you meant something else, please let me know. If you are interested in the modular approach to my system, I am happy to share as it is not my original idea.
« Last Edit: October 20, 2013, 12:08:17 am by marco_c » Logged

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This is what I'm talking about.

"It is also recommended to use a prototyping shield of some sort to connect the led matrices and interface with some sort of controller. (Instructions for this coming soon.) "

Taken from Page 2

Thanks
« Last Edit: October 09, 2013, 10:12:05 pm by alparent » Logged

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I am guessing here that you are referring to the Parola modules and not Mel's clock project :-)

Hey, whatcha got against clocks with scrollie messages....LOL

As an aside, I wrote a Mac program that connects to the clock/scrolling message and allows me completely program it from the computer via bluetooth. I also put in an LDR so the project auto dims at night so as not to light up the room...smiley

I did read that "interesting" line on page 2 as well. Confused the heck out of me. But then, for the most part, I confuse easy any way...

I used my 24 module to do a fake "NYSE" ticker for a friend...these Parola's are still a hoot to use...

Mel
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OK, thanks for pointing that out. It was added by the staff at Tayda, I guess trying to be helpful.

It is now changed to
Quote
The video shows connections from a prototyping shield to connect the led matrices and the controls used to demonstrate the functionality of the software, but any of the usual connection methods will suffice.

The sensor shield is available a number of places, like on eBay http://www.ebay.com.au/itm/Sensor-Shield-V5-For-Arduino-APC220-Bluetooth-Analog-Module-Servo-Motor-TR-/310722948446?pt=AU_B_I_Electrical_Test_Equipment&hash=item485887ed5e. These shields standardise the digital and analog pins to a 3 pin interface (Ground, Voltage, Signal) so that standard connection wires (for example, http://www.ebay.com.au/itm/10pcs-3pin-20cm-2-54mm-Female-to-Female-jumper-wire-Dupont-cable-for-Arduino-/390556203029?pt=LH_DefaultDomain_0&hash=item5aeef6b815) can be used to rapidly connect sensors.

I build the simple circuits on small circuit boards (http://www.ebay.com.au/itm/GRS-24-X-1-Square-Prototype-Circuit-Board-Kit-PCB-Proto-/281140536860?pt=LH_DefaultDomain_0&hash=item417548261c) on which I mount a 3 pin connector for GVS. Boards have switches, LEDs, pots, lasers, IR detectors, Temp sensor, etc, mounted so that I have built a 'library' of standard modules that I can easily cable together to prototype ideas without fiddling with breadboard wires for the simple stuff. I also have some larger boards for LED display through 595 interfaces where the 595 inputs are GVS (3x3 pins) so that I can use these quickly as well.

Works for me and is completely reusable. You see the boards, with switches mounted, in the Parola video.

Hmm, re-reading that seems like a buy a lot of stuff on eBay.
« Last Edit: October 11, 2013, 01:39:46 am by marco_c » Logged

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Hmm, re-reading that seems like a buy a lot of stuff on eBay.

It's OK Marco we won't tell your wife  smiley-cool

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I have reworked the MD_MAX72xx libraries for Parola and the whole system can now run on the more generic hardware modules with connectors at the top and bottom. Library version 2.2 is available in the repository (link below). You need to use the compiler switch USE_PAROLA_HW to switch the code in the library between hardware types. Please read the accompanying html documentation.

Thanks to Mel for Beta testing!
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Thanks Marco - that's going to be a very handy enhancement as I have a few of these laying about too.

Cheers ! Geoff
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