Pages: [1]   Go Down
Author Topic: Problem with MAX7219  (Read 910 times)
0 Members and 1 Guest are viewing this topic.
Offline Offline
Newbie
*
Karma: 0
Posts: 6
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

Hi, I'm having trouble getting to work a couple of MAX7219. I tested the circuit on a breadboard and it worked perfectly, then I soldered all the anodes and cathodes to the MAX7219's to a perfboard and tested them connecting the Data In, Load, Clock, 5+ and Gnd to the Arduino with alligator cables and worked fine but then I soldered them and nothing lights up. I've checked everything for an hour but all seems to be ok. I really have no idea what's gone wrong. The arduino is powering the circuit and the drivers are receiving the voltage they need.

This is the code I'm using to test the matrix. I'm using 2 drivers but for testing purposes I'm just trying to control one. It's pretty basic.
#include <LedControl.h>

LedControl lc=LedControl(12,11,10,1);

void setup()
{
  lc.shutdown(0,false);
  lc.setIntensity(0,8);
  lc.clearDisplay(0);
  lc.setLed(0,0,0,true);
}

void loop()
{
 
}

I don't know if it matters that I didn't use the capacitors though when testing on the breadboard it worked well without them.
Do you have any suggestions where I should check the circuit? I think I just broke my brain or something trying to figure out what's wrong but I can't find anything. Thanks in advance.

I'm attaching a picture of the back of the circuit. Maybe it helps. This is the first time I've soldered so perhaps something is not soldered correctly. I just don't know. There's also the diagram I'm using from the Arduino page.


* MAX72XX_Schematic.jpg (258.45 KB, 1194x1506 - viewed 16 times.)

* photo.jpg (851.74 KB, 1224x1632 - viewed 20 times.)
Logged

Global Moderator
Offline Offline
Brattain Member
*****
Karma: 452
Posts: 18694
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

Quote
This is the first time I've soldered so perhaps something is not soldered correctly.

Yes, that is a workable hypothesis. You should trim the leads short so they don't spill over the edges of the copper and short other things out. It's hard to tell from the photo, but I strongly suspect you have soldering issues.

Try checking the connections with a multimeter (eg. one that beeps for continuity). Check not only that things are connected where they should be, but are not connected where they should not be. For example, check that 5V and Gnd are not connected.
Logged

Offline Offline
Sr. Member
****
Karma: 0
Posts: 339
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

It is hard to say from the pic, but id guess i can see some cold solders there anyway. Another thing, if the caps were on the schematic, then you should use them. Might work for a couple minutes, but doesnt mean that will not blow something after a while on. wouldnt be the firsst nor the last time.
Logged

10 LET Loop=Infinite
20 GO TO 10

South England
Offline Offline
Full Member
***
Karma: 3
Posts: 205
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

Definitely keep the caps in. The tutorials I read on arduino playground to get me started using this chip said they were required and should NOT be left out. I've always used them as instructed and have not had a problem so far.
Logged

Global Moderator
Boston area, metrowest
Offline Offline
Brattain Member
*****
Karma: 437
Posts: 23662
Author of "Arduino for Teens". Available for Design & Build services. Now with Unlimited Eagle board sizes!
View Profile
WWW
 Bigger Bigger  Smaller Smaller  Reset Reset

And that's why I wirewrap ...
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.

Offline Offline
Newbie
*
Karma: 0
Posts: 6
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

Thanks everybody. I'm doing everything again. I still don't understand where do the capacitors exactly go in the circuit or what are they for. I'd appreciate if anybody could make this clear for me.
Logged

Global Moderator
Offline Offline
Brattain Member
*****
Karma: 452
Posts: 18694
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

http://www.thebox.myzen.co.uk/Tutorial/De-coupling.html
Logged

Anaheim CA.
Offline Offline
Faraday Member
**
Karma: 44
Posts: 2808
...
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

That was an exceptional picture of the bottom side of the 'board', I can't (in 40 years) remember when I ever saw it's equivalent.
On the other hand however good soldering is as much in the technique used as it is in the materials used. It is a form of artwork
and Pre-tinning the leads would have done wonders as would a 'cooler' soldering iron. I use an old Hakko 926 and rarely turn it above
650 Deg F.... Unless I have a large repetitive soldering task to do, like those .040 pins and sockets used for interconnects and jumpers.
Capacitors for bypassing noise are the MOST frequent mistake made in ANY design. My own experience is that some heavy stuff at the
PSU input and a .1uF & 1uF ceramic used on each board powered from the Uno is sufficient. Drawing more than 100 mA from the Uno
regulator is also a BAD idea as the currents flowing to the 'external' board also flow in the Uno's ground circuit and WILL cause unusual issues
to crop up ( like mushrooms after a rain). If the Power supply is noisy due to external loads so are the (for example) A/D inputs going to
be 'noisy' as well and a cause for concern in digital transfers (IIC and SPI) as well. They can cause random errors that are most difficult to find.

Doc
Logged

--> WA7EMS <--
“The solution of every problem is another problem.” -Johann Wolfgang von Goethe
I do answer technical questions PM'd to me with whatever is in my clipboard

Pages: [1]   Go Up
Jump to: