MAX7219 + LED matrix module !=

[granddad]

This thread could go on forever lacking so many design specs

At the moment its just a concept . And changes every day ! ........

 

[Ian Rogers]

Just for Info..... I found that there are a ton of Chinese fakes out there, Doing exactly as mine is doing.. Not enough current so they shut down.
MAX7221's on the way...

 

[granddad]

ton of Chinese fakes out there,

perhaps thousands of tons, I just had to return a crimp tool was.. total rubbish

 

[Tony Stewart]

A good example of a random supply glitch is a soldering iron reed relay or coffee plate themalswitch or bathroom fan cutoff timer switch. All of these caused my ceiling PAR30 dimmable LEDs to flicker and my HDMI LCD to blink in a different room. The solution was to be aware of these AC transients that can pass through AC/DC regulators unlike step down linear transformers unregulated supplies that attenuate this CM noise by 60 dB. Then put a 1 to 4 nF metal film cap across the switch.. No more glitches . Been there done that. So find your glitch and suppress it or use a CM line filter or better supply or PE gnd it.

 

[Pommie]

My 7219 code uses a ram buffer for the display and copies it on interrupt 50 times a second. Powered by a USB charger socket (smps) without any problems whatsoever.

Mike.

 

[granddad]

Ive not had any power down issues , The (real) 7219 is still 8+ GBP here in UK from Farnell !

 

[Pommie]

My 32x8 display with four 7219's was $7(US$5) from ebay! And they're still available with free shipping (to Aus).

Mike.

 

[granddad]

Mike, There are various 7219 modules here similar price , It begs the question are the 'normal' distributors hiking the prices, or is the ebay stuff, failed seconds , fake or even good manufactures over runs . It certainly is a useful IC once you get your head round its control...

 

[Nigel Goodwin]

Mike, There are various 7219 modules here similar price , It begs the question are the 'normal' distributors hiking the prices, or is the ebay stuff, failed seconds , fake or even good manufactures over runs . It certainly is a useful IC once you get your head round its control...

The 'normal' distributors are selling full spec devices from the original manufacturer, not cheap Chinese copies.

We buy the bare DIL chips from RS at work (for a project we're developing) and they are pretty pricy.

 

[atferrari]

I played with this device extensively when I worked at Maxim. I designed an Ishihara test using RGB LEDs which was quite effective. I put 10k pull downs on the bus, since the bus can start up in an unknown state. From memory, the MAX7221 fixed this issue

Few days ago, I started to develop software for a non usual diode matrix. Having read the above by Simon, I started using two 10K pull down resistors on the LOAD and CLK pins. After experiencing a huge amount of wrong results, took them out and now everything goes right.

 

[granddad]

I started using two 10K pull down resistors on the LOAD and CLK pins

I only put pull down on the LOAD, I was only copying a previous project that worked ,

 

[atferrari]

Duly noted, abuelo.

I only put pull down on the LOAD, I was only copying a previous project that worked ,