7 seg display using alternative 5v power

msiriwardena

I got the jm_max7219_EZ to work with help .
The jm-demo works well but the LED's were dim.
I had the same display on P! and it was bright.

I applied alternative power supply fromP1 demo board( both + and ground))
I was using P2 edge power(5v) the jm_max demo which
worked as intended.
When I applied alternative power the demo was scrambled
but bright.

I am using a 10 amp power supply for the P2 edge.

Why is the alternative power does not work?

Can some one explain this

Thank you,

Siri

PS : Do I need to connect the 2 grounds together to work?

siri

PropGuy2

Pictures please -

Check your wiring as compared to the P1 setup that you know is working. Only hook up one sub-circuit at at time and make sure it is working OK, then add another sub-circuit and check it...

As a general; rule common grounds are usually needed.

msiriwardena

@PropGuy2

I have no sub-circuits,I unplugged it from P1 and plugged it to
the P2 edge.
The LED works with jm_7seg led demo with no issues except
the LED is not bright as before with P1.
Then connected the power from the P1 board to the 7seg Led
power(only the power connection) the other connections remain
connected to P2.
The LED lights are bright but the Demo does not work as it is
intended.

Thank you for your help
Siri

JonnyMac

The jm-demo works well but the LED's were dim.

Because the library defaults to the dimmest setting. You'll find this line:

  out(BRIGHT, 0)                                                ' start dim

... where it's writing 0 (lowest setting) to the BRIGHTness register.

I've been updating that driver for my presentation on SPI this week. The new version has this method

pub set_brightness(level)

'' Set display brightness
'' -- level is 0 (dim) to 15 (bright)

  out(BRIGHT, 0 #> level <# 15)

That said, had you taken the time to download the data sheet -- something I always recommend -- you'd have found the information on the brightness register and could have written this line to set the display to maximum brightness:

  disp.out(BRIGHT, 15)

msiriwardena

@JonnyMac

Thanks for the help.

I did take your advise and downloaded the data sheet.By referring

to the data sheet I got the pin nomenclature solved.The pin names on

the LED module I have did not match with yours, which reffered to the

pins of the chip,, the drawings in the data sheet helped.but i missed the brightness reference.

Thanks you again.

Siri

PS: I am beginning to understand the timing diagrams

Siri