Free Project - 245 LED Display

[T.Jackson]

Luciano is correct. There is an error on the schematic that shows Q0 instead of Q4 of IC7 connecting to the MR (master reset line) of IC3.

[skimask]

Luciano is correct. There is an error on the schematic that shows Q0 instead of Q4 of IC7 connecting to the MR (master reset line) of IC3.

...which might explain why it worked for me.
I only built a portion of this project using only the first 4017. I 'simulated' the rest of the 4017's using some glue logic, specifically, a PIC setup to pick off the clock pulses into the timer on the PIC and generate a reset pulse after it got to the last column.

[Dan Cata]

So Trent, you say the circuit works just fine for you, but the schematic posted was wrong... did you mistake on purpose? Were we suposed to guess the error in it? I also build the circuit and it runs for me until the LED flashing part, now i can see it all so clearly why ...

[Luciano]

Hi,

I don't think so. The PDF file with the schematic is probably just
a version made for the publication in a magazine so this is probably
not the original schematic use by Trent to make his prototype PCB.

* * *

@ skimask: Less arrogance, more humility!


Best regards,

Luciano

[magu]

next step luciano?

[T.Jackson]

That's right. I normally start off with something roughly hand drawn, sometimes nothing on paper at all - working directly off the top of my head, build a prototype then proceed to document it.

[Luciano]

Hi Magu,

For now use the seven 180 ohm resistors while testing.
You will replace these resistors with the original 18 ohm
resistors when the system works.

While testing with the 180 ohm resistors:

Once the LEDs are driven by the PIC it might be that, in order
to see the LEDs, you will have to reduce the light in the room
where you are testing. This will not be necessary once you replace
the 180 ohm resistors with the original 18 ohm resistors.

* * *

Modify your PCB, connect the pin 15 of IC3 to the
pin 10 of IC7 via the 100k series resistor which is already
present on the schematic.

Place a 100nF capacitor close to each IC present on the circuit.
This capacitor is connected to the pins VDD and GND of the IC.
This capacitor must be close to the ICs. (Max. 10mm).

Program the microcontroller with the HEX file posted by Trent in
the first post of this thread.

Plug all the ICs in their sockets. Follow the instructions posted
by Trent. Power on the board and the circuit should work.


Best regards,

Luciano

[magu]

Hi Magu,

For now use the seven 180 ohm resistors while testing.
You will replace these resistors with the original 18 ohm
resistors when the system works.

While testing with the 180 ohm resistors:

Once the LEDs are driven by the PIC it might be that, in order
to see the LEDs, you will have to reduce the light in the room
where you are testing. This will not be necessary once you replace
the 180 ohm resistors with the original 18 ohm resistors.

* * *

Modify your PCB, connect the pin 15 of IC3 to the
pin 10 of IC7 via the 100k series resistor which is already
present on the schematic.

Place a 100nF capacitor close to each IC present on the circuit.
This capacitor is connected to the pins VDD and GND of the IC.
This capacitor must be close to the ICs. (Max. 10mm).

Program the microcontroller with the HEX file posted by Trent in
the first post of this thread.

Plug all the ICs in their sockets. Follow the instructions posted
by Trent. Power on the board and the circuit should work.


Best regards,

Luciano

it dosen`t work. i program the pic with ICPROG (plug the programer in serial port, open hex file, -> PRogram all)
. these is a picture of the board with all the components included the caps. http://www.zamfirelu.org/led/board.jpg

[Dan Cata]

How about re-doing the scheme and posting it again, in the first post, if that is possible... , so that anyone trying to build it doesn't face the same problem; maybe they don't read the whole 3 pages of posts to see that there is a problem with it!

[Dan Cata]

But you can see clearly that the pdf is a print from OrCad or something that the circuit was made, so it has to be the one that the pcb was made of!