Ill try and explain it,

You have got one 74373 chip that controls the Green Cathodes of the 8x8 matrix, 8 pins of the Green 74373 connects to the 8 transistors that control the 8 cathodes ROWS of GREEN Leds..

Now 1 pin from the green 74373 chip goes to a RESISTOR and then to the TRANSISTOR.. you then have another RESISTOR from the TRANSISTOR to the Cathode of one ROW of green leds..

The last pin on the TRASISTOR connects to Ground..

you then connect the other 7 pins from the Green 74373 chip to the other cathodes using the same connections as i described above..

then you do the same for the RED 74373 chip..

so its goes (red)74373 to a resistor, then to the transistor and from the transistor to a resistor which connects to the cathode of one row of RED leds.


When connecting the Column 74373 to the 8x8 ANODE there are no resistors or transistors connected.


I hope this helps, if not then feel free to ask





But please read the DATASHEET for the type of transistor you use, so you know how to connect it up correctly, heres a picture to help.

Thanks for clearing that out.

-nicolo86-

thats no problem

any problems just ask

OOPS, big mistake by me!

I forgot that we were originally talking about the 8x8 game system schematic. The new schematic that I have been talking about in my last few posts is different (and better) than the 8x8 schematic.

Sorry to confuse you there buddy! Here is the circuit that you need:

Because it is a common ANODE matrix, you would want to use the transistors to provide a connection to VCC for the anodes. Then the connection to ground (to light up either red or green) comes from their own 74373.

This means that you activate one row of anodes at a time by sending a logic 1 to one of the anode 74373 outputs. Then to light up an LED in that row, you send a logic 0 to that particular 74373 output pin.

no problem.

-nicolo86-

Wait a minute. I think you were wrong again because in the schematic that you used for your 8*8 game system the common anode didnt had any transistor neither resistor .

-nicolo86-

No, this schematic is the best way to go - it is a completely new one compared to the 8x8 game system schematic. That is why I had this sentance at the top of my post:

Ahh ok. But the old ones work too. And how is it better.

-nicolo86-

It all has to do with the current carrying capability of a chip. (which is not much when compared to a transistor)

As you know in order to draw an image on the 8x8 matrix, we do it one column at a time. In my new shcematic I do this by turning on a transistor to connect vcc to the common anode connection of one column of eight LED's.

There are actually 16 LED segments in each column because we have both red and green. so if we were to turn on all 16 LED segments then all the current for these LED's would flow through the transistor which would happily handle this current. But if I were to use just one output of a 74373 instead of the transistor to handle all of this current - it wouldn't be able to and the LED's would be quite dim.

Hey brad could you please post a picture with the schematics on how to connect the chips to the PIC.

Please and tanks

-nicolo86-

I will get it done when I get some free time but all you need to do is connect an eight bit port to the eight inputs of all of your 74373's. Then you need seperate latch connections to control which 74373 grabs the data. (since they all receive the same data)

hey brad do you have the schematics on how to connect the chip to the pic. I am asking because i am going on vacation and i would like to finish it up

thanks

-nicolo86-

Sorry I keep forgetting. I have to goto work now but will do it later this afternoon.

In the meantime - have you found any info of how to connect it?

Nope. Not yet but i am still searching.

thanks

-nicolo86-

I just remembered that I have already done this! here is a link to the 8x85 led pov display which shows you exactly how to connect up your 74373's to a single PORT on the microcontroller.

http://www.bradsprojects.com/8x85_pov_files/8x85_pov_schematic.png