Print PDF
Favorite
Email
Step 10Wiring the LED Display Driver
CUTTING THE PERFBOARD
We want to make our board as small as possible, so we need a board that gives us two rows of holes to the left, one to the right (I'll explain that later). No need to have holes available above or below - we're dealing with a tight space here.
Again - If you're like me, and not very good at soldering, I suggest leaving the chips out of the socket for now.
WIRING THE RESISTOR AND V+
To tell the Max7221/7219 what the maximum current/voltage to provide, we have to wire a resistor between the V+ and ISET pins. This resistor is referred to in the DataSheet (PDF Warning) as RSET. See this page for more information on values.
See Picture 2 for how I wired this. See Picture 3 for how this looks from the top.
Leave a good length of wire on the V+ for now - we'll be connecting this shortly, but the extra length is helpful when we're testing before the power switch is wired.
DISC PLACEMENT/POSITION
See picture 4 for how the board for the MAX72XX will be positioned in the Disc. Note that it's upside down. Please note that I positioned my RSET resistor toward the outside of the disc - please don't do this - this made for a very tight fit. Rotate the board so that the resistor is towards the inside of the disc. If you're using a 1/2W resistor instead, you probably won't have such a problem.
GENERAL SUGGESTION ABOUT WIRING
Honestly - this is the first step in the process where the wiring gets a bit out of hand. Just look at picture 4 - It's a mess! Keeping your wires short, but not too short is key. Any extra wire you have has to go somewhere. If you cut them too short, you'll find that when you go to place the board when done, you can't move it enough.
If you're leaving the chip out of the socket for now, make sure you'll have enough room to put it in when you're done.
WIRE GROUND PINS
Wire pins 9 and 4 to ground on your power supply - not to be confused with the grounds coming from your LED groups.
CONNECTING YOUR GROUND WIRES
The DIG pins correspond to the Segments we've created. From the inside of the disc: Segment 0 = left of Inner Ring. Segment 1 = right of Inner Ring. Segment 2 = top left. Segment 3 = Middle Left. Segment 4 = Bottom Left. Segment 5 = Bottom Right. Segment 6 = Right Middle. Segment 7 = Top Right.
CONNECTING YOUR +/SEG WIRES
So I realized it's confusing that I used the wording "Segment" to identify the groups of 8 lights. I'll try to go back later to reword, but for now - please see the notes on the first image for attaching LED's 1-8 to the various SEG pins.
CONNECTING TO THE AVR MCU
See the provided images for pin connections. Since you're only connecting three wires between the two chips (with the exception of V+ and Gnd) - it should be fairly simple.
CHIP -> SOCKET
At this point, if you've left the chip out - put the MAX72XX chip into the socket.
We want to make our board as small as possible, so we need a board that gives us two rows of holes to the left, one to the right (I'll explain that later). No need to have holes available above or below - we're dealing with a tight space here.
Again - If you're like me, and not very good at soldering, I suggest leaving the chips out of the socket for now.
WIRING THE RESISTOR AND V+
To tell the Max7221/7219 what the maximum current/voltage to provide, we have to wire a resistor between the V+ and ISET pins. This resistor is referred to in the DataSheet (PDF Warning) as RSET. See this page for more information on values.
See Picture 2 for how I wired this. See Picture 3 for how this looks from the top.
Leave a good length of wire on the V+ for now - we'll be connecting this shortly, but the extra length is helpful when we're testing before the power switch is wired.
DISC PLACEMENT/POSITION
See picture 4 for how the board for the MAX72XX will be positioned in the Disc. Note that it's upside down. Please note that I positioned my RSET resistor toward the outside of the disc - please don't do this - this made for a very tight fit. Rotate the board so that the resistor is towards the inside of the disc. If you're using a 1/2W resistor instead, you probably won't have such a problem.
GENERAL SUGGESTION ABOUT WIRING
Honestly - this is the first step in the process where the wiring gets a bit out of hand. Just look at picture 4 - It's a mess! Keeping your wires short, but not too short is key. Any extra wire you have has to go somewhere. If you cut them too short, you'll find that when you go to place the board when done, you can't move it enough.
If you're leaving the chip out of the socket for now, make sure you'll have enough room to put it in when you're done.
WIRE GROUND PINS
Wire pins 9 and 4 to ground on your power supply - not to be confused with the grounds coming from your LED groups.
CONNECTING YOUR GROUND WIRES
The DIG pins correspond to the Segments we've created. From the inside of the disc: Segment 0 = left of Inner Ring. Segment 1 = right of Inner Ring. Segment 2 = top left. Segment 3 = Middle Left. Segment 4 = Bottom Left. Segment 5 = Bottom Right. Segment 6 = Right Middle. Segment 7 = Top Right.
CONNECTING YOUR +/SEG WIRES
So I realized it's confusing that I used the wording "Segment" to identify the groups of 8 lights. I'll try to go back later to reword, but for now - please see the notes on the first image for attaching LED's 1-8 to the various SEG pins.
CONNECTING TO THE AVR MCU
See the provided images for pin connections. Since you're only connecting three wires between the two chips (with the exception of V+ and Gnd) - it should be fairly simple.
CHIP -> SOCKET
At this point, if you've left the chip out - put the MAX72XX chip into the socket.
| « Previous Step | Download PDFView All Steps | Next Step » |
 |
Add Comment
|
