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Topic: I"m lost and cornfused (Read 5470 times) previous topic - next topic

PaulRB

#30
Dec 04, 2015, 01:06 pm Last Edit: Dec 04, 2015, 01:11 pm by PaulRB
It will work, but not well.

Not a good idea to use that series.  If you must buy things, buy TPIC6B595s - the shift register version with a proper driver.

Saves you pins on the Arduino.

ULN chips will work absolutely fine with displays like these. However, for displays with blue or white leds (very unlikely to be included in a starter kit), or for use on a 3.3V supply, the TPIC would be a better idea. But for red/yellow and most green displays, on a 5V supply, the higher sturation voltage does not matter, just lower your series resistors a little!

I only suggested ULN because it is 1) a component possibly included in a starter kit such as the OP has and 2) something you might be able to pick up at your local Radio Shack/Maplin. Neither is true of TPIC chips. But if you are buying on-line I agree it is the technically better choice, if not quite as simple for a beginner to get their head around.

larryd

#31
Dec 04, 2015, 04:40 pm Last Edit: Dec 04, 2015, 04:59 pm by LarryD
Quote
ULN chips will work absolutely fine with displays like these.
I did say:
"may not"
;)

Later on, the OP may want to try a MAX7219 and try SPI.
.
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Naneen

Finally got the program loaded. Now to go to work on the breadboard. bought a bigger breadboard. will try to lay it out so you can see how it is wired.

By the way. Thanks for hanging in there with me.

Naneen

ran the program, no go. if I touch the pins with 5V the elements light up. I tried to attach picture but was told there to big. max  1 meg.

Naneen

#34
Dec 05, 2015, 03:50 am Last Edit: Dec 05, 2015, 03:57 am by Naneen
the picture is 3.5 megs. how do I make it smaller? wait I got it. pic coming

larryd

Nice and neat.
Might be nice to use different coloured wires to make things easier to follow.

Can you confirm the color on on the 470 resistors?


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larryd

What is written on the transistors?
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larryd

#37
Dec 05, 2015, 05:03 am Last Edit: Dec 05, 2015, 05:12 am by LarryD
See image:


FYI:
http://www.buildcircuit.com/building-a-circuit-on-breadboard/

I assume there were no errors when you uploaded the sketch to the Arduino.
Are you using Multiplex7SegExample4Counter.ino ?
Please confirm the Yellow wire (GND) is indeed connected to ground.
.
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Naneen

OOPS is my face red. The yellow wire was wrong. PROBLEM. Only D segment is flashing on the last digit and solid on the other digits. Sometimes blinking on and off.

larryd

- What is the color of the 470 ohm resistors that are on segments a-g?
- Are you using Multiplex7SegExample4Counter.ino ?
- What is written on the transistors?

And:

Have you confirmed the pin out of the display?
For segment a
+5v ----- 470 -------  segment a pin11 ------- cathode pin12 to ground (then 9,8,6)
For segment b
+5v ----- 470 ------- segment b pin7 ------- cathode pin12 to ground (then 9,8,6)
For segment c
+5v ----- 470 ------- segment c pin4 ------- cathode pin12 to ground (then 9,8,6)
For segment d
+5v ----- 470 ------- segment d pin2 ------- cathode pin12 to ground (then 9,8,6)
For segment e
+5v ----- 470 ------- segment e pin1 ------- cathode pin12 to ground (then 9,8,6)
For segment f
+5v ----- 470 ------- segment f pin10 ------- cathode pin12 to ground (then 9,8,6)
For segment g
+5v ----- 470 ------- segment g pin5 ------- cathode pin12 to ground (then 9,8,6)
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larryd

#40
Dec 05, 2015, 06:05 am Last Edit: Dec 05, 2015, 06:09 am by LarryD
Note:
Some 2N2222s have the emitters and collectors swapped.
See these images
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Naneen

#41
Dec 05, 2015, 06:21 am Last Edit: Dec 05, 2015, 06:26 am by Naneen
Transistor are PN2222A. Now as to the resistor the package reads 470 ohm but my meter reads 47M These old eyes think the see yellow violet GRAY. that's with the help of a magnifier and flashlight. I have 100K, 10K, and 220 ohm. Can I use 220 and get away with that? Transistor package reads 2N2222 NPN.

larryd

Use 220 ohm
RED / RED  / BROWN

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Naneen

OK I get some 470 ohm at radio shack of they have them. their not the store they was in the fifties or sixies.

larryd

You can use 220 ohm if you have them already.

You really have to manually confirm the pinout of the 7 segment display as in reply #39.
When you do, make sure the Arduino pins are not connected to the display when you do.

 
 :smiley-sleep: time.
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