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Topic: LED problem (Read 2123 times) previous topic - next topic

CrossRoads

Put the 01, 10, 11 as address bits into different logic - like a 74xx138, 74xx139 - selected out (#1, 2, 3) will go low, pull one cathode low.
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

pranoy

I want the LED to be ON one at a time with the ouputs ( 01,10,11)


There is only one 220 ohm resistor at one of the output pins.


I don't have enough pins so i have to go with 2 pins itself.

the ???????????????? is something i got from chatting in fb.

Grumpy_Mike

Quote
There is only one 220 ohm resistor at one of the output pins.

You need another on the output of the logic gate.

pranoy

this is a fair ckt dgm with only one yellow LED

pranoy

thanks mike

but i tried it in a 2 way traffic scenario. but still the yellow light turns ON when Red comes in one of the tracks

CrossRoads

Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.


pranoy


CrossRoads

What does it do?
The LEDs can all be driven thru the IO pins shown:

D1 = 1, D0 = 0 turns on LED1
D1 = 0, D0 = 1 turns on LED2
D1 = D0 turns LED1 & LED2 off
same for 3,4  5,6  7,8
What's the AND gate do that couldn't be done with another IO pin instead?
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

Grumpy_Mike


this is a fair ckt dgm with only one yellow LED

Regarding that diagram, the pins that go through a resistor to the LEDs should not be connected to the input of the AND gate, this should be connected directly to the arduino. I suspect that it is this that is causing a problem because the current flowing through that resistor is holding the input to the AND high and thus keeping the yellow on, which still needs its own series resistor.

pranoy

cross roads

AND gate is for turning LED 3 ON D0-1 & D1-1

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