Pages: 1 [2]   Go Down
Author Topic: LED problem  (Read 1320 times)
0 Members and 1 Guest are viewing this topic.
Global Moderator
Boston area, metrowest
Offline Offline
Brattain Member
*****
Karma: 436
Posts: 23632
Author of "Arduino for Teens". Available for Design & Build services. Now with Unlimited Eagle board sizes!
View Profile
WWW
 Bigger Bigger  Smaller Smaller  Reset Reset

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.
Logged

Designing & building electrical circuits for over 25 years. Check out the ATMega1284P based Bobuino and other '328P & '1284P creations & offerings at  www.crossroadsfencing.com/BobuinoRev17.
Arduino for Teens available at Amazon.com.

Offline Offline
Jr. Member
**
Karma: 0
Posts: 76
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

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.
Logged

Manchester (England England)
Offline Offline
Brattain Member
*****
Karma: 506
Posts: 31345
Solder is electric glue
View Profile
WWW
 Bigger Bigger  Smaller Smaller  Reset Reset

Quote
There is only one 220 ohm resistor at one of the output pins.
You need another on the output of the logic gate.
Logged

Offline Offline
Jr. Member
**
Karma: 0
Posts: 76
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

this is a fair ckt dgm with only one yellow LED


* project_schem.jpg (70.04 KB, 1431x843 - viewed 13 times.)
Logged

Offline Offline
Jr. Member
**
Karma: 0
Posts: 76
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

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
Logged

Global Moderator
Boston area, metrowest
Offline Offline
Brattain Member
*****
Karma: 436
Posts: 23632
Author of "Arduino for Teens". Available for Design & Build services. Now with Unlimited Eagle board sizes!
View Profile
WWW
 Bigger Bigger  Smaller Smaller  Reset Reset

What is IC1?
Logged

Designing & building electrical circuits for over 25 years. Check out the ATMega1284P based Bobuino and other '328P & '1284P creations & offerings at  www.crossroadsfencing.com/BobuinoRev17.
Arduino for Teens available at Amazon.com.

Offline Offline
Jr. Member
**
Karma: 0
Posts: 76
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

7408 and IC
Logged

Offline Offline
Jr. Member
**
Karma: 0
Posts: 76
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

i meant AND ic
Logged

Global Moderator
Boston area, metrowest
Offline Offline
Brattain Member
*****
Karma: 436
Posts: 23632
Author of "Arduino for Teens". Available for Design & Build services. Now with Unlimited Eagle board sizes!
View Profile
WWW
 Bigger Bigger  Smaller Smaller  Reset Reset

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?
Logged

Designing & building electrical circuits for over 25 years. Check out the ATMega1284P based Bobuino and other '328P & '1284P creations & offerings at  www.crossroadsfencing.com/BobuinoRev17.
Arduino for Teens available at Amazon.com.

Manchester (England England)
Offline Offline
Brattain Member
*****
Karma: 506
Posts: 31345
Solder is electric glue
View Profile
WWW
 Bigger Bigger  Smaller Smaller  Reset Reset

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.
Logged

Offline Offline
Jr. Member
**
Karma: 0
Posts: 76
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

cross roads

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

Pages: 1 [2]   Go Up
Jump to: