I am working on a 555 timed blinking LED circuit

Thread Starter

johnboyman

Joined Jun 1, 2019
36
Hello All. I am an electrical engineering student.I have to make a blinking LED as a project. I bought all the right parts and hooked it up right but I cannot get the light to blink. I have two pictures of my circuit.

The circuit uses the following components:
-IC 555 timer B-Dip
-100k Resistor
-10K Resistor
-LED
-9 volts DC
-Jumper Cables
-I use a 1 , 22 and 100 MicroFarad Capacitor

I have looked at many different versions of the circuit they all are very similar. I am stuck on this one because I don't know what could be wrong. Can anyone out there give me a tip or two before I loose my mind. Thanks all.
 

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Zeeus

Joined Apr 17, 2019
580
Hello All. I am an electrical engineering student.I have to make a blinking LED as a project. I bought all the right parts and hooked it up right but I cannot get the light to blink. I have two pictures of my circuit.

The circuit uses the following components:
-IC 555 timer B-Dip
-100k Resistor
-10K Resistor
-LED
-9 volts DC
-Jumper Cables
-I use a 1 , 22 and 100 MicroFarad Capacitor

I have looked at many different versions of the circuit they all are very similar. I am stuck on this one because I don't know what could be wrong. Can anyone out there give me a tip or two before I loose my mind. Thanks all.

Welcome to AAC!
pin 4 is reset pin..Active low.. COnnect it to Vcc and see how it goes
 

dl324

Joined Mar 30, 2015
10,758
Welcome to AAC!

Since this appears to be school work, we're not allowed to just give you answers.
I have looked at many different versions of the circuit they all are very similar. I am stuck on this one because I don't know what could be wrong. Can anyone out there give me a tip or two before I loose my mind.
Can you identify any characteristics in the circuits that work vs yours? Have you read the datasheet to see what it says about any pins you haven't connected?
 

Thread Starter

johnboyman

Joined Jun 1, 2019
36
Which implies that you were not originally. You might have destroyed the LED or the 555 then.

What voltage are you running it at?

Bob
The LED is fine. I have been running this from 5-9 volts. I even tried another 555 timer. I have two of them. Still the light runs but wont blink. Thanks
 

Zeeus

Joined Apr 17, 2019
580
The LED is fine. I have been running this from 5-9 volts. I even tried another 555 timer. I have two of them. Still the light runs but wont blink. Thanks
Maybe it's blinking but can not see?

if calculation is right () : cap discharges through the 10k into pin 7

t = In2 * RC about 0.03secs with 5UF....Maybe change the 10k to 100k and see
 

Daniel Sala

Joined May 28, 2015
60
Hi,

Summary:

Connect reset pin to V+
LED anode (long leg) to pin 3
Turn capacitor around 180º so silver stripe is connected to ground/0V. Your electrolytic capacitor may/should have a minus sign on the stripe.

Doesn't hurt to add 100nF (0.1uF) capacitor from pin 5 to ground/0V
Doesn't hurt to add another 100nF capacitor across pin 8 to pin 1 (from V+ to 0V)
 

Thread Starter

johnboyman

Joined Jun 1, 2019
36
Thanks for all the advice. I am going to make another trip to the store to get new 555 timers, some 100 nF caps and 10 uF caps. Thanks for the help.
 

dl324

Joined Mar 30, 2015
10,758
Thanks for all the advice. I am going to make another trip to the store to get new 555 timers, some 100 nF caps and 10 uF caps. Thanks for the help.
Why don't you try to troubleshoot the circuit first? Start by measuring the voltage on the timing cap. It should be charging and discharging between 1/3Vcc and 2/3Vcc.
 

Audioguru

Joined Dec 20, 2007
11,249
He does not say if he has a powerful LM555 or NE555 that will blow up the LED when he properly connects it to pin 3 or if he has a weak Cmos LMC555, TLC555 or ICM7555 that might not blow up the LED.
 
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