I have made several 555 circuits for flashing a LED. some flash, some have a constant light some don't light at all. I have read several posts on reasons why LED does not flash. Using standard diagram.
+ input on 8
R1 1K on 8
R1 connected to 7 and R2 (100K)
R2 on 7
6-2
- input on 1
-side of 1000uf capacitor on 1
- LED on 1
+ side of capacitor on 2
R3 (1K) on 3
+ LED on 3
4-8
10 uf capacitor 5-1
LED lights whether 1000uf capacitor is connected or not.
greater than 12 v on 5

 

This would go much better if you just post a schematic. Sort of difficult to read what you wrote and connect the dots.

Ron

 

Schematic as requested. What are voltages at pins?

 

I have made several 555 circuits for flashing a LED. some flash, some have a constant light some don't light at all. I have read several posts on reasons why LED does not flash. Using standard diagram.
+ input on 8
R1 1K on 8
R1 connected to 7 and R2 (100K)
R2 on 7
6-2
- input on 1
-side of 1000uf capacitor on 1
- LED on 1
+ side of capacitor on 2
R3 (1K) on 3
+ LED on 3
4-8
10 uf capacitor 5-1
LED lights whether 1000uf capacitor is connected or not.
greater than 12 v on 5

Below is a diagram of a '555 feeding an LED. If R1 = 1k , R2 = 100k, R3 = 1k, C1 = 1000uF, C2 = 10uF then the LED would take over 1 minute to turn on or off. When power is applied it would take over 1 minute before it went off and then another 1 minute before it came back on.
Did you wait that long?

 

Schematic as requested. What are voltages at pins?

That's an absolutely horrible schematic. Even this rotated and clipped version:

Will post a real schematic shortly...

EDIT: Better schematic:

I calculate a period of about 14 seconds.

Measure the voltage on pin 2. The LED should be on until it rises to 2/3Vcc; then the LED should be off until it drops to 1/3Vcc.

 

That's an absolutely horrible schematic. Even this rotated and clipped version:
View attachment 138671
Will post a real schematic shortly...

EDIT: Better schematic:
View attachment 138672
I calculate a period of about 14 seconds.

Measure the voltage on pin 2. The LED should be on until it should rises to 2/3Vcc; then the LED should be off until it drops to 1/3Vcc.

 

Yes, I waited a long time.

Input voltage is 15v. voltage on pin 2 is 10.2v

 

Yes, I waited a long time.

Input voltage is 15v. voltage on pin 2 is 10.2v

Check the connection to pin 7.

 

The expected frequency is 0.007165Hz or a period of 139.6 seconds.

 

The expected frequency is 0.007165Hz or a period of 139.6 seconds.

I calculate about 14 seconds:

 

The expected frequency is 0.007165Hz or a period of 139.6 seconds.

Yiu means 13.9 secondas

 

Check the connection to pin 7.

 

pin 7 has good connection. 15v.

 

So these are all wrong?
https://www.allaboutcircuits.com/tools/555-timer-astable-circuit/
http://www.ohmslawcalculator.com/555-astable-calculator
http://www.555-timer-circuits.com/calculator.html

 

pin 7 has good connection. 15v.

Check the connection between pins 2 and 6.

 

The expected frequency is 0.007165Hz or a period of 139.6 seconds.

connection between pin 2 and 6 good.

 

pin 7 has good connection. 15v.

That isn't indicative of a good connection. That's the discharge transistor. The highest voltage seen at that pin should be 10V. It should be around 0V while the cap is being discharged.

Check your wiring.

 

So these are all wrong?
https://www.allaboutcircuits.com/tools/555-timer-astable-circuit/
http://www.ohmslawcalculator.com/555-astable-calculator
http://www.555-timer-circuits.com/calculator.html

Must be pilot error. I tried the AAC calculator and it gave 1.396e+4mS.

The calculations for the timer in question were so simple that I could do it without a calculator (i.e. in my head). 20 * .7 = 14

 

That isn't indicative of a good connection. That's the discharge transistor. The highest voltage seen at that pin should be 10V.

Check your wiring.

During the on time (which at the moment seems to be all the time) the voltage across the charging capacitor should be rising towards 10V and the discharge transistor should be off but pin 7 is connected by 1k to the 15V supply and by 100k to the capacitor so the voltage at pin 7 should be close to the supply voltage - 15V.

 

During the on time (which at the moment seems to be all the time) the voltage across the charging capacitor should be rising towards 10V and the discharge transistor should be off but pin 7 is connected by 1k to the 15V supply and by 100k to the capacitor so the voltage at pin 7 should be close to the supply voltage - 15V.

My bad. But it should be around ground once the timing cap gets to 10V...