555 tester circuit

[plutes]

Hi can someone more experienced advice me on what too do, Ive built this circuit twice now and all I get is 1 led stay on. which would imply my 555 ic is damaged the thing is I've tried 5 different chips now and they are all doing the same. Two I suspect were already damaged but three brand new and non used ones.

Calculator online suggest these values should flip flop every 2 seconds. Is there a problem with this circuit or have I got 50 bad chips?

from https://www.circuitstoday.com/555-tester-circuit

 

[plutes]

 

[bertus]

Hello,

See comments in picture:

Bertus

 

[Harald Kapp]

all I get is 1 led stay on.

Which one? D1 or D2?
I suspect it may be D2 indicating the Trigger input (pin 2) doesn't reach 1/3 of the operating voltage (1/3 of 9 V = 3 V), One reason for this may be a bad capacitor C1. If the leakage current through C1 is higher than the charging current through R1+R2 (~ 9 V/1650 kΩ = 60 µA), the capcitor will not charge properly.
A few things you can try:

1. Check the voltage on pin 2 to verify or falsify my assumption.
2. Try another capacitor for C1.
3. Reduce R2 to e.g. 15 kΩ. Increasing the charge current may overcome the issue with leakage current through C1. The frequency is still low enough that you'll be able to distinguishg the two LEDs blinking.

Cheers,
Harald Kapp

 

[plutes]

they were touching, its 10uf 250volt/ will swap it to 25v 10uf... yep still single led stays lit

 

[plutes]

Which one? D1 or D2?
I suspect it may be D2 indicating the Trigger input (pin 2) doesn't reach 1/3 of the operating voltage (1/3 of 9 V = 3 V), One reason for this may be a bad capacitor C1. If the leakage current through C1 is higher than the charging current through R1+R2 (~ 9 V/1650 kΩ = 60 µA), the capcitor will not charge properly.
A few things you can try:

1. Check the voltage on pin 2 to verify or falsify my assumption.
2. Try another capacitor for C1.
3. Reduce R2 to e.g. 15 kΩ. Increasing the charge current may overcome the issue with leakage current through C1. The frequency is still low enough that you'll be able to distinguishg the two LEDs blinking.

Cheers,
Harald Kapp

well done, not sure if was cap, I will check in a sec. connected meter across ground and pin 2 and watched it go from 4 volt climb to 5v and started d1 and d2


ok yes the 250v 10uf starts at 0.1volt and climbs very slowly, guessing 5 mins holding would get it flashing. Thanks now I can make a permanent version

 

[bertus]

Hello,

The capacitor voltage should be sweeping between 1/3 Vcc and 2/3 Vcc.
So in case of a 9 Volts battery between 3 and 6 Volts:

Bertus