555 timer Astable not working, only One LED is lit up

[RobertRobot36]

I have been trying to make this circuit work for a few weeks now and it is slowly driving me crazy.

I have on a veroboard a circuit. When i redo the circuit on Yenka (Crocodile clips) It works perfectly.
The circuit is a 555 astable circuit with two LEDs, when i turn it on only one LED lights up (the LED connected to pin 3 and 0v) and i can't get it to flash. When i use my voltmeter to measure, i get 0v on pin 1, 2, 6. Is this right?

I really don't know why it is not working, please help!

 

[Jiggy-Ninja]

It depends on your 555's pinout. Are you sure you've hooked it up properly?

In my datasheet for a National Semiconductor LM555, the pin-out is:

1: Ground
2: Trigger
3: Output
4: Reset
5: Control
6: Threshold
7: Discharge
8: +V_cc

Pin 1 is GND, so you should be reading 0 volts there. But pins 2 and 6 are Threshold and Trigger. If it was hooked up properly, the voltage would be fluctuating between 1/3-2/3 V_cc.

The oscillation frequency might be too high to notice the blinking. Is it greater than 10Hz or so?

Where is the other LED hooked up to?

Can you post a schematic of your hookup, or a picture?

 

[vk6kro]

I don't know either, but I would guess that you didn't cut the tracks on the veroboard where you plugged in the 555.

If the tracks continue across the socket, then the chip will not work.

Also, check where these tracks actually go between various parts of your circuit. These tracks are like wires and a wrong connection can upset the operation of your circuit or even destroy your 555 chip.

 

[RobertRobot36]

http://www.eleinmec.com/article.asp?3
I used the drawing on that about 3/4 of the way down.
I took out the two capacitors and just left in the upwards capacitor connected to pin2 and 0v.
I have cut the tracks in the correct places too. i have checked my circuit over and over again and it matches one one on screen

I am using a 330uf capacitor and these two resistors:
Red Red Brown Gold
Brown red brown Gold

:)

 

[lashari]

Keep in mind that when one led glows then the +ve of -ve half cycle is there. for the other led to glow on that time the polarity of other led must be proper else it would not glow up. If 1st led glow with +ve voltage then after half cycle the voltages are zero so how other led will glow.
www.bestarticlez.com

 

[vk6kro]

http://www.eleinmec.com/article.asp?3
I used the drawing on that about 3/4 of the way down.
I took out the two capacitors and just left in the upwards capacitor connected to pin2 and 0v.
I have cut the tracks in the correct places too. i have checked my circuit over and over again and it matches one one on screen

I am using a 330uf capacitor and these two resistors:
Red Red Brown Gold
Brown red brown Gold

:)

Those resistors are 220 ohms and 120 ohms. These values are too low if you want to see the LED flashing.
The 330 uF capacitor is really too big too. The 555 has to discharge this capacitor every cycle and this would involve switching quite a large current.

Here is a better oscillator circuit (below) to give you an idea of correct resistor values.

https://www.physicsforums.com/showpost.php?p=3207973&postcount=8

There are plenty of 555 calculators on Internet. You can find them by searching on Google. You need a frequency of 1 Hz to 4 Hz to see the flashing.