555 timer issue

[nicksydney]

I'm testing a 555 circuit using this schematics http://waihung.net/wp-content/uploads/2012/02/circuit-flashing-led-schematic1.gif, the IC I'm using is NE555P ( http://www.ti.com/lit/ds/slfs022h/slfs022h.pdf ). The problem I'm having is the LED does not flash it stays on. Following is the reading that I took using multimeter when only connecting a battery to Pin 1 (GND) and Pin 8 (+)

Pin
-----
1 - 7.51
2 - 0.01 (fluctate between 0.01 to 0.02)
3 - 6.93
4 - 0.87
5 - 5.04
6 - 0
7 - 0
8 - 7.51

I'm bit new so I'm attaching the picture of my multimeter with this post to show the kind of multimeter I'm using and also the way I took the reading is turning the knob to 20 and putting the GND to Pin 1 and move around the red cable around the different pins to take the reading (hope I'm doing this the right way in taking the reading).

Can anybody help me ?

Thanks

[rexxar]

You took those measurements without any other components attached? That's not particularly helpful. If you post a picture of your completed circuit, we can figure out what's wrong.

[nicksydney]

You took those measurements without any other components attached? That's not particularly helpful. If you post a picture of your completed circuit, we can figure out what's wrong.

Yes, I did not attach any components. Will take picture with the component attached

[Rerouter]

are you confident in your measurements, as that is saying your ground point is connected to battery + ?

[nicksydney]

are you confident in your measurements, as that is saying your ground point is connected to battery + ?

According to datasheet picture Pin 1 is GND and Pin 8 is to positive and that's what I've done to measure it.

[Rerouter]

Pin
-----
1 - 7.51 Should be 0!
2 - 0.01 (fluctate between 0.01 to 0.02)
3 - 6.93
4 - 0.87
5 - 5.04
6 - 0
7 - 0
8 - 7.51

[nicksydney]

Pin
-----
1 - 7.51 Should be 0!

When I measure it I put the black cable on that pin 1 and red cable on pin 8 and that's the reading I get. Does this mean the IC is not spoilt ?

[rexxar]

Pin
-----
1 - 7.51 Should be 0!

When I measure it I put the black cable on that pin 1 and red cable on pin 8 and that's the reading I get. Does this mean the IC is not spoilt ?

To measure the voltage at pin 1, you need to connect your meter's common (black) probe to ground (the battery's negative terminal) and put the red probe on pin 1. Since pin 1 should be connected to ground, you should see 0 volts, as the probes are essentially connected to the same point.

[nicksydney]

To measure the voltage at pin 1, you need to connect your meter's common (black) probe to ground (the battery's negative terminal) and put the red probe on pin 1. Since pin 1 should be connected to ground, you should see 0 volts, as the probes are essentially connected to the same point.

To measure the other pins (2-7) should I do the same for the connecting the black cable to the GND of the battery or I can use pin 1 for GND and red cable to connect to other pins for reading ?

[rexxar]

To measure the other pins (2-7) should I do the same for the connecting the black cable to the GND of the battery or I can use pin 1 for GND and red cable to connect to other pins for reading ?

You can use pin 1 for your ground point, it's usually easier (I think) to probe that way. Like I said, if you've got it hooked up the right way, pin 1 is going to be at ground potential. For all intents and purposes, it's the same as connecting to the negative of the battery.

[Joule Thief]

Yes, keep your meter's black probe (GND) at the battery minus (-) terminal for measuring the rest of the pins on the IC.

BTW, what type of battery are you using to supply the power to this circuit.  7.5 volts may be an exhausted 9 volt battery 

[Joule Thief]

A ground lead attached to the breadboard ground or power supply ground (dotted line) are for your purposes, the same measurement point..

[nicksydney]

Hi,

Following are measurement readings I took after connecting all the components to breadboard:

Pin
---
1 - 0
2 - 0.7(*)
3 - 2.07
4 - 3.5
5 - 2.34
6 - 1(*)
7 - 2.25(*)
8 - 3.54

When I took measurement for the pin indicated with (*) I noticed that the voltage keep on dropping when the multimeter was attached to the pin - for example pin 2 when I took the measurement it reads at 0.7 and then keep on dropping 0.6, 0.54, 0.4 and so on.

The component that I'm using and the connection

Pin
----
1 - GND
3 - connect to a LED and the LED to GND
4 - connect to to 8 and 4 also connect to GND
5 - connect to a C1 and than connect to GND
6 - connect to R1 that connect to R2 which connect to Pin 7 and than R2 connect to C2 which connect to GND
8 - connect to +


R2 - 10k
R1 - 1K
C1 - written on it 101
C2 - 10uF 25v

Battery I'm using 9v but when I tested it with multimeter it was reading 7 something volt

[nicksydney]

More pics...

[nicksydney]

More pics....

[nicksydney]

Pics of capacitors I'm using...

[nicksydney]

Last pic...

[nicksydney]

Even when the battery is connected and if I remove any of the capacitors or resistors  the LED still turns on.

[andtfoot]

It looks like the breadboard is connected incorrectly.

At a glance, you are missing R3, and the way C1 and the other resistors are hooked up looks wrong. One leg of the cap should be going to pin 2 or 6, but it looks like it goes through a resistor first.

Edit: Also, it looks like the values of the resistors are wrong.

[Joule Thief]

Hi,

Following are measurement readings I took after connecting all the components to breadboard:

Pin
---
1 - 0
2 - 0.7(*)
3 - 2.07
4 - 3.5
5 - 2.34
6 - 1(*)
7 - 2.25(*)
8 - 3.54

When I took measurement for the pin indicated with (*) I noticed that the voltage keep on dropping when the multimeter was attached to the pin -

Pin 1 is now reading only 3.54 volts and should be your battery voltage. Either you need to replace the 9 volt battery due to exhaustion (can not supply 7 volts to circuit due to high internal resistance in the battery)

or

the circuit is wired incorrectly.

Next step is to measure directly across the battery terminals while you are powering the circuit. If the voltage present at the battery terminals reads around 3.5 volts, the battery most likely needs to be replaced.

[nicksydney]

After following Joule Thief advice I search for new battery and found 8 x 1.5v so I use that to make 12v battery and this time it's the same the LED still stays on but the reading is bit different

Pin
----
1 - 0
2 - 9.5
3 - 9.3
4 -12.1
5 - 11.9
6 - 9.5
7 - 9.5
8 - 12.3

Previously I notice few pins were dropping in voltage when measuring but now none of the pin give a voltage reading that dropped...it consistenly stays at approximately same level.

I tried rearranging the pin to connect 2 to 6 and connect the capacitor from pin 2 to GND and then the resistor from pin 6 to 7 and from pin 7 to GND it still doesn't make any difference

[tstanford]

Can't really see the colors on the resistors that well, but here's how i checked color codes when I started.

Code: [Select]

Black Brown Red Orange Yellow Green Blue Violet Gray White
0    1      2      3       4     5   6    7     8      9

If you get out your calculator or number pad, counting along as you say the colors helps. 

First stripe - most significant digit (example in a 10,000 ohm resistor it would be the 1, brown)
Second stripe - next digit (In a 2700 ohm resistor this would be the 7, violet)
Third stripe - the power ten is raised too, or the number of zeros following the first two digits whichever is an easier way to think of. (in a 3300 ohm resistor this would be a 2, red)
Fourth stripe - tolerance.  (gold silver or missing unless its a precision resistor. gold is +- 5%. silver +-10%, none is +-15%

Pneumonic device big boys race our young girls but violet goes wild works (theres a politically incorrect one we used).

[nicksydney]

Did a bit of rearrangement to make it easier to take photos for pin 5-8

[nicksydney]

Another pics

[nicksydney]

Another pics