Why is my 555 Timer not blinking?

In summary: Okay, I was assuming Vo=Vs when the output is high -- that has been my (limited) experience. I was unaware that this is not necessarily the case for all 555 timer variants.
  • #36
negitron said:
Yes, just leave the chip out (but all the ancillary components in place) and check the voltages at the points where the pins of the chip would be. No, the circuit won't function under these conditions, but you will still have some voltages, either directly from +Vs or through a resistor.

Good deal; makes sense now. I'll post right after I get the ratings.
 
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  • #37
Rule of thumb - if the part gets too hot for comfort than it either needs a heatsink or you are doing something wrong (like reverse the polarity). For many chips if your reverse the polarity it will act as a short and will heat up very quickly.

Does your voltmeter have a current measuring ability? If so, try with that (making sure that you connect it in SERIES). Now, also disconnect everything and connect only power and ground and see if it gets even warm. If so then somethign is bad there.
 
  • #38
The 555 is especially vulnerable to external voltage on pin 3, its output.
So, it is important not to plug a new chip in if there is voltage on this socket pinhole.


I found a great website on 555 applications. Sometimes someone just does a superb job with making a website and this is one of them.
http://www.uoguelph.ca/~antoon/gadgets/555/555.html

Anyone here could probably fix that circuit in a few minutes but it can take hours on this Forum to ask the right questions without seeming to be insulting. So, please excuse any questions that seem to be too simple.

I have a couple of breadboards , but I prefer to solder up a circuit on a bit of printed circuit board.
Maybe you would like to try it. You turn the chip so its legs are facing upwards. (this construction method is called "dead bug construction" for this reason).
Any legs that are to be grounded are bent downwards and soldered to the PC board. Also any capacitors etc that need to be grounded are soldered in.
Power leads etc are attached to tag strips and not directly to the IC. (I use header pins cut to shape as tag strips).
This way, you can lay out a circuit as it is in a diagram and quickly see if something is wrong. It is very safe and the IC is in no danger of being pulled apart. And you can easily change a component value if you want to.
 
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  • #39
ShadowPho1 said:
Rule of thumb - if the part gets too hot for comfort than it either needs a heatsink or you are doing something wrong (like reverse the polarity). For many chips if your reverse the polarity it will act as a short and will heat up very quickly.

Does your voltmeter have a current measuring ability? If so, try with that (making sure that you connect it in SERIES). Now, also disconnect everything and connect only power and ground and see if it gets even warm. If so then something is bad there.

Well, I think it's possible that this would explain my problem. After I only connected the V+ and 0v, it still got very hot (people who can verify this will be greatly appreciated)! I guess the bottom line would be that the timer is down right fried/defective. Before I plug in my new timer, I'm going to take a few pictures of my bread boarded circuit before I go ahead and connect the 6v supply.

Again, thank you all for being of so much help! :!)
 
  • #40
vk6kro said:
I have a couple of breadboards , but I prefer to solder up a circuit on a bit of printed circuit board.
Maybe you would like to try it. You turn the chip so its legs are facing upwards. (this construction method is called "dead bug construction" for this reason).
Any legs that are to be grounded are bent downwards and soldered to the PC board. Also any capacitors etc that need to be grounded are soldered in.
Power leads etc are attached to tag strips and not directly to the IC. (I use header pins cut to shape as tag strips).
This way, you can lay out a circuit as it is in a diagram and quickly see if something is wrong. It is very safe and the IC is in no danger of being pulled apart. And you can easily change a component value if you want to.

Does current travel differently in a soldered circuit than in a bread boarded circuit? And also a question, I mind as well ask, in relation is: Can the magnetic field of electricity traveling in a bread boarded circuit be severe enough to effect activity going on in adjacent bus stripes in the bread board?
 
  • #41
Twinfun2 said:
And also a question, I mind as well ask, in relation is: Can the magnetic field of electricity traveling in a bread boarded circuit be severe enough to effect activity going on in adjacent bus stripes in the bread board?

Nah, the breadboard will melt long before there's enough current to create large magnetic fluxes. :smile:
 
  • #42
Does current travel differently in a soldered circuit than in a bread boarded circuit?

No, but the connections are more secure, you can see the whole circuit and wire lengths are shorter meaning you get less inductance in the circuit.

Inductance of a few inches of wire doesn't matter for a 555 light flashing circuit but for any serious circuits at high frequencies, it can mean the difference between a circuit working or not working.
For example, I just measured the reactance of a 4 inch piece of wire at 15 MHz. It had a reactance of 17 ohms. That would be enough to upset most circuits operating at that frequency.

Can the magnetic field of electricity traveling in a bread boarded circuit be severe enough to effect activity going on in adjacent bus stripes in the bread board?


Two such wires anywhere near each other at high frequencies would behave like a transformer and pass power from one to the other and possibly cause an amplifier to oscillate.

At VHF (frequencies above 30 MHz) construction techniques that involve short wire lengths are very important and I build all equipment as if it was for VHF. Good ground planes and short wires on components. It is a good habit to get into.
 
  • #43
vk6kro said:
Two such wires anywhere near each other at high frequencies would behave like a transformer and pass power from one to the other and possibly cause an amplifier to oscillate.


I think we can agree that this is way too small an effect to be of concern here to Twinfun2. :smile:

Twinfun2, what you have is some kind of very large current flowing through your device, either from the supply terminals, or through the output pin (which appears to be the only pin which is not internally current-limited in the NE555N).

- Warren
 
  • #44
The poster did ask about the effect of lead length.
Can the magnetic field of electricity traveling in a bread boarded circuit be severe enough to effect activity going on in adjacent bus stripes in the bread board?

Even if you are making an audio amplifier, most transistors these days can operate at 300 MHz or more and they may well oscillate at those frequencies if the layout is poor.

I used a 2N3563 in a battery charger for NiMH batteries recently. This transistor has a ft of 900 MHz, so I cut the leads very short to try to avoid parasitic oscillation. Good layout never goes astray.

I am hoping the fault will be a wiring error or a faulty IC, but VHF oscillation is a real problem in breadboard circuitry. The 555 may not operate there but it has transistors in it that probably can. It can produce some pretty fast square wave edges.
 
  • #45
At the frequencies Twinfun2 is using, a 555 should work just fine on a solderless breadboard.
 
  • #46
Twinfun2 said:
Well, I think it's possible that this would explain my problem. After I only connected the V+ and 0v, it still got very hot (people who can verify this will be greatly appreciated)!

Still wanting to know if this means that the timer is officially bad.

EDIT: I'm still trying to get a hold of a camera :mad:. I'll wind up drawing my bread board circuit layout on paint or something.
 
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  • #47
Here are my pin ratings according to instruction given by vk6kro, and negitron.

For Reference:
__________

R1:10k
R2:100k
C:10uF
__________

1: 0v
2: 2v
3: 0v
4: 5v
5: 0v
6: 2v
7: 4.5v
8: 5v

(I'm, sadly, using an analog multimeter, and those are the best ratings I have been able to grab.)
 
  • #48
Twinfun2 said:
Still wanting to know if this means that the timer is officially bad.

Yes, the part is bad.

- Warren
 
  • #49
chroot said:
Yes, the part is bad.

- Warren

Muchos gracias. :biggrin:

Now just awaiting if those volt readings are correct, or near correct, before inserting my new timer.
 
  • #50
Twinfun2 said:
3: 0v

This worries me. Pin #3 is the output pin, which supplies current to the load. If nothing is connected to it, it should be floating, and will probably not go all the way down to 0V. If you've connected pin #3 to your LED and resistor, it should have a voltage of around 4-5V on it.

If pin #3 is really all the way down at ground (0V), then a huge amount of current is likely flowing out of it. Something's screwed up with that pin. Disconnect everything from it, and make absolutely sure there's no continuity between it and the ground rail.

- Warren
 
  • #51
chroot said:
This worries me. Pin #3 is the output pin, which supplies current to the load. If nothing is connected to it, it should be floating, and will probably not go all the way down to 0V. If you've connected pin #3 to your LED and resistor, it should have a voltage of around 4-5V on it.

If pin #3 is really all the way down at ground (0V), then a huge amount of current is likely flowing out of it. Something's screwed up with that pin. Disconnect everything from it, and make absolutely sure there's no continuity between it and the ground rail.

- Warren

The way I was told to do it was to disconnect the timer, and place wires where the pins would be, and to read those wires compared to a ground with a multimeter.
 
  • #52
Oh, I see, you removed the timer and those are the voltages on the pins without it present.

Is there any chance that your breadboard is damaged, and there's a short in it that you don't expect? Do you have a multimeter with continuity testing?

At this point, I'd suggest that you dismantle the circuit, and build it again somewhere else on the breadboard. I'd start with just the VCC, RESET, and GND pins, make sure the part doesn't get hot, and then move on to connecting the rest of the circuit.

- Warren
 
  • #53
chroot said:
Oh, I see, you removed the timer and those are the voltages on the pins without it present.

Is there any chance that your breadboard is damaged, and there's a short in it that you don't expect? Do you have a multimeter with continuity testing?

At this point, I'd suggest that you dismantle the circuit, and build it again somewhere else on the breadboard. I'd start with just the VCC, RESET, and GND pins, make sure the part doesn't get hot, and then move on to connecting the rest of the circuit.

- Warren

The word continuity causes my head to make buzzy sounds! :eek:

In other words, what's continuity? (EDIT: Wow, someone explained that to me already in this very thread...the real question: How do I use the multimeter to test continuity?)

This is my multimeter:
http://www.radioshack.com/product/index.jsp?productId=2103170&tab=summary

Also, I just got a hold of a digital camera; going to take as many good shots as possible. I'll be posting them within the next hour or two.
 
  • #54
Ok, I just reconnected everything in a new place, and she is ready for her photo shoot! :smile:
 
  • #55
Twinfun2 said:
In other words, what's continuity? (EDIT: Wow, someone explained that to me already in this very thread...the real question: How do I use the multimeter to test continuity?)

Typically, you turn your multimeter's control dial to the position with a little speaker icon. Next, you touch two different spots with the probes (it doesn't matter which way 'round they are connected). If there is a very low-resistance path between the spots, the meter will beep, letting you know the two spots are electrically the same.

You want to make sure there is no direct connection between pin #3 (output) and any other pin, particularly VCC or GND.

- Warren
 
  • #56
Twinfun2 said:
How do I use the multimeter to test continuity?)

chroot said:
Typically, you turn your multimeter's control dial to the position with a little speaker icon. Next, you touch two different spots with the probes (it doesn't matter which way 'round they are connected). If there is a very low-resistance path between the spots, the meter will beep, letting you know the two spots are electrically the same.

Since the OP's http://rsk.imageg.net/graphics/uc/rsk/Support/ProductManuals/2200223_PM_EN.pdf" does not mention continuity measurement, he can just measure the resistance and look for a (nearly) zero-ohm reading to indicate that two locations are connected, or an infinite-ohm reading to indicate that they are not.
 
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  • #57
As far as I can tell, nobody has posted any schematic of a NE555 LED oscillator. So I built one in 15 minutes (in LTSpice) and turned it on. Here it is...
 

Attachments

  • NE555­_LED_Osc.jpg
    NE555­_LED_Osc.jpg
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  • #58
_______________________________________________

The Pictures: (Picture One Indicates Pin 1)

http://img265.imageshack.us/gal.php?g=oneh.jpg

For Reference:
__________

R1:10k
R2:100k
C:10uF

_______________________________________________
 
  • #59
Looks like the LED+resistor are connected between pin 4 and ground, but it should be pin 3 and ground.

Since pin 4 is tied to Vs, the LED would stay on continuously.

EDIT: that would not have caused the chip to overheat however.
 
  • #60
Redbelly98 said:
Looks like the LED+resistor are connected between pin 4 and ground, but it should be pin 3 and ground.

Since pin 4 is tied to Vs, the LED would stay on continuously.

Just fixed.

(I didn't make that mistake before, so nothing wrong there. :blushing:)

Anything else?
 
  • #61
Take another picture.

- Warren
 
  • #63
Looks good to me... Keep in mind that the horizontal stripes of holes at the top and bottom of the board do not always connect all the way across the board. Make sure that all of your VCC connections, and all of your GND connections, are continuous with your multimeter.

- Warren
 
  • #64
chroot said:
Looks good to me... Keep in mind that the horizontal stripes of holes at the top and bottom of the board do not always connect all the way across the board. Make sure that all of your VCC connections, and all of your GND connections, are continuous with your multimeter.

- Warren

Ok, I will do that, and then insert my new timer afterward.

Wish me luck guys! :biggrin:
 
  • #65
Still no dice guys...light stays on, and the timer is actually STILL getting hot. Could it simply be the breadboard? If so, I might make an attempt at soldering the circuit together instead.

Output of Pin is in this order:

Resistor, LED, Ground

Is there any connections missing? According to the schematic supplied by Bob S, there should be some extra connections that are not included in my circuit.
 
  • #66
At this point I'm at a loss. Have you gone through all the nets in the design, measuring their resistance to all other nets? It is entirely possible that your breadboard is damaged. If it is, it'll show up in those continuity tests.

- Warren
 
  • #67
Could "Rechargeable Batteries" be the culprit?

I'm just looking through every detail now...
 
  • #68
No, rechargeable batteries should not be an issue. Again, there's something going where a lot of current is flowing through your device. You should try:

1) Measuring the resistance between each net and all the others.
2) Using your multimeter to measure currents through the VCC and output pins.

The second test needs to be done with the part installed, of course, but you should be able to get a reading of the current in just a second or two.

- Warren
 
  • #70
I compared each and every node on the breadboard circuit with the ones on the schematic in the OP and they all match. I'd suspect the board at this point.
 

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