NE555 Timer trouble

[Xpand]

Hello! This is my first post here.
So today I went on a 30 mile journey to the nearest electronic shop in the region to buy a few components for an Astable 555 timer circuit.
I got home and installed everything on my breadboard according to the data sheet's astable circuit design.
I was expecting my LED to pulsate with a 46Hz frequency, but the thing just keeps staying lit.
Both my resistors are 1k ohms, my capacitors have a 10uF capacitance, and my energy source is a group 4 alkaline batteries (6V).
I then spent the next 4 hours troubleshooting and making and remaking the circuit over and over again.

I never reversed the input on the chip and I always had enough care to touch a metal object before touching the chip.
I'm waiting to get a speaker to test the actual frequency of the output by sound, because there's the possibility of the LED flashing too fast for me not to notice.

But I still don't know where my calculations fail.

Does any of you know the answer? I sure hope it doesn't involve buying a new chip because I'll only be able to return to the store in a few months because of college work... (I'm not in an electronics course, by the way)

Thank you for your help!

P.S. I'm sorry if this is a repeated thread.
Also, I have a picture of my circuit:
View attachment 64699

 

[ericgibbs]

hi,
Your calculation is correct.
What is the value of the cap on pin#5.?

Try this as a test, increase one of the 1K's to say a 47K, it should flash slower.. a 46/48Hz rate may appear ON all the time.

 

[Xpand]

The capacitor connected to the control pin is 10uF. Exactly the same as the other one.
So you don't think that the chip's broken?
I actually want it to have a high frequency because I'm going to use this as a sound synthesizer. I just need to get a speaker from an old sound system that I have here...
Thanks for your help!

 

[ericgibbs]

hi.
The pin 5 cap is usually 10nf or 100nF, as a test remove it.

Did you try a higher resistor value in order to check if the 555 is running.?

 

[Xpand]

Ok, so I guess I was misinformed about the capacitors...
No I haven't tried a new resistor. I just saw the message, but I'll see if I can find some higher resistor in my old stuff.
Thanks!

 

[jpanhalt]

At that frequency, a capacitor on pin 5 is probably not needed. Take that capacitor and put it in parallel with the other capacitor, which will give you about 20 uF . That should slow the flashing down considerably.

Also, if the flashing is too fast, as Eric suggested, try looking at something else so the led is only seen on the edge of your visual field. Your eye is more sensitive to flickering in its peripheral vision.

John

 

[Xpand]

Okidoki!
I'll try to do that as soon as possible. I'm also going to try to connect a speaker to the output just to see if this is really pulsating at 46Hz or 466Hz with the 100Ω resistors. If everything works with the speaker then it's all good. I'll feedback it here!

Thanks a lot!

 

[ericgibbs]

Okidoki!
I'll try to do that as soon as possible. I'm also going to try to connect a speaker to the output just to see if this is really pulsating at 46Hz or 466Hz with the 100Ω resistors. If everything works with the speaker then it's all good. I'll feedback it here!

Thanks a lot!

Dont connect a speaker directly to the output of the 555 pin 3

Use an intermediate transistor and a coupling cap to the speaker

 

[Xpand]

Hmm, so, can you give me a simple idea of how that works? Like a diagram or something. Because I'm not understanding what transistor/capacitor I should use and how should I use them. The speaker I have in mind is one of those small speakers that are used for computers.

 

[ericgibbs]

Hmm, so, can you give me a simple idea of how that works? Like a diagram or something. Because I'm not understanding what transistor/capacitor I should use and how should I use them. The speaker I have in mind is one of those small speakers that are used for computers.

hi,
Look thru these.
http://www.google.co.uk/search?q=55...s=org.mozilla:en-US:official&client=firefox-a


**broken link removed**

 

[DerStrom8]

I agree with eric. The calculations sound okay, but 46 Hz means it's flashing 46 times per second. At that rate, your eye probably won't even recognize that it's turning off. It's only attracted to the light.

A quick trick to see if something's flashing at a high frequency is to do this: Hold the board up in front of your face, maybe 6-10 inches away, and quickly move it from one side to the other. If the LED isn't flashing, you'll only see a straight, unbroken line (where the light made an imprint on your retina). However, if it's flashing, you'll see the trail of the LED as sequential dots. You might have to experiment a bit with how fast you move it, and how close to your face you hold the board.

A speaker would be a very good test. You'll be able to hear it buzz if it's working properly.

Good luck!
Regards,
Der Strom

P.S. Welcome to the forums!

 

[Xpand]

Thanks a lot!
I just have to go buy some new transistors... Too bad I can't go to the electronic's store that soon...
I should have looked this up better...
Thanks for your help!

 

[Xpand]

Hey! It works with the speaker!
Outstanding!

 

[DerStrom8]

Hey! It works with the speaker!
Outstanding!

Glad to hear it!

Your calculations were fine and the circuit was working the way it was supposed to. Your understanding of Hertz was only a little bit off, but that's easily remedied

Hope this was a great learning experience. Keep it up!

Best wishes

 

[Mickster]

I agree with eric. The calculations sound okay, but 46 Hz means it's flashing 46 times per second. At that rate, your eye probably won't even recognize that it's turning off. It's only attracted to the light.

A quick trick to see if something's flashing at a high frequency is to do this: Hold the board up in front of your face, maybe 6-10 inches away, and quickly move it from one side to the other. If the LED isn't flashing, you'll only see a straight, unbroken line (where the light made an imprint on your retina). However, if it's flashing, you'll see the trail of the LED as sequential dots. You might have to experiment a bit with how fast you move it, and how close to your face you hold the board.

A speaker would be a very good test. You'll be able to hear it buzz if it's working properly.

Good luck!
Regards,
Der Strom

P.S. Welcome to the forums!

This was a great idea and if you look at POV clock and POV air message devices, you'll see why DerStrom8 made the suggestion.

Above a certain frequency, it's difficult for us to ascertain whether an LED is actually flashing, or constantly lit. Introduce movement and, within limits, that LED or group of LED's which appears to be constantly lit, can be 'timed' to produce visible information.

A single LED could be, most easily with a μC, programmed to flash out a morse code message, for instance. A vertical line of 7 or 8 LED's can be used to produce numbers, text and simple bitmaps. And in more complex builds, RBG LED's can be used to create multi-colour animations.

Some links for your perusal:
Bob Blick's POV clock -
**broken link removed**

Jose Pino's Air Display Message -
http://www.josepino.com/?air_display

A very nice RGB clock with animations -
http://www.youtube.com/watch?v=l4F8UbM-1t4

Regards.

 

[Xpand]

Yeah! Thanks!
I kinda forgot that we see at 25 FPS (25Hz) so it's pretty hard to notice something flashing at double of that frequency!

Thanks for your help!