Need help with Circuit: LED Blinking Problem

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Discussion Overview

The discussion centers around troubleshooting a circuit designed to make an LED blink when a switch is pressed. Participants explore the circuit's design, component values, and the effects of different configurations on the LED's behavior. The conversation includes technical explanations and suggestions for adjustments, as well as some personal experiences related to the circuit's performance.

Discussion Character

  • Technical explanation
  • Debate/contested
  • Exploratory

Main Points Raised

  • One participant expresses uncertainty about the circuit's functionality and whether it can work without a switch, using wires instead.
  • Another participant suggests that the output frequency might be too fast for the LED to appear to blink, proposing a change to the capacitor value to achieve a slower flash rate.
  • There is a discussion about the differences between standard and CMOS 555 timers, with concerns about using high resistor values with a standard 555 timer.
  • Participants recommend checking wiring and measuring voltage at various pins of the 555 timer to diagnose issues.
  • One participant realizes a potential mistake in resistor values, leading to a moment of self-reflection about overlooking details in the circuit setup.
  • After several exchanges, a participant confirms that they successfully fixed the circuit by replacing the resistors, expressing gratitude for the assistance received.

Areas of Agreement / Disagreement

Participants generally agree on the need to check wiring and component values, but there are differing opinions on the specific causes of the circuit's issues and the effectiveness of proposed solutions. The discussion remains somewhat unresolved until the final confirmation of the circuit working.

Contextual Notes

Some assumptions about component values and circuit behavior are not explicitly verified, and the discussion includes various suggestions that may depend on specific configurations or components used.

Who May Find This Useful

Individuals interested in electronics troubleshooting, particularly those working with LED circuits and 555 timer configurations, may find this discussion helpful.

Cubeclub
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I'm not sure if this is the right forum to put this in and I never took photos of something to put on the internet but I can't get this circuit to work and I need help. The LED is normally on. When I press the switch the LED should blink, slow down until its original condition. Maybe this should go in the homework forum. I never did this before. I don't have the switch right now but I'm using two wires instead. Will it not work without the switch?

http://img21.imageshack.us/img21/8325/1007495.th.jpg
http://img510.imageshack.us/img510/7609/circuit.th.jpg
http://img21.imageshack.us/img21/3797/1007494.th.jpg
http://img21.imageshack.us/img21/4036/1007493m.th.jpg
http://img21.imageshack.us/img21/1492/1007492k.th.jpg
http://img21.imageshack.us/img21/2503/1007491.th.jpg
 
Last edited by a moderator:
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You have posted about 15 MB of pictures. It is much better to reduce these pictures to less than 100 KB each before posting them. They have to be clear on the screen but not high resolution.

The circuit looks OK but I haven't checked your wiring. You need to do this yourself.

The output frequency might be a bit fast if you are hoping to see the light flash. A program I fed it into said the frequency would be about 10 Hz. This might be a bit too fast to see.
If it is lit but not obviously flashing, it may be flashing too fast to see.

Try making the capacitor on pin 6 a 0.47 uF if this is the case. That should give about 2 flashes a second.

What are you seeing? Is it doing anything? Do you have a multimeter or a CRO?

No, the switch doesn't matter as long as your wires are twisted together.
It won't change its flash rate though, except a brief moment when the 22uF charges up but this would be very fast.
 
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Your circuit looks nearly identical to fig. 1 in :
www.northcountryradio.com/PDFs/column009.pdf[/URL]
 
Last edited by a moderator:
Yes, the circuit is pretty standard, but those chips are the CMOS version.

This OP is using a standard 555 with some pretty big resistors. The CMOS chips have lower leakage values and hence can use higher value resistors. I haven't got a data sheet handy, but I suspect he might be pushing his luck with 470 K's on a normal 555.
 
vk6kro said:
You have posted about 15 MB of pictures. It is much better to reduce these pictures to less than 100 KB each before posting them. They have to be clear on the screen but not high resolution.

The circuit looks OK but I haven't checked your wiring. You need to do this yourself.

The output frequency might be a bit fast if you are hoping to see the light flash. A program I fed it into said the frequency would be about 10 Hz. This might be a bit too fast to see.
If it is lit but not obviously flashing, it may be flashing too fast to see.

Try making the capacitor on pin 6 a 0.47 uF if this is the case. That should give about 2 flashes a second.

What are you seeing? Is it doing anything? Do you have a multimeter or a CRO?

No, the switch doesn't matter as long as your wires are twisted together.
It won't change its flash rate though, except a brief moment when the 22uF charges up but this would be very fast.

Thanks. I'll try putting in the .47 uF Cap. I'll also reduce the size of the pics. Should I reduce them here or just in the future?
 
The LED goes on and when I connect the two wires where the switch would be the LED dims slightly. I put in a .47 Capacitor and I still had the same outcome.
 
Just for the future. Nobody wants to download big pictures if they don't need to.

You need to just follow the wires and make sure they go where they are supposed to go.

If you still have trouble, measure the voltage at each pin of the 555 and post those voltage readings.

If you have a spare 555, or better, a CMOS 555, you could try that as well.
 
I am using a 6 volt battery and I got these voltage readings.
Pin 1: 0V
Pin 2: 1.9V
Pin 3: 5V
Pin 4: 6.4V
Pin 5: 4.3V
Pin 6: .1V
Pin 7: .1V
Pin 8: 6.4V
 
.

Pin 6 and pin 2 should be the same since they are joined together.

Better check your wiring.
 
  • #10
*Fix*
Pin 1: 0V
Pin 2: .1V
Pin 3: 5V
Pin 4: 6.4V
Pin 5: 4.3V
Pin 6: .1V
Pin 7: .1V
Pin 8: 6.4V
 
  • #11
Is it working now?
 
  • #12
No It isn't
 
  • #13
Is the LED lighting up at all?
 
  • #14
Cubeclub said:
The LED goes on and when I connect the two wires where the switch would be the LED dims slightly. I put in a .47 Capacitor and I still had the same outcome.
Same as this
 
  • #15
OK.

Just looking at your picture, it looks like the 470 Ks are really 470 ohms. Is that right?
Can you measure them?


BTW where are you?
 
  • #16
just shoot me. OMG. I can't believe I missed that. I was looking for something harder. I had the circuit on top of a cd case. Is that what you meant by where are you?
 
  • #17
470 K would be yellow, violet, yellow wouldn't it.
 
  • #18
What part of the world are you in? What country? What city?470 K would be yellow, violet, yellow wouldn't it...YES
 
  • #19
North Bellmore, NY
 
  • #20
You live in Australia? I see it in your profile. cool
 
  • #21
You're up late.
I'm in Perth, Australia. It is 2:11 pm here.
 
  • #22
Thanks for all the help. I have to go to sleep now. It's 2:12 am
 
  • #23
Seeya
 
  • #24
It works. I bought the 470K ohm resistors today. It's so amazing. Thank you!
 

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