Troubleshooting a 555 Timer Circuit with Added LEDs | Circuit Issues & Solutions

In summary, the circuit built by the author does not work and the modifications made do not seem to help. The author is having problems with the timer and with inconsistent brightnesses between LED1 and LED2. A diode may help solve the third issue.
  • #1
ColonelPanic
6
0
Hello,

I have designed a circuit based on one that I found on the internet (attached as example.gif). This circuit worked well when I built it on a breadboard.

I made a few minor modifications to the example circuit (attached as schem1.bmp) and I am having a few issues that I do not understand. The modifcations are simple, as all I have done really is add additional LEDs to the circuit in both the LED1 and LED2 positons of the example and also add an additional circuit on the same board that shares the same ground.

I have the following issues with the circuit that I have built:

1) The timer function no longer works at all. I have tried swapping resistors after the 555 pin3, as well as the componnets in R1, R2, and C1.

2) The brightnesses between the LED1 and LED2 positions are inconsistent, when a test voltage is applied.

3) The additional circuit on the board is a simple resistor/led circuit. The issue is that when the LEDs are turned on, you can visually see effects from the frequency of the 555 timer.

Each positive lead was tested using the digital output of an Arduino microcontroller at 5v.

Any help would be greatly appreciated, as it has me stumped...
 

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  • #2
Powered at 5V, you may be only able to source/sink 20-50mA (check the datasheet).
This will light one or two standard LEDs. If you really want to light a lot of LEDs using output of 555 you can try:
1 - powering 555 from higher VCC (some 555's can go up to 16V).
2 - using low power LEDs
3 - buffering output of 555
 
  • #3
Could you elaborate on how I would 'buffer' the output of such a circuit? I am a novice electronics hobbyist who is self-taught, and I have probably not taught myself all of the essentials so my apologies if these questions sound rudimentary or even ludicrous.
 
  • #4
No apologies needed.

Buffering means adding extra parts that can handle higher current to drive more LEDs. There's a lot of ways to do this. The most common way is to add transistors so that the 555 switches the transistors instead of the LEDs and the transistors then turn the LEDs in and off.

Google "transistor buffer 555" or "push pull buffer for logic level LED drive" and you should get lots of hits.
 
  • #5
Antiphon,

Thank you for the REALLY fast reply. That is much appreciated.

I also have a quick question about resolving issue #3 in my post. I have been doing some reading, and I think the appropriate solution would be to use a diode of some type. (The main issue here is that these are two lighting circuits sharing a same ground, and you can visually see the frequency pulse in the second circuit of the shared ground.) Would you know if that would resolve my issue? I believe that the diodes forward direction would be from circuit 2 to the shared ground to eliminate any signal traveling from the ground to circuit 2. Does any of this sound correct in any way?Thanks so much!
 
  • #6
Diode will not help that. The problem is that your power source has a non-negligable resistance. When the 555 LEDs turn on, the voltage at the other LEDs droops a little and they get dimmer.

What you need a is a regulator like a 7805 ahead of the whole circuit. Make sure you heatsink it properly.
 

Related to Troubleshooting a 555 Timer Circuit with Added LEDs | Circuit Issues & Solutions

1. What is a 555 timer circuit?

A 555 timer circuit is an integrated circuit (IC) that is commonly used in electronic devices as a timing or oscillator element. It can generate pulses, oscillate signals, and provide precise timing functions.

2. What are some common issues with 555 timer circuits?

Some common issues with 555 timer circuits include incorrect connections, improper component values, and malfunctioning ICs. These can result in unpredictable or unstable circuit behavior.

3. How can I troubleshoot issues with a 555 timer circuit?

To troubleshoot issues with a 555 timer circuit, you can start by double-checking all connections and component values. You can also use a multimeter to test the voltage and current at different points in the circuit. If the issue persists, try replacing the IC with a new one.

4. Can I modify a 555 timer circuit for different applications?

Yes, a 555 timer circuit can be modified for various applications by changing the values of its resistors and capacitors. This will alter the timing and frequency of the circuit's output signals. Additionally, you can also add external components such as diodes and transistors to enhance the circuit's functionality.

5. Are there any alternatives to a 555 timer circuit?

Yes, there are alternatives to a 555 timer circuit, such as the 556 timer IC, which is a dual version of the 555 timer. Other alternatives include microcontrollers and specialized timing ICs, which offer more precise and customizable timing functions.

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