- #1
daveroderick
- 8
- 0
I have been having a great amount of difficulty with the 555 timer (Texas Instruments NE555P). I am going through a book published by McGraw Hill titled Understanding Electricity and Electronics. While I was waiting for the parts to finish my power supply, I started to work with the 555 timer. I found a tutorial on the 555 which showed a schematic of “the most basic” form of a timing circuit using the 555 timer.
I went to radio shack and purchased a solderless breadboard, the 555 timer, 12 volt LED and all the other various components that I thought I would need. This timer has not worked since I put it together. My first thought was that maybe the timer was bad so I went to radio shack and purchased another 555 timer with the same result. I have come to this forum to find out just what the heck I am doing wrong. Below I have a photo of my breadboard with the 555 timer and all the connections. My power supply is a 12-volt transformer with a bridge rectifier. The LED that I am using is a straight panel mount 12 volt LED. I am using a N.O. momentary switch for the trigger. I am using a 470-microfarad capacitor and a 10 K-ohm resistor. The resistor capacitor combination (if I figured right) should give me a pulse of 5.17 seconds not counting for capacitor leakage or so I have read. When I first power up the circuit there is 4.4 volts at pin 3. If I understand what I have read in the tutorial, shorting pin 2 to ground briefly should start the timing cycle. I am yet to see any cycle with my current configuration. When I push the momentary switch the voltage at pin 3 only rises when the switch is depressed. I have changed resistors, capacitors, timers, looked and pondered and I obviously don’t have a clue why it doesn’t work. Can anyone please tell me where I am going wrong? I did change over to a 9-volt battery for a while with no change in the way the circuit worked (or rather didn’t work).
I am starting school here in Ohio in the fall at Zane State in their Electrical/Electronics Engineering program (after I take the classes I should have taken in High School of course). I am beginning to think that I am way to dense to bother going back to school at the age of 41 if I can’t understand this.
Thanks,
Dave Roderick
I went to radio shack and purchased a solderless breadboard, the 555 timer, 12 volt LED and all the other various components that I thought I would need. This timer has not worked since I put it together. My first thought was that maybe the timer was bad so I went to radio shack and purchased another 555 timer with the same result. I have come to this forum to find out just what the heck I am doing wrong. Below I have a photo of my breadboard with the 555 timer and all the connections. My power supply is a 12-volt transformer with a bridge rectifier. The LED that I am using is a straight panel mount 12 volt LED. I am using a N.O. momentary switch for the trigger. I am using a 470-microfarad capacitor and a 10 K-ohm resistor. The resistor capacitor combination (if I figured right) should give me a pulse of 5.17 seconds not counting for capacitor leakage or so I have read. When I first power up the circuit there is 4.4 volts at pin 3. If I understand what I have read in the tutorial, shorting pin 2 to ground briefly should start the timing cycle. I am yet to see any cycle with my current configuration. When I push the momentary switch the voltage at pin 3 only rises when the switch is depressed. I have changed resistors, capacitors, timers, looked and pondered and I obviously don’t have a clue why it doesn’t work. Can anyone please tell me where I am going wrong? I did change over to a 9-volt battery for a while with no change in the way the circuit worked (or rather didn’t work).
I am starting school here in Ohio in the fall at Zane State in their Electrical/Electronics Engineering program (after I take the classes I should have taken in High School of course). I am beginning to think that I am way to dense to bother going back to school at the age of 41 if I can’t understand this.
Thanks,
Dave Roderick