I want to build some project about metal detector using integrated circuit 555 timer. I already made a schematic in proteus 8 application. I made some change with the original schematic i found on internet. I added some LED on output and resistor 220k. I think my schematic wrong because when i made it in breadboard the project doesn't work. Also, when i run simulation on proteus, led not on.I need help, thank you for your attention. original schematic

my schematic in proteus 8 application

  • \$\begingroup\$ 220K is much too high a value for the resistor in series with the LED - you should use something under 1K or so. Select the resistor to give 5 mA or so through the LED. \$\endgroup\$ – Peter Bennett May 10 '18 at 15:42
  • \$\begingroup\$ Calculate the maximum possible current through the 220k resistor given your powersupply voltage, and ask your self if that would be enough to see the LED light up. Then, ask yourself how high the voltage across the buzzer will be. Is that higher than the forward voltage of the LED? If not, the LED can't light up. \$\endgroup\$ – JRE May 10 '18 at 15:46
  • \$\begingroup\$ Looks like you are using a speaker rather than a buzzer. The voltage will be much lower. Measure the peak to peak voltage across your LED. Probably way too low. \$\endgroup\$ – JRE May 10 '18 at 15:47

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Browse other questions tagged or ask your own question.