555 square wave generator

The published formula for frequency 1.44/((R2 + 2R1).C2) does not give the correct answer as given in published circuits or on-line calculators!

Example: R1=1K, R2=5k, C2=3.3uF by the formula = 62.3 KHz BUT [https://ohmslawcalculator.com/555-astable-calculator] gives 39.75 KHz in agreement with Gadgetronicx published circuit!

Please can someone sort this out for me? I need a 35 - 40 KHz generator..

by Gyroman
September 01, 2023

2 Answers

Answer by Gyroman

All has come clear.. solved. It was all down to multiple errors in the circuit I got from GADGETRONICX..! They switched R1 with R2 so the wrong values went into the formula and then C2 was given as 3.3nF and it should have been 3.3pF. When corrected all became clear. Thanks for the forum.

+1 vote
by Gyroman
September 02, 2023

Answer by edraburris

Your Answer

You must log in or create an account (free!) to answer a question.

Log in Create an account

Go Ad-Free. Activate your CircuitLab membership. No more ads. Save unlimited circuits. Run unlimited simulations.

Search Questions & Answers

Ask a Question

Anyone can ask a question.

Did you already search (see above) to see if a similar question has already been answered? If you can't find the answer, you may ask a question.

About This Site

CircuitLab's Q&A site is a FREE questions and answers forum for electronics and electrical engineering students, hobbyists, and professionals.

We encourage you to use our built-in schematic & simulation software to add more detail to your questions and answers.

Acceptable Questions:

  • Concept or theory questions
  • Practical engineering questions
  • “Homework” questions
  • Software/hardware intersection
  • Best practices
  • Design choices & component selection
  • Troubleshooting

Unacceptable Questions:

  • Non-English language content
  • Non-question discussion
  • Non-electronics questions
  • Vendor-specific topics
  • Pure software questions
  • CircuitLab software support

Please respect that there are both seasoned experts and total newbies here: please be nice, be constructive, and be specific!

About CircuitLab

CircuitLab is an in-browser schematic capture and circuit simulation software tool to help you rapidly design and analyze analog and digital electronics systems.