Wrong voltage in alarm circuit

I am building a small alarm system. Voltage is 12V. The speaker is a small piezo sirene. SW2 should be the sensor. SW1 the activator. I want to have a control LED to see if sensor is open or closed.

If I mesure the voltage at the sirene, it is -10v. If I close switch1 I mesure 3V. If I close switch2 I have 12V like expected.

I am a bit confused about the negative high voltage with all switches open.

by snote
January 25, 2019

there may be some short circuit (high resistance) from top contact of speaker to the negative of battery.

by wangwg88
February 01, 2019

No Answers

No answers yet. Contribute your answer below!

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.