# Electrons circuits

posted by .

Hi everyone! I'm new in here.

Recently I bought a movement monitor which detects micro movement. If the sensor does not detect a movement in 20 seconds, the build-in speaker will beep until the sensor detects a movement. I'm using it for my project and I have a question about it. I want to intercept a wire from the speaker to a micro controller. The point is, in order to "power up" the micro controller, a 9V DC input is needed. Therefore I want to connect a wire from the speaker to the input of the micro controller.

The situation is something like this:
When the alarm is ON (speaker beeps), nearly 9V DC will go into the input of micro controller. When the alarm is OFF (no sound), there is nearly 0V DC going to the input.

As I measured the voltage across the speaker, I got roughly 0.9V to 1.5V AC. Is there any circuit i can build to satisfy this suitation?

• Electrons circuits -

rectify the speaker voltage with a diode followed by a capacitor in parallel with a large resistor (long RC time constant) to allow a discharge path. Then, that voltage will be a dc signal of about 1.3 volts dc, enough to sense.

Using this sense signal, you can operate any number of logic circuits to switch on/off power. A SCR or thyristor comes to mind.

You will be unsuccessful, I suspect trying to use speaker power to provide power to the next microchip, a separate power source is recommended

• Electrons circuits -

I am sorry for my unclear explanation.

Actually the monitor is powered by a 9V 100mA adaptor. I am not sure if the voltage drop across the speaker is AC or DC because the voltage keep changing from 0.9V to 1.5V on my voltmeter. Current is around 3.8mA.

The microcontroller is powered by a 12V 700mA adaptor. In order to send something out by the microcontroller, input with a logical HIGH (more than 7V) is need to perform the action. The microcontroller won't do anything if less than 7V going into the input.

I tried using a non-inverting opamp with voltage gain of 6, supply voltages +V=+9V, -V=-9V by two separate batteries. I tested the circuit using a 1.5V battery, it gave me around 8V. So I think it's ok. When the alarm of the monitor is on, I supposed to get 1V*8=9V at the output of opamp. Instead I just received 2.5V to 3V. How come...?

## Similar Questions

1. ### U.S. History

I am running out of ideas. Question: Did the climate of civil rights and related protest become so militant after 1965 that it was counterproductive, splintering support for civil rights causes and providing an opening for conservative …
2. ### Electricity and Magnetism

This was actually a test question: Additional Information: This question is based on the Hall effect in a wire. Question: I want you to build a magnetic feild sensor. You have all the properties of the materials and the dimentions …
3. ### Math

A sensor light installed on the edge of a home can detect motion for a distance of 50ft. in front and with a range of motion of 192degree. Over what area will the sensor detect motion and become illuminated?
4. ### math

A sensor light can detect motion for a distance of 70ft. with a range of motion of 189 degrees. Over what area will the sensor detect motion and become illuminated?
5. ### Science

Pneumonia is a disease that causes fluid to build up in the alveoli of the lungs. Which of the following would you expect to be impaired in patients with pneumonia?
6. ### analytical question

One application of emission in remote sensing is in the detection of forest fires. The Landsat satellite has a sensor that detects active fires by examining their emission in the wavelength region of 1.55 μm to 1.75 μm. a. …
7. ### Social Studies

Which movement was initiated in the 1960s by Quebecer Réne Lévesque?
8. ### History

which of the following was a significant part of the civil rights movement?
9. ### History

2.The writings of Transcendentalists had the greatest influence on which of the following movements?
10. ### History

What was the Protestant Reformation? a literacy movement to reform censorship practices by monarchies and allow the freedom of speech a political movement to reform feudalistic European governments to represents republics a social

More Similar Questions