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Bells and G Forces

I'm looking into the idea of home growing a door chime beginning with a magnet switch on a door. (All the wireless kind I've seen have crap range and only one receiver and no visual alert.)

I want to make one audio chime and then in a more distant location, make a second audio chime with a light too.

As a beginner, and sometimes slightly more than that, I'm not sure what methods exist to activate a short "ding" or electrical pulse that doesn't continue through the duration of time that the door is open.

~

On another topic, I am interested in measuring G force with acceleration. I've searched around a little bit, but would appreciate a pointer in the right direction.

I'm wondering the name of a circuit/device that can be used measure change in velocity. I'm curious how difficult it is (for an electronics non-genious) to take measurements / read voltages / design circuits based on the outputs of this device.

The maximum expected change in velocity is about 15 feet per second per second.

Thank you.

Reply to
Ryan
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A "one-shot" is a device that generates a single pulse when triggered. There are many circuits, but the simplest way to generate a pulse when a switch closes is to put a capacitor in series with the load. The combination draws a pulse of current, then looks like an open circuit once the capacitor is fully charged. If the load is the coil of a small relay, you can drive a bigger load without needing an inconveniently large capacitor. You will need some path for the capacitor to discharge through when the switch opens, such as a parallel resistor.

A gadget that measures acceleration is called an accelerometer. Tiny solid-state ones are made, but I haven't looked up the prices lately. If you don't need accurate calibration, it's fun to experiment with homebrew approaches, such as a mass on as spring with some way to measure the deflection, or a phonograph cartridge (Do they still make cheap ones? It might be easier to buy an old turntable at a thrift store.) with a small mass attached to the stylus, or maybe a U-tube with colored water and an optical liquid-level detector. The acceleration you mention is about half a gee, so you don't need great sensitivity.

Reply to
Stephen J. Rush

If you are just experimenting, and don't need small size, you might want to try a speaker as the mass-on-a-spring sensor. You will need to attach the desired (non-ferrous) mass to the center of the cone. Measure the response from the speaker terminals. This system will measure acceleration along the axis of the speaker; the speaker suspension prevents motion in other directions.

Best regards,

Bob Masta D A Q A R T A Data AcQuisition And Real-Time Analysis

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Scope, Spectrum, Spectrogram, Signal Generator Science with your sound card!

Reply to
Bob Masta

The switch doesn't move and is not mounted on the door.

Space the switch off the door frame so that the magnet PASSES it. Use normally open contacts or invert the state.

Reply to
JeffM
[SNIP]

Accelerometer

Have a look at some of the datasheets and see what you think. I think that in the simplest form they just produce a voltage proportional to acceleration. Others give out pulses with different duty cycle proportional to acceleration.

Analog Devices make small accelerometers,

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Freescale have a range of similar devices

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Gareth

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