Before building this device I have tried lots of different design but in every circuit there were some issues, either it was also a metal detector or detect human as AC voltage source. I even built a device using instrumentation amplifier, 2nd order band pass filter and ARM mcu to do all the math (FFT) So i can only detect AC voltage and no metal detection or human contact detection. After lot of trouble I was able to achieve this by using this very simple circuit.
Introduction:
Before we start building our easy peasy electricity detector, let me explain the basic functionality of non contact AC voltage detector.
We all know whenever there is current flowing through a conductor there is always a magnetic field around it and if the current flowing through conductor is AC current then the magnetic field varies periodically according to AC frequency. If we bring another conductor near it, a very small voltage will be induced in it due to electromagnetic induction and our easy peasy non contact electricity detector will use it to detect AC voltage.
Components required:
Main components required to built this non contact AC voltage detector are;
- AD620
- LED with resistor, as an indicator
- Multi-turn trim-pot for gain adjustment
- ±3V supply or 6V&3V supplies
In this project ±3V is also a good option to provide power supply this module (only two 3V coin cells).
Schematics:
In this project AD620 is configured to work with single supply (figure 34. on page 14 of datasheet) instead of dual power supply.
Prototype:
Simply make the breadboard circuit as shown in above figure and our first prototype is ready. Here I have used 50k trim-pot and there is ~26kohm gain resistance value.
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Prototype Testing:
After building our first prototype its time to test it.
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No effect of Human Contact |
This easy peasy voltage detector doesn't bother about human contact which is one of the ultimate goal of this device.
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Works Behind Obstacles |
Voltage detector module should work behind obstacles to trace hidden wiring and it does it very easily. During this demo very small testing probe is used. Its sensitivity can be increased by either using bigger testing probe or decreasing the trim-pot resistance value.
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Tiny Probe Demo |
Voltage detector should only detect voltages not metal. This awesome module does exactly the same. It only detect voltages not metals.
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Ultra Sensitive Module |
Let increase the sensitivity of this tiny module by increase the size of testing probe. And now it can detect voltage from distance of few inches.
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Detect Broken Wire |
Another useful feature of this voltage detector is broken wire detection.
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Easy Switch Position Detection |
If you are wonder about any unlabeled switch's current position then this module is perfect for you to find out its current position without disassembling anything.
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Final Assembly:
After testing and concept verification its time to build a final easy to use device with battery and case.
| {gallery} Easy Peasy Electricity Detector |
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IMAGE TITLE: Easy Peasy Non-Contact Electricity Detector (Not a Metal Detector) - Top View Before Final Assembly |
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IMAGE TITLE: Easy Peasy Non-Contact Electricity Detector (Not a Metal Detector) - Bottom View Before Final Assembly |
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IMAGE TITLE: Easy Peasy Non-Contact Electricity Detector (Not a Metal Detector) - After Final Assembly |
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IMAGE TITLE: Easy Peasy Non-Contact Electricity Detector (Not a Metal Detector) - After Final Assembly |
Demo After Final Assembly:
Lets test our newly built enclosed easy peasy non contact electricity (Voltage) tester.
AC voltage detection
Switch Position Detection
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Electric Field Detection
Magnetic Field Detection
Limitations on non-contact voltage testers:
Nothing in this world is perfect so these non contact voltage detector have also some limitations.
- It cannot work with DC voltages.
- It does not actually measure the amount of voltage present. Instead, it only indicate the AC voltage presence
MT3608 Boost IC datasheet: HERE
MP2307 Buck IC datasheet: HERE
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