I should have to make Static Charge Detector. Few Demo and Help needed!

I have few FET but It will work of not I don't know. I have BS170 FET. I found another FET "596s" inside of electret mic. Other FET can't find. Will these two FET able to detect Static cherge like shown in schematic (FET version)?

Another is Transistor verson Detector. Is it sensitive? I want to use 557 as a PNP and another general purposes as a NPN (like 547), is it valid?

Do you have any other simpler ans sensitive?

I hope detector will detect charge without touching its probe (Ant), almost far from few cm.

FET Version:-

Static electricity is very poweful in winter when the outside temperature is very cold. When the inside air is heated then its humidity drops. Humidity in the air drains away static so it cannot build up. Static can produce 20,000V or more.
The static produced by friction can easily destroy your simple circuits that have NOTHING for protection.
The 100M resistor will simply have an arc jump across it like it is shorted.

I think I'd go with the JFET 2N3819. High input impedance (which increases with rising input voltage) is a plus.

Downside is a tendency to be very sensitive to built-up static charges.

Probably a JFET front end device feeding a transistor amp section might be best for an antenna type electroscope (don't know how a "probe" type would be a good idea at all...).

Not solved!

Willen said:

Not solved!

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The Jfet circuit will detect static very well and the Jfet will survive being ZAPPED if you add a protection circuit (a resistor plus a couple of diodes).
You should look for circuits designed by engineers, not designed by little kids.

audioguru said:

The Jfet circuit will detect static very well and the Jfet will survive being ZAPPED if you add a protection circuit (a resistor plus a couple of diodes).
You should look for circuits designed by engineers, not designed by little kids.

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Hahaha may be all are little kids found on internet showing their circuits. And I always found these.

Did you have any?

google "electrometer". i'm thinking an old fashioned lead or gold foil electrometer (gold foil is expensive, and lead foil may be difficult to find because of the various "nanny states" that have declared it hazardous). the ideal foil for an electrometer is a metal that's relatively heavy, and very malleable (aluminum foil is too stiff, and too light)... maybe a good copper foil would work.

a strip of foil about 1cm x 5cm is folded in half and allowed to droop over a piece of stiff wire as a support.. the support wire is connected to a (the inside foil) leyden jar that has the outside grounded, and a probe aalso attached to the inside foil. the leyden jar acts as a capacitor to store the charge you are measuring. as the leyden jar is charged, some of the charge goes to the foil. the bottom ends of the foil, having equal charges of the same polarity repel each other. how far the leaves move apart is proportional to the voltage of the charge. it's not super accurate, but it's simple and it works, and no helpless transistors will be harmed.

lead foil may be difficult to find because of the various "nanny states"

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I bought a reel of solder (60/40 tin lead) this past week from RS Components (No not Radio Shack), the package had a hazard sticker on it and there was a six page MSDS in the package.

Don't you just love ROHS and Elfin Safety in general!

JimB

Hi again after a long time,

Actually after this long time I got few JFETs from a nice American engineer. Now I can experiment almost every JFET based electrometer.

However simplicity of such (attached) basic component based circuit made me attracted me again. What about the circuit? (original circuit had no R1 series input resistor, I added it. But I know it is doing almost nothing.) Will it also can be destroyed? I am little confuse how to make protection circuit using a resistor and diodes as audioguru said before. And is it 'Tarlington'?

Hi Willen,
Static electricity builds up on insulators only when the air is also a good insulator. In Canada in winter, sometimes the temperature outside is low then the humidity in a heated home is also low so static electricity builds up when two insulators are rubbed together. When the outside temperature was -15 degrees C, but was 22 degrees C inside then the humidity inside my home was only 22% and static electricity was everywhere! I do not think the outside temperature is -15 degrees C with very low humidity in Nepal unless you are in a heated cabin very high on Mount Everest.

I think most static electricity is negative because electrons are collected on things. But the items that have their electrons taken away become positive.
Take a rubber or plastic balloon and rub it on some wool or fur. If it sticks to a wall then the balloon is negative because the wool or fur had its electrons removed by the balloon.
Your NPN transistors only turn on when they detect something that is positive.

audioguru said:

I do not think the outside temperature is -15 degrees C with very low humidity in Nepal unless you are in a heated cabin very high on Mount Everest.

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hehe your very careful habit taught lot till now to handle tiny piece of components and many more thing.

Your NPN transistors only turn on when they detect something that is positive.

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Then I am thinking to use circuit to detect 50Hz hum of mains. I hope I can use it to find broken wire in mains like this way, can't I?

A similar circuit will pickup mains radiation.

Hi,
I made simulation of previous 3 transistor tarlington circuit . I set 1000Meg series resistance at signal source to give 5V but too much low current at the base of Q1. Now can I say directly- The circuit has 1000Mega Ohms input impedance for simple? (I just want to know general concept)

The signal source has a resistance of 1000M. The input resistance of the transistors is less than 1000M because if their input resistance is also 1000M then the input signal to the based of Q1 would reach half of 5V but instead it reaches to only about +1.65V and -2.2V. The input positive swing is less than the negative swing because the input resistance changes with the input signal level and polarity.

The peak current in the LED is about 7.3mA for 20% of the time and it blinks on 50 times per second so it appears as dim as an LED lighted with only 1.5mA.