Home Artists Posts Import Register

Content

An experiment to see if modern sensitive LEDs are a good substitute for the neon bulb in a classic electrical test screwdriver.

These screwdrivers rely on the person holding them to complete a circuit to ground, so the environment will determine how bright they are.

https://www.youtube.com/watch?v=YJJtlWjKUas

Files

Reinventing the neon test screwdriver

The classic neon test screwdriver has been around for a long time. It relies on the sensitivity of a small neon indicator bulb in series with a safety resistor to give a slight glow when touched to live electrical connections by finding a return current path through the user. It has a few weaknesses. It's very dim to start with, but even dimmer when the user is well insulated from ground, some have inadequate safety resistors, and it's a very vague test that is not always reliable. With the sensitivity of modern LEDs I thought it might be worth testing to see if they could be substituted in place of the original neon indicator to provide a brighter indication. Note that this experiment involves direct electrical contact with mains referenced circuitry. It is imperative that the resistor is chosen with safety in mind, and that the internal wiring can't short out the safety resistor accidentally. If you enjoy these videos you can help support the channel with a dollar for coffee, cookies and random gadgets for disassembly at:- https://www.bigclive.com/coffee.htm This also keeps the channel independent of YouTube's algorithm quirks, allowing it to be a bit more dangerous and naughty. #ElectronicsCreators

Comments

Nuts 'n' Proud

I still have my ancient 1980 neon screwdriver. I wondered what the wire wound resistor was.

Curtis Hoffmann

BigClive: "It's different." That's all we need to know.

Gadgetman

If these really are the test equipment of choice for DIYers, then they really need to find something safer, or call an electrician in.

Anonymous

Clive great idea. Think i'll make one myself. also manufactures will surely take this up once they see your video.

Anonymous

Taking bets on how long it takes to show up on aliexpress.

Jonathan Hughes

I Know it's only a few Micro amps, 0.00024 @ 240 Volts. but these things just sound like a horrible idea.

John Lundgren ~ Acme Fixer

Do you think that the novice might mistake the green as meaning it is safe to work on? I thought about that when I bought a tape full of amber LEDs for indicators.

bigclive

I suppose you have to play down to the lowest denominator, but the fact it lights at all without batteries should hopefully be a clue.

bigclive

The LEDs are brighter and on two sides. They could also use the Xmas light style side emitting LEDs.

Anonymous

Could you use different leds to determine different voltage levels? Maybe using resistors to tune the necessary voltage for each individual led? That would be an awesome thing to see if you built it

bigclive

Given that there's such low current to start with, it could complicate that.

Anonymous

I have a simple neon tester from the 1950s that I keep in my kit. It still works. But the minimum voltage is 90v.

Matt Cocker

With the proud claim in the listing "as seen on big clive" but they substituted some of the parts

bigclive

The minimum voltage is limited by the strike voltage of the neon bulb. They strike at around 90V.

Bjorn V

Here in Belgium with 230V/240V mains, those Neon testers are much brighter. Some people hate them, but i love them, and use them for years. In my case when i use these, they are not that bright, because it seems that i have a higher body resistance. When i touch the live wire of the mains with my finger, only 11µA of current is flowing. So with the Neon tester with extra 1M resistor, the current is even lower then 11µA.

bigclive

Although you may have a high (dry) skin resistance, the biggest factor in current leakage through the body is your environment. Shoes, carpet and wooden floors are all relatively good insulators (but should not be relied on for isolation.) The resistor in the driver is designed to limit the current to a level where a tingle will not be felt from the driver when the user is strongly referenced to ground.