What Does ESD Do To My Circuit and How Can I Protect Against It?

[Kevin Darrah] is risking the nerves on his index finger to learn about ESD protection. Armed with a white pair of socks, a microfiber couch, and a nylon carpet, like a wizard from a book he summons electricity from his very hands (after a shuffle around the house). His energy focused on a sacrificial 2N7000 small signal MOSFET.

So what happens to a circuit when you shock it? Does it instantly die in a dramatic movie fashion: smoke billowing towards the roof, sirens in the distance? [Kevin] set up a simple circuit to show the truth. It’s got a button, a MOSFET, an LED, and some vitamins. When you press the button the light turns off.

He shuffles a bit, and with a mini thunderclap, electrocutes the MOSFET. After the discharge the MOSFET doesn’t turn the light off all the way. A shocking development.

So how does one protect against these dark energies out to destroy a circuit. Energies that can seemingly be summoned by anyone with a Walmart gift card? How does someone clamp down on this evil?

[Kevin] shows us how two diodes and a resistor can be used to shunt the high voltage from the electrostatic discharge away from the sensitive components. He also experimentally verifies and elucidates on the purpose of each. The resistor does nothing by itself, it’s there to protect the diodes. The diodes are there to protect the MOSFET.

In the end he had a circuit that could withstand the most vigorous shuffling, cotton socks against nylon carpeting, across his floor. It could withstand the mighty electric charge that only a grown man jumping on his couch can summon. Powerful magics indeed. Video after the break.

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Reverse voltage protection with a P-FET

[Afroman’s] latest video shows you how to add reverse voltage protection with minimal power loss. At some point, one of your electronic concoctions will turn out to be very useful. You want to make sure that a battery plugged in the wrong way, or a polarity mistake with your bench PSU doesn’t damage that hardware. It’s easy enough to plop in a diode for protection, but as [Afroman] points out, that wastes power in the form of heat when the circuit is working correctly. His solution is to add a P channel MOSFET which only allows power to flow when the polarity of the source voltage is correct.

The schematic above shows the P-FET on the high side of the circuit. The gate is hooked to ground, allowing current to move across the DS junction when the battery is connected. This design also uses a clamping diode to keep the gate voltage within a safe range. But there are P-FETs out there that wouldn’t need that diode or resistor. This method wastes ten times less power than a simple diode would have.

We’ve embedded the video after the break where [Afroman] shares the math and reasoning behind his component choices.

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Quiet Dust Extractor from Scavenged Materials

As with many of the projects covered on hackaday, [bongodrummer]’s Dust Sniper came about because of a lack of effective commercial solutions, in this case to the problem of quiet dust extraction.

Workshops are generally full of dust and noise, both of which take their toll on the human body. This is why safety regulations exist for noisy and dusty workplaces and–as [bongodrummer] rightly points out–we have to take precautions in our own home and community workshops. Hearing protectors, dust masks and safety goggles are integral, but reducing the amount of dust and noise in the fist place is paramount.

Using mostly scavenged materials [bongodrummer] did a quality job building the Dust Sniper–and all for a bill of materials totaling £20. It has an integrated work surface, automatic switches on 2 vacuum lines to sync up with power tools, a cyclonic air filter that prevents clogging the HEPA filter and reducing suction power, inlet and outlet soundproofing, and a plain old power outlet for good measure.

Whether or not you’re interested in building an integrated workbench/extractor system like this one, we recommend you check out the details of the cyclone filter and the sound reducing components. Not only are they an interesting read, but they could be useful to apply in other projects, for example a soldering station with fume hood.

We think it would be really neat to include more cyclones in our projects. Stick around after the break to see [bongodrummer]’s prototype cyclone filter in action.

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Custom headphones solve wire tangles

One complaint we hear about often is ear-bud’s cables getting tangled within backpacks. [Andrew] was having this “spaghetti” wire problem, and also wanted to listen to his music with ear protection on – where ear-buds are usually uncomfortable. The latter problem is fixed by placing speakers inside of folding ear protectors, and the cable is managed with a 3.5mm disconnect.

For those who can’t make disconnect-able headphones but still suffer from tangled headphone wire, we recommend proper wrapping technique for your wire, and a small carrying pouch. With the combination of the two, we’ve never had a tangled cable.