General Question

blueberry_kid's avatar

If I take something that must be plugged in apart, will I get shocked?

Asked by blueberry_kid (5952points) October 18th, 2014 from iPhone

I found this old kitchen timer at the thrift store, but it requires an outlet (plug it in) to be used. I was thinking of taking it apart for an art project but I’m scared if I do I’ll get shocked. Am I just trippin?

Side note: I can’t seem to find the right screw driver to take apart, can you tell which one I need?

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17 Answers

janbb's avatar

if it is not plugged in to anything, there is no electricity going through it and you won’t get shocked. It looks like you could get it apart with a Philips head screwdriver.

Tropical_Willie's avatar

You’ll need an Allen head wrench. They look like a ”L”.

stanleybmanly's avatar

Allen wrench is right. They’re also called hex wrenches, and usually come in sets of different sizes. Some allen wrenches have “t” handles for leverage instead of the bend. @janbb is probably right about tinkering with the timer being ok if it is unplugged, but there are electrical devices that can kill you even when unplugged. I can remember long ago when a chemistry professor brought up the statistics on people killed handling electrical equipment with capacitors that had been discarded in dumps. It was a day when there was a much more casual attitude regarding the disposal of hazardous waste.

ARE_you_kidding_me's avatar

While it’s safe in this case it’s not always true. Some electronics can store dangerous amounts of energy for a time after being unplugged. Old TVs were notorious for this.
You need a hex wrench to open that.

Lightlyseared's avatar

From experience I can tell you that vacuum cleaners can give you a nasty shock even after they’ve been unplugged.

jerv's avatar

@ARE_you_kidding_me Don’t Flyback transformers get their name from their tendency to make people fly backwards if they forget to discharge them before poking their hands in there?

ARE_you_kidding_me's avatar

That could be, I never even though of that. Only the real old and the very cheapest sets this was a problem. Most of the newer ones had a bleed resistor installed. Without it there could be quite a charge even after days.

Paradox25's avatar

Others have answered the second part of your question, so I’ll only address the other part of it. I’m not familiar with kitchen timers, but from that vague picture that timer looks like a typical mechanical device timer, similar to what’s used to turn on/off things like water heaters, outdoor lights, etc. That device probably only has a small electric motor and gears inside of it, so I highly doubt you’ll get shocked. If it makes you feel better in your mind somehow you can always purchase a multimeter to check the terminals for voltage.

Only capacitors store electrical energy, so it’s possible that a timer that uses electronics, if the voltage being stored is high enough, can shock you. Inductive loads (like transformers and motors) only store energy for a fraction of a second (with some rare exceptions). Taking apart some battery powered devices can be much more dangerous than taking apart a device that uses the standard 120/230 volts due to many electronic devices containing components such as step-up transformers, capacitors and voltage-multiplier circuits. In other words, taking apart your 6 volt battery-powered mini gaming system is probably more dangerous than taking apart a 120 volt timer.

RocketGuy's avatar

@jerv – you’re probably kidding, but I think flyback transformers are used in CRTs to make the electron beam fly back to the nearside of the screen, so that it can begin the next raster scan.

jerv's avatar

@RocketGuy Half-kidding. I think the term got a second definition as the result of smartass technicians.

@Paradox25 Flyback transformers fall under “rare exceptions”, but since kitchen timers are not CRT TVs/monitors, I don’t think OP needs to worry.

Paradox25's avatar

@jerv I’m not a tv repairman, but I know about transformers, and had even taken courses on them. I don’t think a flyback transformer is any more dangerous than other types of step-up transformers, though the flyback’s function is more than just stepping up voltage. It’s the capacitors that’ll do you in when working on a de-energized circuit that isn’t properly discharged.

Voltage multipying circuits can be just as dangerous as any step-up transformer too. Even changing something seemingly simple as an amber light on a battery-powered forktruck can be very dangerous if you don’t ground the capacitors out.

Auto-transformers, like an ignition coil, where a collapsing electrical field (usually from pulsed DC) is used to step up the voltage (like with electric fences), instead of inducing voltage, is probably the most dangerous type of transformer. DC is much more dangerous than AC, but either way a voltage collapse occurs in any type of inductive load.

jerv's avatar

@Paradox25 Navy EM “A”-school taught me a bit about transformers too. And you are technically correct.

However, most flyback transformers I’ve seen have been hooked to a CRT, which often acts as a capacitor (especially the old and/or cheap ones). While the transformer itself doesn’t hold the charge, that doesn’t really make them less dangerous. The fact remains that messing with any part of the circuit risks a discharge. Therefore, it stands to reason that messing with a flyback transformer, something directly attached to effectively a big-ass capacitor, is inherently a bit riskier than dealing with other types of transformer, specifically those not hooked to a big-ass capacitor. And I think that latter category is far more common than the former.

An added danger of flybacks is that one may not realize the capacitance of the CRT. It doesn’t have that cylindrical look, or a little label on it telling how many microfarads it has, so it’s relatively easy to overlook the fact that it has a couple of metal plates and a dielectric, making it a hidden capacitor.

See where I’m coming from now?

Oh, and 400Hz AC is as bad as DC. 60Hz may shake you clear, but 400Hz just locks you up the same as DC. Found out the hard way…

RocketGuy's avatar

Most aircraft use 400 Hz AC. I forget what voltage, though.

Paradox25's avatar

@jerv Yeah, because a higher frequency means less frequent zero potential cycles in the same time span. 600 Hz is even more dangerous yet, and some frequency controllers for high rpm motors do alternate the frequency this high, and even much higher. It really comes down to the voltage being using combined with the frequency. Both need to be proportional, or an AC motor winding will burn up without induction occurring on a frequent enough level because the current will be excessive. Generally this why the voltage will change with frequency on frequency controllers. DC is still more dangerous per se though, when everything else is even.

@RocketGuy I’m in my 40’s and have been working as an industrial and maintenance electrician for 20 years, so I understand the concept. There does come a threshold where the human body can’t tell the difference between two different things affecting it anymore because it can only perceive at a limited level, so at a certain point you can’t tell the difference anymore. The worst shock I ever had wasn’t from anything I’d done in my line of work, but getting a shock from an ignition coil. The drastic voltage rise from a collapsing electrical field in an inductor is super nasty.

jerv's avatar

@RocketGuy The MG sets we used on the carrier to turn 60Hz into 400Hz were 450V on both ends, with stepdown transformers seven decks up just before the power entered the aircraft service station. I forget the output voltage there though; I can only remember the “transmission” voltage.

@Paradox25 There’s reasons I went through more screwdrivers than my shipmates. Breaker panels weren’t always labeled correctly, and I didn’t have enough rank to be trusted with a multimeter (E-5 and above only), so I often shorted things out intentionally and tagged out whatever breaker/fuse tripped. Sometimes the ballast from a fluorescent light would arc-weld my screwdriver or just take a bit off the tip though. Still, my habit of sacrificing tools kept me from getting belted much.

RocketGuy's avatar

I did mech design for several aircraft fans many years ago. They had me put in a 400 Hz AC motors.

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