How to not die when dealing with electronic components

[antonis]

Of course I'm aware 9V aren't going to do nothing to a human but a circuit that works with 9V was my doubt. Logic tells me that if you feed 9V into a circuit, it's not going to go up (I think) but maybe there are ways, I'm just a beginner son I'm not sure.

If you feed a circuit from a 9V battery or fixed voltage regulator, nothing can make voltage go up..!!
(but an almost short-circuit, like a very low resistance load, can make voltage go DOWN..)

[bluebunny]

nothing can make voltage go up..!!

Well...

[antonis]

Well...

       


now you're looking for trouble, Marc.. 

[DeusM]

So you CAN murder someone with a 9V battery 
Don't give people strange ideas 

I'd like to know more about how that works. Do the caps storage enough voltage to then release even more? No wonder that came from R.G. Making 9V batteries potentially dangerous since 2000

[bluebunny]

You're on the right tracks, and no, it wasn't R.G.'s idea!  It's standard charge-pump functionality - nothing sinister.   

[merlinb]

So you CAN murder someone with a 9V battery 

Technically. But you'd have to spend a long time charge-pumping a monster capacitor up to a high voltage do it. And you'd probably only get one shot since the battery would be drained after the first session.

Normally the caps are way too small to store enough energy to cause you harm; the voltage can be high (painful), but the current will be wimpy.

[EBK]

So you CAN murder someone with a 9V battery 
Don't give people strange ideas 

I'd like to know more about how that works. Do the caps storage enough voltage to then release even more? No wonder that came from R.G. Making 9V batteries potentially dangerous since 2000

Imagine what you can with 244 of them:

[Phoenix]

Someone told about circuits that could increase the Voltage or the current or something like that. I'm just too lazy right now to look for it 

There are three ways that 9V can become some higher, potentially dangerous voltage.

The first is easy, if it's 9VAC and you feed it through a transformer with a high turns ratio, the 9VAC is multiplied (or divided) by the turns ratio. So if you have a 1:100 turns ratio and feed 9VAC in, you'll get 900VAC out. If the ratio was 100:1 and you feed 9VAC in, you'd get 0.09VAC out. Usually if this is happening, it's intentional - you've deliberately put the transformer in there to change the voltage.

The second way is often undesireable, and applies to DC voltage, not just AC. I think I explained earlier that capacitors and inductors (also called chokes or reactors or coils) are basically the opposite of each other. Capacitors store energy electrostatically, so they try to maintain a constant voltage across its terminals by feeding out whatever current they need to to maintain that. This means that if a load is connected, the voltage will slowly drop, but if the load is removed, the voltage will stay at that same level unchanged.
An inductor however stores energy electromagnetically, so tries to maintain a constant current through its winding (because the magnetic field is only maintained if there's current flowing). So if a load is disconnected, it will increase the voltage across its terminals to try to maintain that same current flow. This is called "flyback voltage".
An example of when you might see this happen is with a relay, which has a coil of wire that forms an electomagnet to turn a switch on or off. When the relay is turned off, the load is disconnected, so the coil shoots out a voltage to try to maintain its electromagnetic field, potenially (pun intended) up to hundreds of volts (a theoretical perfect inductor would be able to put out an infinite voltage in order to put out whatever current it needed, in reality there are other losses which will drain some of the energy), which can damage transistor drivers which might typically only be rated for 30V by causing semiconductor breakdown. The usual fix for this is to use a reverse-biased diode across the coil which will absorb the energy when the load is disconnected, but an RC (resistor capacitor) snubber can also be used.
But there are also situation where this phenomenon is desirable! Switchmode power supplies (SMPS), which are the basis of all small, efficient power supplies use exactly this to work. They take a DC voltage input (often directly rectified and smoothed from the mains wall voltage), and feed it into an inductor or transformer primary, which has an active device (usually a mosfet, but sometimes a bipolar transistor) to connect and disconnect the return loop of the coil. By pulsing this on and off at a high frequency, you get a changing magnetic field through the coil, which means changing voltage. If it's just an inductor, the changing voltage is rectified and filtered directly from the coil. If it's a transformer, the voltage is rectified and filtered from the secondary of the transformer. Depending on the frequency and duty cyle (percentage of time on vs off) of this pulsing on and off, the voltage can be controlled to either go up, or down.
All modern phone chargers, laptop power supplies, most of the power supplies built into modern audio visual equipment, computers and other consumer goods are based on this technology. By using high frequency the core of the transformer/inductor can be made much smaller than 50/60Hz rated transformers, and by utelising the flyback voltages and duty cycle we can avoid high turns ratios, so fewer windings.

The third and final way you can change 9V to something higher (and the mostly likely way you'll see in an effects pedal) has been detailed above, the charge pump. This uses a number of switches to change the connections to a "switched capacitor", which can be thought of like a bucket. There's also an input and output capacitor. At first the switched cap is put in parallel with the input capacitor, so it charges up to the same voltage. Then, it is instead connected in parallel with the output capacitor, so the output capacitor charges to the same voltage as the switched capacitor. So the voltage of the input capacitor and output capacitor can now be added together, giving either +/-9VDC or 18VDC. Or, if you want to add some extra diodes, like in the above high voltage example originally published by RG, you can get further multiples of the input voltage (but every diode has a voltage drop, so you get less return on investment for every multiplication stage). As mentioned by Merlin though, charge pump circuits are generally not capable of very high currents, so not typically very dangerous - but they can definitely make you wet yourself if you touch the wrong thing by mistake.

[DeusM]

Imagine what you can with 244 of them

Holy! That guy is insane. I would not dare to disarm that thing. I will bury it, put some concrete on top and leave it there 'till it goes out by itself.

Nice explanation phoenix although, I'm a begging so I could understand much of the second way you talked about  but don't worry. Il figure it out someday 

[anotherjim]

Funny, but I have a different take than Pheonix on how an inductor generates that high flyback voltage. Both explanations work I think - you get that a lot in electric stuff.

Background...
A changing current in a coil generates a changing electro magnetic field.
A coil in a changing magnetic field generates a changing voltage across that coil.
A constant current through a coil creates a constant magnetic field.
A coil in a constant magnetic field does nothing.

Switch the current flow off - magnetic field collapses rapidly - it is changing fast.
A new voltage is "induced" across the "inductor" coil. It can be many times higher than the original DC supply voltage if the field collapse is very rapid.
The "Flyback" voltage is ALWAYS in reverse polarity to the original DC supply. This is why a diode wired in reverse polarity across the coil can be used to damp/quell/snub/slug the flyback out. This is what you can do to prevent shock and also protect any connected semiconductor based control from being fried by the high reverse voltage.

Flyback is also called "Back E.M.F". EMF is "Electro-Motive Force" or Voltage.

[Phoenix]

Coincidental timing, Cody's Lab just uploaded a video demonstrating how water can be be used in a "boost converter" arrangment.
Boost Converter With Water (Hydraulic Ram Pump)

[thermionix]

Imagine what you can with 244 of them

Retire.

[bluebunny]

Imagine what you can with 244 of them

Um, buy two of everything that Boss ever made?   



(According to Boss, 119 unique pedals since 1977.)

[thermionix]

I'll take the Super Reverb.  Thanks.

[samhay]

The worse shock I have had was from a camera flash circuit.
For the some-microseconds a large flash unit takes to flash/discharge, it can generate >1000V in the many-amps range. While you probably won't be taking apart any cameras, beware any circuit with transformers and high voltage capacitors, regardless of what it is powered with!

[DeusM]

Coincidental timing, Cody's Lab just uploaded a video demonstrating how water can be be used in a "boost converter" arrangment.
Boost Converter With Water (Hydraulic Ram Pump)

After watching the video I think I get now how flyback voltage works. But I only understand thinking in electron flow rather than conventional current. I think that the magnetic field forces all the electrons in the remaining circuit keep moving, forcing it into a higher differential potential, so when the circuit is connected again, the voltage will have to compensate for the amount of "missing" electrons ans then the it will be higher but in the oposite way beacuse there is a "lagoon" of missing electrons. I'm I correct?

[PRR]

Yes it is possible, now easier than ever, to boost one voltage to another.

Even an old-old car boosts 12V (even 6V) to 10,000+V for the spark plugs.

Such systems are fairly rare. And mostly limited. 9V to 17V is easy, and not much more dangerous. 9V to 150V is frequently done, but the output is weak, collapses when you put much load on it. Tingles, rarely stop-your-heart shock. Sure, higher power voltage converters exist, but not common or cheap.

And while you worry about all that, you get hit by a bus, or your gall-bladder bursts. We can't eliminate "ALL" risk. If you reject technology and live in the jungle, the tiger gets you.

[antonis]

If you reject technology and live in the jungle, the tiger gets you.

Not if you've taken with you a 9V battery and a voltage booster before technology rejection....

[samhay]

To add to PRRs comment, there is also something to be said for the educational benefit of being electrocuted* - there's nothing like converting theory to practice after all.

*Be safe though. Always pet tigers with one hand in your pocket and make sure it's only the baby tigers that are allowed to bite you.

[DeusM]

And while you worry about all that, you get hit by a bus