Welcome
to one of the scariest and dangerous sections of the world of electronics
(also one of the areas I love most!). So you know that electricity goes
'fizz' and 'crackle' and 'bzzzzzzzzzzzzz', but hearing something go
KABOOM isn't something you hear everyday. Well electricity has that
potential, its just a matter of converting that stored energy into sound. |
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Image courtesy of Howstuffworks |
This is actually rather simple, it utilizes the principles of one of the most common electronic components: the capacitor. Capacitors store electric charge. Their amount of charge they can store depends on their value of capacitance and their rated voltage. In short, the energy stored in a capacitor (Joules) = Volts squared x Capacitance. To the left is a typical capacitor found in a camera flash unit. These capacitors have extremely low ESR (equivalent series resistance), meaning they can discharge at very high currents. That's why we use them in these experiments... |
People who work in the electricity
industry will tell you that 16 joules is enough to kill a human. And
That's very easily achievable with capacitors. The capacitor bank that
I use in these experiments consists of 5 paralleled photoflash capacitors,
giving a total of 550uF at 330V. This rounds off to about 27 joules,
so technically very dangerous. |
This space is intentionally
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The schematic...click on the picture for a higher resolution version. |
It can't do much though. With much higher energies (in the thousands of joules), can crushing and railgun construction is possible. The whole aim of this simple, ultra small scale experiment was to see what happened when a couple hundred amps was passed through strips of different metals. So the very simple circuit to the left was designed. |
So for safety's sake, the whole setup was enclosed in a tough industrial plastic case, just in case the capacitors decided to blow on me. There's the important features of the circuit labelled on the Image to the right. I decided to test a few different metals; aluminium, copper, and steel. Strips of these were secured to the discharge terminals, then the capacitors were discharged straight into the poor little strips. Results? Some very nice explosion photos... |
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This is a strip of aluminium
being vapourised on the discharge terminals. |
Again, a strip of aluminium
vapourised during an earlier test run of the circuit. The multimeter
serves no purpose other than tell me how many volts are left in the
capacitor bank after discharge, potentially saving me from a nasty bite
afterwards. Also visible is the battery (7AH SLA) for energizing the
relay. |
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Another strip of aluminium.
Notice how the spark trails of aluminium are relatively straight, indicating
that the bits of aluminium travel at high velocities. Compare this to
steel wool below... |
Steel wool
being vapourised off the discharge terminals. Notice the difference
between steel and aluminium... its not as bright, and the molten steel
bits seem to leave at a much slower speed. |
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Single strand of steel wool
placed across discharge terminals. Again, the molten projectiles are
heavy and fall very quickly. |
A copper strip over the discharge
terminals. Not very interesting is it... probably due to the higher
conductivity of copper (I couldn't find a thinner strand at the time).
Also note how the explosion has a green shade... Copper oxide burns
green. |
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