My cousin's husband asked me about an electric shock circuit. He
remembers at school some kid made joke suitcase, that if picked up
zapped the recipient.
I know the circuit, and I strongly expect it to be the same one used
in the practical joke pens and staplers. It just involves a DPDT
relay, a 100uF capacitor, a small transformer and a 9v battery.
The basic idea is that the capacitor is charged up (to 9v) triggering
the coil which then disconnects the battery and discharges the
capacitor through a transformer which can step the voltage up. The
transformer has primary/secondary impedances of 1.2kOhms / 3.2Ohms
(leading to a step-up factor of about 20).
My question is just - how safe is this circuit? He wants to make it
to demonstrate some electronics to his son (and I agree with him that
there is a lot in it for a boy to learn).
I calculated the output energy of each pulse,
E = 0.5 * C * V^2 = 4 mJ,
which is very low, so I told him it's fine if he's sensible, and keeps
the output away from the face etc. I just want to check here that my
logic is sound.
Thanks.
remembers at school some kid made joke suitcase, that if picked up
zapped the recipient.
I know the circuit, and I strongly expect it to be the same one used
in the practical joke pens and staplers. It just involves a DPDT
relay, a 100uF capacitor, a small transformer and a 9v battery.
The basic idea is that the capacitor is charged up (to 9v) triggering
the coil which then disconnects the battery and discharges the
capacitor through a transformer which can step the voltage up. The
transformer has primary/secondary impedances of 1.2kOhms / 3.2Ohms
(leading to a step-up factor of about 20).
My question is just - how safe is this circuit? He wants to make it
to demonstrate some electronics to his son (and I agree with him that
there is a lot in it for a boy to learn).
I calculated the output energy of each pulse,
E = 0.5 * C * V^2 = 4 mJ,
which is very low, so I told him it's fine if he's sensible, and keeps
the output away from the face etc. I just want to check here that my
logic is sound.
Thanks.