garcia@skat.usc.edu (Robert Garcia) (04/11/88)
Hey Folks, I was wondering if any of you electronic geniuses can help me out. I want to build an inexpensive low powered "electric shocker" for a joke (something what won't harm anyone, yet give a good tingle). Back in high school, I had a friend show me one. From what I remember he had a 1.5 volt battery connected to a step-up transformer (?) and other components. I don't know what those components where because of my unfamiliarity at that time. What I don't understand is how a DC current can work with a transformer. I understood that you need an AC current to work with a transformer, thus there is something I am missing something here. Could someone please tell me how to build one? BTW, what kind of electronic gizmos have you folks created for a joke? It would be interesting to hear about the creativity out in netland. Thanks Rob
spcecdt@ucscb.UCSC.EDU (Space Cadet) (04/11/88)
A transformer will only work with a changing current. The circuit you
are refering to probably simply connected a battery to the primary of a step-up
transformer; the changing current at the moment the primary circuit is closed
and at the moment it is opened will produce high-voltage spikes at the
secondary. The last shocker I made used a simple 555 astable to direct-drive
the input of a small audio tranformer (use one that is listed as having a large
ratio of input to output impedance). DISCLAIMER: BE CAREFUL. A device that
barely tingles when pressed against dry skin can deliver quite a jolt when
touched to wet skin (as my friend found out the hard way... :)
As for other "joke" circuits... my favorite is still "the drip". I saw
the idea in a ca. 1970 electronics magazine and implemented a modern version.
It is a small (hidable) device that emits a periodic chirp. It can drive you
up the wall just as effectively as a dripping water faucet.
The last one I built used a PUJT timer set to produce a pulse every five
minutes. I put a piezo beeper (muRata PKB8-4A0) between the cathode and ground
so that when it triggered the current from the cap would be dumped through the
beeper; it was very efficient since the same current was used for timing and
beeping. In fact the average current was about 2.7 uA, so it would last at
least half a year on a 9v battery...
--
> Hello, lift. # We're going to space if we have to walk. -Jerry Pournelle <
< -Marvin the PA # The meek will inherit the earth. WE will go to the stars! >
> John H. DuBois III # spcecdt@ucscb.ucsc.EDU ...!ucbvax!ucscc!ucscb!spcecdt <strong@tc.fluke.COM (Norm Strong) (04/12/88)
In article <8287@oberon.USC.EDU> garcia@skat.usc.edu () writes: > >What I don't understand is how a DC current can work with a >transformer. I understood that you need an AC current to work with a >transformer, thus there is something I am missing something here. The "something" that you are missing is a chopper, or some means of interrupting the flow of current on a periodic basis. When I was young we used to play around with Model T spark coils. They had a mechanical buzzer on the coil to perform that function. Nowadays, we use transistors to chop the current through the xfmr; when the current drops to zero, the collapsing field around the xfmr generates a back emf that rises until something stops it--like arcover. -- Norm (strong@tc.fluke.com)
barnett@vdsvax.steinmetz.ge.com (Bruce G. Barnett) (04/27/88)
In article <2763@saturn.ucsc.edu> spcecdt@ucscb.UCSC.EDU (Space Cadet) writes:
I once purchased an electronics kit with a Free Mystery Gift -
"A Mystery Shock Box"
It was a cardboard box covered with two pieces of foil.
Inside was a battery, a coil, and a nail that had spiral groves.
The bottom was painted/insulated. The nail was inserted into a metal
connector so that when the box was down, the insulated part of the
nail touched the connector. When the box was picked up, The nail
dropped down and jiggled against the round contact, making and
breaking contact.
It might have been a transformer instead of a coil.
Anyhow, when you picked it up, you got quite a kick!
I made something similar with a relay, wiring it like a buzzer.
I was never able to make one of these that was:
Quiet
Could work over a distance (i.e. up the sleeve)
I will try a 555 and audio transformer.
Question: how far away can the wires be from the transformer?
--
Bruce G. Barnett <barnett@ge-crd.ARPA> <barnett@steinmetz.UUCP>
uunet!steinmetz!barnett