Forums

Detecting best path?

Started by Jymesion October 14, 2012
I'm a writer, and although I keep telling myself I'm still an
electronics amateur, I haven't actually touched a soldering iron in
years. I hope you'll help me anyway. :)

Partway into a story, I've hit a snag because I'm not positive a
necessary 'prop' can be made.

This problem is therefore theoretical in that I won't actually build
it, but my internal editor demands that it could be built, and I have
to know what, if any, limitations there might be.

(Sorry this is so long, but I hate asking for help and then having to
tell people, "That's a great idea, but it won't work here because
<insert something my original post didn't state>.")

Scenario: 
A Cross looks to be of ivory with inlaid gold ribbon spiraling around
it. The stalk is about 2 inches in diameter and 3 feet long. The
crossbar is 1 inch diameter and 1 foot long. It's laying on an altar. 

A suspect is told to pick up the Cross and swear to God he's innocent.
He does, then falls to the floor in agony and begins to go into
convulsions. 

'Real' Situation:
The Cross is tubes of insulating ceramic, and the gold ribbon isn't
continuous -- there are gaps on the back of the Cross, making each
turn a contact plate connected to a voltage multiplier. A remote
control turns it on and off. Output (without load) is 300kV.

If the contact plates simply alternated + - + - + - etc., then it
might only sting the hands of the person holding it, and the effect
must be much more pronounced. (This was a real ritual, and the person
could pick up and hold the Cross in whatever manner they wished.)

What's needed is some method of determining which contact plates will
send the current through the person's body. Once that's been done,
servo motors driving rotary switches can connect the proper plates.

The selection can't be done using the remote because the official's
hands must be in plain view to prevent his making cabalistic signs to
influence the outcome (a tension switch on an armband turns it on when
he flexes his bicep). 

The voltage multiplier, receiver, and servos already take up a lot of
the internal space, and it needs as much battery capacity as possible
because it'll be used repeatedly. 

So: a user-built circuit no more than 1.25 inches in diameter, as
short as possible, using only off-the-shelf components (the circuit
board(s) can be etched as a one-off), to detect resistance(?) or
capacitance(?) between contact plates, determine which two are
optimal, and output their identity as hi/lo on four wires for each
servo. A microprocessor is not an option (the character building it is
competent in basic electronics but not in programming or burning
proms, and he doesn't have time to learn (he can't enlist outside
help)). 

Any ideas?


Any help greatly appreciated!
Jymesion wrote:

> I'm a writer, and although I keep telling myself I'm still an > electronics amateur, I haven't actually touched a soldering iron in > years. I hope you'll help me anyway. :) > > Partway into a story, I've hit a snag because I'm not positive a > necessary 'prop' can be made. > > This problem is therefore theoretical in that I won't actually build > it, but my internal editor demands that it could be built, and I have > to know what, if any, limitations there might be. > > (Sorry this is so long, but I hate asking for help and then having to > tell people, "That's a great idea, but it won't work here because > <insert something my original post didn't state>.") > > Scenario: > A Cross looks to be of ivory with inlaid gold ribbon spiraling around > it. The stalk is about 2 inches in diameter and 3 feet long. The > crossbar is 1 inch diameter and 1 foot long. It's laying on an altar. > > A suspect is told to pick up the Cross and swear to God he's innocent. > He does, then falls to the floor in agony and begins to go into > convulsions. > > 'Real' Situation: > The Cross is tubes of insulating ceramic, and the gold ribbon isn't > continuous -- there are gaps on the back of the Cross, making each > turn a contact plate connected to a voltage multiplier. A remote > control turns it on and off. Output (without load) is 300kV. > > If the contact plates simply alternated + - + - + - etc., then it > might only sting the hands of the person holding it, and the effect > must be much more pronounced. (This was a real ritual, and the person > could pick up and hold the Cross in whatever manner they wished.) > > What's needed is some method of determining which contact plates will > send the current through the person's body. Once that's been done, > servo motors driving rotary switches can connect the proper plates. > > The selection can't be done using the remote because the official's > hands must be in plain view to prevent his making cabalistic signs to > influence the outcome (a tension switch on an armband turns it on when > he flexes his bicep). > > The voltage multiplier, receiver, and servos already take up a lot of > the internal space, and it needs as much battery capacity as possible > because it'll be used repeatedly. > > So: a user-built circuit no more than 1.25 inches in diameter, as > short as possible, using only off-the-shelf components (the circuit > board(s) can be etched as a one-off), to detect resistance(?) or > capacitance(?) between contact plates, determine which two are > optimal, and output their identity as hi/lo on four wires for each > servo. A microprocessor is not an option (the character building it is > competent in basic electronics but not in programming or burning > proms, and he doesn't have time to learn (he can't enlist outside > help)). > > Any ideas? > > > Any help greatly appreciated!
I can't believe I read the whole thing. Jamie
On Sun, 14 Oct 2012 17:29:13 -0400, Jamie
<jamie_ka1lpa_not_valid_after_ka1lpa_@charter.net> wrote:

>Jymesion wrote: >> (Sorry this is so long, but I hate asking for help and then having to >> tell people, "That's a great idea, but it won't work here because >> <insert something my original post didn't state>.") > >I can't believe I read the whole thing. >
:) Any chance you'll be able to solve the problem once your mind un-numbs?
Jymesion wrote:
> > On Sun, 14 Oct 2012 17:29:13 -0400, Jamie > <jamie_ka1lpa_not_valid_after_ka1lpa_@charter.net> wrote: > > >Jymesion wrote: > >> (Sorry this is so long, but I hate asking for help and then having to > >> tell people, "That's a great idea, but it won't work here because > >> <insert something my original post didn't state>.") > > > >I can't believe I read the whole thing. > > > :) > Any chance you'll be able to solve the problem once your mind > un-numbs?
No one will live long enough to see that happen.
On Sun, 14 Oct 2012 15:40:00 -0600, Jymesion wrote:

> I'm a writer, and although I keep telling myself I'm still an > electronics amateur, I haven't actually touched a soldering iron in > years. I hope you'll help me anyway. :) > > Partway into a story, I've hit a snag because I'm not positive a > necessary 'prop' can be made. > > This problem is therefore theoretical in that I won't actually build it, > but my internal editor demands that it could be built, and I have to > know what, if any, limitations there might be. > > (Sorry this is so long, but I hate asking for help and then having to > tell people, "That's a great idea, but it won't work here because > <insert something my original post didn't state>.") > > Scenario: > A Cross looks to be of ivory with inlaid gold ribbon spiraling around > it. The stalk is about 2 inches in diameter and 3 feet long. The > crossbar is 1 inch diameter and 1 foot long. It's laying on an altar. > > A suspect is told to pick up the Cross and swear to God he's innocent. > He does, then falls to the floor in agony and begins to go into > convulsions. > > 'Real' Situation: > The Cross is tubes of insulating ceramic, and the gold ribbon isn't > continuous -- there are gaps on the back of the Cross, making each turn > a contact plate connected to a voltage multiplier. A remote control > turns it on and off. Output (without load) is 300kV. > > If the contact plates simply alternated + - + - + - etc., then it might > only sting the hands of the person holding it, and the effect must be > much more pronounced. (This was a real ritual, and the person could pick > up and hold the Cross in whatever manner they wished.) > > What's needed is some method of determining which contact plates will > send the current through the person's body. Once that's been done, servo > motors driving rotary switches can connect the proper plates. > > The selection can't be done using the remote because the official's > hands must be in plain view to prevent his making cabalistic signs to > influence the outcome (a tension switch on an armband turns it on when > he flexes his bicep). > > The voltage multiplier, receiver, and servos already take up a lot of > the internal space, and it needs as much battery capacity as possible > because it'll be used repeatedly. > > So: a user-built circuit no more than 1.25 inches in diameter, as short > as possible, using only off-the-shelf components (the circuit board(s) > can be etched as a one-off), to detect resistance(?) or capacitance(?) > between contact plates, determine which two are optimal, and output > their identity as hi/lo on four wires for each servo. A microprocessor > is not an option (the character building it is competent in basic > electronics but not in programming or burning proms, and he doesn't have > time to learn (he can't enlist outside help)). > > Any ideas? > > > Any help greatly appreciated!
300kV is way more voltage than you need. Current kills, you only need enough voltage to force that current through. Supposedly 12V will do it on a Really Bad Day; I've survived multiple jolts from 120V as have many other folks (but many others have died for it, mostly in accidents involving water and an inability to get disconnected). 500V to 1000V should do it. 300kV at sufficient current would probably leave a smoking corpse, and would require more battery than you have. In fact, 300kV at sufficient current to kill would be sparking, popping and snapping over distances larger than one foot on a humid day. Some actual research at an actual library may come in handy. Or even Google or Wikipedia. If Poor Doomed Innocent Guy touches the cross then falls to the floor convulsing without keeping a grip on said cross, then I'll put your book down in disgust -- the convulsions only continue for as long as the cross is in hand. After that the guy will be wherever he was thrown from the shock, or stone dead. Servo motors driving rotary switches are kind of lame, unless your villain is pretty lame, too, and your Intrepid Hero is to figure it out because of the whirring noises, and the suppressed curses when some of the Poor Innocent Doomed Guys walk away whistling. Better would be a circuit between each set of contacts, with its own battery, that's switching (for efficiency), current limited to 20mA (or 2-3x fatal), and will go to up to 1000kV. Then when Poor Doomed Innocent Guy grabs it, the circuit will automatically adjust itself for fatality. Use opto-isolators to turn it all on. Or better yet, write political speeches -- the audience is much more willing to suspend disbelief. -- Tim Wescott Control system and signal processing consulting www.wescottdesign.com
On Sun, 14 Oct 2012 22:17:29 -0500, Tim Wescott
<tim@seemywebsite.please> wrote:

>300kV at sufficient current would probably leave a smoking corpse, and >would require more battery than you have. In fact, 300kV at sufficient >current to kill would be sparking, popping and snapping over distances >larger than one foot on a humid day. > >Some actual research at an actual library may come in handy. Or even >Google or Wikipedia.
My research was to find a voltage multiplier module with an output equivalent to the stun gun I have and that would fit in the required space. It took all of three minutes -- there were a lot of options. Funny, none of the advertisements mentioned burning people alive.
On Sun, 14 Oct 2012 23:13:33 -0600, Jymesion
<noreplies@jymes.com> wrote:

>On Sun, 14 Oct 2012 22:17:29 -0500, Tim Wescott ><tim@seemywebsite.please> wrote: > >>300kV at sufficient current would probably leave a smoking corpse, and >>would require more battery than you have. In fact, 300kV at sufficient >>current to kill would be sparking, popping and snapping over distances >>larger than one foot on a humid day. >> >>Some actual research at an actual library may come in handy. Or even >>Google or Wikipedia. > >My research was to find a voltage multiplier module with an output >equivalent to the stun gun I have and that would fit in the required >space. It took all of three minutes -- there were a lot of options. > >Funny, none of the advertisements mentioned burning people alive.
I don't have a problem with the 300 KV as such, though you could surely get by with a bit less. You just need to punch through the outer skin resistance, which could be high if the victim has dry skin. Note that tasers avoid this by physcially poking through the skin. (But you can easily include moist skin in the plot, since the guy is likely to be stressed out about the whole ceremony thingy.) You probably aren't getting too much current from your voltage multiplier anyway, but you could mention it if you really feel it's needed. I don't think most people would bat an eye at that, since they know about tasers and such by now. Tim is dead-on about servos... some sort of solid state switching will sound much more plausible. But I don't think you even need switching. If it were my story, I'd skip this issue entirely and just make it a part of the ceremony that the celebrant must hold the cross in a specific way. Maybe both hands have to be near the bottom, and his forehead touches the top. Or maybe he has to kiss the top. Or maybe the left had has to be at the bottom, and the right hand has to be above it. There's a lot of room to play with here. Best regards, Bob Masta DAQARTA v7.10 Data AcQuisition And Real-Time Analysis www.daqarta.com Scope, Spectrum, Spectrogram, Sound Level Meter Frequency Counter, Pitch Track, Pitch-to-MIDI FREE Signal Generator, DaqMusic generator Science with your sound card!
On 10/15/2012 8:34 AM, Bob Masta wrote:
Snip>
> > If it were my story, I'd skip this issue entirely and just > make it a part of the ceremony that the celebrant must hold > the cross in a specific way. Maybe both hands have to be > near the bottom, and his forehead touches the top. Or maybe > he has to kiss the top. Or maybe the left had has to be at > the bottom, and the right hand has to be above it. There's > a lot of room to play with here. > > Best regards, > > > Bob Masta >
Unless he really wants to build it.
On Sun, 14 Oct 2012 23:13:33 -0600, Jymesion wrote:

> On Sun, 14 Oct 2012 22:17:29 -0500, Tim Wescott > <tim@seemywebsite.please> wrote: > >>300kV at sufficient current would probably leave a smoking corpse, and >>would require more battery than you have. In fact, 300kV at sufficient >>current to kill would be sparking, popping and snapping over distances >>larger than one foot on a humid day. >> >>Some actual research at an actual library may come in handy. Or even >>Google or Wikipedia. > > My research was to find a voltage multiplier module with an output > equivalent to the stun gun I have and that would fit in the required > space. It took all of three minutes -- there were a lot of options. > > Funny, none of the advertisements mentioned burning people alive.
I realized that I assumed you were trying to kill. So, are you trying to kill the guy or just make him shout? Your stun gun doesn't keep generating 300kV when it's actually connected to a person. And, since it's a _stun_ gun, it doesn't generate much current (I don't know what's considered safe, but chances are it's less than what's considered lethal). Regardless, unless the guy has some underlying medical condition, once he's off the current he's going to stop convulsing (unless he pulls a muscle, in which case he'll be convulsing in pain as from any other injury). If you're just going for pain & convulsions, then connect the whole thing together through a resistive divider -- gold - resistor - gold - resistor - etc. Then wherever your Hapless Victim grabs the thing, a current will be established. If I sound a bit cynical, it's because I don't think it would work in real life, on a whole bunch of different levels: getting a reliable honkin' big shock without either piercing the skin or risking death is pretty iffy, and isn't something that you can do right out of the chute, even if you're knowledgeable; having everyone in the room be smart enough to get to the ceremony at the appointed time yet dumb enough not to realize that trickery is involved isn't likely (unless there's time travel involved); having someone dumb enough (or evil) enough to get into the situation while still being smart enough to wire the thing up, etc. -- My liberal friends think I'm a conservative kook. My conservative friends think I'm a liberal kook. Why am I not happy that they have found common ground? Tim Wescott, Communications, Control, Circuits & Software http://www.wescottdesign.com
On Mon, 15 Oct 2012 12:34:22 GMT, N0Spam@daqarta.com (Bob Masta)
wrote:

>If it were my story, I'd skip this issue entirely and just >make it a part of the ceremony that the celebrant must hold >the cross in a specific way. Maybe both hands have to be >near the bottom, and his forehead touches the top. Or maybe >he has to kiss the top. Or maybe the left had has to be at >the bottom, and the right hand has to be above it. There's >a lot of room to play with here.
For me, it's a matter of readers crying foul. It's fine to introduce any absurdity (as long as it's believable), but when including something which existed in the real world, it's immutable unless you can show why/how history was different/changed. Example: tobacco and potatoes in The Lord of the Rings. How pipeweed was introduced is in the text, so that's fine. But readers, a lot of readers, deplore there being potatoes because they didn't exist in that latitude before a certain date. Since my writing is nowhere near that of Tolkein's, my stories will suffer more if the readers see mistakes.