Jabobs ladder
From Grahams Wiki
This is a stupid project that i originally started for a victoriana game. I've made two of them, but there both in different states of repair, cos i didnt bother finishing them when the game got cancelled. Its basically a climbing spark created by a one or two car ignition coils switched by an Oscilator.
In both cases, I used a battery for safety purposes, and both have different safety features which i'm going to replicate in both.
Unsurprisingly, there still both quite dangerous and need to be used with care.
These pictures are from the second one, which is the more powerful one with two coils.
Contents |
[edit] Examples
http://www.youtube.com/v/2vWsdr8PweA
http://www.youtube.com/v/sXmynGvDaeM
[edit] How they work
Really simple, There are two ways to make these things. You need an AC current from somewere.
[edit] Mains (NOT RECOMMENDED!)
If you use the mains, you can just transform it. You need some form of current limiting, and there are other dangers, not least of which is that you will be wired to the mains, and you will have to custom wind a transformer, or use a flourescent light transformer. Also, if your mains is on an RCCB (And most are!) you will reliably trip it as some of the current will be lost.
[edit] Battery
A battery is slightly more complex, however, substantially safer, as you can use car ignition coils or TV flyback transformers, which are designed for the voltages they are transforming. The only issue is that you need to get an AC current from somewere. I do this using a simple NE555 oscilator and a 2n3055 transistor.
As the maximum CE current is 15A, and i'm running of a 6v motorcycle batter, it means the maximum possible current pushed into the coils is 90w.
In reality, its much less than this, as the coils have a restance of about 0.4 ohm at DC, and more at frequencies. the transistor drops 0.7v, The NE555 only outputs about 60ma into the base resistor, which as the DC current gain of the transistor is only 40, which give Ic at 2.4A, leaves the wattage at about 12w.
Therefore after transformation to 20,000v, the current is about 0.6ma, which is well below the threshold of Lethality, although you will still feel it, and it will still burn.
Also, the oscilator is of high enough frequency that it will tend to run along the skin rather than penetrating and touching vital organs.
However, just because you probably wont die, doesnt mean you shouldnt still treat the equipment with respect. The skin is where lots of nerves end up, and it still hurts like hell.
[edit] The ones i have built
Neither of the ones i have built are actually complete. (As in has its complete set of safety things)
The only thing both want doing is the replacement of the resistive cables with copper cables. Resistave cables are used in modern cars to reduce any arcing. This is of course complete the opposite to what I actually want. Due to the physics of it, its not a problem when it fires, however, when the arc starts, the wires become a significant part of the resistance, and therefore the spark isnt as powerful or as bright as it could be.
In both cases, i decided to totally box off all the HT terminals for safey.
[edit] The original one
This one uses a single coil. The relay and control system are in the lid.
Mostly, this one is ok, but, spares have been nicked for the second one. Its missing:
- power transistor.
- I would like to replace the resistive cables with copper cables - Probably make more of a difference with this one.
[edit] My second attempt
My second attempt uses a reciperacal pair of coils to double the voltate at the prongs.
This one is missing
- Dead mans switch
- On switch (Currently controlled by two wires)
- tilt switch.
- I would like to replace the resistive cables with copper cables.
[edit] what it looks like setup
[edit] Running
This is a picture of it running. Unfortunately, it doesnt look very impressive. I need to take a movie of it really. In good weather, it can jump about 5cm, although 3cm makes for more reliable firing. Unfortunately cos its so damp, and the battery needs charging, i'm using it at 7mm.
[edit] Inside the second one
This terrible picture is the inside the second one. To the left is a 12v motorcycle battery which powers all the rubbish. The whole lot is controlled via a relay you can see down the bottom. This is so the control circuit doesnt have to take high current. (When i get around to putting the dead mans switch in)
The metal is actually an aluminium heatsink for the large transistor used to switch the coils, the top of which you can see at the top. just about the right, you can just about see the reed switch. this is used to make sure the thing cant be turned on when the case is open. (V important!)
