The Scariac (Poor Mans Variable Power Controller)

Picture of The Scariac (Poor Mans Variable Power Controller)
Mixing water with electricity is risky, and can be lethal.  However, in this project we're using it to make one of the cheapest kinds of power controller.  The Scariac.
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Step 1: Watch the Video

WARNING: This project is extremely dangerous and should only be attempted by those highly skilled in working with electricity.  High voltages and high currents passing through the water provide an open hazard of electricution, and may cause death.  This design does not include any electrical ground.  This system is not recommended as a safe device.  It's purpose, rather, is to regulate electrical current in a simple and low cost way.  Toxic gases may be released from the solution during operation.  This project should not be attempted without adult supervision and adequate training.  Misuse, or careless use, of tools or projects may result in serious injury.  Use of this video content is at your own risk.

Step 2: Variac vs Scariac

Picture of Variac vs Scariac
I needed a way to adjust the power running to my homemade stick welding system, as seen in the video below;


Even with enough power to the welder, the main problem was finding a system that could vary electrical current without costing an arm and a leg.

In a tight situation, it's good to be aware of options, and that's why I was happy to learn about the idea of the water resistor.

The Scariac is a name I got from in his video and duplicated with permission.  It's a fitting name since the system acts similar to a Variac.  The idea is to use a water based medium as an electrolytic resistor.  A bit of electrolyte is added to the solution to make it slightly conductive, and when two electrodes are placed in the solution, the allow more or less current to flow, depending on whether there are closer or further apart.
wildgunman1 year ago
Pretty cool :) Showing that it slows down the grinder and the saw seems like kind of a cheat though. I guess this works because the current gets rectified after it goes through the scariac and the current loss gets translated to variable voltage.
dkkim1 year ago

1. I enjoy your videos. You are awesome. Insane perhaps, but awesome.
2. Ditto others re: the name. Very aptly named.
3. It is my understanding that a true Variac is a variably transformer, and thus will smoothly vary voltage, whereas this regulates the current (see above comment re: classifying this as a rheostat). It is interesting that you are observing a constant voltage over the range... Did you calculate the resistance you're getting through the range? Prob. just a lot more than your load.
4. Above may be relevant if you would be using a Variac to troubleshoot analog electronics (e.g. last used mine for an old stereo... want lower voltages in that case).
5. Agree re: GFCI.
6. Also agree this is probably too dangerous, as spec'ed for practical routine work (cheaper, though less fun, to work extra hours and buy a used Variac on eBay). And yes I've done crazy things in the past. But it is an excellent thing that you've built it simply as a physics demonstrator.
have you thought of using lemon water. it would be like electroplating but just as conductive
It's not quite as fun as cutting the ends off a power cord an jamming them into tin foil in a bucket of water but since this has a function I guess it's better, not nearly enough potential for death or dismemberment though,
Society sure has changed since I was a kid, lots of you'll poke your eye out paranoid postings
njkeng1 year ago
*** BIG SAFETY IMPROVEMENT *** If anyone is seriously considering building one of these then PLEASE power it using an Earth Leakage Circuit Breaker(ELCB), Residual Current Device (RCD) or whatever they are called in your locality (I'm in Australia). Use of one of these will eliminate the electrical hazards of this project without affecting the scariac's operation. Now, does anyone have any great ideas about how to eliminate the explosion risk?
This is so dangerous I really think that some editorial input is required to remove it before someone old enough to make it, yet young enough not to realise just how dangerous it is, manages to kill themselves.
I used this back in the 1970's after I read about it in an old theatrical techniques book on a means of dimming the "house" lights in an auditorium. It used a wooden barrel and a saline solution, and again , with separated contact pates. Need some kind of barrier to keep plates from ever touching. Also, and more importantly, once you start drawing amps of power, that saline solution is going to get hot - real hot! I needed a means of testing two surplus carbon rods from a carbon-arc spotlight, with a cheap high-power resistor load, and it did the trick to demonstrate it to my satisfaction. Too deadly a contraption to keep around with others wandering about so I dismantled it and never rebuilt.
The poisonous gasses... hint - use sodium bi-carbonate as the ionic solute, and not sodium chloride.

In the cyclotrons (particle accelerators) etc., these are called water resistors, because of the need to de-energise staggering amounts of current at extremely high voltages, and it's EASY to make HUGE resistors, that soak up enormous amounts of power, with the most basic of components.

These water resistors, were used as bleeder resistors, to power down the circuitry.

The great thing is that pure water is non conductive, but by controlling the conductivity of the water, by the amount of ionic added to the water, you could have resistance ranging from very high - almost non conductive, to very very conductive solution.

I think these - especially in some circumstances, are absolutely brilliant.
Exocetid1 year ago
"May" cause death? Definitely will cause death if one is not very, very careful. Electricity and caustic electrolytes--what a combination. This is just waiting for a Darwin Award candidate to come along.

Extremely clever rework of an old design.
Not really - electrocution AND dying, are two sort of interrelated issues.

To properly protect yourself against electrocution is pretty easy.

And this is one of those "Oh Duh" devices - which if properly built, is way safer than using a hair dryer in the bath for instance.

I_StarkGuy1 year ago
Mad project. Cooool!!!

(Please be careful, we want to see more of your projects.)
When this is operating, it's basically electrolysing the water, which means Hydrogen and Oxygen gas are being liberated (though not nearly as much on AC as with DC). If operated for very long, given that the gases are confined, this could potentially explode.
Since this is AC though, its producing all the oxygen and hydrogen gas at the same spots, and it reacts back into water fairly quickly. Just make sure there are vents in the container, and you use it in a well-ventilated area.
joen1 year ago
I was wondering if you could make your Scariac somewhat less "scari" by connecting the wire coming of the light switch first to the wall socket, and then to the rest of the scariac and back to ground.
That way everything but the light switch is on the ground side of the ac circuit. If nothing is connected to the scariac then the only thing that is hot is the light switch and the hot side of the socket. The way you discribed the circuit everything is hot whether anything is plugged in or not.
I hope that makes sense
I'd even go as far as using a double pole switch (disconnect hot and neutral at the same time), PLUS another circuit breaker installed as part of the device.
808Dave1 year ago
As a 14-year-old, I'd have been /all over/ projects like this.

As an old fart, I'm aware that the "build" is of very short lifespan: the particle-board will fail quickly from proximity to water/strong base/splashes, and for the same reasons, the staples will last a couple of weeks tops before falling apart. Corrosion in the connections, switch & receptacle will kill them in short order, since they're directly exposed to the bath vapors.

Adult supervision is mandatory, and your warnings make this fairly clear.  So if my kid wanted to build this, I'd be telling her that we /can/, and she'd learn a lot while building it, but I'd want her not to expect it to be useful for longer than an "oooh, neat, it works" period, after which it's going into the trash. The effort involved in the build to me suggests anyone who builds it is going to want to keep it around longer than that.
Metalyc1 year ago
Saw this in an old popular mechanics mag, except in a pickle jar instead of a box and with a extension cord spliced to soup-can lids instead of all your fancy circuitry and copper. The project was for a carbon arc gouger, two AA batteries opened up, attached to either lead, and placed on a piece of wood. Hey, there is a mini project for ya.
ssamc1 year ago
I learn something new today
veeguy1 year ago
Great idea, but you are correct, it's a bit scary looking! This is the same setup that used to be used in the theater to regulate lime lights and kleig lights. Your setup is a lot more sanitary looking and both better and safer in it's operation though. (I wonder if I could use it to regulate the lightning bolts before running them into my monster's neck studs?)
farmboy791 year ago
The technical name for this device is a liquid rheostat. And as stated below they were used for large motor speed control and other high current variable controls until SCR technology matured into modern variable speed drives. They became obsolete because they require a lot of maintenance to replace corroded parts and the electrolyte.
cyberdove1 year ago
The unit should be plugged into a GFCI
Treknology1 year ago
The "Scari" part of the name definitely fits!
this variable controller was used in the past to change the speed of electrical tramways.
Wyle_E1 year ago
This sort of thing was used to dim lights in the earliest electric theater lighting systems. International Rectifier makes big SCR modules that can do this job more efficiently and a *lot* more safely.
Sometimes I think that instead of the Instructables having warnings, the comment system should have them...
VadimS Wyle_E1 year ago
An scr and a resistor are not the same thing, this unit has a use.
nanosec121 year ago
I think calling this the "Scariac" is a very appropriate is a very scary machine (at least to me) and I could see how a slight mis-handling could be very disastrous. I am thankful for your very thorough warning/caution statement, I just hope people read it and heed it.
i second this thought, maybe if i had more desk space in my shop and less clutter and mess i could trust myself to make this but as i stand right now i'd probably end up killing something trying to make this...
thomas96661 year ago
Is there anything you can't do???
I'm envisioning a 5-gallon bucket modification of this setup that used a single "plunger" to raise the cathode to raise Electrode 1 toward electrode 2(mounted at top of fluid level), in case of catastrophic failure(of which I can imagine several), gravity itself will aid in severing the connection. The savings cost can also be used to replace the cheap light switch with an appropriately sized breaker(especially if you happen to be using this with thekingofrandom's welder contraption and the re-wound transformers happen to short in the primary coil).

Anyway, thanks for this! It is quite the idea, when/if I build one, I will post pictures.
rimar20001 year ago
Very neat work. This is very useful, too.
Hi It's very Interesting project.
Scariac, the big reistor!

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