The Scariac (Poor Mans Variable Power Controller)





Introduction: The Scariac (Poor Mans Variable Power Controller)

About: Random Weekend Projects

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.

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

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.

Step 3: "How I Did" Vs "How To"

In its simplest form, this device is just a glorified version of 2 wires in a bucket of water.

Although I've taken thought to minimize risks in operation, I have to stress that I don't consider this device safe or fool proof.  It has the potential to be lethal, and even though I show step-by-step how it was made, this is more of a "How I did" project rather than a "How to".

The system has a power lever to vary current output, and a loop of wire for connecting an ammeter.

The outlet on the board is where the devices plug in, and the switch acts as a kill switch to turn the device completely on or off at will.


There is no grounding wire connected, and always possibility of failure in any part of the system, so extreme caution and respect is needed when operating.  The device doesn't have any internal fuse/circuit breaker/current limiting device so there is also risk of fire if the system shorted out and your home circuit protection system failed.  This fire could potentially happen inside the walls of your home.

Step 4: Electrolyte As Variable Resistor

I used a water based medium for the variable resistance.  

2 gallons of tap water (Distilled water will also work great, but is more expensive)
1/4 teaspoons of 100% Lye (NaOH)

Even though the amount of lye is very low, it makes the water conductive very quickly.

I found my lye in a drain cleaner from the hardware store.  100% lye infact!  

Any salts could probably be used as an electrolyte, but using something like table salt (NaCl) seemed to introduce the possibility of generating Chlorine gas, and that's why I went with the NaOH instead. 

Step 5: Additional Considerations

During operation, the electrolysis does produce some gas, however it seems to be minimal when supplying with AC power.  DC would be a much greater concern.

The system is also open (ventilated) so any gas generation escapes quickly.  In my experience, this doesn't give Hydrogen and Oxygen gases enough time to build up to a dangerous level, and I wasn't able to achieve any gas explosions, even at ultra high power settings, despite trying..  However, it is good to be aware of the risks, and operate in a well ventilated area as a precaution.

Well, there you have it!  That's how I sacrificed safety to build a variable power controller on a very small budget.

If you haven't see the video yet, it's not too late.  Watch it here!

If you like this project perhaps you'll like some of my others. Check them out at



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    36 Discussions

    So it's basically a voltage dimmer? It would be awesome to make a smaller scale of one or these for those huge LED panels for filming...

    1 reply

    Very nice! I would suggest to add a grounding loop around the rim of the container though, or even better to enclose the whole contraption in a grounded metal container :)

    Awesome build sir! Thanks to you I am about to have a variable speed pump. Love the current meter loop addition.

    is it possible to use a toy train set variable power control instead of this?

    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.


    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


    5 years 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.

    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.

    1 reply

    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.

    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

    1 reply

    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.

    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.

    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.

    I learn something new today