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According to the United States Defense Department, zapping your brain with electricity can turn novices into experts – of anything.The application of current to the brain – known as transcranial Direct Current Stimulation (tDCS) – received funding from DARPA, the US Defense Department, and more. And you can build your own with about $10 in parts, simple tools and some soldering experience.

tDCS applies a small current from a 9v battery to the brain. This stimulation proved to enhance human cognitive powers (have a listen to NYC Radiolab episode entitled “9 Volt Nirvana” if you’re skeptical). Applying this current to different parts of the brain can give its users temporary (and sometimes permanent) cognitive enhancement. Research indicates that tDCS also works on depression, anxiety, and as a meditation aid. The most famous portion of the brain – the so-called F3 region – offers up to 40% improvement in specific categories of learning. Unfortunately, the long-term effects on neuroplasticity, brain function and more, remain unknown.

The path to cerebral augmentation remains fraught with dangers – born from either your capacity for error and from the unknown long-term effects of artificial neural stimulation. Use this guide at your own peril! I cannot emphasize enough that users exercise the highest degree of safety in constructing their own tDCS device. Please read the section on “Electrode Placement” at the bottom of this article.

Can it Kill You?

In the 60s, a US Navy Sailor experimented with a 9V battery – by accident, he pushed negative and positive electrodes through the surface of his skin, and hooked it up to a 9V battery. As it turned out, blood (which contains iron) offers very little electrical resistance. As biological creatures, our bodies conduct electricity like a circuit. Many of our internal organs receive electrical current from our brains. A direct current can disrupt this signal, causing heart-failure.

Furthermore, we know nothing about the long-term effects of tDCS on human physiology. While the electrical current of a 9V battery isn’t much at all when applied to a tongue, internal application is deadly.

Step 0: The Inthinkerator MK. I Design


The tDCS device we’re building in this guide, the Inthinkerator MK. I, is from Reddit /r/tdcs user Kulty. The open-source nature of Kulty’s design allows us to borrow and modify it.

From my perspective – as an amateur hobbyist – the design looks good. It includes short protection and is safer than other commercial devices such as the (our review of the tDCS Headset Review and Giveaway tDCS Headset Review and Giveaway The $249 device shoots an electrical current into the brain – boosting one's cognitive abilities. Read More ). With proper build technique, the risk of creating a short-circuit is very, very low. Keep in mind that the design comes without warranty and could potentially fry your brains – you were warned.

Step 1: Parts Required

The total cost for parts should come out to around $10-20, but you’ll also require some basic tools as with any electronics project.

Step 2: Lay Out Your Breadboard

Test the circuit first on a breadboard to determine if the parts are working and the circuit is correct – you won’t need all the parts yet. Note that we’re using a 220 Ohm resistor as a test load to simulate skin contact.

The exact holes where the parts plug into don’t matter too much – focus on completing the circuit. If you’re unsure about using a breadboard, be sure to read our beginner skills needed for electronic projects Beginner's Electronics: 10 Skills You Need to Know Beginner's Electronics: 10 Skills You Need to Know Many of us have never even touched a soldering iron - but making things can incredibly rewarding. Here's ten of the most basic DIY electronics skills to help you get started. Read More guide first.

When finished, you can attach the battery connector to your 9v battery and plug it into the positive and negative rails, on the side of the breadboard. If everything works, you should see the LED light turn on. If it doesn’t work, reanalyze the circuit to make sure it’s correctly wired.

Step 3: Lay Out Your Project Box

Now take the project box and mark the location of the following components using a marker:

  • Positive banana plug (red)
  • Negative banana plug (black)
  • Trim potentiometer
  • Toggle switch
  • NPN transistor
  • Potentiometer
  • Project box (of course)

Step 4: Drilling Holes

You will need to drill six holes. I suggest drilling from inside of the case, rather than from the outside. Also, make sure your components actually fit before moving onto the next hole.

  • Hole 1 & 2: Drill two holes at the top of the box. These need to accommodate the screws on the cathode and anode banana jack. Roughly 1/4 to 1/3 of an inch will do.
  • Hole 3: Drill a large hole, approximately 1/2 of an inch in diameter, to place the LED light and its chrome housing.
  • Hole 4: Drill another large hole, approximately ½ of an inch in diameter in the center of the box to accommodate the potentiometer.
  • Hole 5 (not drilled in picture): Drill a small hole, about 5/16th of an inch in diameter, to accommodate the trim potentiometer’s adjustable dial.
  • Hole 6: Drill a hole, about 1/16th of an inch in diameter, to fit the power switch.

Step 5: Placement of Components in Box

Both banana plugs go at the top of the project box. This step won’t require much effort. Just drill two holes at the top of the box, remove the nut on the plugs and insert. You will then use the lug-nut to tighten the device into place. The only exceptions are the NPN transistor and the trim potentiometer, which you will hot-glue into place.

NPN transistor: Make sure to place this with the round portion facing up and that the three pins point toward the right.

Trim potentiometer: You will want to place this with the brass dial poking through the hole in the case. When you place the trim potentiometer in the case, make sure that the brass dial is secured using a lugnut. The lugnut is screwed onto the brass dial, once its been pushed through the hole in the project box.

Step 6: Potentiometer

Of the three pins on the potentiometer, you will solder insulated wires to two of them. Solder a medium length wire to the central pin. Then solder a short-length wire to the outside pin.

Step 7: Trim Potentiometer

Again, you will only use two pins. Solder the central pin to the 1k Ohm resistor. You’ll notice that in the picture below, I’ve already wired this to the Emitter pin on the NPN transistor.

Then take the wire soldered to the central pin of the potentiometer and solder this to the outside pin on the trim potentiometer.  You may need to bend some of these pins for easier access. Don’t bend the trim potentiometer’s pins too much. A little bend won’t harm it – over-bending will cause the pin to snap off.

Step 8: The NPN Transistor

There are three kinds of pins on the NPN transistor: Collector, Emitter and Base. Each pin corresponds with a different soldered connection. You will want to make certain that the pins are correctly wired or otherwise the circuit won’t work. You also need to make sure that the flat side of the NPN transistor is facing down.

  1. Collector: Solder a medium length insulated wire.
  2. Base: Solder a short length wire.
  3. Emitter: Solder to the 1k Ohm resistor, from the central pin on the trim potentiometer.

Step 9: Toggle Switch

You will solder three wires to the toggle switch. Each one of the toggle switch’s pins are rectangular, with a hole in the middle. You can loop wires through the holes, which aids soldering. Before getting started with connections to the toggle switch, take a long-length wire, and join an end of it with a 680 Ohm resistor. As with almost all physical connections, you will solder these together.

On the left (outside) pin, you will solder two parts. First, take the wire/resistor (depicted above) and solder this to the outside pin on the toggle switch. Second, solder a 3.3k resistor to the to the left (outside) pin. Soldering both at the same time is a lot easier than soldering each on individually.

Then solder the red (positive) 9v battery connector to the central pin on the toggle switch. Remember to not connect the battery until you are completely finished.

Step 10: LED

The LED has two pins. Most LEDs use a long pin to designate a positive connector. That means the short pin is negative. If you wire this improperly, the circuit’s design will prevent the LED from lighting, but the circuit will still conduct a current.

The negative (short) pin connects to the pin on the side (not the central pin) on the potentiometer. Take the short wire from the outside pin on the potentiometer and solder it to the middle of the LED. At the top of the pin, solder the 9V battery connector’s negative (black) wire.

On the positive pin, solder a connection to the NPN transistor’s Base pin (central pin). In the middle of the LED’s positive pin, solder the 3.3k resistor from the toggle switch.

Step 11: Anode and Cathode

Take the resistor end of the resistor/wire, already soldered to the outside pin on the toggle switch, and tighten it into the anode banana plug. You can tighten this without soldering, by using a lugnut. Just place the resistor’s wire against the first lugnut and tighten the second lugnut until it makes snug contact with the first lugnut.

Take the medium length insulated wire from the Collector pin on the NPN transistor and tighten it onto the cathode banana jack, using the same method outlined in the previous step.

Step 12: Testing Your tDCS Device

This phase requires a multimeter and a small jeweler’s Flathead screwdriver. Testing won’t take much time. You’ll notice that at the base of the electrode connector (where it plugs into the banana jacks), there are two holes. These can be used to test the electrical output of the device.

The Inthinkerator’s maximum output is 2 milliamps. I suggest turning the potentiometer’s dial all the way up to the right (clockwise) and measuring the output. If it falls outside of the specified 2mA, you must use the trim. potentiometer to fine-tune the output.

And You’re Done!

And there you have it! A completed tDCS device that cost around $10 to build. However, you won’t be able to use the Inthinkerator until you have suitable electrodes to attach it to your head. You can buy off-the-shelf electrodes or build your own. Keep in mind that saline-soaked sponges are the easiest to deploy, because they conduct through hair. However, if you would just like to experiment, gel-electrodes offer low-cost (and low reusability).

One DIY solution I found comes from (again) Reddit user Kulty, using some sponge cloth and aluminium mesh.

Electrode Placement

I won’t get into electrode placement, but one of the best websites for visualizing where the electrodes go is tDCSPlacements and Reddit/r/tDCS.

I should also note that some “montages” or electrode placements can cause serious health concerns for those suffering from brain abnormalities. If you have a history of epilepsy DO NOT use tDCS of any kind. If you have brain implants, such as metal plates, similarly: DO NOT use tDCS. It can kill you. Additionally, some parts of your brain may function at a reduced rate — particularly regions near the anode.

Let’s talk about tDCS in the comments – have you seen positive results? Has it made you feel anything unusual?

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