Column: Thorndike

by Nathaniel Zhu

Building a Transcranial Direct-Current Stimulation Kit; a How-To
INTRODUCTION In 1801, Italian Physicist Giovanni Aldini’s research in transcranial administration of electric currents helped treat patients suffering from mental disorders. Today, transcranial direct-current stimulation has been used in similar applications as a way of enhancing the signaling between neurons. tDCS research has shown that rewards have no effect on behavioral outcomes. One can infer that in the studied tasks, tDCS inhibits the mechanism for conditioning behaviors; tDCS doesn’t care for consequences, and thus becomes an ideal device to treat addictions associated with reward-based behaviors. Due to its ability to enhance signaling, tDCS has also been used to increase memory and focus, creating the potential for mental expansion in otherwise healthy adults. With the construction of the device being a manageable task, and modern study’s typical use between 1 – 2 milliamps (mA) of current—a fairly safe range—homemade devices have become more prevalent. One need only to search YouTube, visit the subreddit for tDCS—which carries the blunt disclaimer: “1. Using a tDCS device safely requires (at minimum) a basic understanding of Ohm’s law and its implications. If you don’t understand why you can be killed by a 9-volt battery, you probably shouldn’t be tDCSing yourself,” or simply read ahead.

OBTAINING THE COMPONENTS Various equipment and supplies are required to solder a simple but functional version of a tDCS device. The device requires:

Multimeter Soldering iron Solder Perfboard 12-volt battery 12-volt battery case Switch Transistor (LM334Z) 600 Ohm resistor 3300 Ohm resistor 2 small sponges 2 2-foot insulated wires A pair of wire strippers Alligator Clips

PREPARATION Plug in the soldering iron and hot glue gun and allow both instruments to heat. Be careful not to touch the hot metal rod of the soldering iron. Place nearby for easy access.

INSERTING THE TRANSISTOR The transistor is the heart of the device. It allows for constant current flow from the battery. The constant current transistor used is the LM334Z, which can be purchased online. Samples may be obtained from A perfboard is the framework that all of the components will be mounted on and connected to. Obtain a rectangle of perfboard at least four inches length and two inches wide,
a larger board may also be used. A perfboard can be purchased at Radio Shack.

The LM334Z constant current source has three pins, a negative pin(V-), an adjacent pin(R), and a positive pin(V+).


Slide the current regulating transistor (LM334) into three holes on the perfboard. Allow space on the flat side of the transistor.


ADJUSTING THE TRANSISTOR'S CONSTANT CURRENT REGULATOR A resistor is used to adjust the current in the transistor. Place the two legs of the 33 Ohm resistor into two holes on the perfboard. The transistor has three pins, a positive(V+), adjacent pin(R), and negative(V-). The legs of the resistor should line up with the positive (V+) and adjacent(R) legs of the transistor. The positive pin and the adjacent pin need to be connected to the resistor to adjust the current output through the regulator.


Place a second resistor into two holes in front of the transistor making sure to line up the negative pin of the transistor (V-) to one of the legs of the resistor. Both sides of the resistor are equal so it does not matter which leg of the resistor is placed in front of the negative leg.


Flip the board over and bend the legs of the transistor and resistors so that the legs of the transistor and resistor are touching. At this point, you should have three connected legs and two unconnected legs.


To make a more permanent connection, use the soldering iron to solder the three legs together. This is done by melting solder metal onto the soldering iron and then rubbing the melted metal so that it touches both legs of the connection. When the soldering iron is removed, the metal will cool and solidify into a solid connection.

ATTACHING THE BATTERY A 12-volt battery powers the device. The battery is mounted in a 12-volt battery case. A hot glue gun is used to glue the battery holder onto the perf board.


CONNECTING THE SWITCH A switch is a very simply component that opens and closes a circuit. In this project, a switch can be placed anywhere in the entire circuit. A switch typically contains two legs. Glue the switch onto the perfboard. Now, pick any wire currently attached to the board—preferably one that is easy to access such as the negative wire (black wire) pictured—and cut in half. Then, simply solder each half of the wire onto the pins on the switch to recomplete the circuit.


FINISHING THE DEVICE If every step has been completed successfully, you should have only two unconnected wires. Those wires will be attached to a sponge and placed on the skull. It is not advisable to perform this action without proper measurements.


TESTING THE DEVICE Touch the leads of the multimeter onto both sponges. If the current reading is between 1 mA – 2 mA, the device is functioning within the safe zone of electrical current.

CONCLUSION The Air Force has used tDCS to halve the time it takes to train drone pilots. DARPA (Defense Advanced Research Projects Agency) has used tDCS to accelerate the training of snipers. Indeed, the effects of tDCS are extensive and vary depending on the part of that brain being stimulated.

I use this device to enhance my memory and attention. My goal is to eradicate human diseases (including heart disease, Alzheimer’s, and cancer) to enhance human health and lifespan. Such a feat would require the acquisition of an extensive body of knowledge about medicine, nanotechnology, biochemistry, genetics, biology, and computer science amongst others. Anodal stimulation of the dorsolateral prefrontal cortex provides a memory/attention boost after 13 minutes of use that lasts a few hours. Like any medical practice, moderation is key. Too little stimulation, and the effect wears off immediately. Too long a stimulation may result in headaches and reduced effect—and of course, there’s the death by 9-volt battery thing.

Title: From God’s mirror - lost in sky. Photographer: Mária Švarbová /Aria Baro.