Step 1: Overview

First instructable! I hope it is good.

In this instructable, I will show you how to make and use a "brain cap" a tDCS device that can be worn while it is being used. tDCS stands for transcranial direct current stimulation, a form of brain stimulation involving direct current (aka a battery) that can be used to treat depression, chronic pain, and other illnesses as well as reduce time needed to learn certain tasks. It does so by passing a small electrical current through the skull, which stimulates a certain patch of neurons. Don't worry, tDCS is completely safe; it only produces 2mA of current. To learn more, I would suggest searching "tDCS" in your browser since there are a lot of good articles on it online.

Step 2: Safety

Before we get started building, let's go over some safety. Though tDCS is very safe, it can be dangerous if built or used improperly. Don'ts are ordered from highest to lowest amount of danger.
-Never use a power source that isn't a 9 volt battery. You run the risk of exposure to a high current, which can be life-threatening.
-A 5mA fuse is part of the list of materials. Though it is not required for the circuit to work, it is HIGHLY RECOMMENDED! Currents over 5mA can be harmful if not deadly.
-Do NOT use tDCS for more than 30 minutes at a time. Doing so isn't necessarily hazardous, but you may get a headache.

Step 3: Materials

Below is a list of materials, where to get them, and what their price is.

For the Circuit:
-LM334Z Voltage Regulator $4.25
http://www.amazon.com/gp/aw/d/B00B5LUIW8/ref=mp_s_a_1_1?qid=1399344204&sr=8-1&pi=SX200_QL40
-33 Ohm Resistor $1.50
http://www.radioshack.com/product/index.jsp?productId=2062312
-9 Volt Battery $18.00
http://www.amazon.com/gp/aw/d/B002UGVWA4?pc_redir=1399207041&robot_redir=1
-5 milliAmp Fuse $27.00
http://www.digikey.com/product-detail/en/0279.005V/F5932-ND/553339
-Wires $6.00
http://www.adafruit.com/products/153
-Toggle Switch $4.00
http://www.radioshack.com/product/index.jsp?productId=2062494
-Battery Clip $3.00
http://www.amazon.com/gp/aw/d/B0002ZPFU8?pc_redir=1399183008&robot_redir=1
-Breadboard $4.00
http://www.amazon.com/gp/aw/d/B0040Z1ERO?pc_redir=1399146396&robot_redir=1
-2 Amrex sponges $10
http://www.amazon.com/gp/aw/d/B0008E95CM?pc_redir=1398139315&robot_redir=1
-Solder

For the Hat
-Superglue $8.00
http://www.amazon.com/gp/aw/d/B000LGPD64?pc_redir=1399228787&robot_redir=1
-Baseball Cap $15.00
http://www.amazon.com/gp/aw/d/B00F0RP8BY/ref=mp_s_a_1_1?qid=1399343407&sr=1-1&pi=SX200_QL40
-Velcro $9.00
http://www.amazon.com/gp/aw/d/B00347A8GM?pc_redir=1399193548&robot_redir=1
-A small platform to mount the circuit (optional, so no price or seller listed)

For Construction and Operation
-Soldering Iron $10.00 http://www.amazon.com/gp/aw/d/B0006NGZK0?pc_redir=1399143411&robot_redir=1
-Syringe $4.00
http://m.cvs.com/mt/www.cvs.com/shop/product-detail/CVS-Childrens-Easy-Syringe?skuId=916633
-Multimeter $16.00
http://www.amazon.com/gp/aw/d/B001O1X65A/ref=mp_s_a_1_2?qid=1399353162&sr=1-2&pi=SY200_QL40
-Measuring Tape

For Each Use
-Water (from the tap)
-Salt (regular table salt)

Some of these materials you may already have; that should cut the cost of this project. Also note that I did not use some of the products that I linked to to make my device.

Step 4: Constructing the Circuit

Start with the breadboard. You can use Velcro or another method to put it onto the baseball cap or a mounting platform. (Shown in the photo) If so, be sure you will be able to Remove it later when constructing the hat. Add Velcro to the mounting platform or directly to the baseball cap for the battery.

Step 5:

Attach the positive and negative leads from the battery clip into their respective holes in the breadboard. Attach Velcro to the battery.

Step 6:

Attach the 5mA fuse to the breadboard from the negative power source to a space on the breadboard where shown in the picture. Attach a wire to the top of the breadboard connecting the positive power source to the another space on the breadboard.

Step 7:

Attach the 33 Ohm resistor right below the wire that was attached in the photo before so that it takes up the 2 holes under it.

Step 8:

Add the LM334Z Voltage Regulator to the circuit so that it is in the correct orientation as seen in the photo. Make sure the flat side of the voltage regulator is facing the resistor.

Step 9:

Before continuing the circuit, we need to do a bit of soldering.

Time to take out the Amrex Sponges. Attach a long wire to the 2 aluminum electrodes. Then solder the two together using a soldering iron. From experience, it can be difficult to solder them; I recommend wrapping the wire around the electrode a few times as seen in the photo and then soldering.

Step 10:

Now to set up the switch. Depending on your type of switch, you may need to deviate from these instructions slightly.

Attach the rubber pads to the 2 electrodes.

Attach 3 wires to the switch as shown in the picture. This can be done by unscrewing the screws and wrapping the end of the wires around the screw and screwed them back in place. The long wire should be one of the two soldered to the electrode. This is the anode. The toggle switch should be able to switch between both smaller wires.

Step 11:

Add the switch to the circuit. One of the two wires should be attached to the hole to the left of the resistor as shown in the picture. Attach the other wire to some other place on the circuit that is not connected to anything.

Step 12:

Attach the other wire connected to the electrode to the hole on the left of the 5 mA fuse. This is the cathode.
Put the battery on the Velcro.

Step 13:

The circuitry is now finished. Use the multimeter to check whether 2mA of current are being produced when the switched is turned on. If not, recheck the previous steps to see if everything was wired correctly.

After making sure the circuit works, add the sponges to the electrodes.

Then, add superglue to the 2 wires in the photo in order to make sure that the circuit stays more intact with wear in tear.

Step 14: Hat Construction

In order to effectively use the tDCS device, you will need to know where to position it. In order to do so, we will be using the 10/20 positioning system. Put on the hat and use the instructions in this link (http://www.trans-cranial.com/local/manuals/10_20_pos_man_v1_0_pdf.pdf)
to find out where each electrode position is. It may be helpful to get another person to make note of where each position is.

After that is noted, add Velcro to the areas on the hat corresponding to where each position is. You may need to add superglue to make sure they are strongly bonded to the hat. Then add Velcro to the backs of the sponge electrodes.

Now mount the circuit to the baseball cap. Make sure it can fit comfortably on your head.

Step 15: Hat Operation

Congratulations! You have finished construction!

In order to operate the brain cap, be sure to wet the sponge electrodes with a conductive salt solution. The best way to do this is with a syringe.

After the sponges are wet, decide which montage you would like to use (see photo from getlimitless.com and link at bottom of the page) and attach the electrodes to the Velcro where you need to position it. Note the positions of the anode and cathode.

Make sure to switch the circuit off when not in use and turn it on only when both electrodes are on your head. You should feel an itching sensation when it is on. Remember to only use it for 20-30 minutes at a time per montage.

See http://speakwisdom.wordpress.com/2013/08/31/the-foc-us-tdcs-headset-review-part-4-electrode-placements/
And
http://speakwisdom.wordpress.com/2012/09/22/tdcs-putting-it-all-together/
For tDCS positions.

Enjoy and thanks for reading!