Introduction

I am so pleased that an assortment of excellent tDCS* devices is now reaching the market – making the benefits of tDCS available to more and more people worldwide. The range of devices is impressive – from simple and cheap to expensive and very sophisticated.

I won’t take the time or space here to detail all the potential benefits of tDCS or why you should consider obtaining a device – but suffice it to say that millions of people could dramatically improve their lives with tDCS. tDCS can be used to treat depression, chronic pain, enhance memory, and much more. See the web sites I list below as a good starting point for more information on tDCS.

(Apex Type A Main Unit)

The Apex Type A

The Apex type A “Adjustable Direct Current Generator” is a low priced but well-built device that uses a classic tDCS design that includes a 9 volt battery, an LM334 current regulator, a programming resistor to limit delivered current to about 2 mA and a meter to monitor current delivered. This design (and variations) have been used by do-it-yourselfers for years (I’ve built several myself) and has proven to be very reliable, simple, and safe.

Apex saves you the considerable time and trouble to locate all the parts to build your own device by manufacturing a solid unit that looks like it will last for many years. The base unit alone sells for about $99 and a complete kit including head-band, electrodes, wires, etc. is about $139 (plus shipping).

Apex kit
(Apex Type A and accessories – from the Apexdevice.net web site)

As with most other tDCS device manufacturers, Apex does not provide medical advice, information about which tDCS electrode placements will work for you, etc. They leave it up to you to do your homework by reading the considerable about of material available online (see example links below) to decide if tDCS is right for you and what treatment method will work best.

The Apex Type A comes with a well written user guide that takes the user step-by-step through installing a 9 volt battery, connecting wires and electrodes, and running a simple test to see that the unit is working as it should. There are two controls and two indicators on the type A:

On-off switch: clearly marked
Current adjustment dial: clockwise rotation raises current, the opposite to reduce current
Indicator LED: glows blue when the unit is turned on
Meter: I consider this almost a must-have in a consumer tDCS device. It clearly shows the amount of current being delivered during a tDCS session.

It’s also worth noting that the Apex Type A allows for the simultaneous connection of two sets of electrodes. Most users would rarely if ever do this – and it’s important to remember that device output current (max 2 mA) will divide between the sets of electrodes (probably not evenly – due to different resistance through the head at different locations.)

Testing and Use

As I mentioned above, I’m very familiar with the classic design of the Apex Type A and can say that the device performed exactly as expected – delivering a clean, DC current at a maximum of 2 mA (depending on dial setting.)

Construction

As you can see from the photos of the inside of the unit, build quality is very high. All solder joints are well-made and clean, and mechanical attachment of the circuit board, controls, etc. is very solid. Some may object to the use of hand-assembly / perf-board instead of machine assembly / printed circuit board – and I might too except that the electronics of this classic design are very simple and as you can see involve only six solder joints on the circuit board itself. As long as Apex continues good quality control and inspection procedures, this method of construction is perfectly fine.

(Construction is simple and solid.)

(Assembly is neat and well done.

Is 9 Volts Enough?

As far as a tDCS device is concerned, a human head is nothing but a big, liquid filled resistor. All the device does is try its best to deliver a consistent, stable one to two milliamps to cause the desired treatment effect. 9 volts is about the minimum that can reliably deliver the desired current level given circuit, hair, skin, etc. resistance that does it’s best to limit current flow. Many commercial tDCS devices use 12 or 18 volts – some go as high as 80 volts! The higher voltages make it easier to overcome higher resistance (for example if one electrode is on the forehead and one on the shoulder). But the higher the voltage, the more opportunity there is for a painful (if not dangerous) experience if something goes wrong. So many of the simpler tDCS devices elect to use a single 9 volt battery (or sometimes two in series).

Given the low voltage of the Apex Type A, it is very important that you do at least the following to make sure your treatment current is as you select:

Use saline water and sponge electrodes (you can make your own saline and sponge electrodes if you like)
Get the sponges really wet, then squeeze them out a bit (you don’t want water dripping down your head)
Use a good head-band. Your head-band will need to be tight – not uncomfortably so, but tight

(Controls are simple and work well. This is a Type A set for maximum current, with a new battery and shorted anode and cathode leads. Note the maximum current of about 2 mA.)

When you start a tDCS session, expect current to rise slowly (over two or three minutes) as your scalp or skin gets wetter. You may find it desirable to adjust the current control on the Apex Type A once or twice during your tDCS session.

Finally

Apex does a nice job of providing a simple, reliable, well-built tDCS device that will do exactly what it is supposed to do – provide clean 1 to 2 mA DC for your tDCS application. They provide good operation instructions with the device and have a wide array of backup material on their web site. Well done Apex!