Why I Love tDCS and the New tDCS Device from SSD

Introduction: Why I Love tDCS

I’ve been involved with transcranial direct current stimulation (tDCS) research and application for almost three years now.  When I stumbled upon it, I could not believe (like most of you) that something so simple could do so much good. A 9-volt battery curing depression, relieving chronic pain, improving memory, speeding learning, and much more – really?!  It turns out to be true.

(The new SSD tDCS Device. see below)

I’ve provided information on tDCS to dozens of people (thousands via my blog) with an array of needs and interests who have had great success helping themselves improve their lives through tDCS.  I could provide many examples, but here is one to illustrate my point:

A woman, (friend of the family), came to me describing deep, debilitating depression – to the point of becoming suicidal. Normally I would immediately refer such a person to Dr. James Fugedy, a tDCS practitioner in Atlanta – as I am a PhD, not MD.  But she had already failed on other kinds of treatments via other doctors, including medication, talk therapy, and was at the end of her rope. She was very, very depressed – but wanted to get better – she just had no idea how to go about it.

I talked to her about tDCS and the published information that shows improvement for some challenging depression cases. I showed her how to use a tDCS device and where studies have shown electrodes should be placed for treating depression – but left it up to her to treat herself or not.  She immediately started once-a-day 25 minute tDCS sessions (1.5 mA). Within five days her mood had lifted greatly and I think she had moved out of the suicide danger zone. She continued daily tDCS treatments for the next four weeks. As she did so, her depression fully lifted. She recovered so well that she felt motivated to enroll in a technical school to learn a new skill – and in her classes scored the highest on all tests (a side-effect of the tDCS?)

She now lives a normal, happy life (yes – with its ups and downs like anyone.)

Seeing people get their lives back in such a simple way, with no debilitating side-effects, has made me a cheerleader for tDCS.

Does it work for everyone? It won’t work for everyone – but what treatment (or pill) does? My observation is that tDCS works for those motivated and willing to consistently use it in the way research studies have shown it should be used. tDCS in combination with talk-therapy seems particularly well suited to treating depression – which in many has its roots in a brain dysfunction – not evil-spirits, selfishness, or a bad attitude as some suggest. By modifying the firing potential of the neurons in key portions of the brain it seems real healing can be achieved.

Review: New tDCS Device from SSD

Super Specific Devices has released a tDCS device that might be just right for that DIY tDCS person on your holiday shopping list (perhaps yourself!) The new tDCS device is a well-built variant of a DIY tDCS design that has floated around the internet for about two years now.

The Super Specific Devices (SSD) device offers solid performance, based on a 9 volt battery, and provides a feature I consider nearly essential – a meter that allows you to verify the current being delivered during your tDCS session.  That is coupled with a potentiometer (dial) that allows you to vary current level, making it easy to set 1, 1.5, or 2 mA or anywhere in between.  The user can also gently ramp current up and down using the dial – so discomfort and phosphenes are reduced or eliminated.

(Jack on the side for standard TENS style electrode cables)

What Comes in the Box

The SSD tDCS device is fully assembled and comes with a starter set of stick-on electrodes, a couple of sponges, a connecting wire, basic instructions, and a headband. The unit does not come with a 9 volt battery or any sort of an application manual.  Like many of the US-based cottage-industry building tDCS devices, they leave it up to the purchaser to do their own research on the internet to decide what additional electrodes, electrode placements, etc. are appropriate to the purchaser’s situation.  The intent is probably to keep the company off of the FDA’s radar as the SSD (and similar devices) are not marketed as medical devices – nor does the company provide medical advice.


To use the SSD tDCS device, one needs to insert a 9 volt battery into the socket on the side of the unit, plug in and apply electrodes, and then use the power on-off switch and dial to operate the unit.  To start a session, the dial should be rotated fully counter-clockwise (minimum current) and then switched on. An LED indicator just above the on-off switch will light to show that power is on.  Assuming electrodes are in place, the user then begins rotating the dial clockwise, watching the meter for rising current level.  Note that due to skin resistance, there is a lag between dialing in a higher current level and that level actually being achieved.  It can take a couple minutes or more for current to rise to a set level and stop. An alternative is to turn the dial significantly clockwise and turn it back down as your desired current level is achieved.

On my sample unit, even with electrodes shorted and the dial set fully clockwise, the unit would not deliver more than about 2.7 mA. On the inside is an LM 334 current regulator and a series-connected current limiting diode that limits output current to 2.7 mA – as I found in my testing (good safety feature). This is a nice, simple, practical, current control setup that should prove reliable for many, many years.

(Good build quality. LM 334, CRD and resistors on small circuit board, solder joints were solid, wires nicely dressed.)

Another nice feature of the SSD tDCS device is having a jack on the side of the unit for electrode wire attachment – it’s the standard TENS size that lets you use a variety of connecting wires supplied by Amazon, medical supply houses, etc.

(Electrode wire jack and current adjustment knob can be seen here.)

What Would I Change?

I’ve built several tDCS devices using the same basic design of the SSD tDCS unit.  So I’m very familiar with use, operation, and limitations of this type of device – and I’m allowed to nit-pick.

First, let’s be clear – it’s my opinion that this unit will operate as described by the company and will provide clean, regulated DC current for most common tDCS scenarios.

I happen to prefer using a type 23a 12 volt battery in my tDCS device designs.  Why? 9 volts is sometimes insufficient to overcome losses in the electronics, electrodes, and skin to provide the desired 1, 1.5 or 2 mA used in tDCS sessions.  In fact, 9 volts will probably not be sufficient if one of the electrodes is located on the shoulder or arm for a montage you wish to use. Sometimes a 12 volt battery will barely do it – but the additional 3 volts really seems to help. The downside of the type 23a battery is they don’t last long (2 or 3 months is normal with a lot of use.) But they, like 9 volt batteries (which last much longer in a tDCS device) are cheap (Amazon, Ebay.) I’m betting SSD went for long battery life (and easy availability of cheap batteries) in their design criteria.

( 9 v battery socket on the side. Aesthetically, it would be nicer to locate it inside the roomy box.)

By the way, many “commercial grade” tDCS devices use a voltage boost circuit that can raise delivered voltage to between 60 and 80 volts – as needed – to overcome skin and electrode resistance (like foc.us, Activa Dose II, and others). These boost circuits sometimes add discomfort for the user, increase device cost significantly, and so are not present in lower price tDCS devices like the one from SSD.


If you are looking for a well-built, inexpensive, tDCS device that includes a lot of good features (meter, adjustability, good current regulation and protection, and more) then this might just be the unit for you (or someone you know.)  You’ll need to do your own research on tDCS, its appropriateness for your situation, tDCS safety, and the electrode placements that address your need.  See any of the following as a starting point:




www.pubmed.gov (search for tdcs)

…and Google search tDCS

The Super Specific Devices tDCS device sells for $90 at http://www.superspecificdevices.com/ Oddly it sells for a bit more on ebay.com (go to ebay, search for tDCS). SSD also sells the same unit with a digital display for $20 more if you prefer (at their web site and ebay).

Based on my evaluation and use of a sample unit, it’s my opinion that the SSD tDCS device (design, build, and features) is a good value.


The foc.us tDCS Headset, Part 2, Electrode Basics


(foc.us tDCS headset showing “built-on” electrodes and sponges)

Impressive – But…

I continue to be very impressed with the new foc.us tDCS headset.  It brings to the table a huge array of features in a package that is relatively user-friendly (and will become more-so when its iOS and Android apps are available.)  If your interest is learning enhancement or treatment of depression, the headset alone is probably all you need.  So far, I have found it easy to use and reliable.

The accessory kit adds capabilities for placing electrodes in other locations on the head and shoulders for treatment of chronic pain, experimenting with “savant” learning, and other research projects. In this blog post, I want to briefly summarize the basics of electrode use using the “built-on” and accessory electrodes. I have also included a summary of basic operation for those curious about using the headset (or those having trouble understanding the manual.)

Electrode Placement

The “built-on” electrodes place the anode above the left eye and high on the left forehead (two sponges.)  The cathode is in the same positions but on the right side.  These positions, while perhaps not “ideal” in the eyes of some are probably close enough to published locations for learning enhancement and depression treatment for many or most users.  For depression, some have a preference for moving the cathode off to the right shoulder, but that requires the accessory kit. The headset itself is quite capable and will probably satisfy the needs of most.

Using the External Electrodes

You have to give foc.us some applause.  They designed a LOT of capability in to a fairly inexpensive package.  This is the first really versatile tDCS device that has a clean, simple design, has high ease-of-use – and doesn’t cost a fortune as many other “commercial” offerings do.  tDCS is now within reach of many more who really need it! For those not satisfied with the built-on electrodes, you can do your own thing for special treatments or research with the accessory kit.  It includes necessary wires (and other items) along with a small number of “TENS” style stick-on electrodes.


(Cathode wire plugged into the back of the headset)

Important: The Wires

The kit includes a two-wire (anode & cathode) lead with good length, allowing placement pretty much as you see fit.  Uniquely, there is a single wire anode and single wire cathode included too. These are very useful when you want to use the built-on anode (or cathode) and have the opposite charge applied at a different location.  As mentioned, for depression, users may prefer the built-on anode, but want the cathode placed on the right shoulder.  The single cathode wire makes this simple to do.


(Leads plug in to the back of the headset)

CAUTION: Voltage continues to be available via the built-on electrodes even if one of the accessory leads is plugged in.  You will need to remove the appropriate sponges (cathode or anode) when using an accessory wire.  So for example, a person seeking to treat depression would leave the anode (left) sponges in place, remove the cathode sponges (right side), and then use the cathode wire to place an electrode on the right shoulder.

If you leave sponges out, you need to be VERY CAREFUL that skin cannot come in contact with the copper plate inside the sponge holder (from an odd skin-wrinkle or tag.) If it does, a burn could result. An accessory CAP of some kind would be a nice safety feature – to cover the unused sponge holders. Perhaps the iOS/Android apps will allow disabling unused built-on electrodes – we’ll have to wait and see.  Safety caps would still be a good idea.

CAUTION: The plus and minus marking on the anode and cathode leads is BARELY visible and could easily lead to an error.  I suggest MARKING the leads in some much more visible manner (I used red and black zip-ties for the purpose.)


(Can you see the minus sign on the back of the electrode clip?)


(You will want to clearly mark lead polarity. Zip ties work.)

Coming in Part 3

In my next blog post I’ll have more information on operation, use, electrode placements, and more.  Please feel free to send along any questions or comment.  I’ll try to address those in the next post or two.  brent@speakwisdom.com

FYI: Summary of Basic Operation

Make sure the headset is charged

  1. Switch in “W” position
  2. Green light indicates charging

Turn it ON

  1. Flick the switch to the “O” position
  2. Touch the sensor (center back of the headset) for TWO SECONDS to activate it
  3. If you touch the sensor for three seconds or longer, the headset enters pairing mode (fine if desired, otherwise, switch to “W” then back to “O” and return to 1. above.)

To BEGIN a tDCS Session Already Configured

  1. Touch the sensor ONCE
  2. A four second count-down begins (time to put the headset on!) Current then ramps up to the desired level (more below.)
  3. Current will automatically ramp down at the end of the session

To END a tDCS Session

  1. Touch the sensor
  2. Switch to the “W” position to turn off the headset

Changing Session Settings

Set Mode

  1. Turn the headset on (switch set to “O”)
  2. Hold the sensor for two seconds to activate the headset
  3. Tap the sensor TWICE
  4. The headset will cycle through its four modes
    1. DC Sine-Wave – Logo brightness will rise and fall over 5 seconds
    2. Constant DC (DEFAULT) – Logo remains on for 5 seconds
    3. Pulsed Current (0.5 mA min) – Logo brightens and dim in 5 seconds
    4. Random Noise (0.5 mA to max random) – Logo brightness changes erratically
  5. When the logo reaches the state you desire, touch the sensor ONCE

Current Setting

  1. Next, the Logo will glow for three seconds at each of the below. Press the Logo to select.
    1. 0.5
    2. 1.0
    3. 1.5
    4. 2.0 (Only settable for use with external electrodes)
  2. Once current is set, foc.us headset returns to the ready state. You can begin a tDCS session by touching the sensor ONCE or…

To Confirm Settings

  1. Touch the sensor THREE times and the above Logo displays will appear for confirmation.

Factory Reset

  1. Touch and hold the sensor for 30 seconds.

The New foc.us tDCS Headset, Part 1

Let the Healing Begin!

The long-awaited arrival of consumer-oriented tDCS devices has begun.  I received one of the first shipments of the innovative and interesting foc.us headsets (www.foc.us) and want to share with you my initial thoughts. Be prepared, there is a lot of ground to cover, so I will do it over a few shorter blog posts rather than one giant one. While marketed as a “gamer” accessory (probably to limit FDA flack), this headset offers great potential to those seeking a tDCS device to help with depression, enhanced learning, and more.


First, what the heck is tDCS? Transcranial Direct Current Stimulation is a ground-breaking technology that allows for simple, nearly side-effect free treatment of depression, chronic pain, enhancement of learning and memory, and more.  For more details on the basics of tDCS, please see the articles on my blog, www.speakwisdom.com.  I also suggest www.diytdcs.com and www.transcranialbrainstimulation.com.

The foc.us headset is not the first attempt to get a consumer-oriented (read user-friendly) tDCS device into the market. www.biocurrent.kit offers a less expensive, less-elegant, but very versatile solution for those seeking a tDCS device. There are also lots of do-it-yourself schematics and plans for tDCS devices available via the internet.  Your choices now boil down to a DIY device for about $50, the biocurrent kit for about $200, the foc.us headset for about $300, a repurposed iontophoresis device for about $350, or more expensive research devices ranging from about $500 to $5000!

Is the foc.us headset perfect? No! But it is a wonderful start to what will likely grow to become a “standard” as new features are added and annoying bugs are worked out.

Let’s start at the beginning! Unpacking!


(The larger box is the headset kit, the smaller is the optional accessory kit)

The foc.us headset arrives in an attractive and professionally prepared box. Inside is a travel and storage case containing the headset, sponges, USB charging cord, a small bottle for water, instructions, and foc.us stickers (ala Apple.)


(The case containing the foc.us headset and other essential items)


(The headset resting in its travel and storage case)

If you purchase the accessory kit, you receive a second smaller box containing electrode wires, some “TENS” style stick-on electrodes, a stand for your headset, some extra sponges for the headset, and a nice carry bag.


(The accessory kit)

Charge the Headset

Before you start fiddling, I suggest a good charge of the headset. Just plug the USB charger cord into the bottom of the headset and some convenient USB ac-adapter (or PC) and give it a couple of hours. Make sure the switch on the bottom is set to “W”.  Oddly the headset uses “O” for on and “W” for off.  First suggestion for version two – use the internationally recognized 1 and 0 for on and off.

Electrode Position

The comfortable and light headset has a “fixed” position for its electrodes. placing them on the forehead and upper forehead. The position selected by foc.us will be of interest to a large audience. Why? It happens to correspond nicely to an accepted location for treatment of depression (yes, there are others) and a position described in various studies for learning enhancement. Electrode placements not addressed by the headset itself are handled with the wire electrodes in the accessory kit. I’ll have much more on electrode placement later.

For the slightly technical, you will want to know that the left electrodes (sponges) are the ANODE and the right are the CATHODE.  Two electrodes on each side? Think of it as a way to have one larger sponge on each side covering more of the frontal lobe area.


For those who may have already been using a DIY tDCS device built around an LM334 or current limiting diode (CLD), you are in for a bit of a shock (almost literally).  The inverter circuitry of the foc.us headset allows voltage to rise as high as 60 volts (according to the specs) to overcome resistance between the anode and cathode.  I measured 65 volts between the electrodes with no load (head) in place. Dangerous? No, since current is limited to 2 mA.  But the charge can feel uncomfortable! Most DIY tDCS devices are built around a simple current limiting device so electrode voltage can never rise above that of the source battery – so no discomfort from a higher voltage – but they also need really good electrode to skin contact.

To avoid irritation, you’ll want to make sure your foc.us electrodes are wet (not dripping) and placed flat against your forehead and upper forehead.

Basic Operation

The included instruction manual does a good job of providing basic operating instructions.  It does not go into details of electrode placement, tDCS theory, etc.  That information can come from other sources.  The main operating control is a “touch button” on the back of the headset.  It allows setting treatment type, current level, and starting and stopping treatment sessions. Default session length is 10 minutes.

Much of the versatility in treatment customization will come via the iOS and Androids foc.us apps (not yet released as of this writing.)

Part 2 and Beyond

There is MUCH to cover about the foc.us headset.  I’ll discuss day-to-day operation, electrode placements, use of the iOS app (when it becomes available) and much more.  Stay tuned! You may find this is the tDCS device you have been waiting for!