Time to Take Another Look At foc.us tDCS and more

History

About two years ago foc.us burst on the do-it-yourself tDCS scene with a headset marketed to “gamers” – claiming to offer improved game performance (higher scores).  A few folks like myself recognized the foc.us headset (V1) for what it was – a remarkable, capable tDCS device that could be used for ANY tDCS related purpose including treating depression, chronic pain, enhancing memory, etc. – and yes, improving game scores!  The V1 headset was truly a leap beyond anything else available to the DIY community offering an all-in-one headset that could be controlled via Bluetooth, offered built-on and external electrodes, all in a very nicely designed package.

(Famous or infamous foc.us V1 ad campaign)

Critics quickly emerged, as they often do, describing customer relations related problems with foc.us – many justified, and technical issues with the product – many unjustified.  It seemed foc.us was surprised by their own success and unprepared for the order volume and normal support requirements of such a leading edge product. By the time foc.us got its organizational problems resolved, the V1 was winding down and the company was preparing to launch the V2.

The foc.us V2

Several months ago, Transcranial Ltd. launched it’s new foc.us tDCS product, the V2. It, like the V1, sets a  high bar for the DIY tDCS market. In a tiny package easily small enough to misplace with your car-keys, foc.us engineers included all of the technical features of the V1, plus the added versatility of upgradeable firmware (new features), display screen with scrollable selection, redesigned and industry leading headsets, the ability to use 3^rd party headsets and related accessories, and more!

(The foc.us V2. Tiny! Awesome!)

Interestingly, foc.us via their advertising, now seems to recognize the value of their technology for what it is, a real cranial stimulation device – not just for gamers – but for anyone seeking the benefits of tDCS and more.

(The V2 ad campaign is more general – making clearer the broad capabilities of the V2.)

Since my initial posting about the V2 (see http://bit.ly/1Jilfpg ) Transcranial Ltd. has upgraded the feature set of the V2 in significant ways!  The V2 now supports tDCS, tACS, tPCS, and tRNS as well an upgraded application for Android devices and soon iOS. The V2 can no longer be referred to as just a tDCS device – it’s now a fully capable, research grade, cranial stimulation device!

It’s a Software World Now!

If you purchase a V2 (or own one now), you may wish to update its firmware periodically to take advantage of new features.  Here are some key steps:

1. Go to the foc.us web site and create an account: https://www.foc.us/customer/account/login/
2. Log in with the account
3. Connect your V2 doc to your capable PC (or Mac)
4. On the left of your screen (once logged in), select “My Downloadable Products”
5. Click the “Microsoft Software” (or Mac) download button and install
6. Run the installed application and allow it to check and upgrade your V2 to the latest firmware

Apps

An Android app is available (search for wave tdcs in the store.) An iOS app for the V2 is due anytime (the old V1 app does not seem to work with the current V2 firmware.) I will say that the on-screen display of the foc.us V2 is so good and so versatile that I’m not convinced that the apps currently add much value. Transcranial Ltd. is soon to release a EEG capability called “Quantum” that will apparently link to the V2 – and will probably make the apps very functional and important to use.

(foc.us Android app)

Anyway, you must pair the foc.us device to your Android or iOS device to use an app. Here are normal pairing procedures:

1. Make sure Bluetooth is turned on on your Android or iOS device
2. Turn on the foc.us V2 and scroll to Settings, Bluetooth, and make sure Bluetooth is On.
3. Very quickly your handheld device should find the foc.us device and request you type in a code number that you will find displayed on the foc.us device. Do that and you are ready to go!
4. Run the foc.us app, set the desired mode (tDCS, etc.), max voltage (20 is typically fine), current (1 to 2 mA), time (typically 20-25 minutes), sham should be off, and START

I’ve noticed that the Android app does not display remaining session time.  You can see it easily on the foc.us device by tapping the blue joystick.

More Detailed Instructions?

Like most tDCS vendors, Transcranial Ltd. is trying to stay off of the FDA’s radar by making it clear that they are not producing a medical device – so they shy away from writing application guides and notes. This frustrates some. Users are left to their own creativity to learn how to properly use and get full advantage from a foc.us device (V1 or V2). To help V1 headset users, I wrote a pretty detailed set of instructions ( see http://bit.ly/1FSf6wb ) that seem to be popular.  Would you like an equally detailed set of instructions for the V2? Let me know – if there is sufficient interest I’ll be happy to put that together.

Finally, I’ve taken a good bit of heat via email and blogs for being a fan of foc.us. Unlike some, I saw very early on that their unique product(s), if used correctly, could be used to improve the lives of many – and that has turned out to be true. Foc.us continues to be one of my favorites in the world of tDCS and cranial stimulation and I, for one, anxiously await their next DIY leading-edge products and the pace they set for the industry.

I look forward to your comments and questions.

Brent

brent@speakwisdom.com

Notes:
1. Photos in this blog are from the internet and include images from foc.us and speakwisdom
2. If you are new to tDCS, please read and study carefully before taking any action related to tDCS or any cranial stimulation technology.  I suggest as a starting point:
a. speakwisdom.wordpress.com/tdcs/
b. diytdcs.com
c. www.reddit.com/r/tdcs
d. http://www.pubmed.gov (search for tDCS)

Advertisement

Summer is Here! Time for The Brain Stimulator Travel Model!

(The Brain Stimulator Travel Model shown with available electrodes, wires, and headband. The tDCS module itself is very small and easy to transport.)

I am a longtime fan and proponent of tDCS.  There is plenty of evidence that this simple, safe, technology can be used to reduce or eliminate depression, treat chronic pain (including migraine headaches), enhance memory and learning, and more!  If you are new to tDCS, take a look at the index of tDCS articles I’ve posted at https://speakwisdom.wordpress.com/tdcs/

If you are looking for a high quality tDCS device that also happens to be ideal for summer travel, you should consider “The Brain Stimulator Travel Model”.  This is a well-built, basic, tDCS device that can deliver 1 or 2 mA with the flick of a switch and can stand-up to being repeatedly tossed into a suit-case or travel bag, jostled around, and still come out ready to go and deliver a reliable tDCS session.  Depending on the configuration you buy, it can cost as little as $55 – or a bit more with high quality electrodes and other accessories.

The Brain Stimulator Travel Model also makes an excellent first tDCS device or a supplemental device if you already own something more sophisticated.  It is built by JD Leadam and his team at Neurolectrics – real pioneers in the DIY tDCS marketplace.

 

(The packaging of the devices is simple, neat, and able to withstand travel related abuse.)

Neurolectics used a tried and true design built around a current regulator and a 9 volt battery. It’s simple, safe, and reliable – but because a 9 volt battery is used as its energy source, it is very important that sponge-electrodes be used and that they be well wetted with a saline solution in order to assure delivery of 1 or 2 mA (depending on switch setting).

I always prefer that a DIY tDCS device have some monitoring capability (digital or analog meter) to assure that the desired current level is being delivered. Neurolectrics chose not to take that path with this device – I assume to keep cost at a minimum and the package as small as possible.  If you are a frequent tDCS user, I’d suggest changing the 9 volt battery every couple of months – and again – be sure to use well wetted sponge electrodes to help assure you receive the selected stimulation level.

(Neurolectrics places all significant components on a nicely manufactured PC board. This limits point-to-point wiring and makes for a more reliable device – important for a travel device.)

The Brain Stimulator Travel Model could not be easier to use!  Simply wet the electrode sponges, place the electrodes as desired with a headband, flip the switch to 1 or 2 mA, and begin timing your tDCS session (20 to 25 minutes is typical.) When done, switch off the device, take off and stow the electrodes and you are done.  If you really are traveling with the device, I suggest you remove the sponges from the electrode shells and place them in a small water-tight container.  You should also wash them frequently with good soap and plenty of water to prevent anything undesirable from growing in them!

I’ve taken several trips (including through airports and airport security) with the The Brain Stimulator Travel Model and found it to be quite handy for personal use and for demonstrating tDCS as seminars.  Don’t expect any flashing lights or fancy meter with this unit.  It’s basic tDCS – and it works.

Visit the Neurolectics website at https://thebrainstimulator.net/

I welcome your comments and questions.

Brent

 

 

Interview: JD Leadam, Neurolectrics

Here’s a chance to meet the founder and CEO of Neurolectrics – the creator of the BrainStimulator and the BrainStimulator Travel Model.  JD is a true pioneer in the DIY tDCS field and I hope you will find this podcast to be interesting and informative.

Click HERE to listen or download the mp3.  Total length is about 27 minutes, 12.5 MB

JD’s web site is HERE

Enjoy!

THE ROADMAP TO tDCS SUCCESS

Transcranial Direct Current Stimulation (tDCS) is a relatively new technology for treating illnesses like depression, chronic pain (and more) and for enhancing memory, creativity, and various kinds of learning. tDCS is simple, safe (according to current studies), and involves equipment and techniques that are available to almost anyone willing to put in the effort required to learn to use it correctly.

This article is designed to provide a roadmap to successful and safe use of tDCS and so points to a number of references that should be reviewed before any attempt at using tDCS is made. If you will carefully examine the items listed below, you will be much better informed as you make decisions about tDCS and its appropriateness for you and your situation.

1. What is tDCS and How Does it Work?

If you want to understand tDCS and what it is all about, you have to dig a little.

Start with the basics: https://speakwisdom.wordpress.com/2013/11/05/can-a-9-volt-battery-save-a-life-even-yours/

Please watch this video:
Prof. Vince Clark from UC Davis tDCS Summit 2013: https://www.youtube.com/watch?v=dUMUIXNeBRQ

Then read this article (it’s a bit dense, but get what you can):
Transcranial DC Stimulation by Dave Siever, CET: https://www.mindalive.com/1_0/article%2011.pdf

You should also review these safety standards:
tDCS Safety Standards: https://speakwisdom.wordpress.com/2013/10/31/diy-tdcs-code-of-safety/

2. Pick a tDCS Device

You have two choices – either build your own tDCS device or buy a commercial unit.

Build it Yourself

A Simple tDCS Design: https://speakwisdom.wordpress.com/2013/04/02/a-very-simple-current-regulated-tdcs-device/

Or a little more sophisticated device: https://speakwisdom.wordpress.com/2013/02/10/user-built-tdcs-research-device/

Buy a tDCS Device

Very Simple, Inexpensive: www.tdcs-kit.com (review at http://www.speakwisdom.com )

Also simple and inexpensive: http://thebrainstimulator.net/

The foc.us headset is sophisticated and capable: www.foc.us (I have a series of review articles on the foc.us headset at http://www.speakwisdom.com.)

Another very capable tDCS Device: www.trans-cranial.com

The ActivaDose II is very popular. Technically it is an iontophoresis device but can be used for tDCS: http://www.scriphessco.com/products/activa-activadose-ii-iontophoresis-device/

Electrodes

Look carefully at the electrodes that are (or are not) supplied with the tDCS device you purchase. The foc.us headset, for example, includes electrode sponges and is ready to go. Other suppliers provide stick-on electrodes which are generally not preferred. Most tDCS users and researchers have adopted reusable 3×3 sponge electrodes as a starting point. Amrex is a popular brand and is sold widely (including on Amazon.com). The Amrex sponges use a “banana” plug for connection. As such, you may need an adapter to go from your tDCS device to the Amrex sponges. Most medical suppliers carry adapters (www.scriphessco.com for example) or your tDCS device supplier may have them.

3. USING A tDCS DEVICE

As already mentioned, tDCS can be used to treat an assortment of illnesses or can be used to speed learning, improve memory, enhance creativity and more. Check these links for information on the “montage” that best suits your needs.

General Electrode Placement: http://www.jove.com/video/2744/electrode-positioning-montage-transcranial-direct-current

General Electrode Placements for learning, memory, depression, savant learning, and chronic pain: https://speakwisdom.wordpress.com/2013/08/31/the-foc-us-tdcs-headset-review-part-4-electrode-placements/

Depression: https://speakwisdom.wordpress.com/2012/12/06/area-25-is-way-more-important-than-area-51/

Depression: https://speakwisdom.wordpress.com/2013/03/23/4-inthe-youtube-series-treating-depression-with-tdcs/

Researchers generally start with a treatment time of 20 minutes once per day for up to five days per week. A current level of 1 mA is suggested while you adapt to the scalp tingle that tDCS may create. 2 mA is generally too high for beginners and can cause considerable discomfort.

4. FINAL NOTES

tDCS is a new and developing area of research. You should use due caution when attempting anything related to tDCS. Better, seek out a medical professional for tDCS guidance and assistance. In Atlanta, www.transcranialbrainstimulation.com is a great resource. You should also monitor multiple tDCS information resources such as www.pubmed.gov (search for tDCS), www.diytdcs.com, www.reddit.com/r/tDCS/ , and Google.

I hope you find the information contained in this article useful and will visit all of the postings I have on http://www.speakwisdom.com.

 

 

 

 

 

Thoughts on the Use of tDCS in Education Settings

Why the Interest in tDCS?

Research studies and anecdotal evidence show that tDCS, a simple and safe way to stimulate the brain, does have the ability to enhance memory, speed learning, improve physical skill, and enhance creativity.  There are now well over 1,000 published studies of tDCS with more underway and research participation of institutions ranging from Harvard Medical, MIT, Emory University, to the University of Alabama and dozens more.

(tDCS headset. http://www.foc.us)

Already, high-school and college students are catching on to just what tDCS may do for them.  There are many YouTube and blog posts from and by students discussing their experience with tDCS and others asking for help in setting up and using a tDCS device.  Some indicate substantial improvement in their performance with tDCS. As tDCS devices become more accessible and word of it continues to spread through popular press and internet resources (NYT, Nature, Scientific American and many others have already published tDCS articles), educators can eventually expect to be confronted with some significant ethical and policy questions.

While it’s difficult to pin-down an exact percentage improvement students see in their work, (more studies are required), students use words like “significant”, “substantial”, and “surprising” in their comments. As time goes on, not only will more students demand access to tDCS, it is likely that parents, seeking greater success for their children, will encourage its use.

How Might tDCS Be Used by Students

• During study for tests – including high-stakes (SAT, etc.)
• Learning lists of material (names, dates, places, events, etc.)
• Learning new languages (spoken and written)
• Improving athletic skill
• Enhancing creativity in writing, art, film production, etc.
• To reduce or eliminate depression (a common problem in student populations)

Ethical Issues

Educators must face the reality that certain students will “brain boost” using tDCS and by doing so, improve their classroom performance as well as on assorted tests that are common in education settings. Even “high-stakes” test outcome could be positively influenced for students making proper use of tDCS. Student athletes may use tDCS to improve their performance on the tennis court or football field.

• If a student using tDCS for study can perform 10% better on an SAT test than an equally talented student who does not possess a tDCS device, is there a fairness or ethical issue?
• If a student has a learning disability and through the use of tDCS is able to perform at “non-disability” levels, is there a fairness or ethical issue?
• Will we now enter a new era of “haves and have not’s” in K-12 and higher-education learning?
• Will students from middle-class and above families, able to afford a device and related training, take advantage of it while lower income, less advantaged students will go without?

If tDCS, well used, can improve test scores, is that not ultimately going to be very significant in the lives of some students?

(George Mason University)

Policy Questions

If tDCS is going to play some role in the lives of K-12 and higher ed students in the coming years, then perhaps it’s time to begin creating policy to address tDCS – including:

1. Will tDCS use be permitted (even though it will be impossible to regulate home use)?
2. Will students be trained in proper tDCS use in school? (or after school)
3. Will schools provide tDCS devices for students when the family cannot afford it?
4. Will schools encourage tDCS as a means to improve test scores?
5. Will school clinics offer tDCS treatments for those suffering with depression (rather than medicate them?)
6. Will legal liability issues limit the ability of schools to responsibly encourage and direct the use of tDCS in education settings?

tDCS is a wonderful thing! It has the potential to help the human condition on so many levels – from depression to Parkinson’s disease, with learning enhancements thrown in as a bonus. How will we, as educators, respond to this fascinating new capability – which students have already discovered?

Let the dialog begin!

Contact me via brent@speakwisdom.com

For more information on tDCS see www.speakwisdom.com, http://www.diytdcs.com, http://www.transcranialbrainstimulation.com, http://www.pubmed.gov, and Google!

DIY tDCS Safety Standards

The do-it-yourself transcranial direct current stimulation (DIY tDCS) community is growing in numbers and sophistication – particularly as new studies are published and tDCS devices emerge in the marketplace.  It may be time to be a bit more proactive in providing safety information to many who will become curious enough about tDCS to want to try it.

I’d like to propose DIY tDCS Safety Standards (better name welcome).  Below is a draft for your comment.  Perhaps if we can get some agreement on content and wording, those of us who publish tDCS blogs and websites as well as vendors could consider posting it somewhere on their site.

By proposing this code of safety, I’m not encouraging anyone to try tDCS, but I know it’s happening – so guidance is appropriate and necessary.

DRAFT DRAFT DRAFT (Your comments welcome. I’ll repost blog this as I edit it with your suggestions.)

As a potential or current do-it-yourself tDCS user I agree to the following:

1.   I will, if reasonably possible, seek out a medical professional for tDCS advice, treatments and follow-up.

2.   If I have cranial scar tissue, an implant, or other unusual medical condition, I will seek clearance from my doctor before using tDCS. If I have a seizure disorder I will refrain from using tDCS or use it only under direct supervision of qualified medical personnel.

3.   I will not, under any circumstances, directly connect a battery to my head. I understand that I could greatly exceed the maximum 2 mA current limit used by tDCS researchers, possibly harming myself in the process.

4.   I understand that electronic components can fail unpredictably. For this reason, I will never plug a tDCS device directly or indirectly into an electrical outlet. I understand that by doing so a simple component failure could result in death (or worse).

4a. If I do not have a solid understanding of electrical and electronic concepts, components, and procedures, I will not attempt to build a tDCS device.

5.   I will not exceed 30 minutes in a tDCS session. This is the maximum used in tDCS research. I will use the “buddy system” and never proceed with a tDCS session without someone else present who is familiar with the shutdown process for my tDCS device – or who can at least remove electrodes and summon additional help should that be necessary.

6.   I will use some means to verify the current level being produced by my tDCS device. This could be from a built-in ammeter or an external digital volt meter (DVM). I will never exceed the 2 mA limit used by tDCS researchers.

7.   I will use electrode placements that have been studied and published by respected researchers and not simply guess or experiment with electrode placement. I will do my best to stay abreast of tDCS research and development.

8.   If I detect any undesirable effect from tDCS, I will immediately cease use until the cause is clearly understood and corrected.

9.   I will not experiment on friends, family, associates, or others. It is up to each individual to read, research, and understand the risks, benefits, and limitations of tDCS and make their own decision about its appropriateness to their situation, preferably in consultation with a medical professional. I will never use tDCS on children or animals.

10. I understand that, with regard to DIY tDCS and any actions I might take, I am responsible for my own well-being and above all else, safety and wise decisions will be my primary concerns.

tDCS – Thoughts on Safety for the Amateur

Introduction

According to various reports and studies that can be read on the web, tDCS has potential to help with a wide array of brain-related maladies including depression, fibromyalgia, learning disability, and much more. It has also been shown to improve comprehension, learning speed, and more, making it attractive to students and professionals. Press articles have added fuel to the fire of public awareness by discussing how simple tDCS is and potential benefits it brings with little or no risk.

(YouTube, WorldNews, etc.)

A number of enterprising individuals have taken to building their own tDCS devices – some with little or no understanding of what they are doing. Viewing a few YouTube videos and blog posts about tDCS will quickly convince one that there is an information gap that needs to be filled before someone gets hurt.

I am not recommending anyone try building their own tDCS via this post. But the fact is many people are building them and hopefully this post will clarify what tDCS systems are all about.

In this post, I want to review a few of the more popular tDCS designs that are floating around the web and comment on them with a focus on safety.

tDCS Quick Review
tDCS involves passing a very low current (typically 1 milliamp, 1 ma) through the head for 20 minutes, once per day, for 30 or 60 days. Where the current is applied and for how long is varied by the treatment effect desired (called a montage.)

There are plenty of articles about the details of tDCS treatment on the web. Start with transcranialbrainstimulation.com as a good entry point.

tDCS Device Safety
1. If at all possible, seek out a professional for tDCS treatments. Though a bit rare right now, they are out there.

2. Do not, under any circumstances, directly connect a 9 volt battery (or any other) to your head. It’s very likely that you will greatly exceed the maximum 2 mA current limit used by tDCS researchers. You could do serious harm.

3. Never plug a tDCS device into a wall electrical outlet. Low voltage battery power only!

4. Never exceed 20 minutes in a tDCS session. Again this is the limit used by most tDCS researchers. Use a timer that will turn off your tDCS device – or at least have a very loud alarm to wake you should you fall asleep during a session.

5. Always use a digital volt meter (DVM), inexpensive, available at Radio Shack, Home Depot, etc.) to monitor current being delivered by a tDCS system.

6. If you have cranial scar tissue, an implant, or other unusual medical condition, you should seek out a medical professional before you attempt to use tDCS.

Design #1 – 9 Volt Battery and Resistor (Source of design unknown – use of this design not recommended – but it helps explain how a tDCS device works.)

The key safety element in this tDCS device is a resistor. While the correct value of resistor can indeed limit current to 1 mA, this design suffers because it is not adjustable and current flow will rise throughout a 20 minute tDCS session (typically about 25%.)

Resistor Value

Here’s a little equation known to anyone who has covered electricity in a science class or elsewhere:

i=e/r That is, current (amps) is equal to voltage (volts) divided by resistance (ohms)

If you divide 9 volts by 4,700 ohms (a standard resistor value) you get about 1.9 mA. If you build the circuit above and short the leads, this is how much current will flow through the resistor.

i=e/r 9/4700 = 0.001915A or 1.9mA

(4,700 ohm resistor in series with 9 volt battery. Closed circuit.)

If you use the same circuit above and connect and press saline wetted sponges together, so current flows through the sponges, current will be about 1.5 mA (varies with sponges).

(4.7k resistor in series with a 9 volt battery, sponges touching)

In an actual tDCS session with the above setup, current drops even further to about 0.5mA due to skin, skull, etc. resistance. This is below what researchers are commonly using.

A better alternative would be to use a 1,000 ohm (1k) resister in series with each lead of the battery. When shorted, the current flow will be 9 volts /2000 ohms = 0.0045A or 4.5mA

Saline wetted sponges connected and touching will result in about 3.5mA flow (depending sponges used.)

In an actual tDCS montage, current will be in the vicinity of 1 mA (depending on patient, sponges, etc.) However, current flow must be monitored!

(Montage in progress: 9 volt battery, 1k resistor in each battery lead, saline wetted sponges)

IMPORTANT: You can expect current to rise about 25% or more during a 20 minute session – for example, from about 1mA to 1.25mA due to saline water penetration of the skin and other factors. Thus you MUST monitor with a DVM.

Design #2: Using an LM317 Voltage Regulator – from http://brmlab.cz/project/brain_hacking/tdcs DESIGN NOT RECOMMENDED… See below.

This design is widely copied and tweaked for various feature enhancements. Note that a 9 volt battery is used as the source and a widely available LM317 voltage regulator is used to control current and prevent it from rising as it did in the design above. Current setting is controlled by a resistor connected to pin 1 and 2 of the LM317.

What value to use? I suggest a FIXED resistor of about 150 ohms in series with VARIABLE resistor (called a potentiometer) with a rating of about 2k or more ohms should give you the flexibility you need to get about 1 mA during a treatment session. The fixed resistor provides an upper safety limit of about 8 mA to shorted leads.

You will need a DVM in series with the anode (positive) lead in order to verify current being delivered by the system. 1 mA is the target and once the potentiometer is adjusted to achieve it, the regulator should keep it pretty close. Watch the DVM.

CAUTION: There is concern on the web that the LM317 regulator used in the brmlab.cz design may not be “stable” at low current levels. Some have suggested that the LM334 is a better, safer, regulator choice. The “GoFlow” design (below) uses the LM334.

(The brmlab.cz design also incorporates an on/off switch and a little LED battery test circuit.)

(brmlab.cz design built from Radio Shack parts)

Design # 3: GoFlow – http://flowstateengaged.com/

The folks involved with GoFlow have an ambitious plan to release a tDCS kit to the market fairly soon. Assuming they can get it going, they probably will sell as many as they can make! They have released the schematic for their device so that anyone can build a rough equivalent.

The GoFlow design uses an LM334 regulator to maintain a constant current. Rather than use a variable resistor, the GoFlow uses four fixed resistors of different values connected to a multi-position switch. The intent is to offer treatment levels from 0.5 mA to 2.0 mA.

The only thing the GoFlow design lacks is a way to monitor the current actually entering your head. If you build your own from scratch, you can simply connect a DVM in series with the anode (positive) lead. Problem solved.

(GoFlow circuit diagram)

Conclusion

If you are going to build your own tDCS device, your focus should be on safety. Part of being safe is knowing what your are putting in your head! I’ve mentioned several times the importance of using a DVM – but you can also use a panel meter, available from many sources to monitor the very low current of a tDCS session.

(0-3 mA Panel Meter, about $7 on EBay)

However, a DVM is still a good and easy to obtain tool. They are commonly $20 to $50 at Radio Shack, on EBay, etc.

(Example Digital Volt Meter, DVM)

Building a tDCS device? Use your head!