Introduction
In part 1 of my series on the new foc.us V2 tDCS device, I introduced the basic components of the V2 as well as its user interface. I continue to be pleased with the V2 as a user and want to pass along some ideas related to electrode use.
The foc.us Gamer Headset
Foc.us offers two headsets for the V2, the Edge and the Gamer. The EDGE is a special purpose headset designed to facilitate experimentation and research on the use of tDCS to improve athletic ability. As I mentioned in the last post, this is an area of tDCS that is ripe for exploration. A few studies have already been posted that hint at possible uses for tDCS and improvements in physical ability. This will be a very interesting application of tDCS to watch as results from various tests are posted. The EDGE headset is not a general-purpose tDCS headset and should NOT be selected by most users.
The GAMER headset is a more versatile headset for the new or experienced tDCS user. It is made up of a flexible metal band and two electrodes that attach to the band. It is highly adjustable for head-size and comfort. “Out of the box” it is designed to allow stimulation of the pre-frontal cortex, an area associated with memory, learning, etc. It happens that the electrodes of the GAMER can be used independent of the included band – allowing electrode positioning for “savant learning”, treatment of chronic pain, depression, etc. Note: the electrode plainly marked “Left” on the inside of the sponge frame is the anode (+) and the electrode marked “Right” is the cathode (-).
(The Gamer headset. Best choice for most.)
(The Gamer headset in its case.)
(The Gamer on my “test head”. Note electrodes are positions over the pre-frontal area.)
(You can use the Gamer electrodes without the supplied metal band and place them where you want. Here I’ve used an elastic band to position the electrodes for “savant learning”.)
(Here is another example with the electrodes positioned to treat chronic pain. In this example, the cathode would be placed on the upper arm or shoulder with another band.)
UPDATE – March 2015
foc.us has updated the firmware on the V2 so that the resistor that tells the tDCS module which headset is connected is no longer needed. FURTHER – they are also released a patch cable to make attaching 3rd party electrodes even easier. See ( http://www.foc.us/tdcs-tens-cable-adaptor ). The text below is left for historical reference only.
Using Your Own Electrodes (Amrex)
If you are pretty good with a soldering iron you can easily adapt any electrodes you prefer for use with the foc.us V2. The jack on the V2 tDCS device is a four conductor, 2.5 mm type that has been used on some cell-phones and portable audio gear. Connect your electrodes to a four conductor, 2.5 mm plug and a small resistor and away you go!
Plug Wiring
Tip and Ring 1 – a resistor across these two tells the tDCS device the model of headset connected. (300 ohms for the Edge, and 2,000 ohms for the Gamer by my measurements)
Ring 2 – Cathode connection (-)
Ring 3 – Anode connection (+)
To test this, I used a small RadioShack proto-board and broke out the 4 conductors for easy investigation and tinkering. I used a 100 and 200 ohm resistor in series to get the 300 ohms needed to let the V2 “think” I am connecting an Edge headset, even though I use popular Amrex 3x3s. Actually it seems not to matter whether the V2 thinks an Edge or Gamer is connected – you can still set all the desired tDCS treatment times and current levels.
(Note the four conductor plug. It is broken out on the proto-board with T, 1, 2, 3 as described above. I use this example with Amrex 3×3 electrodes.)
Perhaps in future firmware, foc.us will include special features for 3rd party headsets that use a different resistance identifier.
BTW Soldering wires to a four conductor, 2.5 mm plug is not for the faint of heart. It’s very easy to short contacts and generally make a mess. I suggest buying a pre-wired 2.5 mm plug from Parts Express (or similar). Their part number is 090-504.
Summary
So there you have it. I suggest that you either buy the foc.us GAMER headset with your V2 and use it as is or with your own headband as I have shown above – or do your own thing with a 4 conductor plug and whatever electrodes you prefer.
Please feel free to send along comments and suggestions related to this post or a future one you would like to see.
SpeakWisdom 
Interesting. Does the difference in ohms have any practical impact on the TDCS, or is this purely an identification thing?
Personally I’ve been considering using the edge headset, but putting in a 2.5mm to 3.5mm plug, and then butchering a cheap pair of earphones and using alligator clips and some electrical tape to allow one or more amrex electrodes to act as a cathode. Do you think it would work?
So far as I can tell, the resistor is just there so the firmware know what kind of headset is plugged in.
I don’t understand your second comment / question.
Brent
Hi, Thank you for the extensive review. I will be a first time user and would like to know if the device offers current control. Or does it just deliver 2 milliammperes?
You can set the current level at whatever you like up to 2mA.
Brent
I hope you bought it though paypal, Foc.us seems to have died. http://www.reddit.com/r/tDCS/comments/2t2xxc/my_focus_unit_was_deadonarrival_focus_not/
I feel sad to read about Foc.us not responding to customers who have been trying to reach them – I was just going to order one. I do have a question I was going to ask before all this came up: Can the Foc.us v2 be powered by a battery or does it need to be plugged in? Thank you.
It has its own built-in rechargeable battery.
Brent
Just bought a Foc.us V2 device and Im trying to use it with Amrex electrodes the way you described Brend. But when I configure the parameters I want to be produce in stimulation and try to select START nothing happens. The start selection just stays there. Did you experience anything like this Brent? Thnx.
Tomas
If nothing happens, the V2 thinks electrodes are not connected or it doesn’t see the correct resistance on the electrode identification leads (tip and ring 1). Double-check your wiring and perhaps verify the resistor value used with a DVM.
Brent
I have double checked your photo of proto-board and found that actual resistors which you soldered serially are 1 kohm and 2.2 kohm (color strips on resistors represent that). Could you commend on that ?
Tomas
I am not a geek. I have TBI (traumatic brain injury) as a result of an auto accident when I was 18 months old. Because Of the TBI, I have short-term memory loss and cognitive lag (on new information, not previously familiar, I am often times cognitively delayed from anywhere of 45 seconds to a couple minutes. Once I have cognitive recognition, there is nothing wrong with my intelligence. The doctors who diagnose my situation have told me the problem is a physical one and not reflective of intelligence, but also, they deemed it permanent. So far I have not found “a cure” but I have found that wearing a magnetic head band (Nikken Inc) My brain function improves dramatically, so, my intelligence tells me that magnetism in combination with electrical stimulus, could very well be a further improvement. Have you had any other inquiries along the same line? And if you have, to your knowledge, could you relay to me their experiences! Everything in terms of traditional approaches i.e. Western medicine is done finished, end of the line, Kaput, no more. It is now up to me to find what works and because it is up to me, I take full responsibility for any and all consequences that happen in my efforts to progress in achieving even greater self-reliance. I look forward to your answers, thanks a lot and may God bless you!
Sincerely,
Forrest W Byers
Hi Forrest,
I have no experience with a similar case – so I have no idea if tDCS can help you. You might was to pose your question to Dr. Fugedy via http://www.tramscranialbrainstimulation.com
Good luck to you.
Brent
Hi Brent, I am reaching out to you because the Foc.us people don’t seem to answer emails. I ring that the website is totally inadequate for giving new users details about the products and information that could answer many user questions. I was wondering if there is any way to avoid burns. I have used my gamer 4 times on 1.0 mLA but it does burn my head. It is a burning sensations the entire session and leaves 2 red squares on my head. I really want to give this a chance, and just praying it works for me but I am concerned about the burning. Is this normal? the red marks go away, but is this normal? I also bought an edge for the purpose of excersize. I work out everyday and was a hardcore runner. My ability to run has gone way down hill, and i figured it does not hurt to try this. The website fails to mention if you are supposed to use it prior to excersise or during the excersise. Any infer you can give would be a tremendous help. I would have been lost without this website.
A burning sensation is not normal. Some tingling during a session with a bit of redness on the skin after the session is not unusual. A good moisturizer after should be enough to take care of the skin issue. If you are experiencing anything more severe then you should stop using your tDCS device and try to determine what is going wrong. Here are some possibilities:
1. Electrodes are not wet enough or you may need a bit more salt in your saline mix
2. Current level is too high for your skin to tollerate
3. You may have very sensitive skin – so should reduce tDCS session time and/or current level
Worst cast is that you may not be able to tolerate tDCS. I’ve seen this in a couple of cases in the last few years.
If you are able to continue using tDCS I’d be curious to know if tDCS seems to improve your athletic ability over time. This is an area ripe for experimentation – not much has been published about it so far.
Best of luck.
Brent
Thanks for your reply. i was not using saline, just water, maybe that is the problem. Am i supposed to wear the edge during exercise or before????
My email to Mike from Foc.us was answered within twelve hours. I thought that was pretty quick. I know that some folks were complaining about how they didn’t respond, but I wonder if that had more to do with the questions that were posed? I imagine that they need to be very discreet in how they answer questions as they do not want to sound like they are giving medical advise.
Anyways, The headset is positive and the armset is negative.
True. They cannot make any claim about its medical benefits or even answer any question that may make it seem it has medical benefits. They cannot even link you to tDCS references. The FDA will go after them if they do.
Now that Foc.us has come out with an adapter for using 3rd party electrodes, can you tell us how to use the adapter? Foc.us has no instructions on how to use it. What kind of male plug can you put into the female plug? What is the anode, and cathode? Help.
I don’t have one of the adapters on hand to test. I would think 3.5 mm MONO plug (two conductor, tip and one right) should work fine. I would suspect the tip is the anode – but would want to verify that with a DVM. Anyone done that already?
Brent
I unscrewed the 3.5 female end of the adapter. It is arranged as a 2-conductor mono plug. The tip of the 3.5 female is the Anode and corresponds to the 3rd ring of the 2.5 male plug. The ring is the Cathode and corresponds to the 2nd ring of the 2.5 mm male plug.
With this information, I can now simply create my own y-cable that has a 2.5 mm male plug and two banana-plugs that go into the 3-inch Amrex Electrodes. This is a lot simpler than using adapters and avoids current loss – though the Foc.us device can compensate for this.
Note that the Foc.us headset uses 3 x 3 cm or 1.2″ square electrodes. These are 9 square centimeters. For 2 mA of power, the electrodes need to be at least 13 square centimeters in order to keep the current density safe – per reddit tDCS FAQ. So the Foc.us headset electrodes are too small for some people to tolerate. The Amrex 3-inch electrodes on the other hand give you an abundant measure of safety with 58-square centimeters. And the 2-inch electrodes give you 25.8 square centimeters.
I find the Foc.us headset electrodes are too small to keep the current density safe. There is a risk of getting a second-degree burn with these electrodes with prolonged use, multiple daily use, or if one’s skin is sensitive to the current at 2 mA. For the longer protocols such as for migraine where tDCS is run for 40 minutes, I would recommend using larger electrodes.
Will the Foc.us adapter work with a 3.5 mm 2 conductor TENS wire like http://www.amazon.com/Omron-Connectors-Conductive-Electrode-Garments/dp/B00J3FSLEK/ref=pd_sim_hpc_4?ie=UTF8&refRID=0VTE3JVYR5Z9RHY6EG1Z?
I don’t have an adapter to test – but my best guess is that the cable you suggest should work fine.
Brent
The biggest advantage of the Foc.us tDCS is that it has programmability. For example, a recent study found tDCS on the frontal lobes impairs performance on IQ tests. This is understandable since tDCS reduces Glutamate signaling and increases GABA signaling. Both neurotransmitter responses slow brain metabolism and slow speed of thought processing – an important factor for IQ testing where speed of answering questions is a parameter. tDCS by increasing BDNF would help improve memory, overall cognition since neurons and glial cells can grow and make new connections.
Interestingly, the Foc.us device can do tRNS – random noise stimulation. This increases glutamate signaling. I would expect this to improve cognitive performance on IQ testing. And the Foc.us device is the only affordable device to do this mode of electric stimulation.
Check out the new foc.us headset! http://www.foc.us/moovs
1. I just don’t know how it attaches. But you can use it for numerous 2-electrode montages.
2. Is it large enough to avoid burning your skin due to high current density?
3. Do you need gel to attach it?
Can you elaborate on positioning the electrodes for “savant learning” — as in specific details about where, and how this is different from the gaming positions. I note the foc.us website seems to veer away from this (ie: no mention).
I suggest you take a look at http://www.tdcsplacements.com for more detail on the two montages.
Brent