Tag Archives: diy

You Can Be a “Real” Energy Worker

In my last post on hypnosis, I primarily addressed show hypnosis, and why I think it’s usually done wrong all over the world. Hypnosis however, can be a wonderful tool for giving. It has certain qualities and components that allow the hypnotist to elicit certain feelings that, for some people, are incredibly rare commodities. Sometimes you’ll find people crying just from being put into trance.

So now I’d like to invite my readers for a virtual workshop. You can imagine attending a burn and sitting at a theme camp workshop before going out to party for the night. I’ll be informal, brief and on to target, and tell you how you can utilize a few of the core components of hypnosis in improving your intimate human connections, and become a “Real Energy Worker” in your own right.

That sounds like corny mentalist stage patter, right? When people talk about “energies” in an occult context, what they really mean is “feelings”. Like someone saying “this building has a foreboding energy” really means “I have a foreboding feeling in this building.” Of course then they put all kinds of beliefs and theories behind that, but we’ll generously disregard all that. I’ve been told multiple times after using the following approaches that I must be a high level energy worker. Well I never paid a guru for an initiation, but I cultivate empathy and love, and apparently that is enough to deliver positive “energy” (ie. feelings) to the people I connect with.

First, for what hypnosis is, please read my previous post on the topic, in case you haven’t already. Read it? Good. Because I won’t be teaching you hypnosis. Some of you wouldn’t believe that I could teach you in a single blog post, while some would claim that I couldn’t deliver the necessary way of thinking, including safety & security. The former would be wrong, the latter would be right. So no hypnosis here. I’ll talk about approaches that are just as good for delivering positive feelings to people.

And these will, in my opinion, not only make you a Real Energy Worker, but a better hypnotist as well, should you ever decide to learn that craft.

Step one to Energy Working: Learn how to Hug

This is a truly wonderful discovery I made in the magical world of hippies, and it’s so simple. Becoming a person with a reassuring, emotionally healing hug is really easy, you just need to learn two things not to do in a hug, and only one thing to do.

Here’s the two things you shouldn’t do in a hug: push, or pull.

Here’s the one thing you should do in a hug: be present.

CONSENT CLAUSE: The first step to hugging someone is making sure whether they want to hug. Pushing includes pushing a hug on someone who doesn’t want it. Don’t do it.

So hopefully you’re in a consensual hug with someone, and they are hugging you back. If you are hugging a person who isn’t hugging you back, there’d better be a good reason for that (like their arms are in casts). In a regular situation the lack of reciprocity is a good sign that you should withdraw from the hug, as it’s not welcome.

So first, don’t push. This is especially important with lovers. Unless you’re just coincidentally hugging each other while having sex anyway, do not initiate any kind of erotic activity, do not feel your partner up, do not try to french kiss, etc. You can also get pushy in a non-sexual way, so if the other person’s body language indicates that they would like to leave the hug, gently disengage.

Then, don’t pull. If you’re in a hurry somewhere, don’t offer hugs, or at least prefix them by saying “sorry I’m in a hurry mwah-mwah gotta go kthxbye”. But that’s not a proper hug, just a formality. So don’t pull away from a hug. You decided to give it, stand by your decision. Don’t disengage, or make motions to disengage, before the other person does.

(What happens when both people follow this advice? They will possibly spend a wonderful few minutes to a few hours together. Don’t worry about that for now, you’ll know when it’s time to part as it happens. If you decide to give, then stand by that.)

Some people will loosen their grip, but then pull you in tighter. So don’t try to escape at the first sign of their letting go. Make it a nonverbal conversation: “Time to leave?” “Yes?” “Okay, I still love you.” “Love you, bye.” And definitely not “Leaving? Okay! Imouttahere, kthxbye!”

So not doing these things is already a lot more than what most people will give, and will by themselves elevate you to being a walking source of love and happiness. Now for what you should do: be present.

Keep a stable, safe hold of the other person, let yourself be there and pay attention to their movements and breathing. Don’t let yourself be distracted by what you should be doing, your phone, the traffic, etc. You’re there for the other person. Allow yourself to feel them, and feel your own reactions to being there. If you do this, you’ll notice that your breathing will naturally synchronize, maybe even your heartbeat after a while.

After letting go of the hug, stay with them. Don’t run, keep looking at the other person. Appreciate them and smile.

Sounds simple, right? It’s sad that so few people actually do this. Sure, it’s easy to do with a new lover. It comes naturally to many people in that situation. But how about with your mother or father? When was the last time you gave them your love and attention like this? Or a long-term partner with whom your relationship is strained?

I challenge you to hug your mom the next time you meet her, and follow my guidelines. Seriously. If you still have a mom, do it. You’ll be really thankful to yourself that you did. If your relationship is less then perfect, she might ask you what made you so affectionate all of a sudden. In that case, just tell her that you realized how much you love her. That’s explanation enough.

Step two to Energy Working: Learn how to Hold someone

In the article about hypnosis, I passingly mentioned regression. Not to be confused with various past life and alien abduction recall stuff (that, I personally, see as questionable and potentially amounting to malpractice), regression is a mental state where one regresses (lit. “returns”) to emotional patterns characteristic of a younger age. This experience, while an important part of healthy human psychology, is rather rare in modern society, and there are few socially normalized places for most adult Westerners to experience it without stigma.

It can be an extremely healing experience, and something that is not all that hard to give. Well-delivered hypnosis can provide this feeling, but it’s really not necessary. What is necessary is giving clear permission to the other person to let go, and ensuring them that we have the capacity to hold them as they do. This is a step up from hugging: it’s not reciprocal, it’s a gift of kindness. Also, it needs a higher level of consent: being put in an unfamiliar situation without prior discussion can make someone feel uncomfortable or unsafe, defeating the whole purpose.

So if you want to give this to someone, make sure that you are in a social relationship where something like this isn’t completely off the wall. Then, ask them if they would appreciate being held. If the answer is affirmative, the key to this is assuming a comfortable position, better sitting than standing, while holding much of their body weight. Calculate for your own fatigue, it’s important that you’re comfortable too. You can assume any position you like, the key is a) to communicate control and support, holding someone in a way you’d hold a child is generally a great approach, and b) to make sure nothing you do has a sexual overtone. Sexuality can be a trigger, and you don’t want to bring it in, even if you do otherwise have sexual tension going with the other person. Generally, if you’d feel inappropriate touching a small child in a certain way, make sure not to touch the other person like that.

So once you have the other person in your lap, or in a spoon, hold them reassuringly, and follow the advice about hugging. Don’t push or pull, and make sure to be present. One thing to note, in order to elicit a deep feeling of regression, you need to be somewhat firmer about your intention to hold and protect. You shouldn’t disengage immediately if the other person moves. Make it a drawn-out nonverbal, and potentially verbal discussion about whether they really want to leave, or just need a calming voice telling them that their Twitter notifications can wait for another ten minutes. WARNING: This does not mean you should hold anyone after consent had been revoked! If you cannot discern fuss from withdrawn consent, I advise you not to try this at all until you can.

Step three to Energy Working: Touch with feeling and intention

There are points on the human body that are more sensitive to touch than others. No, I’m not talking about erogenous zones. Take your right hand in your left, and move your thumb across your palm. You’ll find spots that are particularly sensitive, like the base joints of your fingers, and the soft areas right inbetween them. The human body is full of spots like these.

Explore yourself, and find as many as you can. Find the optimal pressure that is the most intense, without being painful. Gently drawing your finger on your skin, find spots where you are ticklish, and find what kinds of touch feel good, and what kinds of touch feel uncomfortable. Knowing these spots gives you the “where” of touch. It won’t teach you how to heal cancer with accupressure or somesuch (honestly I’m very skeptical of people claiming similar things), but it will definitely teach you how to heal a chronic lack of human touch. WARNING: Note that many of these points are considered highly intimate due to the feelings they elicit, and you should seek consent before touching, even if you are already hugging or holding someone.

As for the “how” of touch, here’s what you shouldn’t do. You don’t poke, and you don’t boop. (A boop is a short touch immediately withdrawn, like how you’d playfully “boop” your child on the nose.) That’s a form of tickling, and can be part of your playful touch repertoire for sexy times, but not for anything hugging, holding, or hypnosis related. You touch slowly, deliberately, with gentle pressure. You can imagine giving time for your finger or palm to transmit your body heat to the other person.

Also, you don’t grab. This is important as heck. Not by the pussy or balls, not by the ass, not by the waist, not by anything. Grabbing is possessive, even if it’s not expressly sexual (though, usually it is). So no grabbing. Touching with your palm should be done with an open palm, slightly relaxed and spread fingers. All pressure should be on your palm, and none on your fingers. Holding hands is okay and encouraged, but let the person you’re holding initiate it first. Gently placing a palm on their hands is nice though.

And well, I decided to tell you all these guidelines because I’ve seen otherwise really nice people being completely illiterate about human touch, but don’t follow it to the letter. Follow it to the spirit. You need the right intention, which is to comfort and hold, and never to possess or dominate. And the most important part, again is being present, and mirroring the other person. If you pay attention, you’ll be able to see their reactions, their small signals telling you what they would like, what they enjoy and what makes them uncomfortable.

Step four to Energy Working: Be prepared for abreactions

As I said, some people will burst out crying just from being put in a trance. These feelings are so rare that for some people, a regular hug will be something they last had when they were four years old. They might have had sex, but it was about power and control and possession, they might have hugged their children, but weren’t present to give and receive, and here comes a random hippie and gives them a hug, and suddenly they are reminded of all their feelings they convinced themselves of not having.

So while the reaction of most people will be positive, you’ll potentially encounter negative emotions. The easiest of which is having a crying person. As you’re not their therapist, don’t try to analyze them, or give them guidance. Make sure that they know you’re not inconvenienced by their emotional outburst. Ask them what would feel best for them, do they want you to stay with them, do they want to talk. Stay with them, unless they ask for time alone. (Hearing someone out is not the same as providing therapy or coaching! Hear them out without judgement, and refrain from giving advice.)

It’s possible that you get strange and hard to interpret reactions like shaking, jolts of movement, moans, sighs, strange vocalizations, tears or drool, etc. Hitchhiker’s Guide rules apply, don’t panic. Also don’t try to solve or fix anything. Make sure that they are okay. There are two questions you should ask. “Are you okay?”, and regardless to the answer to that one, “Would you like me to keep holding you?” If the answer is affirmative, keep holding them. If they told you they aren’t okay, also ask them if they need anything. Applying pressure with your palm over the chest, or the head can be comforting in case they are “not okay”.

A worse situation is an outburst of anger or other negative feelings. This can result in an immediate withdrawal of consent. You’re not their therapist, so it’s not up to you to fix them, and you didn’t do anything to them that you need to feel guilty about, so in such a case simply withdraw, be polite and respectful, and remember not to push.

It’s not strictly an abreaction, but a potentially unexpected occurrence, that they go into a deep trance all by themselves. This can result in becoming nonverbal, in infantile body language (snuggling, taking up a fetal pose, changes to facial expression) or body catalepsy (becoming immobile). This is a good thing. It means you gave them something wonderful, and they trust you enough to let go. In such a case, there are two things you must never do: get scared, or attempt giving hypnotic suggestions.

You don’t get scared, because in this state, your fright will be a traumatic experience for the person you are holding. And you don’t attempt giving suggestions because you didn’t receive consent for it, and you’re probably not trained how to do that well anyway. Don’t try to shake them awake, that’s just evil. You can ask the person if they are okay (you’ll likely get the slightest of nods along with a sigh or a hum), but don’t ask open questions. Asking a nonverbal person to talk is… well… not very nice. Let them be nonverbal. And tell them it’s okay, and that you’ve got them. Handling a regressed person follows exactly the same guidelines as holding a baby, only that they are a lot bigger and heavier.

You’d better not have anyplace to go in the following hour or so. If you, for some reason, do, or after an hour the other person is still in a trance, you can gently ask them to slowly come back, as you’ll need to leave soon. Don’t shake them awake!!! That’s extremely rude! Have you ever heard the phrase “a rude awakening”? So no shaking! They will come back soon enough. If they don’t, just repeat it gently several times, until they do. Don’t raise your voice. Be patient, and they will come back. Anything else, and you’d be breaking your implicit social contract formed by you offering to hold them, and can result in a break in interpersonal trust. Even if it’s the tiniest of cracks, it’s still a crack, You want to avoid that.

Step five to Energy Working: Hold your own boundaries

Just because you’re starting out in control of the situation, doesn’t mean that you need to disregard your own boundaries. Have a good grasp of what forms of touch you want to accept from the other person. It’s quite possible to hold someone while not allowing them to proactively touch you at all, but make sure to communicate this beforehand. Even if you’re okay with being touched, the gesture you provide can be misinterpreted as sexual, so it’s a good idea to lay down the groundwork before the first touch.

As you are in the situation with the other person, and they attempt to overstep your boundaries (like touching you on an erogenous zone, or starting to talk dirty, or similar), firmly but gently stop them. Remember that the other person is in a very vulnerable place, so being gentle at first is important. Like, take the offending hand, firmly return it to fetal position, hold it there, saying, for example “don’t. your hand remains here, okay?” Now if the other person doesn’t listen, and keeps pushing against your well-stated boundaries, then extract yourself, and tell them that they made you uncomfortable, and you don’t want to touch anymore.

Protect yourself, because if you don’t, you cannot protect anyone else either.

There are a few things to note. First, you should be able to discern a childish thirst for touch, that is pretty natural in a regressed state, from sexual attempts. Be equally firm in all cases that make you uncomfortable, but if the other person is in the mindset of a child, handle them as you would handle a real child. It’s easy to cause severe emotional damage to someone in this sort of altered state. As for opportunistic feel-ups and harrassment, as I said first be firm but gentle (unless you expressly discussed boundaries beforehand, and the other person wilfully disregarded it), and the second time is a great time to call “three strikes out”. Also, if you are holding a male bodied person, erections are not an indication of either sexual intent or desire, so don’t treat them (or lack of them) as anything other than an involuntary physiological phenomenon.

So that’s it for today. Go out and be nice to others.

Five years gone

It’s been five years since my last post, nearly, and now I decided I need a place to blog again. So why not here. I left the blog online, as I think there’s some important information here for the DIY tDCS crowd, and didn’t want to take that away. Too much stupid was (and sometimes is) going on in the biohacking scene, and a sane voice is always a good thing.

It’s been a long and busy 5 years for me. Things changed. I hopped countries again. Probably will do it again soon. I went through a major crisis, came out, and found new callings. I’m still a hacker, and now I’m a burner, too. The Burning Man movement and subculture has shown me that life can be worth living, and pulled out some deeply buried childhood dreams. Like that of being a clown.

I don’t feel talented at clowning, only motivated. I’ve never been very good at theater arts. That said, the very mild neuroatypia I grew up with may have the benefit that I can see humans one step removed, and I do think I have the right heart for this. So now I’m applying the stuff I blogged about in How to Be Someone Else years ago. Learning to see the world through the lens of poetic comedy, learning flow arts, and hanging out with burners and amateur circus people. And somehow I have the feeling that if I can learn to be a clown, I’ll at the same time learn to be a good human being.

As for tDCS, I started getting headaches after stimulation, so I don’t use it frequently anymore. I do want to experiment with tACS still, I just need time and energy to design and build a device I can trust. I was, and am keeping myself busy with a number of things at all times, and this kinda slid to the bottom of the product backlog of my life.

I’ll probably be blogging about more psychological, philosophical and artistic topics going forward, with some hacking thrown in.

What is the resistance of your head

It’s the first question I asked when I set out to design a tDCS device. I didn’t find any sources that were too accurate or particular.

There is some information out there on the galvanic resistance of the human body including on Wikipedia. Also it’s an interesting fact that galvanic skin resistance is highly dependent on sympathetic nervous system activation, can change rapidly, and is used as an important measurement in psychology and psychiatry experiments, in polygraph machines, and in the “e-meter” used for confessionals in Scientology.

Bottom line is, the resistance of dry skin can be anywhere between 10 kOhm and 1 MOhm, while the resistance of the wet stuff inside us is in the few hundred Ohms range. Do note that electrolytic fluids, such as the insides of our body, are non-ohmic conductors: they do not obey Ohm’s law. So when we’re talking about the resistance of the human body, we’re necessarily making a simplification of reality. There is a voltage drop, but not an actual ohmic resistance. However, for the voltages and currents used in tDCS, this simplification is adequate for sizing our voltage sources.

In AC stimulation like TENS, the impedance of dry skin is greatly reduced due to the AC nature of the applied electricity, because the electrode and the wet matter below the skin form a capacitor, which allows AC through while blocking DC. With tDCS, naturally we cannot rely on this.

To reduce the resistance of the dry outer skin layer, in medicine people usually use wet electrodes, like gel electrodes in EKG and EEG, and saline-soaked sponges for stimulation and iontophoresis. In fact, there is a good reason why most tDCS systems use wet sponges. It’s really simple, doesn’t cause a mess (not having to wash your hair is a plus), hair doesn’t really mess with the results, and it can handle Wattages that would heat up or break down gels.

While there’s a lot of talk about resistance of the electrodes, the fact is that if they aren’t dry, it’s safe to consider them a dead short. I’ve used sponge electrodes with an approximate area of 25 cm2 and with half as much at about 10 cm2, without any noticeable difference in the voltage dropped.

As for HD tDCS and gel electrodes, there was a research paper by HD tDCS pioneers Soterix Medical some time back, where they tested various electrode configurations. Most of them heated up, broke down under DC, their resistance skyrocketing, but their “winner” stayed below 10 Volts of drop throughout. In fact, I’m convinced a simple wet sponge fares just as well, or probably better, for a fraction of the price. In their case, there were other considerations in favor of gel electrodes &ndash like integration with existing QEEG positioning meshes and electrode bodies.

My experience is that for extracranial electrode configurations (ie. with one electrode placed on a shoulder, arm or otherwise not on the head), the total resistance of electrodes plus body tends to be 3500—4000 Ohms, while with both electrodes on the head, it’s more around 1000—2000 Ohms. These values are for quality sponge electrodes (Amrex) with a metal mesh backplate, and soaked (but not dripping) with standard .9% saline solution.

This means that for a tDCS device to provide enough juice for most scenarios, it has to be able to provide up to 8 Volts on its terminals. Most devices go somewhat above this, to deal with suboptimal connections, but my opinion is that for a DIY, or otherwise non-medical device, it’s better to stay around this value for sake of safety.

Building a good tDCS device – part 2

So basically, to have my super simple and easy to build, yet safe (as can be under the circumstances) brain zapper, I determined the following block components as necessary:

  • Current source
  • Protection against reversed polarity
  • Manual current shunt for start and stop
  • Transient suppression
  • Test points for measuring current and voltage
  • Voltage indicator LED

Current source

I wanted to be able to experiment with various current levels, so I opted for using miltiple CRDs in parallel. Using jumpers to turn them on or off allows me to set the current to 1.0, 1.5 or 2.0 milliAmps.

CRDs are kind of expensive as loose components go, so I wouldn’t necessary do the same for a device that goes into mass production, but that wasn’t the goal here.

Protection against reversed polarity

This one is needed because a CRD acts as a short circuit (well, actually it acts like a forward biased diode) when biased in reverse. Since I was going to build this on a veroboard with an el cheapo pinheader to connect the battery holder, I needed to make sure there won’t be any surprises if I ever connect the thing backwards.

Solution: I just added a diode between the battery and the positive rail. Since I’m using two 9V batteries, the .6 Volts I’m losing there is insignificant.

Manual current shunt for start and stop

If we add a potentiometer the the simple circuit I linked to in my last post, there are two ways we can do it. Either in series with, or parallel to the load (ie. our head).

Manual start/stop configurations

Manual start/stop configurations
a) Potentiometer in series
b) Potentiometer in parallel (shunt)

Now the series configuration is absolute rubbish, the only reason I included it here is to explain what’s wrong with it. We can treat the CRD, for all intents and purposes, as a “smart” resistor that sets its value to whatever is necessary to maintain a specific level of current flow through its terminals. (In reality, what varies is the voltage dropped across it, but that’s just a technicality in this extremely simple design.)

It is meant to nullify the effect of whatever changes might come along in series resistance or input voltage, and keep the current static, as long as there’s enough voltage to keep things up. So it would end up fighting any series element meant for start or stop. Regardless of the value of the potentiometer I use, the result will always be quite inadequate.

Current curve for potentiometer in series

Potentiometer in series:
This is how the current would change in response to turning the knob. Not so pretty, huh?

The better, and safer way to cut current flow to one’s head is to reroute it, to create an adjustable shunt to ground in parallel with the load. Now this has its own fleas. Due to the nonlinear nature of the current divider equation, I still get most of the current turned on (or off) on the first 10% of the pot’s rotation, and the rest changes naught.

However, “audio taper” potentiometers came to my rescue. They are pots with a nonlinear curve optimized for volume adjustments, to compensate for the logarithmic nature of human perception. In this case, they compensate adequately for the nonlinearity of the current divider law. While not perfectly linear, and subject to change as the resistance of the load changes, it’s good enough.

Current curve for potentiometer in parallel

Potentiometer in parallel:
This is how the current would change in response to turning the knob.

As you can see though on the diagram, we will always lose about 10% of the current with a 50k potentiometer, and an average 3.5k resistance across the electodes (in my experience, using standard 2″ saline sponge electrodes, resistance varies between 1.5 and 4k, so this is a good approximation). Since my CRDs were off by about +10% compared to their nominal value, I decided this might be a good thing even.

Transient suppression

What happens when I connect the trodes to the device after it has been turned on? What happens if the potentiometer malfunctions? If a wire breaks? Well, even though none of these should be dangerous in the strictest sense, they would potentially lead to voltage and current spikes on my brain, which are, in the very least, extremely unpleasant.

The worst case scenario is suddenly connecting up an open circuit. If the loop is broken, the current is zero, and so is the resistance of the CRD. It allows almost the full input voltage onto the terminals. When you first connect up a loop like this, and your head happens to be the last element to be added, you’ll be treated to almost the full 18 Volts for a few moments, and before the CRDs catch up and stop the current, you’ll get transient currents potentially higher than 2mA.

You don’t even have to be an idiot for this to happen. A wire could break, and then by a minute movement, become reconnected, resulting in the above scenario. So what can be done about it? I explained my disdain for “soft start capacitors”. A CRD works by varying voltage in order to keep current stable. A capacitor resists changes in voltage. They are “enemies”, fire and water.

However, an inductor does the exact opposite. It resists changes in current. Just what we need, huh? It’s kind of the electric equivalent of a flywheel. The only problem is that a DC choke large enough to make a noticeable difference is big and heavy – this time I decided to accept the big and heavy, and got a 10H choke, but unfortunately, for a portable device this would be far too much bulk in my opinion.

Note: a choke needs a flyback diode (a diode biased in reverse across its terminals), to make sure it doesn’t create crazy voltages when you take the current away, allowing it to wind down.

I’ll post some oscilloscope screenshots, for now you’ll just have to take my word that without the choke, there was significant ringing, and transient currents up to 4mA upon connecting up a broken loop. With the choke added, the overshoot and ringing were gone, and the current never passed the 2mA threshold.

Test points for measuring current and voltage

Well, I have two multimeters, so I didn’t want to burden the design with any dials or digital meters. Added a 1k precision resistor as a current shunt (making 1V of measured voltage equivalent to 1mA of current), and test points for measuring voltage across the current shunt, across the load, and across the battery terminals.

Voltage indicator LED

My last idea to make this as safe as possible was to include a LED that would light up if there is a voltage on the terminals. Just to make sure I’d never plug my head into a live connector.

To isolate the LED from the load (I sure as hell don’t want a LED’s 30 milliAmps on my head, no matter what happens), I used a 1M resistor, and a darlington pair…

Putting it all together

Based on the above, this is the final design, and the device. It’s pretty small, fit on the tiniest veroboard I could find, is safe, and works good enough. All in all it cost me less than $50, and a few hours of work.

Schematic for my diy device

Schematic for my diy device

The device built

Building a good tDCS device – part 1

After reading all up about tDCS, and deciding it might be a good idea to take a crack at it, I was faced with a dilemma. You see, professional tDCS devices cost a lot, and are medical devices, ie. you can’t just buy them off Amazon.

Of course, there were a few options beside that. One of the awesome things about tDCS is that the technology is so easy it’s almost ridiculous. To have a fully functional tDCS device that does exactly what the professional ones do, all you need is a current regulator set for 2mA, some wire, and two saline sponge electrodes.

Since it caught the fancy of many geeks and makers, there was an awful lot of resources out there. I first came across an initiative to create a kit, called GoFlow. Their webpage is still up and dandy, though the project itself went under years ago. It was intended to be a simple device with a standard bifrontal electrode layout (more on that stuff later, do some googling if you’re interested).

Now even if it was available, it has its shortcomings. For example, they have this big ass, 470uF electrolytic capacitor across the ‘trodes. I fail to see how that would EVER be a good idea in a current regulated loop. I do love the concept pic tho’, all those Apple-esque colors…

The next candidate was the foc.us. If you haven’t seen it already, it’s the big game in town. I’m not entirely convinced what they are doing is legal, but they are popular and the device looks cool. That said, it’s expensive for what it is, requires an iPhone 4S to access all functionality (a regular iPhone 4 just won’t cut it), and seems to have been designed by a herd of insane marketing managers high on MDMA.

So, I decided against it. Since then, it turns out I was even more right than I thought I was. The foc.us is a dog with fleas. I’m particularly struck by the fact that it goes to the length of having 64 Volts as its maximum driving voltage. How irresponsible is that?

That’s when I read this article on the Speakwisdom blog. It’s a beautifully simple design, and as far as I know at least two commercially sold kits (the kind of pricey Biocurrent kit, and the humbly named – and priced – tdcs kit) are based on it.

Simple tDCS design

The design is based on a so-called current regulating diode, or CRD, which is a simple and robust device. It’s a FET wired in a current limiting configuration, and factory-tuned for a specific current level. They are quite stable, very low maintenance.

So I got some, plugged them up in a breadboard, wired up a pair of Amrex electrodes, and well… It worked. However, I felt quite shocked when I turned the thing on, and had lights flash in front of my eyes when I disconnected it. Of course these side effects are well known and harmless (the flashing lights are called phosphenes and are due to some neurons firing in the retina or the optical nerve), but I just couldn’t shake the thought that it could be made safer and nicer.

Of course I wouldn’t think of connecting a big ass “soft start” capacitor across the terminals, like the crazy GoFlow guys, especially not that my design is not a nice, single package like theirs, ensuring constant electrode contact. Things can get disconnected, a wire can break, and then the “soft start capacitor” gets a new job as a “very hard start capacitor”, or more aptly the “help a donkey kicked me in the head capacitor”.

Adding a potentiometer for manual starts and stops seemed like a good idea, but it wasn’t trivial either, due to the nonlinear nature of the entire system. The trick is to get a setup where the intensity is at least somewhat linearly distributed across the movement range of the pot. I didn’t want the current to come up in a jolt at either end – I wanted a smooth, nice ramp.

While I was thinking about solving that, I also gathered a few further requirements pertaining to the device:

  • Should be cheap,
  • Should be simple enough to build on a veroboard,
  • Should be as safe as I can make it,
  • I should be able to build it in a day or two once I have the components delivered…

I think I came pretty close.