Penile Plethysmograph

[Jabber]

Thanks for the hint about MyUS. I'll look into that.

And the idea to use a microphone to detect muscle activity and heartbeat is really good. Using this approach, we can avoid quite a lot of issues.

[Xenophobe]

So, it sounds like one plethysmograph opens the possibility to measure all kinds of relevant things: pulse rate, "twitches", and of course, girth. Right?

[slave alexander]

I agree

[impulse321]

[/quote]

The range went from 1.1 Ω to 1.3 Ω. So to turn this into a device that is useful for our purposes, we simply need to create something that can measure resistance fairly accurately within that range and that can be hooked up to a computer. Can't be too difficult, can it?

Problem is that the resistance is so low. So we have to trade-off between picking up a lot of AC mains noise, or use a lot of power (but not so much power that the plethysmograph runs too hot).

There is a circuit here: http://bayimg.com/image/kaonhaabf.jpg

Please note that I am not an electrical engineer, and I have not tried building it. It uses about 50 milliamperes, and less than 1 milliwatt in the plethysmograph. It should be possible to use another instrumentation amplifier than the INA122, but the gain should be about 1000 with this input bridge.

There's no particular reason why the arms of a wheatstone bridge circuit have to be equal (although they're often shown that way), so long as the proportions are the same. (OK there are subtle impedance issues with noise, but we can skip that here.)
We can use different resistor values, so long as the proportions match, like so:

Code: Select all

------------------   Vexe  (~~5 volts)
         |        |
         \         \
100 ohms /         /  100 ohms
         \         \
         /         /
         +------- | --------
         |        |           >>-->> to instrumentation Amplifier
         |        +---------
         \         \
1.2 ohms /         /  In/Ga Gage (1.1 -- 1.3 ohms)
         \         \
         /         /
         |        |
----------------------- Ground

This would give around .05 amps through each leg of the bridge, dissapating 1/4 watt in each of the 100 ohm resistors (so use 1/2 watt or higher rating.) That 50 mA applied to a change of +/- 0.1 ohms would give +/- 5 millivolts. That's plenty for use with an instr amp like the IA126 (or the dual IA2126.) A gain of 500 on the inst amp. would give this a full-scale swing of 5 volts, easy to use with an Arduino or similar.

-- Larry

[impulse321]

As Jabber mentioned, the vendor apparently isn't selling the induim/gallium gage outside the US.

> Unfortunately it looks like Behavioral Technology isn't selling the plethysmograph outside the US, so I will
> not be able to build this nice project as I have found no other place where this is sold.

I haven't tried this yet, but I think a rubber tube, filled with an electrolyte (salt solution or similar) and capped with conductive plugs (like stainless steel or brass) might work similarly. -- And one could adjust the concentration of the solution to get the resistance into a convenient range (1 -- 10K, IMHO) I've seen some references suggesting that copper sulphate solution and brass electrodes would be a good combination. Similarly, stainless steel and KOH (but I'm not eager to have lye near my family jewels....)
FYI, see: "Water Resistors" http://home.earthlink.net/~jimlux/hv/rwater.htm
and/or "Electrolytic Strain gage" http://www.bitech.ca/pdf/GeoTechNews/20 ... ch2004.pdf (esp. pp 3-4 and figures 1 and 2)

-- Larry

[smallhorse]

I know this is a very old thread, but I thought I would reopen it and post some more information.

Well, since a long time I have thought about building something like an orgasm detection device. Since I am a submissive type of guy I was always fascinated by being teased right to the brink, but being denied the final release. I noticed myself all those facts that have been discussed here before, like the muscle contractions before the orgasm and the increase of blood pressure in the penis and therefor the circumfence increase.

I have built some sort of computer-controller that can controll two vibrating toys. You can use a small motor from a vib and fix it near the head of your penis for pleasure and use the other motor-control-port for other devices like eg. a butt-plug etc.

This device is working very well and I made some program that can control those devices in random or predefined routines, increasing or decreasing the intensity etc. I have to admit, that I can't hold off very long when the motors reach full intensity.

Since I am also into bondage (and sadly without a partner into self-bondage), I occassionally used this controlling-device to make the bondage-time nice. However it is short lived fun if the motors just vibrate on without any knowledge off your arousal level. Of course you can use a lower vibration level, but then the fun might not be as intense and when you use a higher vibration setting you might come before any length of time.

Then I found this thread and I thought, hey, it would definitly be ultra-cool to build such a device. So, I got myself two of those penile plethysmographs and started building a board. The final result is visible in the attachments here. Actually I used some suggestions from the posts here and modified the layout just a little bit.

Here are some details about the board i built. It uses a 5v voltage (which can be driven by 6-30V input) regulator and a diode to prevent wrong connection of source. Then there is a normal Wheatstone Bridge which uses 100OHM resistors.

Previously I used much higher resistors (eg. 1k) however I noticed that my USB experiment board would not get good readings anymore. It might have been a problem with the ultra-low current design. So after using 100OHM resistors the current usage is around 50ma and I am getting very good readings.

One arm of the Bridge contains 100OHM + the resistance of the gauge. The opposit arm contains a 160OHM resistor which is in parallel with 197OHM + 100OHM Potentiometer. This way the total resistance of this arm can be adjusted from around 88OHM to 103OHM (depending on resistor variance) in very small steps. The Potentiometer is a 25turn Potentiometer, therefor you can finetune the Bridge very well. Initially I simply Nulled the bridge at the millivolt level using a simple voltmeter.

The voltage difference of the bridge is then used as input of the INA122 and the second potentiometer is a 1k 25Turn potentiometer used to adjust the voltage-gain by the INA. Actually this potentiometer is used only 1 time to adjust the gain to a desired level and then it doesn't need to be touched anymore.

The output of the INA is then put through a RC high-pass filter with 15,9HZ cut-off frequenzy (100k/0.1uF). This filters out all the high-frequenzy noise that you pick up. Since the INA is driven with the regulated 5V source the output of the INA is 0-5V ... however after the high-pass filter there is only about 2.8V left. Which either leaves you to amplify it again or just use it like it is.

I opted for the later and simply used the 2,8 volt range which is enough in my opinion. The final output is then simply fed into an analog-digital 8bit converter of my USB experiment board (which also controls those nasty motors by the way ) and can be used further from thereon.
After putting on the gauge one needs to adjust the offset-voltage since it is strained a bit already. When the penis is errect one can adjust the wheatstone-bridge until good readings are aquired. For best results I set the offset to near NULL level when nearly fully aroused. This leaves enough room upwards for further expansion (eg. muscle contractions) while enabling a huge gain value (since we want to pick up very small changes).

The software itself is also quite simple. It measures the value of the gauge each 50ms. It then calculates an average of those values from the last second (sum of the last 20 values divided by 20). And if the last read value is higher than the average of the last second + THRESHOLD then the muscles have been contracted.

If a contraction is detected, the motors are stopped for 5 seconds. During this timeout period the average is not updated. This allows the errection to change upwards gradually, but does not allow quick changes (eg. when the muscles are contracted). It also has some nasty side-effects. Eg. if you contract your muscles and the penis becomes more errect than before and the arousal level is > THRESHOLD, then the motors wont start again until your arousal level goes below your previous average level. Can be very nasty since you have to try keeping calm and letting the arousal rise slowly without forcing contractions...

I tried this out and I have to say it kept me on edge for nearly 1 hour! However at the end I noticed that the 5 seconds motor break is too short at such high arousal levels. An orgasm was possible, however not a very satisfying one since the vibs stopped right at the beginning of the last contractions.

For further improvement I would like to try out the following:
- Use a programmable resistor for voltage-offset adjustment of the bridge.
This would allow the computer to automatically keep the voltage near the center level. The benefit is that you could put on the gauge and not require any potentiometer adjustments at all. No matter what the arousal level is and also theoretically if used by more than one person it would adapt to the person using it (eg. penis circumfence etc.) and would allow different sized gauges to be used without any potentiometer tuning.

- Increase the motor-vibration-timeout to a random value. eg. 8-30 seconds and if the muscle contractions come in too short time-periods stop vibrations for longer eg 3-10minutes to allow some cooldown. Perhaps just keep the buttplug vibrating meanwhile

Would like to hear your suggestions and comments!

Greets,
Smally

[camel]

BRAVO! Congrats.

You had asked for suggestions. This one's complicated but pretty diabolical if it works the way I think it would.

Instead of a 5 second stop, try to make an algorithm that aims to make you twitch you every 30 seconds. After 5 seconds rest, start the vibrations gently and ramp up to full power, and adjusting how fast you ramp up to full power based on how quickly the previous few cycles ended.

So, if 5 seconds rest and then ramping from 0 to full in 25 seconds is too much stimulation, then it will ramp up even more slowly, adjusting each time, until you're edging every 30 seconds even though it doesn't even get up to half speed. If you think of really unsexy things, then the cycle would take longer, and the algorithm would compensate by ramping up a little more aggressively, always trying to keep you at 30 seconds/cycle.

The reason I think it should ramp up from low, rather than simply have a flat speed that gets lower and lower each cycle, is to help prevent... accidents..., and because I'm guessing it would be more frustrating.

If you could get to the point where the ramp is nearly flat (i.e. after 5 seconds rest, even a constant, low vibration causes you to twitch too soon), then the game could change to a new goal... edge you with 10 seconds of gentle vibration, resting a minimum of 5 seconds between each edge. If after 20 seconds rest you still twitch within 10 seconds of gentle vibration, the seconds of rest increases. If somehow you loose interest in the game and with only 5 seconds of rest it takes over 25 seconds of gentle vibration before you twitch, then it reverts back to the previous algorithm, slowly increasing the ramp speed until you're edging every 30 seconds again.

The only way to cum from this that I can think of is that, after too much arousal, you can't get hard any more and cum while soft.


- - -

Another idea would be using it for self-bondage forced orgasm: have the vibes running on high (or better yet, a pattern like a sine wave or simply changing between high and low speeds each second), and hook the contraction detector up to something that will release you from bondage, programmed not to release you until either an hour has expired, or you haven't twitched in 5 minutes.

[smallhorse]

Thanks for the cool suggestions.

Before reading this post I tried out some new things. First of all I tried using both motors (vib and plug) running them with some routines I previously designed.

And almost like you suggested I did some more timing. So if you twitch within 10 seconds after the vibration restarts, the timeout would be 5 + (10 - twich-delay). So if you twitch right after the vibs start again the new timeout would be 15 seconds. If you then twitch within 5 seconds the next timeout is 20 seconds and so on. If you manage not to twitch within 10 seconds after restart the timeout goes back to 5 seconds.

Sounds nice, but I encountered some problems I noticed, that it is nearly impossible to NOT twitch when the vibrator speed changes too quick. Eg. if you have a sawtooth pattern or a quick sine-wave or quick on-off pattern you twitch reflectory no matter if at the edge or not. So I tried ramping up like you suggested, however my ramp was going up too quick (only 2 seconds) and this of course just set off more twitching and instant stop of action again.

I also noticed, that the motors would influence the sensor to some amount. My initial tests have been with just a single motor and worked great. When using both motors I noticed some spikes in the sensor readings without me twitching. However that might be because I did not use any shielding around the sensor cable.

I didn't try since then, but my next try would be to shield the sensor and twist the sensor cable (I was using a strainght 2 wire cable which picks up noise VERY well). Perhaps I can also add a third cable to the sensor line which can be used to compensate the noise picked up by the sensor cable. Or I could try moving the sensor-amplificator closer to the sensor.

Your suggestion for the self-bondage session is great too! Indeed, after coming you can hold out quite a long time without twitching. I think it might also be possible to perhaps detect an orgasm by the patterns of the twitches and the penis going soft afterwards. I am not sure about this, I might need to record the twitching and tumescence over some orgasms to see a pattern to it. Since of course I don't want to be able to "simulate" it just to get out of bondage

So now I am searching for a good release mechanism. I think magnetic-door holders might work. They can be VERY powerful and I think it is nearly impossible to forcefully pull off the magnet when fully powered. Other techniques might be some form of electric locking-bolt. Anyway, there needs to be a backup of course like the good-old melting-ice cubes. Just in case the electric fails somehow or there is an error in the software or whatever can go wrong.

Actually I ordered some more equipment from Farnell, like a microcontroller etc. to experiment some more with various ideas to go further with the ultimate teasing tool Especially the auto-adjust feature that keeps the DC output offset constant so that twitching can be recognized in rigid or non-rigid state.

I also want to try out the suggestion somewhere in this thread of self-building those strain-gauge sensors with salt-water/glyzerine instead of the indium-gallium. Since the original bought gauges are very delicate and made for one-time usage actually I think that they will make problems sooner or later, wear out, tear or whatever. It would be great to know that selfmade devices work too, so I will try it out.

Thanks again for the suggestions and keep em coming

[camel]

Two suggestions for self bondage I would have are:

Solenoids... loop rope through something that can be released via solenoid. something that doesn't have a lot of strain, though, or else the solenoid might be stuck.

Or you can use the magnetic door holders but use them to hold keys (and weight if necessary) on a string so that the string falls within reach when released. It doesn't have to be strong enough to restrain you, it just needs to keep your method of release out of reach.

Keep in mind that I've never used either of these. I just have a fertile imagination to this. Test these things, and have a backup plan. One backup plan I read of a woman who did self bondage was that she tied a rope to a key and bucket of motor oil on a chair. If her primary method of release jammed, or something else went wrong, she could always free herself but be in cleanup hell later.

Other secondary releases include inviting someone over who has a key to your place, x hours after you'll be done, just in case. Better an embarrassed smallhorse than a dessicated smallhorse.

[smallhorse]

Thanks once more

And no fears, I have done self-bondage before and yes I have always used some sort of backup plan

Selenoids and magnets to hold keys are fine. But then you need to restrain yourself in a way to be able to use both hands to get to a lock and turn the key etc. When you like spread-eagled this is not possible since you end not being able to use both hands.

Until now I used a very simple method. Just put some ice-cubes in a sock, pull the sock through a ring (like 2-3cm diameter). The ring is tied to a rope and the end of the sock is tied to a rope. If you pull on the rope you can not pull the sock through the ring until enough ice has melted.

At first I thought that with enough force the sock could simply be ripped apart, but if you use a good cotton sock it is impossible to rip it, no matter how much you pull, and trust me, I pulled!

This method is as far as I can think off very failproof. The ice WILL melt sometime and then the sock can be pulled through the ring. There is no place the sock could get stuck or anything, there are no sharp parts nor crevices or anything where the sock could wedge somehow. And since you are directly able to apply force to the sock you are also not depending on gravity or luck with keys falling into your hands, your hands not being numb etc.

Anyway, using magnets it would definitly be cool if the magnet could indeed hold me Imagine you build some wrist-shackles that are attached with short chains to some metal-plates and you have those strong electromagnets fixed to the floor. You could get yourself in some very nice positions this way. Like on all fours for example. You can prepare everything, tie your legs, body, etc. apply whatever mean stuff you have like dildos, weights, gags, etc. and when you place your hands close to the magnets they are automatically locked in place and you have to hold out until the magnets turn off. As backup you can use a timer to shut off the power at a specific time and additionally you could use the ice method on one leg for example so that when you free your leg you could pull out the power-cord, reach a power-switch or have other means of undoing the bondage.

[cumhardy]

smallhorse your invention sounds amazing. although I dont understand half the technical things you mentioned
Maybe there could be a way to detect heartbeat, perspiration, brainwaves of some kind of sensor to better tell when you are on the edge. Not sure if that is technically possible, I just read it in a fictional story once...

[Nezhul]

it is possible with EEG devices like http://www.grasstechnologies.com/produc ... meeg1.html or similar to it. This device is placed on the head like a tight rubber hat, that pushes electrods to your skin (not sure, but maybe I'v heard that newer models use only a band-like rung of electrods). Also electrods are attached to your ears.
This device tracks electrical activity of the brain, and in fact so sencitive, that today is tested a special version and software, which helps handicaped people to interact to others. It simply allows to type a text when a person wearing it concentrates on letters he would like to be typed. So it basically recognises the brainwaves of letters.

Orgasm edge is a very big event for the brain, because it's basically is happening there, and can be tracked easily. The problem is software, whish will interpretate the readings. I doubt someone would bother writing and studying such a thing.

[seraph0x]

First off, CONGRATS to Smally for being the first to create a working "holy grail device". - Great job!

As for EEG - I happen to own a consumer grade EEG device. I'd be happy to volunteer to record EEG during orgasm. I don't have very high expectations though:

http://www.springerlink.com/content/j113425601x3276x/

EEG-polygraph recordings were obtained under rigorously controlled conditions in four normal male subjects during masturbation and ejaculation. The EEG data were subjected to both impressionistic and quantitative analyses. They showed no remarkable changes during the sequence of relevant physiological responses.

And that's what I would have expected from previous (non-sex-related) experiments with EEG. It requires a lot of smoothing, so it's not precise and certainly not quick to react. The high-end scientific EEGs may fare better, but these are simply not affordable. The only thing you can really measure well with EEG is general levels of concentration and activity. So my intuition at this point is that EEG is not the most useful for our purposes. (Unless maybe if somebody wants to go into a hypnofetish/meditation direction.)

I do like the idea of adding a heartbeat sensor or GSR though. So simple, so cheap and you can get a sense whether the user is bored out of his mind or about to have a heart attack. Definitely useful information if we're talking about pre-programmed adaptive sessions.

Pain has a very high impact on stress, so I believe if you had an automated session with some kind of pain involved (via e-stim I would imagine), you might monitor heart rate to try and regulate so it doesn't become overwhelming for the user.

[Nezhul]

Been thinking about building something like that lately. I meen a teasing-machine. Though I can't figure out what's the best way to detect closing orgasm would be (and for reasonable prise, because I won't be buying a high-tech medical center anytime soon )

So If anyone can give some real advice, I would be glad.

Oh, btw, I'm a programmer, not engineer, so my ability to construct something is most likely limited to Arduino device and programming it the right way. Most of it is pretty clear to me, the only part I don't really know is what sensor should I use. I'm no doctor too, so hardly know what the physical signs of incoming orgasm might be.

[les]

sorry wrong thread



les