I had discounted the idea of pressure measurement for detection of PC muscle activity as it required the construction of a closed vessel possibly filled with a liquid as the volume differential would be low so the pressure differential would also be low thus making the system inherently susceptible to noise, especially of the sort being induced by the vibrator head. however i cam across this which has a nice cheep pressure vessel head. All the material bio-compatibility stuff has been thought of and it has been designed to have a low volume so that nice pressures are generated. so i have bought one and i will order up a pressure transducer and with a modicum of luck it will all work and when it gets squeezed the transducer will, along with associated ancillary electronics, produce a nice output. This then gets fed to an ADC pin on the uC which will run a little algorithm that will generally reduce the strength of vibrations if it sees a pulse then slowly ramp up again. There is an inherent danger that this could lead to conditioning that will reduce PC muscle activity in response to stimulation but this can be overcome by using a second programme that will generate a pulse of vibrations only when the system sees a pressure. using both programmes should allow long periods of titillation and PC muscle exercise.
Lets just hope it works….
07/09/2008 at 05:24 am
So, I’ve talked to a couple of people who’ve built something similar to this. For instance, the Electric Orifice Orchestra at Arse Elektronika last year (Warning: Painful video, but it at least shows that it… “worked”) - http://www.youtube.com/watch?v=7tFCXXlcUng
I can try and dig out the plans or at least put you in contact if you’d like, just throw me an email.
07/09/2008 at 01:01 pm
I think I saw this video when you first published it and thought that they could do with a bit of tuning. The idea is sound, however I think the implementation of the was not as good as it could be. What would be interesting would be to find out what they used as the compression volume, the diameter and length of pipe they used, the pressure sensor they used and the pressure difference they saw. from this pic ( http://www.flickr.com/photos/metaphorge/1495885933/sizes/l/in/set-72157602302921425/ ) it looks like it was about a 1/4″ tube about 4′ long which will have a comparable volume to the change in volume of the thing being squeezed and that will meen that the system will be low resolution and will saturate quickly (in this case that means the thing has been squished flat) which would explain the pump bulb and pressure gage there as to stop saturation the thing would need to be pressurised. This is why I thought it would need to be filled with a liquid, so that the change in volume is reduced and the sensor will have a larger range and not saturate. The probe I bought off the shelf has a bulk piece inside it thus reducing the total gas volume of the system and has a 2mm id pipe about 4″ long so the force exerted on it acts almost entirely on the gas in the probe so both resolution and no saturation (assuming the user is not too strong) are assured. With suitable sensor it should generate a good output. the sort of sensor I am looking at is this http://uk.farnell.com/731687 They are nice and cheep and easy to use.