02/04/2009 by peter.

Finally the boards have arrived. now to populate them

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05/03/2009 by peter.

while I was looking at the PCB design I felt it was a bit wasteful of space so I started from scratch and redid it. it is now just 3.5″x1.85″.

After looking for a board house to make up PCBs for this little endeavour I found that crazily if i get them made in the UK there are few people with on-line shops for that sort of thing. if I go to mainland Europe the best I can hope for is still £50+ but if I use Sparkfun’s little side company, BatchPCB, the cost drops off enormously. They only charge $2.50 a square inch plus $10 and then postage. What is crazy though is that it is actually manufactured in china. so my design goes to America, where it is then sent to china for production, then the board goes back to America and then from there to me and that’s cheaper than going down the road to get it done!!!

anyway, boards are now ordered and should arrive sometime this month.

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01/03/2009 by peter.

Well after much faffing around I have finally finished the first draft of the PCB for this thing.

Its not pretty or well laid out but with a bit of luck it will work.

Getting there….

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29/11/2008 by peter.

To machine the various square orifices required for the USB port and the LCD display I need to use my rebuilt Boxford. One problem, the software was still buggy and I haven’t written anything to generate control codes to give it. Simple solution, write a manual controller. That took all of 2 days of spare time to add all the features I wanted and with this I set about making the rectangular hole for the LCD. After much standing and watching the machine produce fine swarf as it slowly ploughed through the metal I had a nice rectangular hole. I de-clamped the box to admire my work when I realised I hadn’t drilled the display mounting holes which would be a lot easier under numeric control. Unfortunately while edge finding the rectangular cut-out, I crashed the machine into the top corner of said orifice (hit “End” instead of “Page up”) then I got the holes slightly in the wrong place but that’s one reason why I will make 2 of them. The first to screw up one and second so that I can test new code and features on my own one before sending the updates of to a beta tester.
The other minor annoyance is the lack of M2.5 nuts to fit the M2.5 LCD retaining bolts. For reasons of stupidity, I ordered M2 nuts. Well it will have to wait until I have a few more bits to order. There’s no point in paying postage on only one tiny bag of nuts.

Anyhoo. Piccies of the box so far

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08/11/2008 by peter.

With about 99% of the parts now arrived I have commenced the construction. The first part to be completed is the measurement head. “Why such a small part?” you may ask, well it is simple, I need to cut out a rectangular hole for the LCD and that requires me to find the clamping screws for the CNC mill which I have ever so carefully put somewhere safe. Once I find them then I can cut that out along with the hole for the USB port.

This is what I have so far. A box with a pressure transducer in one side and an M8 4 pin industrial connector in the other.

Onwards!!!

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12/09/2008 by peter.

After much faffing around (about a year since i started this particular folly) I have actually got a Beta version finished. WOOHOHOO!!!

Some videos to show what it does.

http://www.vimeo.com/1718065 :showing the bootloader in action (only changing the version number in this example)
http://www.vimeo.com/1718090 :Biofeedback 1
http://www.vimeo.com/1718106 :Biofeedback 2

Now just to polish the code and make up the final beta hardware…

Always something else to do

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12/09/2008 by peter.

So far there are 2 biofeedback algorithms in the this contraption although this is by no means all that there could be.
One is a straight feedback system that simply adds the input form the sensor to a pre-set in a way which will have no overflow control. This means that with zero pre-set the output will be positively proportional to input. With a little pre-set, less force is needed to reach high power and the motor can be kept ticking over. With a good bit of pre-set then to get max output muscle action must be maintained below a threshold or there will be an overflow and the thing will stop until the muscle relaxes again. finally with a lot of pre-set then the device will be at max at rest and the more force excreted the vibrations will drop off and then ramp up with pressure.
The second will have a time delay in it so it will ramp up slowly, then once a muscle pulse larger than a pre-set value comes along it will drop off, wait and then start ramping again. This can be tweaked in a number of ways e.g. the dead time can be modified based upon the frequency of pulses received or the pre-set could vary with time, either increasing or decreasing.
Of course data can be fed back and forth to the computer which will be able to carry out more complex algorithms which opens up amazing possibilities….

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12/09/2008 by peter.

With my new 24PCBFA6G sensor and Myself Probe (which was nice enough to fit together with minimal faffing) I can detect squishing of the probe by simply measuring the output of the pressure sensor on my shiny new scope.

and as you can see a squish provides a good positive response (yellow and blue are the 2 outputs form the bridge and red is the difference between them ie the output)

(yes I know the 2 channels are on different scales, that’s just my incompetence but it demonstrates the point anyway)

EDIT: This is a better example

All that is required now is an input amp and some software to make the PIC do something interesting with these pulses.

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07/09/2008 by peter.

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….

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24/08/2008 by peter.

Once again i haven’t updated for a bit but have no fear the project has not died.

Apart from my oscilloscope being phut which has meant i cant do any of the analogue system design, I have been looking over the options for embedded processing and you can see the range i have been looking at here

For what is required for this project the Altera Cyclone might be a bit overkill and in fact it looks as if the old PIC in assembly might be best option. However expect more woderfulll things to be built around some of these technologies.

P

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