16/12/2007 by peter.

Although it may look like this project is dead, it is not. I have just been coding away quietly in free moments and getting side tracked. This is project is in fact a side track to a side track. Anyhoo, progress is as follows:

menu programme written and in debug phase,
main modes of operation written,
PWM code update formulated.
GPS code half way through being written,
LCD code written (yup, we got ourselves a 16×2 LCD on this project!!)
Vibrator heads bought. (see here)

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07/10/2007 by peter.

Right, After a slight detour through the world of cloak making I’m back.

Firstly GPS still not communicating with PIC, thas the first problem to solve then onto the next phase.

I have obtained some new sensors, a triaxial accelerometer and a WiFi sniffer. Both from the marvellous Elektor. (See below).

The WiFi board is the Cyprus module (mounted on its interface board for testing) and the wee thingy in the bag is the acceleromiter, the battery is for scale. (one nice thing about doing a spot of tailoring, I now have some nice photographic backdrop material. the composition of the photo is so bad because the camera battery died while doing this shot where i was trying not to get glare of the bag.)

more to follow

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21/09/2007 by peter.

Before you think this project has lost all momentum there are just no posts for a bit at the moment due to other things going on, normal service should be resumed in a few weeks.

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23/08/2007 by peter.

After much faffing around i ported the PWM/RNG software to a PIC10F222 since I had some lying around and they are a little more suitable for this project. This involved a bit of wire sculpture between 2 DIP8 sockets to make an adaptor for the Low Pin Count board but was doable.

The next thing was to have a go at controlling a push-pull solenoid. The idea is to create a more controllable vibration generation system so that things like triaxial accelerometers or gyros can be connected to 3 orthogonally arranged vibration sub assemblies to give different sensations depending on movement of the user (or the movement of someone, or something else *insert imagination here*). An eccentrically wieghted motor generates a conical vibration pattern which has all sorts of problems with inertia and also vibrates in 2 rotational axes. One solution would be to get a motor which has a spindle out of each end (similar to those used in model rail, HO, OO scale would be a good start but those used in N and Z scales are tiny enough to have al sorts of possibilities) and attach a weight to each end of the shaft such that the weights are coaxial and that that axis is parallel to the axis of rotation. This would give vibration in 2 linear axis. Far better is to have an inertial mass being oscillated along one axis only. Which is where a push-pull, or more accurately opposed pull-pull, solenoid comes in.

As you can see from the above pic, the board with PIC (10F222), the psu board and a driver board (consisting of 2 MOSFETs, 2 1N4004s and 2 1M res) are connected by a handful of wires together and to a pair of solenoids attached to a base and whose shuttles have been wired together. The code was so short that it didn’t even go off the bottom of the screen (I say to all you people who write programmes in the Mb and Gb range, PAH!!) It takes in the ADC value from the input connected to the pot and uses that to change the time between and duration of the pulses going to the 2 solenoids making the combined shuttles shoot back and forth at a contorted rate. These solenoids are 12V and are not very good with the 9V battery I have to hand so a small lead acid bat will need to be ordered (and possibly some smaller solenoids)

next :

Since I’m doing this in totally the wrong order (more to do with what piece of technology i get my hands on next) the next fun thing is GPS. Just need to write some code to take the data from the GPS unit and then interpret that in a cleaver way, but as you see the thing is rather impressively small (reception inside a person may pose a problem so this may have to be connected to a small RF link like ZigBee or bluetooth and put in a location with more skyview, like a hat).

Anyhoo… Onwards!!!!

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15/08/2007 by peter.

So after much tinkering and coding I have a motor who’s speed is random and the amount of time it runs for at any given speed is also random.

The photo below show the finished article. The Green PCB is a Microchip Low Pin count prototyping board (came with the PICkit2) which contains a PIC16F690. A header splitter is then attached to the port on the side of the board giving me the ability to plug 2 daughter boards into the main board. On this there is a motor drive board and a hardware RNG. The RNG has already been explained, the motor drive board has a diode (1n4148) coming off the PWM output pin going to a simple low pass filter made from a 1nF cap and a 100R resistor which then drives a Darlington voltage follower to run the motor. the Darlington pair is infact a bc547 and a TIP31A since the motor is drawing up to 300mA and 2 x bc547s had a tendency to get a bit hot. There is no fly back since the LP filter should stop di/dt from getting to high (in theory). The other board is simply a LM7805 giving 5V for the PIC and 9v for the RNG. The rest, as they say, is software.

Once my wee camera decides to work again, i shall take a video of the thing working.

Edit: 100_1584.MOV

Anyone wanting more info, leave a comment and I will do schematics and tidy up and post code.

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12/08/2007 by peter.

Electromyograph electrodes. Since any company that sells them only sell them to research institutions so they look rather hard to get hold of as an private individual/mad inventor. BUT WAIT!! Thanks to the internet and those intrepid sexual adventurers we have e-stim, although I knew of its existence before, what i didn’t know/think of until I stumbled across it, they use the thing I’m looking for in reverse, these!! and what’s more they even sell the conductive gell. Well that’s that sourcing problem sorted out, just need to find a photoplethysmometer/Geer gauge.

Oh and the volunteer to try it all on.

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12/08/2007 by peter.

After getting my little photo sensor (one of theses) attached to my PIC I started playing with it using a torch and my little finger i can sometimes pick up a pulse but it is very sensitive to movement and the pulse only shows up in the 2 LSBs. This problem may be alleviated somewhat when measuring form inside someone. Anyhoo that is a problem to be sorted when I have a willing subject to test on.

But that aside, the electromyograph idea still needed a bit of thinking before anything could be built and I had no Idea if the output from it could be useful. Then I found this. Looks like we may be onto something here. All I need now is the person and the electrodes. Oh and the amplifier hardware. Oh and a data logging device. Hmmm… This is turning into a bit of a big project.

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11/08/2007 by peter.

Here you can see my wee set-up. the LED sits there and changes its brightness about once a second (software settable up to about 30 secs) the board with the 9V bat is the RNG using built from 3x 2n2222, 3 resistors and a .1uF cap.

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11/08/2007 by peter.

So after a week away and doing far less coding than I anticipated, I have finished the first programme and prototyped the hardware (well most of it). I wrote the code in MPLAB and used MPSIM to simulate it then used the PICkit2 to do the real world testing. It takes a hardware RNG intput, a PIC16F690 (a bit of over kill but it came with the kit and gives plenty of room for improvements and add ons) uses the rendom number with accumulator, ignores the overflow and then shifts 2 places left to give a nice random looking string of numbers since my RNG hasn’t got the right amplification at the moment to give a full scale for the ADC. This is then used to control a PWM loop (until I can work out how to use the PWM port). A couple of other loops hold the output at a level for a set time and then it repeats. the next stage is to run a motor off this output with a single transistor follower, work out how to set up the on board PWM port and do a quick amplifier for the RNG to give a better output.

Since no one has commented on this blog there is probably no one reading it. Therefore if anyone is acctually reading it and interested in the code, let me know and I will post it.

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04/08/2007 by peter.

Temperature measurement.

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