easy for you, difficult for me

[jwhooper]

I'm 46 years old, so my old Electronics teacher, Mr. Sparks (no kidding) is probably retired. I should have paid more attention back when I had the chance. As much as I might come across like a kid in short pants, I have actually had a two decade career as a software architect and developer.

Anyway, I went back to your schematic, Hippy, and hooked it up. I had to guess at the resistors you left blank. I chose to make them 660, having no idea. It certainly makes every bit as pretty a +5/-5 volt output as my original two pin circuit. My cheap multimeter seems to not want to measure amperage. Or maybe it is too low to measure.

I have to confess that I am still not complete sure how this circuit works, but I won't try your patience with more questions.

Thanks.

 

[hippy]

Please do keep asking questions and apologies if anything said was patronising and I admit I misjudged your age and experience - Your unbridled enthusiasm befits a younger person so please accept that as a compliment.

Are any of your friends teachers or lecturers or do any of them know one they could put you in touch with who could help ? I won't suggest kidnapping a schoolchild, but perhaps you could find a parent whose child is into electronics and eager to share ? Again, I don't mean that patronisingly. I found the kids in the park to be most helpful when I was trying to learn to roller-blade. They weren't the ones who looked on with disdain and contempt at a 40-something flat on their backside. Laughed ? Sure, I expected that, along with being called a 'wuss' for the helmet and all the protectors

As to the current; because it's now high frequency AC the meter probably isn't registering anything. If you measure between (either) one ear contact and the PICAXE 0V you'll measure twice the current ( only goes through one R ), but it's only there for half the time. Unfortunately I don't think that 'averages out' quite so simply to be the actual current.

You could just rely on ohms law; I=V/R, I = 5V/660R = 7.58mA, halved = 3.8mA. In fact the R's were calculated by doing the reverse, knowing the current limit and the PICAXE voltage.

I forgot to mark the other resistors. They can probably be 1K or even 10K without causing any problems to the circuit operation. You can leave them as 660R's but taking them higher will reduce current drain on the battery.

To check the circuit is working you can put a LED ( pointy end down to 0V ) and the other end to the ear contact. It should glow when the 15kHz is applied and be off when it isn't. That will also help check the 0.1Hz on-off is working as well.

 

[jwhooper]

OK, thanks for the advice. I just aquired a multimeter that is capable of logging data, and it has functions for Hz/Duty/Width. If it lives up to the pretty pictures I should be able to examine the output of this circuit on my computer. Not in real time, but that doesn't matter much for my purposes.

I'll post the output back here after I figure out this new meter and software.

 

[jwhooper]

I did the data logging and with regular output it cycles +/- 500 uA at .5 Hz as expected.

I then changed it to pwmout at 15 kHz at 100 Hz. When I look at the frequency, it is around 7 kHz, which would seem to be pretty close to what I should expect. The amperage stays steady at +275 uA. I'm not sure why it is positive, but I'm sure I've far exceeded the capabilities of my multimeter.

An electrical engineer I used to work with says I can use his scope, so I'll take him up on that offer.

 

[esecallum]

I did the data logging and with regular output it cycles +/- 500 uA at .5 Hz as expected.

I then changed it to pwmout at 15 kHz at 100 Hz. When I look at the frequency, it is around 7 kHz, which would seem to be pretty close to what I should expect. The amperage stays steady at +275 uA. I'm not sure why it is positive, but I'm sure I've far exceeded the capabilities of my multimeter.

An electrical engineer I used to work with says I can use his scope, so I'll take him up on that offer.

hello.

i too am interested in reproducing the waveform of the alpha stim as it is too expensive to buy.


method 1:-

so i think a way to do it would be to recording it using a high quality microphone by connecting the output of the alpha stim to a speaker or a piezo output device and recording it ona mp3 player on HQ setting.

once this is done the pulses or output of the mp3 player can be used to drive a a logic gate which would have the output electrodes connected to it...

you could even transfer it to a cd...


method 2.

method 2 would be to connect the output of the alpha stim to the input of a pc sound card via direct connection or again via piezo sounder to high quality microphone and record for 10,20 or 60 minutes and record it to either wav or mp3 again...

the signal is then played on your pc with your soundcard output attached to electrodes...or burned onto a cd for portable devices or converted to mp3 for use on a mp3 player which again will use your earpiece wires attached to conductive foam electrodes...

the output of the alpha stim should be set low enough so as to not damage your pc card and also to avoid distortion of the waveform...

the volume control on your pc/mp3 player/cd player on playback can be adjusted to control output level...


method 3
What i am suggesting is a software program solution which would emulate the waveform
and record it to a cd/mp3...


i invite all parties to further comment or improve on this proposal....

 

[BeanieBots]

Using an audio recording/playback device does of course assume that all components of the waveform are within the audio range which unfortunately they are not.
A quality DSO would do the recording job properly and much of the analysis required to spec what is needed to reproduce the waveform.

 

[Rickharris]

Hi where did you do your electronics learning - The teacher that inspired me to get into electronics was also Mr Sparks. At Scunthorpe Grammar School.- Although I am a bit older than you.

 

[Rickharris]

Don't different heads/brains/ears have different impedances? (comments here please!)

How r you controlling current with that in mind?

I have a lot of students who are pretty thick is that the same thing?

We measure individuals hand to hand resistance with a multi meter as an experiment - in general they are in similar ranges.