OT? DIY electronics?

[The Legal Occupier]

Hi occupiers,

Is this the right NG for DIY electronics, or is there a more relevant one?

I mean, I'm sure I would get better answers here than anywhere else, but I just wanted to be sure.

[Theo]

There is sci.electronics.*, in particular sci.electronics.design. However you need a decent killfile to filter out posters of spam and noise. (not unlike here)

I think you'd probably get equivalently good answers here. Could always post to both - doesn't seem to be massive amounts of traffic.

Theo

[Fredxx]

Fire away.

As Theo has said there is a sci.electronics group but I've given up on down to the rubbish that's posted there. There is very little electronics that's posted, and even then it tends to end acrimoniously!

[Paul]

sci.electronics comp.arch.fpga

Interfacing an RPi, that could be a web forum. (Not because they're good at electronics, but because they know of ready-made modules to solve problems. You go back to sci.electronics and have them laugh at the schematics from the web forum.)

Paul

[Theo]

comp.arch.embedded too, although a bit quiet these days.

On that front there's comp.sys.raspberry-pi, although that has a strong tendency to wander off into alt.folklore.computers territory. (not staying on topic and actually answering the question is one of the irritations I have with it)

Theo

[Adrian Caspersz]

Here, and sci.electronics.basics worth a go, the sci.electronics.design bunch care more about their cleaning guns and taking pot shots at Democrats.

[The Legal Occupier]

Well basically, when I lived in Italy, there was a magazine called "Nuova Elettronica" (a bit like Elektor but more pedantic and old-fashioned), which also made good quality electronic kits: one of them was an electro-magnet therapy. I bought and built a few of them, they were all very good.

Then the magazine went belly up about 10 years ago.

I wonder if it would be possible to build a home made electromagnet therapy.

The electronic circuit shouldn't be too difficult. I built some variations myself in the 90s, using a 555 and a square wave. The problem would be the coils, which were the expensive parts.

The magazine is bust but copies are available on line, I can post links if interested. I try to avoid that because it's all copyrighted material. Obviously the text is in Italian. Just Google "nuova elettronica magnetoterapia bf pdf"

BF = low frequency

AF = High frequency

Two different kind of therapy.Never used the high frequency one, the low frequency was very good but more expensive.

[GB]

Is there any reason to believe that magnet therapy would cure whatever it is you have wrong with you?

[Theo]

I found this one:

looks overcomplicated with a display and a microcontroller - but I think that is just offering a UI to set strength, frequency and time. A few knobs would do just as well.

Otherwise it looks like some MOSFETs to drive slugs of current through a pair of coils. It doesn't say much about the coils but I think you're supposed to wind them yourself? (1300 turns)

There is this one:

which is a much simpler circuit of oscillators. The coil looks like something you could get etched at a PCB service (eg jlcpcb.com, $2 for 5 units of a small PCB).

Not that I expect they are going to do anything medically...

Theo

[Tim Streater]

What is "electromagnet therapy"?

[Animal]

Of course it's doable. Give us a clue which of the many search results you're referring to

[The Legal Occupier]

[The Legal Occupier]

Yes, I built this one, but I agree it was overcomplicated.

I was thinking of the older model, this one:

Page 40.

However, I then modified the circuit (this was in 1997). I changed the frequencies from the default 1, 3, 6, 7, 14 hz to roughly 10, 25, 50,

75, 100 hz and the square wave cycle to 10% to 50% (don't ask me how I did, I played around with a simple NE555). Then I used the coils from the circuit above (nuova-elettronica-230) and it worked perfectly for about 15 years, then the coils developed a fault.

I have no idea how to reproduce the coils. It might be a trial and error process.

[The Legal Occupier]

Unfortunately it won't cure whatever is wrong with you.

[The Legal Occupier]

See my earlier reply to Theo.

[Tim Streater]

Hmmm. The evidence for this being of any use appears skimpy at best.

[Brian Gaff]

OK, I'm not going to avoid the obvious question here: What proven medical principal is this therapy based on. I see adverts for mattress toppers with embedded rare earth magnets for back pain, but am not sure if it might not be the placebo effect at work, that is not to say of course that this is not a valid way to treat pain. What are the claims for electro magnets, other than erasing any magnetic media you might have on your person at the time? Brian

[Brian Gaff]

Maybe one could repurpose those amazing electronic water softeners that just clamp around the pipe and send magnetic pulses to the water inside. In my experience this can tend to clump the little particles together and in the end you find they either block the pipe up gradually, or more likely after a while there are so many little magnetic particles that the effect is almost no existent. I suppose if arthritis has little magnetic particles it may be able to affect bonding to the bone, who really knows. Brian

[Theo]

Hmm, judging by NE's wikipedia entry:

magazine had a habit of including custom components, which you could only buy from them, without describing what they did. That one looks like the GAL wouldn't be hard to reproduce in a few logic chips (there isn't space for very much in a GAL)

(the style of the magazine is quite cute though)

So I suppose what you want is field strength, which is governed by the current and the number of turns.

Working back from that, pick a current that you can handle (eg sensible to generate from your PSU) and decide on a number of turns that gives you the strength that you want. The wire gauge will be set by the current and any heating effect in the coil (thinner wire is smaller but will get hotter).

If there's a magnetic core it will act to concentrate the field, potentially allowing a smaller coil. However a magnetic core will increase the inductance of the coil.

The inductance will set the impedance at whatever frequency you're driving it at. So you'd then design the driver circuit to drive the load at that impedance for maximum power transfer.

Because the inductance will 'fight back' you won't get the full current through the coil, like you would at DC. But if the drive frequency is low the impedance at that frequency might be relatively insignifcant. You could also increase the supply voltage to achieve the desired current with the coil at that impedance.

Should be doable with the equations and some back of the envelope calculation, at least for a basic air-cored coil.

Theo

[Robin]

It's been taken seriously as a possibility with NICE devoting 640 pages to their draft review of the evidence on electrotherapy for treatment of osteoarthritis. But the conclusion in their draft guidance was "there is not enough evidence to recommend electrotherapy".