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From: "Anthony Q. Bachler"
Subject: Re: what is this type of oscillator?
X-Newsreader: Microsoft Outlook Express 6.00.2800.1106
Date: Wed, 01 Jan 2003 09:25:25 GMT
NNTP-Posting-Date: Wed, 01 Jan 2003 01:25:25 PST
Organization: EarthLink Inc. -- http://www.EarthLink.net
Any information on what voltages are necessary on the pad to induce
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"Terry Moreau" wrote in message
> "Dave" wrote in message
> > I want to make an oscillator that has a frequency of 2500hz but the
> > the pulse should be 200 or 300 microseconds. what is this type of
> > oscillator called and what is the simplest way to implement it? it's
> > muscle stimulator.
> > thanks
> Sounds like you want a variable duty-cycle oscillator. A 555 IC circuit
> example is given in with most 555 datasheets and/or app notes. You may
> need a power transistor driver before the step-up transformer.
> I did a muscle stimulator cicuit one time and found that waveform envelope
> control was also quite important for optimal patient comfort and muscle
> response. A gentle attack and prompt decay seems to better "prepare" the
> muscle to contract and reduce patient discomfort and stress. I recall
> frequency of the AC was not a big issue but if too low (below 100Hz there
> was more discomfort felt). Amplitude, envelope, and duration were all
> critical. Also the contact area, placement, and dispersive conductivity
> the body pads make a huge difference. I considered having a special
> of the pads isolated and used as feedback of actual pad voltage, and to
> monitor output current, thus having the circuit regulate actual pad
> and/or control the source impedance of the high voltage AC but I never got
> around to putting the idea into practice.
> Muscle stimulation requires a threshold level to be exceeded to create
> actual contraction but also staying below patient discomfort levels. A
> muscle contracted too strongly will cause pain and the high voltage AC
> applied too quick or too slow or at the wrong level can also cause
> complaints of too much electrical tingling feeling. An over the counter
> pain medication such as Tylenol or Advil can help reduce discomfort during
> treatments. A good stiff drink is another option!
> You could vary the dutytime from 200-300us as you propose, however in my
> circuit I left it fixed and varied the DC voltage to the final driver
> instead. That was controlled by a second 555 circuit that let me adjust
> repetition rate, duration, attack/decay times, and amplitude. In the end
> the box looking like a multi-track mixing console, full of knobs!
> Such circuits should have some sort of fail-safes. NEVER use these
> where they can shoot a path directly through or near the heart or head or
> internal vital organs!
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