January 2010

muscle Electro microcontroller

about three years ago had bought a muscle stimulator (carito paid enough) and it was a disaster!, After 3 months the baton this stopped walking and had left lying around.

In December last year that could be reviewed and I find very dangerous circuit, where all is wrong, do not have the slightest measure of security, no design, no nothing.

Then there comes this project, which may sound easy but it is not at all.

measures must be implemented security and is being applied to 100v people, and must be careful not to exceed 100mA (something the previous SI was to put it out with the electrodes connected with the open pot, mom pain!)

As I said higher than 100mA may cause cardiac fibrillation.

These are the requirements for a design worthy of a stimulator. Requirements

1. Security measures
1.1. Double or triple electrical insulation, through switching transformer or power, then by transforming common line or transformer
1.2. Mains filter

1.3. Fuses!
1.4. Intentionally or demand stimulation, ie, the person has in his hands the key that toggles the stimulation when something happens that does not like.
1.5. When you turn on or turn off your computer should start without voltage / s output / s.
1.6. When you start the stimulation must verify that the current control potentiometers are closed.

2. Specifications
2.1. Power: 220vac 50hz.
2.2. Pulse: from 0v to 100v maximum of at least 200us, square or triangular, phase (continuous pulse) or biphasic (alternating).
2.3. Ability to modify the width, pause and frequency.
2.4. Train Driving pulse.
2.5. Pc configurable.
2.6. Adjustable voltage and current.
2.7. The cheapest (but surely) possible designs Possible

1. LM555 with a line transformer: It has no way to generate monophasic or trains of pulses, pauses for configuration control, or security measures, a line transformer goes about the necessary characteristics. $ 15 to $ 3 a common one, among other things.

2. Multiplier voltage: Problem already explained in previous post, there is no insulation, the discharge of the capacitors are nice as some think ...

3. Step-up Converter It would work something like investors 12vdc to 110vac, the back problem is the lack of electrical isolation and the risk that an error causes a very high voltage actually do test and attest to it.

4. Similar to 1, but with a normal transformer, converting the DC voltage and drain current in a microcontroller. Problem, such as generating alternatives from continuous -> inverter H-bridge polarity

I think the best / cheapest is 4, until further notice, I have a 12V 300mA transformer,

means that if P = 12V * 0.3A = 3.6W

Regulo stream draining the 12V output for the other side 100VAC (220V input). Across

P remains at 3.6W, then the maximum current that can deliver the transformer is:

P = V * I -> I = P / V = \u200b\u200b3.6W/100V = 0.036A, ie maximum current applied to one person may be only 36mA maximum
which gives us an acceptable safety margin, with more than 40mA some people do not support it.

Square Wave