Re: Updated website

--- In CAD_CAM_EDM_DRO@y..., "mariss92705" <mariss92705@y...> wrote:

> Here's what the diodes do. Let's say the "upper left" and "lower
> right" transistors are on, the current in the coil builds up and the
> direction of current will be left to right. The coil has inductance
> and inductance does not like current to change abruptly.
>
> Now the previously on transistors turn off and the opposite
> pair turn n (lower left and upper right). The current direction
> in the coil will still be left to right. Here's where things
> get interesting.
>
> That condition would require current to flow out of the
> "lower left" collector and into the emitter of the "upper
> right" transistors. You can't do that. Because you can't,
> it would rupture both transistors; the coil inductance
> would generate whatever voltage it took to do that.
>
> This is where the diodes come in. They provide the path
> for this current to flow while it decays. The transistors
> don't carry any current until the coil decays to zero
> current. Then the direction of current can reverse and
> build in the opposite direction, now supplied by the
> transistors again.

Mariss:

I'm not sure we are talking about the same circuit.
The one I am talking about has the following URL:

http://www.pilotltd.net/hbridge.gif

This is FET H-bridge, not a transistor H-bridge.

In addition, the diodes I am talking about (D2-D9)
are attached to the gates of the FETS, not the
sources or drains. While it is quite clear to me
that the voltages from the motor will vary between
Vs +.5 volts to -.5 volts, I just do not see how
the voltage from motor can get through the FET
gates. Maybe this is a mental block of mine about
FETs, but my understanding is that there is on
conductive path from the source/drain to the gate.

I'm still confused, and any further illumination
would be greatly appreciated.

Thanks,

-Wayne