Quote:
Originally Posted by DaGrinch
Yeah, I've been reading about the issue on the Dynamax threads, also. You just have to wonder what is happening where humidity and/or moisture is getting at these controllers and not any other controllers, like say in my Sunseeker. Is it the position/location of the boards?
Believe me, if DW wants something even IF it has had problems, as long as she thinks I can fix it or make it work, it won't keep her from not wanting to purchase one. 
Larry |
The following is speculation. I have never been near a Dynamax and know only that a digital circuit is affected by moisture, either in proximity or at a remote switch. I'm speaking as a professional electronics engineer with a few college degrees and a half-century of experience.
A dozen years ago everything was controlled by relays and solenoids or by direct application of voltage. The impedance of those motors, relays, solenoids, and latches was so low that it was acceptable practice to apply voltage to actuate a system, and open (float) the circuit when it wasn't actuated.
Now CMOS microcontrollers are widely used. It's easy to operate them from a touchscreen, remote, wireless device, or switch. But their inputs are extremely high impedance. The input actually terminates on a very thin layer of glass inside the chip. A transistor "channel" on the other side of the glass either allows current to flow or inhibits it, based on the voltage on the input (gate).
It's easy to induce a voltage on this high impedance. On a dry day you could wave your hands or scuff your leather-sole shoes across a carpet. And on a damp day the input could be influenced by voltage at a nearby point. This could happen in the vicinity of the CMOS chip or remotely at a switch.
Best practice is to never let an input float. An option would be to use a switch which applies voltage to the input lead when on, and grounds it when off. A better option is simply to use a moderately high resistance "pulldown" resistor to ground on the input. That's preferred over the first option because there's never a gap in time where the lead floats when the switching occurs.
I'm wondering if a pulldown (sometimes pullup) resistor was omitted. This is purely speculation.
Linear Mode
