"Larry W4CSC" wrote in message
...
"Roger Long" wrote in
:

Did I blow the diode by hooking up with reverse
polarity?


Yep. The diode only conducts when the field in the coil of the relay
collapses, when you turn the power to it off. The diode is reverse biased
(+ power to its banded cathode end, - power to its anode) when the relay
is
energized. You had it connected up backward, zapping the diode to a
short.

Oops....

+12-------coil----------12

| |
--|--
band noband

Not clear. Fuse is blown but one would have to check to see if the diode is
blown. Suppression diodes are generally rugged little things. They may well
last long enough to blow the fuse without going out.

There are only a zillion or two diodes launched in this application. I
don't think I would use a solenoid or a relay without one. If worried get a
bigger diode.

Nope. It was a dead short. I'm putting in the 10 ohm / .01 mfd
suppressors instead.

--

Roger Long

Roger,
You can do that if you want to, but diodes work better. You may still
get a spike on the line with the RC setup, but that won't matter to
anything but the electronics. The RC set does what it does by thying to
limit the rate of rise when the switch opens, but the diode makes the
power from the widing stay in the winding.

That is why little DIN (automotive default these days) relays are marked
87 for signal and 31 for ground.

Newer cars have a lot of this stuff going on.

Matt Colie

Roger Long wrote:
Nope. It was a dead short. I'm putting in the 10 ohm / .01 mfd
suppressors instead.

Interesting point. I can wire the diodes on the outside of my
controller just as easily as the snubber. If I do see any evidence of
spikes, I'll do that.

For future reference, do you know which diodes to use? I foolishly
tossed the ones I cut out of the sockets.

It's unlikely I'll see a problem though. The water will probably only
get to the high switch in our boat if the stuffing box hose splits.
If the boat is unattended, the minimal electronics we have will be
off. Mostly, this system will be operated by picking up one of the
float switches when checking the bilge. The most used feature of it
will be not having to hang down there holding the switch until the
bilge empties. Just being able to flip it up and forget it will be
worth all the effort I put into it. Operating in that mode, the relay
never engages.

--

Roger Long



"Matt Colie" wrote in message
...
Roger,
You can do that if you want to, but diodes work better. You may
still get a spike on the line with the RC setup, but that won't
matter to anything but the electronics. The RC set does what it
does by thying to limit the rate of rise when the switch opens, but
the diode makes the power from the widing stay in the winding.

That is why little DIN (automotive default these days) relays are
marked 87 for signal and 31 for ground.

Newer cars have a lot of this stuff going on.

Matt Colie

Roger Long wrote:
Nope. It was a dead short. I'm putting in the 10 ohm / .01 mfd
suppressors instead.