Hi Jeff, that sounds like a really nifty device. Personally, I like the
idea of having an air flow switch and your heat sensor. Easy for me to say
huh?
It seems that the air flow sensor could be set for the lowest blower speed
to be covered for all higher speeds. I have not worked with one so perhaps
there are unfamiliar issues here.
It does seem reasonable that the heat sensor could be set slightly above
the normal air exhaust temperature at the lowest blower setting and provide
the protection you want. Knowing that heat tends to rise and that you would
never run the tube that close to meltdown makes one think there would be
ample time to sense a failure act on it.
You can do a lot of controlled testing by lowering or removing the
operating bias to let the tube plate current increase the standing dissipation
and
heat.
Please do let us know your results.
73,
Gerald K5GW
In a message dated 11/7/2010 10:27:58 P.M. Central Standard Time,
keepwalking188@yahoo.com writes:
The traditional monitor for a failed blower is a air pressure sensor. But
this is harder to implement with a variable speed fan arrangement.
I was working on a fail-safe for this case and thought a solution. Wanted
to run that idea by the board to see what the comments are...
Here’s the idea...
1. The cut-out mechanism would be one of these TO220 sized bimetal
switches. They are available in a variety of trip points.
2. The switch has no electronics inside and should be RF immune.
3. The switch can be set in the chimney near the silicon wall and would
not significantly impede airflow.
4. The switch has a very low thermal mass and will switch quickly.
5. Even with a failed blower, the tube would be dissipating tons of heat
and convection would ensure heat-up of the switch.
73, Jeff ACØC
www.ac0c.com
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|