[App_rpt-users] Slight mod to DMK GPIO driver circuit when used for a fan controller

Bob Brown - WØNQX bbrown at byrg.net
Wed Feb 1 11:10:48 EST 2012

Hey Bryan

Send me a picture of your "Rube Goldberg Special"

With the wires hanging out of course :)

Thanks in Advance

   Bob Brown, WØNQX

   Kansas City Metro Area





Quis custodiet ipsos custodes?

Its not how many watts you have,
its the SIZE of your watts that matter! -- Johnny Marshall, W0JM-SK


On Wed, Feb 1, 2012 at 8:07 AM, Bryan D. Boyle <bdboyle at bdboyle.com> wrote:

> In hacking (thanks, Kyle) through getting both the script working (hey,
> had to modify it for my own install, which is a good thing...:)) and
> addressing the proper node/dongle number...and getting the parts to build
> the circuit (at Radio Shack, believe it or not...) as shown at the DMK site
> so I could actually drive my cooling fans (with 3 repeaters, a 100w amp,
> and batwing spectra transmitter that gets Real Toasty even at 12w out, the
> amount of constant noise is a bit much, even in the basement...not to
> mention the electricity consumption), it's all up and working.
> However, in talking with Scott KB2EAR, he brought up the issue of the
> possibility (not remote..) of the controller or a dongle hanging or going
> brain dead in between the time that the radio keys up and the fan
> controller script turns on the relay...with the possibility that the radio
> would key (along with the amp...) but the fans would never come up.
> So...belt and suspenders time.  I have an extra box of shalco
> thermoswitches...NO contacts, close at 115c, reopen at 95c or thereabouts.
>  Since the relay (I like electromechanical stuff, ok? Nothing like the
> sound of contactors closing all around the shack when you press one
> button...brings me back to the days of running BIG transmitters and the
> plate contactor closing when you pressed 'PLATE ON' and saw the plate
> voltage meter swing to 18KV @ 2.6A) that's being driven by the DMK circuit
> is actually controlling the B+ to the fan string...putting one of the
> thermo switches across the armature and NO contact of the relay...well, if
> the computer hangs, or the relay fails, and the transmitter and amps are
> up...when they get warm enough, the secondary mechanical (rather than
> logical) circuit takes over and STILL turns the fan on.  I'd rather fail,
> if that's the scenario, with cooling flow across the heat sinks than not.
> Obviously, this implies that the logical circuit is driven from the same
> power supply as the fans (mine are...) to eliminate that issue.
> Anyway...wired that up as an addition to the relay circuit; actually, it's
> just a pair of wires coming back from the shalco and paralleled across the
> leads from the relay.
> Just throwing that out there for y'all's consideration, if you're building
> the circuit from DMK to do something like this.
> (Still have to mount the DMK circuit on perfboard in a small project box
> and clean up the wiring...right now, it's just hanging by its wires in
> front of the repeater shelving unit (plastic...one of those Sears 5-shelf
> organizers...).
> Final cost, by the by, of the DMK circuit, using bits and pieces from the
> Shack, was under $10 USD, btw.  And the biggest cost was the big piece of
> perfboard (which I cut down, so I have lots extra to use for other
> projects) and the small DPDT relay.  Bought the 10-pack of transistors,
> 10-pack of diodes, and couple sleeves of the 4.7K resistors, so, have some
> extras to build other interfaces...
> 73
> --
> Bryan
> In this world, you must be oh so smart or oh so pleasant.
> Well, for years I was smart. I recommend pleasant.
> You may quote me.
> Sent from my MacBook Pro.
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