As a thought, why not convert the 110ac to 24ac...run it up the tower and
then convert it back to 110 ac if you really require this voltage for the
relays? This way, you also limit the amount of current availabe by the
size of the transformers used. All you need is 2 110/24 transformers.
Mike VA3MW
At 10:31 AM 02/12/97 -0500, \"Dick Green\". wrote:
>Incidentally, U.S. Tower runs 110VAC to their tower raising motors, which
>are attached to the lowest section about ten feet off the ground. If you
>have one of these towers, make sure it is is well grounded and turn off the
>AC before doing any work on it. A GFI circuit breaker would be advisable,
>too.
>
>Incredibly, U.S. Tower also uses 110VAC control signals in its remote
>control package. The remote control box simply sends 110VAC signals down the
>multiwire control cable (like rotor cable) to enable the main motor relay,
>switch the tower-mounted relays to raise or lower the tower, and from the
>limit switches to turn on the "full up" and "full down" control box neon
>lights. That means that the cables running up the lowest section to the
>limit switches carry 110VAC. These cables are rather exposed to damage
>during shipping, installation, and maintenance, so check them carefully.
>
>I ran the control cable for the tower in a 250' conduit before I knew that
>it would have to carry 110VAC. That's undoubtedly a major code violation and
>a dangerous situation. My top priority winter project this year is to build
>a remote relay board that will allow me to send 12VDC or 24VDC down the
>cable instead. I've roughed out the schematic and it's very simple to do.
>The relay board goes in the weather-proof electrical box on the tower. A
>control box with switches and LEDs replaces the U.S. Tower control box in
>the shack. The control box sends low voltage signals to the relays on the
>board, which switch 110VAC available in the box to the stock relays. A pair
>of 110VAC relays controlled by the limit switch signals will switch low
>voltage relays to light LEDs at the shack end. In all, it takes six relays.
>
>An auxilliary project is to mate a small DC motor with the new control box
>to run a mechanical counter that keeps track of the current tower height.
>
>While we're on the subject, I'm still pondering whether to use 12VDC or
>24VDC to control the relays. 12VDC would be much easier, because I can just
>tap into the shack 12VDC power supply. My Ameritron RCSV-8 coax switch works
>just fine at 12VDC on the 250' run to the tower. Would 24VDC be any better?
>I might have to build a power supply for that unless the combined current
>draw can be handled by a wall cube. Since there's a certain amount of drop
>at either voltage, it seems to me that it's just a matter of the sensitivity
>of the relays. How do I determine the sensitivity of the relays that I need
>to buy for this application?
>
>73, Dick, WC1M
>
>-----Original Message-----
>From: K7LXC@aol.com <K7LXC@aol.com>
>To: ddjones@nas.com <ddjones@nas.com>; towertalk@contesting.com
><towertalk@contesting.com>
To: <towertalk@contesting.com>
>Date: Tuesday, December 02, 1997 9:40 AM
>Subject: Re: [TowerTalk] 110 Vac up a tower
>
>
>>In a message dated 97-12-02 04:35:26 EST, ddjones@nas.com writes:
>>
>>> In responding to the querry about what type of coax to use, KC5UOO
>>> suggested running 110 Vac to the top of a tower to operate an antenna
>>> switch. Please note that this is potentially LETHAL unless industrial
>>> grade installation guidelines are used throughout the project. That
>>> means running metal-type conduit up the tower for the AC power line.
>>>
>>> It is far safer to run 12 Volts ac or dc to the top of a tower to
>>> operate switches, so long as the relay coils are consistent with
>>> that voltage.
>>>
>>> Just a word of caution........Avoid running 110 Vac up to the top of
>>> a tower if at all possible, or if you EVER intend to climb that tower
>>> with the AC power on!!
>
=================================================
Mike Walker VA3MW
Corbeil Contest Club
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