RE: [ATM] Kendrick Controller?

[Ken Lowther <hermit@outofoptions.org>]

The Clement dew heater circuit is lots cheaper if you want to build one.  I
would imagine for $85 you could build a couple dozen.
http://atmsite.org

Ken

Quoting Bob Nonnemann <bob.nonnemann@insightbb.com>:

>
> Heat is generated wherever the electricity flows through a resistance.
> Using a potentiometer will result in a second source of heat -- the
> potentiometer will get warm, depending on its setting. So while you could
> use a pot, just be aware it too will be generating heat and that you will be
> spending battery power to generate heat in place where you don't want it.
> As you suspected, the Kendrick controllers cycle the DC on and off.  This is
> much more efficient, as very little current is drawn when the Kendrick is
> cycled off, and virtually all of the energy is directed to the heater when
> it switches on.
>
>
>
> -----Original Message-----
> From: atm-bounces@atmlist.net [mailto:atm-bounces@atmlist.net] On Behalf Of
> Doug Williams
> Sent: Wednesday, February 02, 2005 7:51 AM
> To: atm@atmlist.net
> Subject: [ATM] Kendrick Controller?
>
> Hi all,
>
> I was thinking of getting a Telrad Heater from Moonlight Telescopes.  My fan
> keeps my mirrors clear, so I don't need to worry about that.  Anyway, since
> the Moonlight Telrad heater only draws .16 amps, I wonder if it is worth
> bothering with a controller at all.  I also wonder why a simple
> Potentiometer or "dimmer switch" wouldn't work to control the heat output,
> rather than the $85 Kendrick controller.  I understand that the Kendrick
> controller is more advanced than this, but do I need this?  Why does the
> Kendrick cycle the power on and off rather than just reduce the voltage?
>
>
>
> Doug
>
>
>
>> From the Moonlight webpage:
>
> Moonlight Telrad Heater
> This simple 2 watt dew heater is the best thing that ever happened to a
> Telrad. The 12 volt dew heater slides into place in seconds and keeps the
> Telrad clear, even in the most severe conditions. It's easy on the
> batteries, only drawing .16 amps and plugs into your existing controller. Or
> cut the plug off and wire it directly to your 12 volt battery.
>
>> From the Kendrick webpage:
>
> The power output from the 2001 Model VI controller can be varied from 40% to
> 100%. As the standard controller is a duty cycle switch, it controls the
> power getting to your heaters by shutting it on and off many times each
> minute. When the standard controller is set on low, the heaters will
> continue to draw the same amount of current, only 40% of the time. Low to
> medium is the recommended setting for most observing conditions.
>
>
>
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>
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