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RE: [ATM] Kendrick Controller?
Bob,
Thanks for the explanation. I suppose that I don't need a controller if I
am only going to run the .16 amp Moonlight Telrad Heater (in comparison, the
Kendrick Telrad Heater draws .8 amps).
But I suppose I'll have to get a controller if I decide to add heaters for
my optical finder and an eyepiece.
Doug
-----Original Message-----
From: atm-bounces@atmlist.net [mailto:atm-bounces@atmlist.net] On Behalf Of
Bob Nonnemann
Sent: Wednesday, February 02, 2005 6:53 AM
To: atm@atmlist.net
Subject: RE: [ATM] Kendrick Controller?
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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