Anyone use this...curious to get comments...does it work as well as the Kendrick products.
Thousand Oaks Dew Controller
Started by jkurtz555, 05/10/2006 01:52PM
Posted 05/10/2006 01:52PM
Opening Post
Posted 05/10/2006 03:41PM
#1
Jeffrey Kurtz said:
Anyone use this...curious to get comments...does it work as well as the Kendrick products.
I ran across a Gentleman in Kentucky who owned one. The night we used it wasn't a particularly cool/damp evening but it seemed to work acceptably. Sorry I can't give you a better or more direct comparison to Kendrick's. From the one night using the Thousand Oaks, it does seem to work well.
Clear Skies, Bill
Posted 05/13/2006 03:54AM
#2
It uses a pulse width modulation circuit with a one second window. Therefore, at 50% power the current is fully on for half a second and cut off completely for half a second. This means there is no heat wasted in a series resistor as it's the same as if you turned a switch on and off. It's very efficient way of controlling power, but you will hear your scope mount motors speed up and slow down as the current increases and decreases as the circuit switches power on and off to the heaters, especially if your battery is rather small. This is most noticeable on the fastest slew speed on my LXD75 mount and 10 AH battery pack. I use quiet slew mode anyway, and since the motors draw much less current that way, the effect is much less noticeable.
You can get a 555 timer circuit cookbook from Radio Shack and rig up your own similar circuit. The timer will switch a solid state relay which lets current flow in the heater circuit. A potentiometer controls the on/off cycle during the timing window as it is a variable resistor used to control charging current into the timing capacitor which allows a trigger voltage to rise, after which it discharges and the cycle repeats. Really simple stuff.
An improvement would be to put the LED for each channel in the current path and let it light when heating current is applied and turn off when current is off, so that an instant check of power percentage is available without turning on a light to check the setting of each control knob. An easy thing to add to the circuit for anybody with elementary electronic skills. If the light is on and off half the time, you have half power. For full power, it's on all the time.
I'll probably make my own controllers in the future rather than buy any more. I can get my hands on much better parts than Kendrick or Thousand Oaks uses in these things. For one thing, an RCA plug and jack is junk as far as a high current application is concerned, especially one exposed to dew and the elements. You need o-ring sealed AMP connectors and such, if you really want it done right and not give trouble later on. This is for serious people that need equipment that works, not guys out for occasional thrills and looking for low end consumer electronic prices. The RCA jack and plug is an old cheapo consumer audio connector that is practically never seen in pro level audio gear. It has no place in a low impedance, high current heater circuit. That is the sorry low grade state of affairs in much of amateur astronomy. The vinyl plastic used in scope heater cabling is also a sore point with me. It becomes very stiff on cold nights, and rubber insulation that stays very supple at low temperatures is used in electrical cabling in many other types of products. Amateur astronomers need to demand better electrical design and materials. Electrical problems are my biggest equipment complaints on cold nights. My hand controller goes nuts when it gets too cold, and it would have been simple to install an internal heating element.
Phil
You can get a 555 timer circuit cookbook from Radio Shack and rig up your own similar circuit. The timer will switch a solid state relay which lets current flow in the heater circuit. A potentiometer controls the on/off cycle during the timing window as it is a variable resistor used to control charging current into the timing capacitor which allows a trigger voltage to rise, after which it discharges and the cycle repeats. Really simple stuff.
An improvement would be to put the LED for each channel in the current path and let it light when heating current is applied and turn off when current is off, so that an instant check of power percentage is available without turning on a light to check the setting of each control knob. An easy thing to add to the circuit for anybody with elementary electronic skills. If the light is on and off half the time, you have half power. For full power, it's on all the time.
I'll probably make my own controllers in the future rather than buy any more. I can get my hands on much better parts than Kendrick or Thousand Oaks uses in these things. For one thing, an RCA plug and jack is junk as far as a high current application is concerned, especially one exposed to dew and the elements. You need o-ring sealed AMP connectors and such, if you really want it done right and not give trouble later on. This is for serious people that need equipment that works, not guys out for occasional thrills and looking for low end consumer electronic prices. The RCA jack and plug is an old cheapo consumer audio connector that is practically never seen in pro level audio gear. It has no place in a low impedance, high current heater circuit. That is the sorry low grade state of affairs in much of amateur astronomy. The vinyl plastic used in scope heater cabling is also a sore point with me. It becomes very stiff on cold nights, and rubber insulation that stays very supple at low temperatures is used in electrical cabling in many other types of products. Amateur astronomers need to demand better electrical design and materials. Electrical problems are my biggest equipment complaints on cold nights. My hand controller goes nuts when it gets too cold, and it would have been simple to install an internal heating element.
Phil
Posted 05/13/2006 10:52PM
#3
Jeff,
I use the Thousand Oakes Dew Controller and really like the ability to control each individual outlet. Also I am using the new Dew--not heater strips which are significantly less expensive and use approximately 50% less power then others (they work on some sort of film basis instead of the resistance wire type set-up. See: http://store.yahoo.com/yhst-1469288697390/dewheaters.html
Although I have only had a chance to use this equipment a few times I am impressed with both the quality and function of it as compared to others. BTW Phil Dew-Not also sells a pad for a telescope hand controller as well-smile.
Take care,
Dan
I use the Thousand Oakes Dew Controller and really like the ability to control each individual outlet. Also I am using the new Dew--not heater strips which are significantly less expensive and use approximately 50% less power then others (they work on some sort of film basis instead of the resistance wire type set-up. See: http://store.yahoo.com/yhst-1469288697390/dewheaters.html
Although I have only had a chance to use this equipment a few times I am impressed with both the quality and function of it as compared to others. BTW Phil Dew-Not also sells a pad for a telescope hand controller as well-smile.
Take care,
Dan
Danny Halstead
Moderator APM Forum
Funding Member
