To finish of my Dew Heater and Fan system, I need to get a control box, but I have searched Jaycar and Dock Smith websites and cannot seem to find what I am after. (we have both Jaycar and D Smith in Ballarat)
Does anyone know if this item is available 'ready-made' or do I have to buy all the components seperately and build it.
The item I want: A small box with 3 outlets with variable control on each outlet, with one inlet socket.
Use: 15 volt power supply plugged into the inlet socket, then split into the 3 outlet sockets with adjustable output.
I am able to go to Ballarat tomorrow to purchase this item (or the parts) as long as they aren't too expensive.
Ken, I doubt you'll find anything that doesn't require assembly, short of a commercially made dew controller, I made my own from scratch, some others have built a PWM (Pulse Width Modulation) controller from a Dick Smith or Jaycar Kit. There's a how to here on the kit option as well. Good Luck.
Ken i have one of those pwm kits here and they are cheap and easy to build.
It is driving my equatorial mount and can regulate the speed perfectly, so it is ideal as an dew controller.
These kits come with good instructions and are simple to follow.
Ken, ahh well anybody really: how certain are you that a controller is needed????? Obviously some have them, but do the really need them?
I mean a low wattage heater is simply not going to melt down the Object glass. I don't have one, I don't need one so why do others? I inserted a thermocouple between the heater ( an Astrozap) and the corrector lens assy initially, and watched. Before there was much of a temperature change, the heat lost by exchange equalled the heat input by the pad::: no dangerous heating of the corrector. The lower the ambient temp, the more power was needed, but certainly no controller.
BTW, using a series resistor to control what? Temp? Current? is gross inefficiency. At a minimum, use a pass transistor, but really try using your heater without a controller. If your heater is about 20 watts or so as also indicated by Bert, you will find that you will not need a controller.
Ken, ahh well anybody really: how certain are you that a controller is needed????? Obviously some have them, but do the really need them?
I mean a low wattage heater is simply not going to melt down the Object glass. I don't have one, I don't need one so why do others? I inserted a thermocouple between the heater ( an Astrozap) and the corrector lens assy initially, and watched. Before there was much of a temperature change, the heat lost by exchange equalled the heat input by the pad::: no dangerous heating of the corrector. The lower the ambient temp, the more power was needed, but certainly no controller.
BTW, using a series resistor to control what? Temp? Current? is gross inefficiency. At a minimum, use a pass transistor, but really try using your heater without a controller. If your heater is about 20 watts or so as also indicated by Bert, you will find that you will not need a controller.
Ok, thanks Doug.
The 'Pots' were just to lower the temp if I turned the power up to 18v or 20v etc.
I'll make the heater strips work without pots then, but I'll still need one for the fan. At 15v it seems like its about to fly off into orbit!!!
Must admit I don't like the term 'Pulse width Modulation' when used with anything other than rf Transmitter/ receivers. Pulse width control seems more descriptive, but ohh well...
I'm not familiar with these kits but wonder if they have provision for thermocouple input? How else would they control temperature?
Ken, a series resistor is too lossy to efficiently run a fan. Granted it is the easiest most straight forward way. Wait and see what you need to get the dew heaters working well first. At 15v, you are really a bit too low to efficiently use a Zener reference for the 12v fan,(in theory it will work) but certainly, if you have to go as high as 18V on the heater, a zenner reference diode circuit would not be beyond your ability to construct (2 components)
One fits in a small box, but then again you could stack 3 above eachother.
They cost $23.95 at the jaycar, 12V 10A
You have to wire a socket into the kit.
Ken, a pot (on it's own) is really only suited to regulating very small current loads (a few milliwats) (e.g. a led). Pots that would be suitable for regulating a 10 watt or 20 watt load would be large, wire wound and generate lots of heat at the same time as wasting power (of concern when running from battery power) The DSE PWM circuit is simple, if you can solder, then you should be able to easily put one (or more) together. The circuit board is pre-made and there will be instructions showing you every component's place and orientation. I'm sure you are capable of doing it.
Geez Doug, I'm already lost, and you throw in another name
For any controller to work, you need some device that tells the controller what temperature you have: it needs to know if it is to keep heating or to shut down for a spell, just like the kitchen oven regulates the temp so that the cakes don't come out black.
And a thermocouple would characteristicly be fed into a comparitor circuit opps sorry Ken more gobledygook, can you see why I'm set against
all this nonesense?
One fits in a small box, but then again you could stack 3 above eachother.
They cost $23.95 at the jaycar, 12V 10A
You have to wire a socket into the kit.
The DSE PWM circuit is simple, if you can solder, then you should be able to easily put one (or more) together. The circuit board is pre-made and there will be instructions showing you every component's place and orientation.
How come this is so hard and complicated????? I don't understand almost everything being said.
All I want to do is plug in 2 heaters and have a variable fan speed.
Kit things aren't my thing. I'll have solder all over the shop.
I think I'll just let the fan spin its guts out at 15 volts and just plug everything into the 15 volts and be done with it. This is getting way too complicated.
That one is at least getting warm (Xcuse the pun)
But Arghh what about the supply voltage, the possible higher heater voltage?
KISS it first Ken and see where you need to go if anywhere.
Ken lets see what voltage you need to run the heaters at first. If it will be practicle and needful to regulate that voltage down to 12V for a fan, PM me with your address and I'll post you free gratis a zenner regulator for your fan.
Ken ill make it easy.
When i come to the snake valley camp in november ill bring a ready made box with 3 outputs for you.
1* fan + 2* heater output for free.
You only have to tell me what kind of connectors you have on the heater and fan (please with some pics of both).
It's got all sorts of electronic things inside it 
