IR dimmer switch load query

[BrendanP]

Some time ago I made a picaxe controlled incubator to hatch duck eggs. It works well. When I made it I attempted to use a light dimmer switch to control the light globes I was using as the heat source. I had problems getting the dimmer app to work as I wanted so I gave up at the time and went with a I/O relay set up. I like the dimmer control idea so the temp in the 'bator is more constant, a flat line on a graph rather than a square wave as the lamps turn on and off. I'm going to hatch goose eggs this year and they are a bit finicky compared to ducks and chooks.

I am going to use a IR remote controlled 240AC dimmer switch out of the UK I found on ebay. http://www.ebay.com.au/itm/160661625573?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1438.l2649#ht_2732wt_1396

I propose to use picaxe Irout command to controll the switch. I'm hoping on the picaxe generated commands will be recognised by the receiver.....

My question is about the load handling capability of the switch. It is rated at 400 watts. Does this mean that I can only connect a 400watt load to it ot does it mean that is the max load to which it will provide full power?
ie. if I connected a 800watt load to it would it only run the load at half power, ie supply only 400 watts to it ?

I propose to use a electrical element with it out of a old oven or dryer. Here's a good article about hacking such elements.
http://www.thebackshed.com/windmill/articles/BuildingEncapsulatedResistors.asp

I can mod the element down to =<400 watt according to the article in anycase.

 

[hippy]

The module can likely only be used with a 400W load; if you connect an 800W load it will probably blow a fuse rather than limit the current. If you limited to 50% you could perhaps use an 800W load but it would be best to stick to a 400W maximum.

I very much doubt the unit can be controlled by IROUT commands and you'll probably need a remote to analyse the protocol and then have to bit-bang that.

All-in it's probably better to build / find a proper power controller you can drive via PWM.

 

[BrendanP]

Thanks Hippy. I too thought along those lines first off. I thought there would be something off the shelf I could control with serial/SPI etc.

I'm looking for a quick fix, so maybe the ultimate hack, a manual dimmer and a servo under picaxe control, a forum user suggested that last time I was working on the incubator.

btw, I'm doing well mate, I've had a lot of injection molding tooling made in China for a project that I protoed with picaxe, we went avr/C++ for production units.

 

[techElder]

There's nothing to keep you from wiring 2 of your 800 W. loads in series to control them with that 400 W. controller provided that you can get useable heat that way.

... It is rated at 400 watts. Does this mean that I can only connect a 400watt load to it ot does it mean that is the max load to which it will provide full power?
ie. if I connected a 800watt load to it would it only run the load at half power, ie supply only 400 watts to it ?

 

[Goeytex]

Most popular hobby incubators use a 125 to 250 watt heater element. A 250 watt element is adequate for an incubator the size of an common household refrigerator. For reliability, I would not use the dimmer at its max rating of 400W but rather at 250 to 300 W. A beefier and more reliable control device might be a 25 Amp solid state relay. Most dimmers use phase angle firing and can add significant "noise" to the mains. Personally, I would not even consider one for use in an incubator.

Precise humidity control is arguably more important than temperature with goose eggs.

 

[bluejets]

Dimmers ratings are usually VA rather than watts. Reason is the load on AC is governed by reactance of the load.
For example if connected to a coil, there would be an inductive reactance load (perhaps at 0.6 power factor)and the end result would be 400VA * 0.6 = 240W.

Using light globes may give you a higher load capability but I would tend to go on the "safe side" at 240W.

However, I agree with Goeytex's solution, much better approach.

 

[BrendanP]

Thanks guys for the input.

I'm on to the humidity angle. I plan to use the honeywell humidity sensor to monitor/control the humidity side of things. The picaxe will control a fan that blows air across a water bath.

Temp is important for geese, including allowing the eggs to cool at times, I plan to add that function as well. No doubt the eggs have evolved to tolerate the goose getting off the nest to feed etc.

Rotation/frequency and angle of the eggs is also important.

This article has some interesting info.
http://www.dpi.nsw.gov.au/agriculture/livestock/poultry/species/geese-raising/egg-production