Heating element for small incubator (how to incorporate into plastic parts)

[cpb]

Dear all,

I am planning to create a small incubator (air) for beekeping. The temp. range is between lets say 30-max.65 degrees Celcius controlled by an arduino board.

My question is:

1) What is a suitable (and small) heating element that nicely fits into the small incubator (the heating cables for terrariums have too low temps)? I had one of those in my mind:
http://www.aliexpress.com/store/prod...399108362.html
-> Use e.g. coffee maker or yoghurt maker.

But that thing heats up to 120 Celcius!

If I print with ABS then I certainly hit the glass transition temp. I can not (so far) print a high temp filament.

2) How do I mount the heater in a plastic component and ensure good heat dissipation and NO plastic melting a basic idea of mine was to attach it to a PCB board. But what with the upper parts (eg. heat shield)?

Any ideas would be highly appreciated. Also links to other heating elements.

Thanks a lot.

Best regards,
Chris

[Mjolinor]

It doesn't matter that it is capable of heating to 120 C because your control circuitry should prevent it from getting that high.

Unless you specifically want to do a project for your own education using an Arduino it is a lot easier to just buy a PID temperature controller such as:
http://www.ebay.co.uk/itm/Hot-PID-Di...item3d0002a096

That is jsut hte first hit on ebay, you need to read about the spec but I am quite sure that any of them will do what you want.

[cpb]

That is a good input about the PID. But the temp-control needs to follow some protocol.

But I am extremly worried about the heat source (and its heat dissipitation) -> e.g. the given PTC Thermistor heats up to 120°C ... and with the PID I measure the ambient temp. So if that thing starts to heat it melts the plastic.

Or what heat source would you recommend with the PID?

Thanks for your help!

Best wishes,
Chris

[Mjolinor]

If oyu are going to use an arduino anyway then just stick two temperature measurement devices in there, one for ambient which is the temperature you need to work at and one stuck to the heater itself to prevent the temperature of the heater going too high.

[cpb]

Hi Mjolinor,

ok, that is one thing I also thought about.

How would you install the PTC? Or would you recommend another heating element?

Controlling the PTC temp would lead to constant on/of cycles ... any recommendations on a relay or MOSFET that will survive the

1) on/off cycles
2) can handle the current (e.g. planed a 50-60 W -> 4.1-5 A)

Thanks!

[Mjolinor]

I would use one of this type:

http://www.ebay.co.uk/itm/9-5-x-80mm...item2c9f857170

fastened to a heat sink.

As I have absolutely no idea of the volume you need to heat or the insulation you are going to use to prevent heat escaping I have no idea of the specifics of the heater you need.

It can only be a series of on - off cycles because if you want to control the element temperature in an analogue manner you need some serious transistors to do it.

Decide on the power you need to get the temperature you want in the volume you have.
Decide how much heat you will lose
Decide how quickly you need to get to temperature
Decide your acceptable temperature variation

Do some arithmetic to end up with a figure for the power of the heater you need to satisfy your design criteria.

Only you can do that because only you know what you want.

[cpb]

Hi Mjolinor,

thanks. The incubator dimension is somewhere around max. 30x30x30.

For heating element I had something in mind like that: http://www.ebay.co.uk/itm/Car-70mmx3...item1c55cd1def

There I would avoid "fidddling" with 220V.

Your points are all very valid. However, even the heat sink hast to be attached to the plastic part - an there I absolutely have no clue how to attach. Maybe use a washer to avoid direct plastic contact (but the washer heats as well)?

[Mjolinor]

Your software would keep the heat sink below the glass trasistion temperature so it doesn't matter how you fasten it or what oyu fasten it to.

mm/cm/inches/feet/yards/chains/furlongs/km/miles

Take your pick but 30x30x30 doesn't mean an awful lot.