PolyMorphThermostat

From TAMI
Jump to: navigation, search

The polymorph thermostat

controls an electric kettle or an electric plate so that when it is filled with water, its temperature is kept constant at 62 degrees or any other temperature you set.
This allows you to throw your polymorph plastic bits into the water, and take them out when they are completely soft and transparent.


lmH6jHX.jpg

what is PCL

Polycaprolactone (a.k.a PCL, Polymorph)
is a plastic material that melts/becomes soft at 62 degrees celcius.
It also becomes transparent at this temperature.
When it cools down, it becomes hard and non-transparent again.
in its hardened state it canebe painted, drilled and sanded.
And most important, it is fully recyclable!! Take all your remaining PCL pieces and you can melt them again and again for reuse!!


(The picture above shows the water temperature at 79 degrees. This should not happen normally, but shown here when the controller was still running with older settings.
Under normal usage conditions, the temperature may fluctuate no higher than a few degrees above the set temperature).

internals

The box has one 220V power input, one output that is turned on when the temperature controller senses that it is too cold outside.

tu5ouIw.jpg

The PID controller can be bought on the markets for a 10-20$ - RX-700 manual (pdf)

C700 modification

The C100/C700 that are typically sold pn eBay have a relay output. This is an output with a pair of passive contacts that may be either connected or disconnected. These contacts are limited to a current of 3A, and given the nature of the mechanical relay, cannot be switched on and off very rapidly.
When more current and higher switching speed is desired, an SSR can be used. The SSR has two control pins that must be driven with no more than 7-8mA, and two more contacts that can connect or disconnect a 110V/220V voltage source with a current of up to 25A or 40A (depending on the SSR type). In order to use an SSR instead of a relay, the relay itself needs to be removed, and the 12V source used to drive the Relay coil is driven outside with a series resistor limit the current. The viode below shows this modification being done to the smaller model of the PID, the C100.

The C700 modification is very similar, but there is no video of it. The original Relay had been partly soldered (just one or two legs to keep it in place) in the location of the Alarm 2 relay, so that it won't get lost, but it is of course unused. The SSR output can be thought of as a CPU output with logic levels 0V or 12V, and a series resistor of 1K to limit the current to the SSR. In addition, the 3rd pad on the C700 had been drive directly with the 12V control output. This can be used, in combination with the GND pin, to drive the 12V fan left inside from the original PC power supply. The full details, and exact pin numbers can be found on the C700 itself, on its sticker.

TODO

The box is fully functional, but there are a few rough edges that needs to be fixed:

  1. The Solid State Relay inside the box needs to be screwed on the chassis. This should provide adequate cooling for it, since it is hardly turned on.
    In order to do this, the chassis needs to be drilled at 2 places and 2 screws needs to be added to hold the SSR in place.
  2. We need to label the box and its cables.
  3. Make sure the cables are kept with it - I prepared a special cable for it that ends with a regular 220V socket for the kettle to be plugged into.
  4. Get a dedicated electric kettle for it and saw it in half for easier access, or get an electric pan, which is wider and more convenient.
    If anyone knows where to get a used one, it would be great.
  5. Add 4 rubber feets (the simple ones with the hole in the middle). The Power supply box housing the PID controller already has 4 screws ready for something like this. We copuld use something along the line of: http://www.amazon.com/Rubber-Feet-Large-Tapered-Washers/dp/B004H6A0KI
  6. Add a sticker/printed paper with a QR code pointing to this page!