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  • Author Author: genebren
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Playing with Polydoh

genebren

I know that  has mentioned Polydoh in several blog entries.  I have always been interested in this product, so earlier this year I ordered some.  I have been waiting for a suitable project to try it out and today I have finally come up with a need.  First some background.

Over the past couple of years, I have been working on a solar power water feature (bird bath/watering station) for our back yard.  I am not finished, but I am getting very close. Now, when I want a fountain/birdbath, I don't go down to a home improvement store and buy one, no I design and build my own.  Here are some pictures of the nearly complete fountain/birdbath:

imageimage

The Solar system is a 35W panel with 12V 18Ah batteries.  I am adding a wireless controller to the system to allow for datalogging and control of the pump module embedded into the fountain.  The wireless link is eOcean 902Mhz.

Today, I am working on a temperature/humidity sensor that I adding to the solar charging system.  I have purchased an AHT21 with a I2C interface, that I want to imbed into a 1/2" PVC connector that will be mounted into one of the cable entry holes on the charger encloser. I want to mount the sensor into the connector, which will be facing downward, preventing direct rain penetration, but allowing temperature and humidity sensing.  Here are some images of the sensor mounting into the connector:

image image

I slightly notched the inside of the PVC connector to accept the sensor PCB.  I then melted my polydoh and filled the backside of the connector and carefully added polydoh to the front side of the connector, over the PCB, but leaving the sensor open.  The polydoh molded easily and hardened very nicely.  My first attempt, I was working to carefully and did not apply enough to firmly seat the sensor into the connector.  I re-heated the polydoh in the microwave and then applied much more generous amounts to both the front and back of the connector, this time getting the polydoh to completely surround the PCB and lock the sensor into place.

image

I then took a really crappy picture of my workstation screen (PC with an attached eOcean transceiver) to talk to the Solar Controller module to query the attached I2C devices and read the sensor data (and converted the data into readable values). No to clear, but the readings were 75.9F and 55.1%, which correlated the thermostat readings.

I was very pleased with the Polydoh.  I can see this as becoming yet another tool to use in building and repairing projects in the future. 

  • in reply to obones

    Thanks, I'll have to reevaluate the situation cause I've used PVC pipes as a "frame" for the outdoor table cover so that water can dribble out of it, and after a year, half of them had bent quite a bit. I attributed this to the temperature making the PVC softer allowing to change its shape.
    Hence the reason I was asking about the reaction of PolyDoh in those conditions. It would not completely melt, but I'm worried it would move down after some time

  • in reply to shabaz

    Great tip!  I will be trying this out in a couple of other parts of this project, so this may a handy tip.

  • in reply to obones

    Although I have not tried outdoors, I believe it will not be possible to melt it just outdoors alone (without a way of concentrating sun energy at it), it's hard to re-melt a large amount of PolyDoh, because of just inability to get the heat through it all, i.e. even if the outside reaches melting point, the surface will feel tacky, but deeper down it still remains firm. It would have to be heated for a very long time sufficiently for the energy to make it's way through the entire lump I think. It is supplied as small granules so that there's a lot more surface area for melting it.

  • in reply to obones

    Polydoh melting point is 145°F/63°C, so I think it should be able to handle the outside temperatures.  I am planning on doing some sort of radiation shielding (and insect proofing) around the sensor.  My current plan is to use a short section of 1/2" PVC pipe, with some holes drilled through it and a fine mesh screening either inside or outside of the pipe.  I then want to use another section of larger diameter pipe around that, again with holes to allow for some airflow, but no direct sunlight.

    I will monitor the temps and the condition of the sensor/Polydoh to see how they are holding up to the extreme temperature we can get here in Texas.

  • Wouldn't it "melt" by itself if the enclosing tube be exposed to direct sunlight?

    I mean, at least here, it can reach 50°C in the summer, a reason why I can't use PLA for my outdoor prints, and I have a feeling that PolyDoh has a lower softening/melting point than PLA.

    Anyone got any insights on long term reaction to outdoor conditions?