Ideas & Bug Fixes for Ver. 1.0

Here we are gathering ideas and fixes for the Ver 1.0, but not everything that's here will carry over to Ver. 1.0.

Ideas

  • Try to channel the thermistor leads and cable through the wool insulation and under the bottom hole. With this method we will not have to run the cables outside of the wooden box. An idea is to tie the wool insulation up until the last layer. On the last layer we can put the cable on the wool and then tie another extra layer to cover the cable too. This way the cable wont touch the hot glass and we wont have melting problems.  Its also possible that for this connection between the cable and the thermistor leads we will need a leadless solder. (DONE WORKS QUITE NICE)
  • Try using PID control in the software in order to get a more stable temperature . With the current bang-bang method (on/off) we actually fluctuate between +2  and -7 degrees from the target temperature. While we are not sure if this fluctuation is important enough, its worth trying using the reprap PID control. There is a possible load on the MOSFET. and we should check the temperature on the MOSFET. The reason behind this temperature is the actual PWM nature of PID control. By turning on and off the heat thousand times per second when the temperature is close to the desired one, the MOSFET can get hot as there is a position where the mosfet is semi-on or semi-off. In the datasheet this is called rise time and fall time. 
  • Considering making the 40W heating element the "standard". The positive effect would be quicker heat-up times, the negative effect is stressing the batteries more at 2A current draw. (DONE WORKS QUITE NICE, OPTIONAL)
  • Better insulation. In the current version the wood does heat up at around 40-50 degrees. While not actually too hot to touch, this means lost heat which should better be concentrated on the heatsink and not on the outside. Woolen thread is actually a nice and safe option, maybe more layers can be an answer. The problem here is the size of the wood hole. A 22mm hole on a 28mm wood piece means 3mm wood left from each side. Quite marginal if you get a bigger hole.

Bug Fixes

General Information & Research

Did a small test using both 30W and 40W heating elements on different Voltages. The following table will also help determine the power supply needs for the desktop version also.

Voltage Amperage
Variety 30W 40W
6.6 1.3 1.8
7.8 1.5 2.0
12 2.43 3.2
16 3.3 4.2
19 3.8 5.0

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