Background I am working on a project that involves heating air inside a small box, then measuring the temperature over time. The purpose of the box is to be a basic test chamber for PID experiments.
Initial Test I made a 10 cm * 10 cm * 10 cm box from 3 mm plywood. I then placed a small ~1 W heater inside with a temperature probe and observed the temperature rise... very slowly.
Proposed New Prototype I am going to construct a new prototype once I decide how to calculate the approximate time to warm the air inside the box to a set-point. Some specifications and assumptions are laid out below:
- The ~1 W heater consists of 4 parallel 100 ohm resistors and a 5 V power supply (there is also a 330 ohm resistor and an LED for visual indication). I don't want to change this heater design, as the intention is that this is easy to replicate and uses readily accessible 5 V power sources and electronic components.
- Currently no fan has been used but I have a small 20 mm, 5 V fan on order, so will integrate this into the design at some point.
- The box will be used at room temperature between 21–23 °C
- Ideally a temperature rise up to 30 °C (or more) would be possible over a 5-10 minute time interval
- The new proposed box size is 5 cm * 5 cm * 5 cm, 8 times smaller than the previous prototype. This is open to change depending on the previous 2 requirements of maximum temperature rise and time taken to achieve that change.
I am not after exact timings - I am aware that losses through the box will have an effect. But if this effect is minimal, then a simplified approximate solution is preferable as some design parameters may change slightly. I am looking for any guidance and calculations that will save me time instead of having to make different boxes and learn by trial and error.