Timeline for Temperature control of a system with variable setpoint and variable outside temperature
Current License: CC BY-SA 4.0
6 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| Jul 21, 2023 at 20:57 | comment | added | Voltage Spike♦ | Please use the voting and answer system | |
| Jul 21, 2023 at 20:03 | comment | added | irilinir | I have an additional question. Is the described system a first order system, and what exactly determines its DC gain? The time constant depends on the water volume (capacity) and heat resistance, but what the gain depends on? I presume that I will need to change the Kp of the PID on some conditions (changing water volume, switching between heating and cooling, as the peltier cooling is proportional to the current, but heating is to the current + the square of the current). But do I need to change it on changes of outside temperature? | |
| Jun 22, 2023 at 16:51 | comment | added | irilinir | Also I can read the outside temperature and make some adjustments of the starting power. For example if I have outside temp of 29 degrees and I need to heat from 17 to 18 degrees, I could start with peltier turned off and check if the outside temp influence is not enough, and even correct in the negative direction if it is too much. But if the outside temperature is 20 degrees and I need to go from 24 to 25 degrees, I will need to start with heating directly. | |
| Jun 22, 2023 at 16:39 | comment | added | irilinir | I was thinking about something like this: Divide the hour interval in smaller ones, for example 6 minutes. If I consider that the outside temperature is almost constant in one hour interval, its influence of the internal volume will be even closer to constant too. So I start the first 6 minutes with low power and measure the temperature at the end of this period. Then I calculate the speed of change and try to estimate if this speed is enough to get to the setpoint at the end of the hour interval. If it is not, then I recalculate the needed power and increase it. Then repeat. | |
| Jun 22, 2023 at 16:32 | comment | added | irilinir | I need to read about MPC. I will controll the peltiers by DC - DC buck convertor. I have modified the current control and now it has digital potentiometer instead of the normal one. So I have 255 values at disposal. The drawback is that I cannot go bellow certain current (about 0.7-0.9A) because the regulator provide below about 1.4V, but I'll play a little bit more with the circuit to lower this border. However, I can turn it off easily when needed. | |
| Jun 22, 2023 at 15:58 | history | answered | Voltage Spike♦ | CC BY-SA 4.0 |