8. Output Devices#
This week’s group assignment is to measure the power consumption of an output device.
This week’s group assignment is to measure the power consumption of output devices.
We got a range of Peltier Devices, this group assignment is to find out the power consumption of these different-sized Peltier Devices.
Because Peltier Devices can get really hot, we mounted them on a cooling rig, fixed them with heat-conductive tape - and submerged the cooling rig into water to dissipate the heat.
- P is the power measured in watts
- V is the voltage measured across the conductor in volts
- I is the current measured in Ampere
The relationships between P, V, I and R is shown in detail in the an Ohm’s Law Pie Chart.
How to measure the Power?#
We have a Kungber Stabilized DC Power Supply at Fablab Kamakura, which can be used to set max values for both Voltage and Ampere, and allows you to observe the power consumption. The Kungber Power Supply has 2 controls for each V and I, allow for coarse and fine control.
The Peltier Device Lineup:
|Name||Size (mm)||Vmax||Imax||Max Δ Temp (ºC)||Links|
|TEC1-12708||40 x 40||15.4V||8.5A||66||Get, Datasheet|
|TEC1-12739||30 x 30||16.0V||4.6A||70||Get, Datasheet|
|TEC-40865A-00||17 x 17||8.2V||2.1A||67||Get, Datasheet|
|Melcore-CP1.0-1-05||3.5 x 3.35||0.12V||3.9A||67||Get, Datasheet|
Decoding Peltier Devices#
- TEC1-12708: stands for Thermo-Electric
- TEC1-12708: Either C or S. S for Smaller
- TEC1-12708: Number of Stages, in this case: 1
- TEC1-12708: Number of Thermocouples: 127
- TEC1-12708: Max Ampere Rating: 8
It seems Peltier Devices do not always following this convention.
As the max Voltage for this device is 8V, I did not test at 10V.
The Melcore-CP1.0-1-05 has a max voltage of 0.120V or 120mV, it was not possible to test it with this setup, as the power supply could not create a stable output at 120mV.
TODO: Find other ways to measure the power consumption.
We observed that the more voltage we applied the more the Peltier device cooled. At some point the hot side overwhelmed the cool side and started heated the cool side as well, resulting in a temperature rise of the cool side.
If higher or cooler temperature are necessary, Peltier devices can be stacked.
Further experiments regarding the correct cooling parameter are necessary.
We also managed to make (a small amount of) ice!
Reverse Peltier: The Seebeck Effect#
After turning the V and I down, we could observe that the still hold/cold Peltier device was creating electricity. This is the thermoelectric effect or Seebeck-Effect</span, which apparently was discovered (or re-discovered) by Thomas Johann Seebeck in 1821. Seebeck was a Baltic German, which fits into the story I was once told, that Samovars (самовар, “self-brewer”, metal container to boil and keep hot water, mainly used in Russia) have been used to generate electricity. Makes sense… If someone has more details, please do let me know.
Usage of Regulated power supply#
Once set Voltage on
Regulated power supply and delive power to circuit, you can see current on display. If current will over the maximum, it automatically suppressed to the upper limit.
Digital Multi Meter can see current, resitor, voltage value. However, when using for measure current, we should include its internal resistance in the calculation.
The image below shoes result of 3 kinds of solenoids.