Cloud Chamber Physics

At Science Hack Day SF 2013 there was a project to build a thermoelectric cooled cloud chamber. These are some notes about the hardware.

Thermoelectric Cooling

The typical thermoelectric cooler (TEC) will typically produce a maximum temperature difference of 70°C. The amount of heat that can be absorbed is proportional to the current and time.

$$\begin{equation}\dot Q = k_PI\end{equation}$$

where $\dot Q$ is heat flow rate, $k_P$ is the Peltier coefficient of the TEC, and $I$ is the current.

Power

So for a given heat rate and a known TEC we can guess the electrical power requirements.

$$\begin{equation}I = \frac{\dot Q}{k_P}\end{equation}$$$$\begin{align} P &= IV \nonumber \\\ &= \frac{V\dot Q}{k_P} \end{align}$$

We can computer how big of a power supply we need for each TEC:

In [1]:
# Define TECs
TEC_12 = {
    'v': 12,     # 12 volt version, TEC1-12710
    'kp': 9.6,   # pelter coef
}

TEC_5 = {
    'v': 5,     # 5 volt version
    'kp': 9.6,  # pelter coef
}

# calc power
def power(Q, tec):
    v = tec['v']
    k = tec['kp']
    return (v*Q)/k

We want to suck the maximum power from both, which according to the datasheets is about 90 Watts(thermal)

In [2]:
print "Power supply for bottom TEC: ", power(90, TEC_12), '  Watts'
print "Power supply for top TEC      ", power(90, TEC_5), 'Watts' 
Power supply for bottom TEC:  112.5   Watts
Power supply for top TEC       46.875 Watts

Luckily we have two ~100 watt power supplies.