Heater

Overview

Our payload will include a heater made from resistors. The FieldSat microcontroller is responsible for turning the heater on and off according to readings from the temperature sensor.

Status

The heater has not been built.

Theory

The electrical equation we will use is:

P = I * V = V² / R

Where:

P = Power
I = Current
V = Voltage
R = Resistance

Since we are using approximatley 5 Volts from our battery(ies), we can reduce the expression to:

P = 25 / R

Or, to find the resistance needed for a given power:

R = P / 25

If we wanted a 10W heating element, we would need:

R = 10 / 25 = 0.4 Ohms of resistance

But, no one makes a 0.4 Ohm resitor, we need to make that resistance from multiple resistors in parallel. Let's round our needed resistance to 0.5 Ohms, which could be made from twenty 10 Ohm resistors in parallel. The folowing equation will give you the number (n) of a given individual, identical resistors (R_i) in parallel to equal a given resistance (R_total)

R_total = 1 / ( n / R_i )

For the number of resistors:

n = R_i / R_total

What we need to do now, is to find out how big of a heater (Wattage) we will need to keep our package within the operating temperature range of our electronics. This is up the alley of our mechanical engineers. We probably build our heater larger that we need so that we can turn it on and off, like a furnace in a house and still keep it warm. Look at our spec sheets, we will need to find the component with the highest minimum operating temperature and compute for a temperature a little higher than that.

Costs