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Voltage Divider Analogy

 

Light
Dark
Heat
Cold
Moisture
Touch
Position

 

Understanding Input Sensing circuits

The sensing circuits we are using are known as "voltage dividers". They are made up from 3 components:

-a battery
-the sensor
-a variable resistor

The sensing circuit produces a changing voltage at its output. You can think of the battery as a packet of sweets that is being divided out between two people. The two people represent a variable resistor (at the top) and a sensor (at the bottom) - see below.

packet
of
sweets
=
the battery


Example 1

Person at top =
the variable resistor

 

Person at bottom =
the sensor

In Example 1:

Q1, If each sweet is equal to 1 volt, how many volts does our sweet packet battery have?

Q2, How many sweets does each person have ? - Please look carefully.

 


Example 2

In Example 2:

Q3, How many sweets / volts do the two people have each and how many do they have altogether?

Q4, If the person at the bottom wanted more sweets beacause they were cold, what name could you give to this type of sensor?

Q5, If the person at the bottom was very hot and not hungry, would they put up more or less resistance to the other person at the top having the sweets?

Q6, How do you think the sweets might be shared out now for the people in question 5? - Have a guess at how many they might have each!

Q7, Why do you think the sweet stacks have always got a red and black sweet at the top and bottom?

Conclusions

-The battery voltage is divided between the sensor and the variable resistor.

-If the sensor has the greater resistance then it will have a  higher voltage  across it.

-If the sensor has the lower resistance then it will have a lower voltage  across it.

-If either resistance changes, it can effect the way the voltage is divided up  or shared in the circuit.