# I. Voltage Division and Loading > [!table] Initial Supply Voltage > | Expected Voltage (V) | Measured Voltage (V) | Percent Error | > | -------------------- | -------------------- | ------------- | > | 5.000 | 5.0002 | 0.004% | --- > [!table] Potentiometer Total Resistance > | Expected Resistance ($\Omega$) | Measured Resistance ($\Omega$) | Percent Error | > | ------------------------------ | ------------------------------ | ------------- | > | 10,000 | 10,520 | 5.20% | --- > [!table] Potentiometer Settings and $V_{out}$ > | Desired $V_{out}$ (V) | $R_1$ Initial ($\Omega$) | $R_2$ Initial ($\Omega$) | Measured $V_{out}$ (V) | Best Adjusted $V_{out}$ (V) | $R_1$ Adjusted ($\Omega$) | $R_2$ Adjusted ($\Omega$) | > | ---------------------: | ------------------------: | ------------------------: | -------------------------: | ------------------------------: | --------------------------: | --------------------------: | > | 3.3 | 5310 | 5026 | 2.497 | 3.308 | 3512 | 7067 | > | 1.5 | 3512 | 7067 | 1.494 | 1.494 | 7239 | 3205 | > | 2.5 | 7239 | 3205 | 2.502 | 2.502 | 5255 | 5505 | --- > [!table] Measured vs Expected Source Current > | Calculated Load Resistance ($\Omega$) | Measured Load Resistance ($\Omega$) | Percent Error | Measured $V_{out}$ (V) | Measured $I_R$ (mA) | Expected $I_R$ (mA) | Percent Error | > | ------------------------------------: | ----------------------------------: | ------------: | ------------------------: | --------------------: | --------------------: | ------------: | > | 100,000 | 100.012k | 0.012% | 2.403 | 0.491 | 0.510 | 3.73% | > | 4,700 | 4,704 | 0.085% | 1.67 | 0.665 | 0.670 | 0.746% | > | 10 | 10.59 | 5.9% | 0.0099 | 0.996 | 1.030 | 3.30% | > | 0 | 7.2 | N/A | 0.0005 | 1.00 | 1.00 | 0% | --- - Potentiometer benefits - Allows $V_{out}$ to be quickly adjusted without replacing resistors - Makes loading effects easy to observe - Useful for calibration and prototyping - Potentiometer disadvantages - Small wiper movements can noticeably change resistance and voltage - Less suitable for circuits requiring a fixed, precise resistance - Potentiometers are useful for testing, calibration, and user-adjustable controls, but fixed resistors are preferable when stability and precision are important. --- - High-resistance loads had relatively little effect on $V_{out}$. - As load resistance decreased, the effective resistance across the lower portion of the voltage divider decreased. - This caused $V_{out}$ to decrease and source current to increase. - The results demonstrate why the load connected to a voltage divider must be considered when designing the circuit. # II. Voltage Division with an LDR > [!table] Measured LDR Resistance at Different Light Levels > | Light Level | Measured Resistance ($\Omega$) | > | ----------- | -----------------------------: | > | Low | 7,500 | > | Normal | 1,300 | > | Bright | 380 | --- The voltage divider relationship is $ V_{out}=V_{in}\frac{R_2}{R_1+R_2} $ The LDR is placed at $R_2$ so that its increasing resistance in low light causes $V_{out}$ to increase. Using the normal LDR resistance, $ R_2=1300\Omega,\qquad V_{in}=5V,\qquad V_{out}=3.3V $ $ 3.3=5\left(\frac{1300}{R_1+1300}\right) $ Solving for the paired resistor, $ R_1\approx670\Omega $ - Ideal paired resistance: $670\Omega$ - Actual paired resistance: $670\Omega$ --- > [!figures] LDR Voltage Divider Schematic > ![[Pasted image 20260917184508.png|center|350]] --- > [!table] LDR Output Voltage vs Light Level > Determined location of LDR: $R_2$ > > | Light Level | $V_{out}$ (V) | > | ----------- | ------------: | > | Low | 4.7 | > | Medium | 3.35 | > | High | 0.881 | --- - The voltage divider responded as expected. - As light intensity increased, the LDR resistance decreased, causing $V_{out}$ to decrease. - Switching the LDR and $R_1$ reverses the circuit response because the output depends on which component is connected to the supply and which is connected to ground. - The measured output changed from $4.7V$ in low light to $0.881V$ in bright light, giving a clear signal that can be used to control another circuit. # III. Making the Relay Work with the Voltage Divider > [!figures] LDR-Controlled Relay Module for Automatic Lamp Switching > ![[Pasted image 20260917184525.png|center|350]] --- - When environmental lighting was low, the lamp turned on. - When environmental lighting increased, the lamp turned off. - The LDR voltage divider therefore successfully provided the control signal for the relay. --- > [!table] Relay Switching Voltages > | Measurement | Voltage (V) | > | ----------- | ----------: | > | Turn On | 2.033 | > | Turn Off | 1.807 | --- - The relay turns on and off at slightly different voltages because the voltage required to activate the relay is not exactly the same as the voltage required to keep it activated. - This small difference helps prevent rapid switching when the input voltage is near the switching point. - Overall, the LDR voltage divider and relay operated successfully as an automatic light-controlled switching circuit.