RC Circuit Time Constant: Circuit, Measurements and Online Simulator

To build this RC Circuit Time Constant circuit you need a function generator, an oscilloscope, a 1 kΩ resistor and a 1 µF ceramic capacitor. A square wave through 1 kΩ into 1 µF: the capacitor charges and discharges with time constant τ = RC = 1 ms. CH1 is the input, CH2 the capacitor. Make the 6 connections in the wiring table, press Run, and the yellow square wave is the input; the blue curve is the capacitor charging to 63% in one τ = 1 ms. Turn TIME/DIV, and change C to 10 µ to see it slow down.

Open this circuit in the free Electronics bench simulator

Parts list

Qty	Part	What it does
1	Function Generator	Sine, square, triangle or sawtooth from 1 Hz to 100 kHz, into a 50 Ω output. COM is earth. Watch it on the oscilloscope.
1	Oscilloscope	Two channels against earth (GND). Turn TIME/DIV and VOLTS/DIV to fit the wave, set the trigger level to steady it, and read Vpp, RMS and frequency. X-Y mode draws Lissajous figures. Choose a digital (DSO) or phosphor (CRO) screen.
1	1 kΩ resistor	Limits current. 220 Ω in series with an LED; 10 kΩ as a pull-up or pull-down.
1	1 µF ceramic capacitor	Stores charge; blocks DC, passes AC. With a resistor it sets a time constant τ = RC (1 kΩ × 1 µF = 1 ms). Not polarised.

Wiring

#	From	To
1	Function Generator OUT	1 kΩ resistor leg 1
2	1 kΩ resistor leg 2	1 µF ceramic capacitor 1
3	1 µF ceramic capacitor 2	Function Generator COM
4	Function Generator OUT	Oscilloscope CH1
5	1 µF ceramic capacitor 1	Oscilloscope CH2
6	Function Generator COM	Oscilloscope GND

Step by step

Open the electronics bench. Open the BitForBytes Embedded Lab in your browser. A circuit with no microcontroller runs on the analog bench: no install or account is needed.
Add the parts. Add a function generator, an oscilloscope, a 1 kΩ resistor and a 1 µF ceramic capacitor from the parts palette (Instruments, Power, Passive and Semiconductors).
Wire 1. Connect Function Generator OUT to 1 kΩ resistor leg 1.
Wire 2. Connect 1 kΩ resistor leg 2 to 1 µF ceramic capacitor 1.
Wire 3. Connect 1 µF ceramic capacitor 2 to Function Generator COM.
Wire 4. Connect Function Generator OUT to Oscilloscope CH1.
Wire 5. Connect 1 µF ceramic capacitor 1 to Oscilloscope CH2.
Wire 6. Connect Function Generator COM to Oscilloscope GND.
Run and measure. Press Run. The yellow square wave is the input; the blue curve is the capacitor charging to 63% in one τ = 1 ms. Turn TIME/DIV, and change C to 10 µ to see it slow down.

Lab sheet

// Electronics bench: RC time constant
//
// Function generator: square wave, 100 Hz, 5 Vpp, +2.5 V offset (0 to 5 V).
// OUT -> 1 kΩ -> 1 µF -> COM.  Scope CH1 on the generator, CH2 on the capacitor.
//
// τ = R·C = 1 kΩ × 1 µF = 1 ms. After one τ the capacitor reaches 63 %,
// after five τ it is fully charged. Measure it: set TIME/DIV to 1 ms and
// count divisions until CH2 reaches 3.16 V.
//
// No code runs here: press Run and use the instruments.

What to try

Press Run. The yellow square wave is the input; the blue curve is the capacitor charging to 63% in one τ = 1 ms. Turn TIME/DIV, and change C to 10 µ to see it slow down.

Frequently asked questions

How do I wire the RC Circuit Time Constant circuit?

Make 6 connections: Function Generator OUT to 1 kΩ resistor leg 1; 1 kΩ resistor leg 2 to 1 µF ceramic capacitor 1; 1 µF ceramic capacitor 2 to Function Generator COM; Function Generator OUT to Oscilloscope CH1; 1 µF ceramic capacitor 1 to Oscilloscope CH2; Function Generator COM to Oscilloscope GND.

What parts do I need for the RC Circuit Time Constant?

A function generator, an oscilloscope, a 1 kΩ resistor and a 1 µF ceramic capacitor.

Can I simulate the RC Circuit Time Constant online for free?

Yes. The BitForBytes Embedded Lab solves the circuit in time, the way SPICE does (nodal analysis with real diode, transistor and capacitor models), and gives you a bench power supply, function generator, oscilloscope and multimeter to measure it — free, in the browser.

What does this circuit show?

A square wave through 1 kΩ into 1 µF: the capacitor charges and discharges with time constant τ = RC = 1 ms. CH1 is the input, CH2 the capacitor.