AR1 · DC Circuits · Final Project

Capturing
the Circuit

A step-by-step guide to building your 555 timer servo control circuit in Tinkercad.

Step 1 · The Starting Design

This is your starting point.

A blank breadboard with all the components you need ready to place. Get familiar with the layout before connecting anything.

Blank breadboard with 555 timer, resistors, capacitor, diode, switch, and servo connector ready to place

Step 2 · Place the 555 Timer

Place the 555 chip in the center of the breadboard.

Pin numbering: the white dot marks pin 1. Pins 2 through 8 continue counter-clockwise around the chip.

555 timer chip placed in the center of the breadboard, straddling the center gap

Step 3a · Power

Connect 5V to the positive bus.

5V power wire connected to the positive (red) bus rail at the top of the breadboard

Step 3b · Power

Connect the positive bus to pin 8 of the 555 (power pin).

Wire running from the positive bus to pin 8 at the top-right of the 555 chip

Step 3c1 · Power

Connect the top and bottom positive buses together.

Wire bridging the top positive bus to the bottom positive bus on the left side of the breadboard

Step 3c2 · Power

Connect the bottom positive bus to pin 4 of the 555 (reset pin).

Wire from the bottom positive bus to pin 4 of the 555 chip, holding reset high

Step 4a · Ground

Connect ground to the negative bus.

Ground wire connected to the negative (blue) bus rail at the top of the breadboard

Step 4b · Ground

Connect the top and bottom negative buses together.

Wire bridging the top negative bus to the bottom negative bus on the left side of the breadboard

Step 4c · Ground

Connect the negative bus to pin 1 of the 555 (ground pin).

Wire from the negative bus to pin 1 at the bottom-left of the 555 chip

Step 5a · Timing Capacitor

Add capacitor C1 between pin 1 and pin 2 of the 555.

Capacitor C1 placed on the breadboard with one lead at pin 1 and the other at pin 2 of the 555

Step 5b · Timing Capacitor

Click C1 to open its properties and enter the capacitance value (0.1μF).

Tinkercad component properties panel open for C1, showing the capacitance value field

Step 6a · Timing Diode

Add diode D1: connect the unmarked (anode) side to pin 7 of the 555.

Diode D1 placed on the breadboard with its anode connected to pin 7 of the 555

Step 6b · Timing Diode

Connect the marked (cathode) side of D1 to pin 6 of the 555 with a wire.

Wire from the cathode of D1 running to pin 6 of the 555 chip

Step 7 · Timing Resistor R2

Add R2 in parallel with D1.

R2 and D1 are in parallel. R2 sets the discharge time t₂ when the capacitor discharges through it toward pin 7.

Resistor R2 placed on the breadboard in parallel with diode D1

Step 8 · Threshold / Trigger

Connect pins 2 and 6 of the 555 together with a wire.

Tying the threshold (pin 6) and trigger (pin 2) together creates the oscillator feedback loop.

Wire connecting pin 2 and pin 6 of the 555 chip to close the oscillator feedback loop

Step 9a · Switch

Add switch S1 in the empty space on the left side of the breadboard.

Pushbutton switch S1 placed on the left half of the breadboard

Step 9b · Switch

Connect the common pin of S1 to the +5V bus.

Wire from the common pin of S1 to the positive bus

Step 10 · Charge Resistor R1A

Add R1A: connect one end to terminal 1 of S1, bridging across the center gap to the bottom half of the breadboard.

Resistor R1A bridging from terminal 1 of S1 across the center gap to the bottom side of the breadboard

Step 11a · Charge Resistor R1B

Add R1B: connect one end to terminal 3 of S1, bridging across the center gap to the bottom half of the breadboard.

Resistor R1B bridging from terminal 3 of S1 across the center gap to the bottom side of the breadboard

Step 11b · Charge Resistor R1B

Run a wire from the far end of R1B to pin 7 of the 555.

Wire from the right end of R1B connecting to pin 7 of the 555 chip

Step 12 · Charge Resistor R1A

Run a wire from the far end of R1A to the junction of R1B and pin 7.

Both R1A and R1B now meet at pin 7. Switching S1 selects R1A or R1B, changing the charge time t₁.

Wire connecting the far end of R1A to the junction of R1B and pin 7 of the 555

Step 13a · Servo Connection

Run a wire from pin 3 of the 555 to an open column on the right side of the breadboard.

Pin 3 is the output pin. This wire will carry the PWM signal to the servo control input.

Wire running from pin 3 of the 555 to an open column on the right edge of the breadboard

Step 13b · Servo Connection

Connect +5V to the column just to the right of the pin 3 wire.

Wire from the positive bus to the servo power column, one column to the right of the PWM signal column

Step 13c · Servo Connection

Connect ground to the column just to the right of the +5V column.

Wire from the negative bus to the servo ground column, one column to the right of the power column

Step 13d · Servo Connection

Plug the servo connector into these three columns: control, power, and ground.

Servo connector attached to the three-column group carrying control signal, 5V, and ground

Step 14 · Oscilloscope

Connect the positive probe of the oscilloscope to the servo control wire to monitor the PWM signal.

Run the simulation and press the switch. You should see the pulse width change on the scope when you press and release S1.

Oscilloscope positive probe connected to the servo control wire, ready to display the PWM output