Ramp wave generator
LM324, 555
Oscillateurs   /    Oscillators
Électronique / Electronic

In this project, you're going to make a circuit for generating a ramp wave that is highly linear and accurate.

When you finish wiring, turn power ON.

LED 1 gradually becomes brighter, indicating that a ramp wave is generated. And, suddenly the LED goes out. Press the start key S1 just for a moment, and LED 1 again becomes gradually brighter.

Try to rotate the control volume to speed or slow the brightening of LED 1.

The OP amplifier U1A and Q1 form a constant-current source circuit. The current value of the constant-current source circuit varies with rotation of the control volume.

A constant current flows from the collector of Q1 into the capacitor C3, thus the voltage across C3 rises linearly. The voltage of C3 receives current amplification by the voltage follower of the OP amplifier U1D, so the increasing voltage of C3 makes LED 1 brighter and brighter.

Over time, when the voltage of C3 exceeds the voltage at pin 6 (Threshold) of U2 555, C3 is quickly discharged through pin 7 (Discharge). When the start key S1 is pressed, C3 again begins charging.