LED pulse driver

Circuit diagram:

Component:

R1, R2___________4K7 1/4W resistor;
R3_____________22K 1/4W resistor;
R4______________2M2 1/4W resistor (see note);
R5_____________10K 1/4W resistor;
R6_____________47R 1/4W resistor (see note);
C1______________1µF 63V polyester capacitor;
D1_____________5mm red LED (see note);
IC1__________LM358 low-power dual operational amplifier;
Q1___________BC337 45V 800mA NPN transistor.

Circuit operation:

This circuit operates the LED in pulse mode, meaning the LED gradually brightens from an off state, then gradually dims, and so on.
This operating mode is achieved using a triangular wave generator consisting of two operational amplifiers packaged in a very inexpensive 8-pin DIL package IC. Q1 ensures current buffering for better load drive.
R4 and C1 are timing components: using the values ​​shown in the parts list, the total period is approximately 4 seconds.

Note:

• The most satisfactory results can be obtained by using an R4 value in the range of 220K to 4M7.
• If the R4 value is below 220K, the pulse effect will be indistinguishable from a normal flicker effect.
• LEDs can be of any type and color.
• You can use an incandescent bulb instead of an LED, provided that its rating is in the range of 3.2V to 6V and a maximum of 200mA.
• When using a light bulb as a load, R6 must be omitted.
• The power supply voltage range is 4V to 6V: 4.5V is the best compromise.
• Do not supply more than 6V to the circuit: otherwise the circuit will not function properly and Q1 may be damaged when a light bulb is used as a load.
• With a 6V power supply, increase the value of R6 to 100 ohms.