Monostable Delay Timer (Up To 10 Minutes)

A delay timer circuit is an electronic design that creates a controlled time delay before a device turns ON or OFF. These circuits are needed whenever precise timing is important, such as starting a motor after a few minutes, keeping an alarm active for a fixed period, or removing the bounce from a mechanical switch. Delay timers are widely used in automation, safety systems, and everyday electronics.

Among the different options, the monostable 555 timer is one of the most popular choices. It produces a single, accurate pulse whenever it is triggered, making it ideal for delay switches, pulse stretching, and timing control. This circuit board is ideal for applications such as delay switches, pulse stretching, and timing control adjustable up to 10 minutes.

12V DC To 6V DC Buck Converter

Many electronic circuits and gadgets like small DC motors, LED strips, sensors, and portable devices don't run directly on 12V. They need a lower voltage like 6V to work safely. If you only have a 12V battery or adapter, you can't connect it directly because it may damage the components. A DC‑DC 12V to 6V buck converter solves this problem by stepping down the voltage efficiently without wasting much power as heat.

One of the most popular ICs for this purpose is the MC34063A. With it, you can build a compact and reliable 6V, 1.5A non‑isolated step‑down power supply module for your projects.

Components assembly

As per the circuit, the components are assembled on a Vero board as shown below.

Top View	Bottom View

12V DC To Regulated 5V DC USB Power Supply

In many situations we have a 12V DC source available, such as car batteries, adapters, or general power supplies. However, most electronic devices and microcontrollers need only 5V DC to work safely. Supplying 12V directly can damage sensitive electronic components on circuit boards, so we need a circuit that converts 12V into a stable 5V regulated output. The LM7805 IC is a simple and reliable voltage regulator that makes this conversion easy.

This module converts a 7-15V DC input into a regulated 5V DC output at up to 1 Amp with thermal overload protection and output short circuit protection. The built‑in USB Type‑A port provides a convenient plug‑and‑play solution. It can be used to charge devices such as smartphones, earphones, and power banks in emergency situations from a 12V battery, or adapters to power USB‑based circuit boards such as microcontrollers and sensors.

Components list

The following components are required to build this power supply circuit board.

1. U1: LM7805CT voltage regulator IC (1 pcs)
2. J1: DC barrel female connector (1 pcs)
3. J2: USB type-A 4-pins female connector (1 pcs)
4. D1, D2: 1N4007 general purpose diode (2 pcs)
5. LED1: 3mm green LED (1 pcs)
6. C1: 220uF, 50V electrolytic capacitor (1 pcs)
7. C2: 220uF, 16V electrolytic capacitor (1 pcs)
8. C3: 330nF ceramic capacitor (1 pcs)
9. R1: 1kΩ 1/4W resistor (1 pcs)
10. R2: 330Ω 1/4W resistor (1 pcs)
11. TO-220 aluminium heatsink (1 pcs)
12. M3 x 10mm pan head screw (2 pcs)
13. Vero board (1 pcs)

Circuit diagram

Schematic of 12V DC to regulated 5V DC USB power supply circuit as shown below.

Components assembly

As per the circuit, the components are assembled on a Vero board as shown below.

Top View	Bottom View

Multi-Rail Regulated DC Power Supply (±35V to ±24V, ±15V, and ±5V)

Modern PCBAs use both analog and digital circuits, where each part requires different voltages to work properly. Digital chips often require +5V or +3.3V, analog circuits like op‑amps need ±15V, and power drivers or industrial modules may use ±24V. A single DC power source cannot provide all these voltages at once, which is why we use a multi‑rail regulated DC power supply. This module can deliver DC ±24V, ±15V, and ±5V stable voltages at the same time. It allows engineers to test bench circuits under real operating conditions, making prototyping safer, troubleshooting easier, and eliminating the need for multiple separate supplies.

Schematic of ±35V to multi-rail ±24V, ±15V, ±5V regulated dc power supply circuit as shown below.