Choosing the Right Power Supply

Choosing the Right Power Supply for Electronics Projects

Power supply choice is the foundation of any reliable electronics project. The wrong choice causes brownouts, heat damage, battery drain, and unreliable behavior. This guide covers the power supply modules you will encounter in maker and IoT projects — what they do, when to use them, and what to watch out for.

Linear Regulators: Simple but Inefficient

LM7805: The classic 5V linear regulator. Input 7–35V, output 5V fixed, 1.5A max. Efficiency is (Vout/Vin) × 100. At 12V input delivering 5V at 1A: efficiency = 42%. The remaining 58% becomes heat — the LM7805 needs a heatsink for currents above 300 mA from a 12V supply. Simple and reliable for low-power applications where heat dissipation is not a constraint. Price: ₹10–20.

AMS1117-3.3: 3.3V LDO regulator, 800 mA max, dropout voltage ~1.3V. Input must be at least 4.6V. Standard choice for 3.3V generation from 5V. Used on virtually every ESP32, NodeMCU, and Raspberry Pi board. Price: ₹5–15 per IC, ₹20–40 as a module.

Use linear regulators when input and output voltages are close (less than 3V difference), or when low noise on the output rail matters (linear regulators have lower output noise than switchers).

Buck Converters: Efficient Step-Down

LM2596 adjustable buck module: Input 4.5–40V, output 1.25–35V adjustable, 3A. Efficiency 75–92%. Has an onboard potentiometer to set voltage. Price: ₹40–80 per module. Use for 12V to 5V conversion for ESP32 projects, 12V to variable for motor projects, or any step-down application where efficiency matters.

MP1584EN mini buck module: Smaller than LM2596, input 4.5–28V, 3A, same adjustable output. Better choice when PCB space is limited. Price: ₹50–100.

Buck converters generate some switching noise on the output rail. For noise-sensitive analog circuits, add 100 µF + 100 nF output capacitors and consider an LC filter.

Boost Converters: Step-Up

MT3608 boost module: Input 2–24V, output 5–28V adjustable (must be higher than input), 2A. Use when powering 5V circuits from a 3.7V LiPo battery, or 12V output from 5V USB. Price: ₹30–60.

Mains to DC: HLK-PM Series

HLK-PM01: 100–240VAC to 5V/600 mA. Compact (34 × 20 mm), isolated, UL/CE certified. Fits inside Indian electrical boxes. Price: ₹180–250. The standard choice for mains-powered ESP32 home automation projects.

HLK-PM03: 100–240VAC to 3.3V/900 mA. Direct 3.3V from mains — eliminates the need for an LDO regulator. Price: ₹200–280.

HLK-PM12: 100–240VAC to 12V/1W. Use when you need 12V for solenoids, door locks, or relays alongside a 5V ESP32 supply.

LiPo Battery Charging: TP4056

The TP4056 module charges single-cell 3.7V LiPo batteries via USB. Built-in overcharge protection (cuts off at 4.2V). Current set by a resistor (1A by default on most modules). Some modules include a protection IC (DW01A) for overdischarge protection — check the product listing. Price: ₹20–40.

The TP4056 output goes directly to the battery — to also power your circuit simultaneously while charging, add a Schottky diode from the battery positive to your circuit VCC, and another from the TP4056 output to circuit VCC. This prevents the charging circuit and discharge path from conflicting.

Calculating Power Requirements

Add up the current draw of every component:

• ESP32 active: 150 mA
• 4-channel relay board (all on): 4 × 70 mA = 280 mA
• OLED display: 20 mA
• DHT22 sensor: 1.5 mA
• Total: ~450 mA at 5V

Add 20% safety margin: need at least 540 mA. HLK-PM01 at 600 mA is sufficient for this example. For an 8-relay system, use a dedicated 5V/2A adapter for the relay board.

Browse power supply modules at Circuitkar — LM2596, AMS1117, HLK-PM01, TP4056, and MT3608 all in stock.