NTC 5D-15 Thermistor - Inrush Current Limiter & Temperature Sensor
The NTC 5D-15 is a negative temperature coefficient thermistor rated 5 ohms at 25C, primarily used as an inrush current limiter in power supply circuits, motor drives, and capacitive input stages. At startup, the thermistor presents high resistance that absorbs the surge of current into large filter capacitors and transformer primaries. As current flows and the component self-heats within seconds, resistance drops sharply - allowing normal operating current to pass with minimal power loss.
With a wide -55C to +200C operating range, 76-second thermal response time, and 30mW power dissipation rating, the 5D-15 is a standard protective component for switch-mode power supplies, LED driver boards, HVAC motor controllers, and DIY bench power projects. The 16.5mm disc package is through-hole compatible with standard PCB footprints and fits easily on any solderless breadboard.
For Arduino and ESP32 temperature sensing projects: Connected in a voltage divider with a known reference resistor, NTC thermistors make precise analog temperature sensors. Read the midpoint voltage on an analog input pin, apply the Steinhart-Hart equation or a beta-value approximation, and you have a calibrated temperature reading with no external library required. The 5D-15 covers a wide enough range for both ambient room temperature monitoring and high-heat motor or heater applications.
Specifications
| Resistance at 25C | 5 ohm |
|---|---|
| Operating Range | -55C to +200C |
| Response Time | 76 seconds |
| Package Size | 16.5mm |
| Power Dissipation | 30mW |
| Type | NTC (Negative Temperature Coefficient) |
Frequently Asked Questions
What does NTC mean and how does the 5D-15 work as an inrush limiter?
NTC stands for Negative Temperature Coefficient - as the component heats up, its resistance decreases. In an inrush current limiting application, the thermistor starts cold with high resistance (5 ohm at 25C), absorbing the current surge when a power supply first switches on. As it self-heats within seconds, resistance drops to a fraction of an ohm, allowing normal operating current to flow with very low power loss.
What does '5D-15' mean in the part number?
In NTC thermistor naming conventions, '5D' indicates 5 ohm resistance at 25C, and '15' refers to the disc body diameter of approximately 15mm. The 5D-15 is a widely used standard for inrush current limiting in consumer electronics power supplies, LED lighting drivers, and motor control circuits.
Can I use this as a temperature sensor with an Arduino or ESP32?
Yes. Wire the thermistor in a voltage divider with a 10k ohm reference resistor: one end to 3.3V or 5V, the other end to GND through the resistor, and read the midpoint on an analog input pin. Apply the Steinhart-Hart equation or a simpler beta-value formula to convert ADC voltage to temperature. Example code and wiring diagrams are widely available for both Arduino IDE and MicroPython.
What is the difference between this NTC thermistor and a digital sensor like the DS18B20?
The NTC thermistor is an analog component requiring an ADC pin, a reference resistor, and a conversion formula. It costs less, tolerates higher temperatures, and needs no library. A digital sensor like the DS18B20 outputs calibrated data over a serial bus and costs more but requires no math. Use the thermistor when cost, temperature range, or inrush limiting is a priority; use a digital sensor when plug-and-play accuracy matters most.
How many thermistors come in this listing?
Each listing is for one (1) NTC 5D-15 thermistor. If you need multiple units, simply increase the quantity before adding to cart. With 90 in stock, bulk orders are no problem.