Sensor and Special Resistor Pack – Photoresistors, NTC Thermistors, Varistors and Resistor Networks (435 Parts)

Description

Sensors and special resistors in one pack

Five kinds of resistor that change with the world around them or do a job a plain resistor cannot: photoresistors that react to light, NTC thermistors in epoxy and glass for measuring temperature, varistors that clamp voltage surges, and SIP resistor networks that put up to nine pull-up or pull-down resistors in a single row of pins. 435 parts, every type bagged and labelled.

What's in the pack

Photoresistors (LDR), 5 mm, 10 of each

Resistance falls as light gets brighter. Pick a lower-resistance type for dim rooms and a higher one for daylight; use one leg of a voltage divider into an analog input.

Metal oxide varistors, ±10 %, 10 of each

The code gives the disc size (5D = 5 mm) and the voltage in three digits (471 = 47 × 10 = 470 V); a larger disc absorbs bigger surges. The 27 V and 33 V types suit 12–24 V DC equipment, the others mains-powered circuits.

NTC thermistors MF52 (epoxy bead), B = 3950, ±5 %, 10 of each

The small black bead reacts quickly and is the usual choice for room, battery and 3D-printer bed temperature readings (about −40 to +125 °C).

NTC thermistors MF58 (glass), B = 3950, ±5 %, 10 of each

Sealed in glass, these stand higher temperatures than the epoxy beads (typically up to about 200 °C) and are the type used in kettles, ovens and hot ends; the high values suit the hot end of that range.

SIP resistor networks (bussed), 5 of each

Bussed ("A" type) networks: pin 1, marked with a dot, is common to all resistors and every other pin is one resistor. Ideal as pull-ups for a data bus or keypad, or current limiting for a row of LEDs (220–470 Ω).

Good to know

• Varistors go across the supply they protect, usually after a fuse. Working on mains-powered circuits is only for people qualified to do so.
• Thermistor resistance falls as temperature rises. Most microcontroller libraries convert the reading with the B value (3950) and the resistance at 25 °C; pair the thermistor with a fixed resistor of the same value.
• Photoresistors are cadmium sulphide cells: they respond in tens of milliseconds, fine for day/night and light-level sensing but not for data. Dispose of them as electronic waste.
• Parts are bagged and labelled by value or part number and packed by hand by our supplier, so a bag can occasionally hold a few pieces more or less than listed, or a close substitute value. Some bag labels are printed in Chinese next to the part numbers.
• Contains small parts. Not a toy; keep away from young children.