Choosing the Right Ultrasonic Sensor: HC-SR04 vs US-100 vs HY-SRF05

Whether you’re building a line-following robot, a contactless dispenser, or a smart trash-bin lid, picking the correct ultrasonic module can make or break your project. In this guide, we compare three popular choices—HC-SR04, US-100, and HY-SRF05—through the lens of ultrasonic sensor operation, power needs, measurement stability, and real-world integration with Arduino and other microcontrollers.

How Ultrasonic Sensing Works (In Short)

All three modules transmit a short burst of high-frequency sound (typically ~40 kHz) and measure the time it takes for the echo to return. Distance is computed from time-of-flight. The practical results depend on transducer quality, signal processing, firmware (onboard or host-driven), and mounting. When evaluating ultrasonic sensor range claims, remember that material, angle, and environmental noise can shift measurements by several centimeters.

Quick Picks: Which One Should You Choose?

• Choose HC-SR04 (budget classic) if you need the lowest cost, basic 2-pin (Trig/Echo) timing, and you can tolerate 2–4 cm jitter indoors.
• Choose US-100 (feature-rich) if you want UART output, optional temperature compensation, and better low-distance stability—great for compact, battery-powered builds.
• Choose HY-SRF05 (tunable & “SR04-plus”) if you want SR04-style wiring but improved minimum distance and longer maximum range for robotics.

HC-SR04 — The Affordable Workhorse

The hc sr04 is ubiquitous because it’s simple and inexpensive. It uses a 5 V supply and exposes Trig and Echo pins. Your microcontroller generates a 10 µs pulse, then measures the echo pulse width to compute distance. Typical usable range is ~2 cm to 200–300 cm. It’s perfect for beginners and classroom demos, but readings can drift with soft materials, angled targets, or in noisy spaces (fans, servos, or other sonics).

• Pros: Cheapest, huge library support, countless examples for arduino and ultrasonic sensor projects.
• Cons: No built-in temperature compensation; struggles below ~2 cm; can exhibit echo “ringing” and cross-talk with multiple modules.
• Best for: Budget robots, basic obstacle avoidance, distance-triggered LEDs/relays.

US-100 — UART Output & Smarter Features

US-100 adds a microcontroller on the board and supports two interfaces: traditional Trig/Echo or TTL UART (9600 bps). In UART mode, the module calculates distance internally and returns it as bytes—no timing math required. Many versions also enable temperature reading for compensated distances, making it more stable over temperature swings. This is ideal when the host MCU has limited timers or you want cleaner code.

• Pros: UART mode reduces CPU overhead; optional temperature compensation; slightly better near-field behavior than SR04.
• Cons: Costs a bit more; 5 V logic; some clones vary in firmware, so check documentation.
• Best for: Battery builds, compact enclosures, smart trash lids, water-level sensing where stable ultrasonic sensor operation matters.

HY-SRF05 — Extended Range with SR04-Style Wiring

HY-SRF05 looks and wires like an SR04 but can reach a longer range and lower minimum distance. Many users report slightly tighter repeatability indoors. If you already have SR04 code and want a quick upgrade without re-architecting your project, SRF05 is a drop-in path with more headroom for medium-range robotics.

• Pros: Extended range vs SR04; familiar 2-pin interface; better echo filtering on many boards.
• Cons: A bit pricier than SR04; specs vary among vendors; still susceptible to soft/angled targets.
• Best for: Mobile robots, pan-tilt scanners, entry counters where you need extra reach.

Arduino Integration & Wiring Tips

For arduino and ultrasonic sensor setups, supply 5 V and ground from the Arduino (or a regulated supply) and wire signal lines to digital pins. Keep sensor cables short and avoid routing alongside high-current motor wires. If you’re mixing 3.3 V boards (ESP32/ESP8266) with 5 V sensors, use a level shifter on the Echo line to protect the MCU.

• HC-SR04: 4 wires (VCC, GND, Trig, Echo). Use a timing library or pulseIn; add a 10–20 ms measurement interval.
• US-100: Option A: Trig/Echo like SR04. Option B: UART (VCC, GND, TX, RX) for one-line distance reads.
• HY-SRF05: Same as SR04. Many sketches drop in without changes; just adjust constants for range.

Accuracy, Stability & Environment

Quoted precision (±1–3 cm) assumes hard, perpendicular targets. Cloth, foam, or slanted surfaces scatter sound and degrade results. To maximize stability:

• Mount the sensor firmly; vibration creates jitter.
• Aim perpendicular to the target; small angles reduce echo strength.
• Add a small moving average (3–5 samples) or median filter to reject spikes.
• Use a consistent measurement window (e.g., 10 Hz) to avoid aliasing with motor noise.
• For multiple sensors, stagger triggers (e.g., 30–60 ms apart) to avoid cross-talk.

Range, Power & Update Rate

Realistic ultrasonic sensor range for these modules is typically up to 2–4 m in controlled indoor conditions. Outdoors, wind and ambient noise reduce effective range. Current draw is modest (tens of milliamps) during bursts. If you’re on batteries, pick US-100 with UART to shorten CPU-heavy timing loops and consider duty-cycling (sleep between pings).

• HC-SR04: ~2–300 cm typical, ~15–20 mA active. Best at 5–10 Hz ping rate.
• US-100: Similar envelope but steadier near-field; UART lets you sample cleanly at 10 Hz+.
• HY-SRF05: Often reaches a bit farther than SR04 with tighter minimum distance.

Price & Availability

If you’re deciding by budget, check the current ultrasonic sensor price across variants and bundles. HC-SR04 is usually the lowest-cost entry. HY-SRF05 and US-100 are slightly higher but can save time with cleaner readings and fewer code workarounds. For production or classroom buys, consider multi-packs to keep module behavior consistent.

Troubleshooting Checklist

• No reading / always zero: Verify 5 V supply and common ground; ensure Trig pulse ≥10 µs.
• Constant max distance: Target too close/soft, or sensor misaligned; try a flat board target.
• Jittery values: Add averaging/median; isolate from motor wires; reduce ping rate to 10 Hz.
• Multiple sensors interference: Trigger in sequence with delays; consider small baffles.
• 3.3 V MCU: Use a resistor divider or level shifter on Echo to protect the input.

Decision Guide

Still unsure? Use this quick rule-of-thumb:

• Lowest cost prototype: HC-SR04.
• Cleaner code & temp compensation (UART): US-100.
• Drop-in SR04 upgrade with more reach: HY-SRF05.

Whichever you choose, design around fundamentals of ultrasonic sensor operation: perpendicular aiming, stable mounts, filtering, and proper trigger timing. That ensures dependable results, whether you’re logging tank levels, mapping a room, or building an arduino and ultrasonic sensor obstacle-avoiding rover.

FAQ

Q1. Which is best for very close objects (< 3 cm)?
US-100 or HY-SRF05 generally behave better in the near-field than SR04. For sub-2 cm, consider IR or ToF sensors.

Q2. Can I use them outdoors?
Yes, but expect reduced range and more noise. Shield from wind, and retry/average readings. For rain-prone setups, look at sealed waterproof variants.

Q3. Do I need libraries?
Not strictly. A simple pulse-timing routine works for SR04/SRF05. US-100 in UART mode is even simpler—just read the bytes. Libraries help with filtering and smoothing.

Q4. Why do two identical modules read differently?
Tolerance across budget modules varies. Calibrate with a known distance and apply an offset in code. Buy multiples from the same batch when consistent behavior matters.

Conclusion

HC-SR04, US-100, and HY-SRF05 all serve the same purpose but shine in different contexts. SR04 wins on cost and ecosystem support, US-100 brings smarter outputs and steadier readings, and SRF05 gives you SR04 familiarity with more range. As you plan your next build, compare needs for interface (Trig/Echo vs UART), minimum and maximum ultrasonic sensor range, and code complexity—then choose the board that reduces friction in your design.

Explore current options, kits, and bundles on KitsGuru to match your requirements for performance, power, and ultrasonic sensor price. A few minutes spent choosing the right module now will save hours of debugging later.