Overspeed wrecks engines — fast. Rebuilds easily run $7,000–$15,000+, not counting lost harvest or site downtime.
The Bolec SS501 watches RPM/shaft speed and acts before damage: alarm, cut-off, or flashing warning — whatever your job needs.
Price: $275.00.
Farming
- Vineyard frost fans: stop runaway at night.
- Irrigation pumps: warn/cut when RPM strays.
- Tractors/harvesters: protect engines under load.
Construction & Industrial
- Compressors & generators: avoid dangerous overspeed.
- Loaders/excavators: alarm operators immediately.
- Conveyors/shafts: detect slip or stall by speed.
Why it sticks
- Dual channel: monitor two signals, drive two relays.
- 12/24 V systems; easy wiring into alarms or solenoids.
- Simple setpoints: high/low thresholds, or 1 Hz pulse.
Setpoints are frequency-based (Hz) from your tacho/shaft sensor.
- Diesel engine overspeed rebuild: $7,000–$15,000+
- Lost day in harvest or on site: $1,000+ /day
- SS501 protection (once-off): $275.00
One avoided failure pays for the SS501 many times over.
1) Watch
The SS501 reads a frequency signal from your engine tacho, hall sensor or magnetic pickup and converts it to “speed”.
2) Decide
You set High (overspeed) and Low (underspeed) thresholds for each channel. Hit the number — it reacts.
3) Act
Drive a relay for alarm/buzzer, flashing lamp (1 Hz), or cut-off solenoid. Two channels can act independently or together.
- Mount near the fuse panel or dash; keep wiring tidy and protected.
- Works on 12 V / 24 V, negative ground. Inputs suit tacho/shaft sensors; use included pull-ups for hall sensors when required.
- Relay outputs are volt-free 5 A (drive alarms, lamps, or a cut-off solenoid via a power relay).
- Not waterproof: install away from direct spray/moisture; orient terminals downward in vehicles/enclosures.
- When driving coils (relays/solenoids) add a diode across the coil to protect contacts.
For safety logic, keep a gap (hysteresis) between High/Low to avoid chatter. A pulsing mode (1 Hz) is available for attention-grabbing warnings.
Prefer to purchase via trade? Quote part no. SS501 to your wholesaler and request dispatch from Bolec-stock.
Images: product & PCB/DIP references courtesy of Bolec Electronics.