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Under Speed Warning Alarm for Magnetic Pickup sensor – Frequency Controlled Switch
This is an under-speed sensor module that provides an audible warning and signals output when the speed of a machine is below the set point. The module can be used in applications such as Engines, Machines, Sports machines, Fitness Equipment, Speed of the machine or engine can be detected using a magnetic pickup sensor. The project can be used in many applications where an under-speed monitor is important. The project is based on the LM2907 chip which works as a frequency to voltage converter, interfacing magnetic pickup as shown in the figure below. A typical magnetic pickup for automotive applications will provide a thousand pulses per mile so that at 60 mph the incoming frequency will be ~16.6 Hz. If the reference level on the comparator is set by two equal resistors R2 and R6 then the desired value of C5 and R4 can be determined from the simple relationship:
The buzzer is activated when Frequency ≥ (1/(2XR4C5))
From the RC selection chart, we can choose the suitable values for R5 and C5. In the current circuit, the frequency is set to 500Hz approx. A frequency trigger point can be changed as per user requirement using the above equation. The module supports any sensor with voltage levels 20mV to 28V.
Magnetic Pickup
A magnetic pickup consists of a permanent magnet, a pole-piece, and a sensing coil all encapsulated in a cylindrical case. A magnetic pickup is most frequently used to sense passing teeth on a gear, sprocket, or timing belt wheel, to bolt-heads, key-ways, or other moving machine-mounted targets.
Features
- Supply 12 to 15V DC @ 20mA
- Optimized for Magnetic Pickup Sensor
- Other Optical Sensors, Mechanical sensors, Tachometer sensors can be used
- Inputs Voltage Level 20mV to 28V
- Buzzer Operates when the Input frequency is below 500Hz
- Provide Low Output When Speed is below Setpoint
- Header Connector for Supply Input and Output
- 2 Pin Header for Sensor
- D1 Power LED
- PCB Dimensions 38.42 x 16.19 mm
Applications
- Engines
- Tachometer Under/Over Speed
- Fitness Equipment
- Sports Machines
- Machine Automation
- AC/DC Motor Speed Monitor
Schematic
Parts List
| NO | QNTY | REF. | DESC | MANUFACTURER | SUPPLIER | PART NO |
|---|---|---|---|---|---|---|
| 1 | 1 | BZ1 | BUZZER 5V SMD SIZE 12MM | CUI DEVICES | DIGIKEY | 102-CMI-1295-1285T-ND |
| 2 | 1 | CN1 | 6 PIN MALE HEADER PITCH 2.54MM | WURTH | DIGIKEY | 732-5319-ND |
| 3 | 1 | CN2 | 2 PIN MALE HEADER PITCH 2.54MM | WURTH | DIGIKEY | 732-5315-ND |
| 4 | 1 | C3 | 1uF/25V SMD SIZE 1206 | MURATA/YAGEO | DIGIKEY | |
| 5 | 1 | C2 | 0.1uF/50V SMD SIZE 0805 | MURATA/YAGEO | DIGIKEY | |
| 6 | 1 | C4 | DNP | |||
| 7 | 1 | C5 | 0.01uF/50V SMD SIZE 0805 | MURATA/YAGEO | DIGIKEY | |
| 8 | 1 | D1 | LED SMD SIZE 0805 | LITE ON INC | DIGIKEY | 160-1427-1-ND |
| 9 | 1 | Q1 | BC847AL | MICRO COMMERCIAL | DIGIKEY | BC847B-TPCT-ND |
| 10 | 2 | R1,R7 | 1K 5% SMD SIZE 0805 | MURATA/YAGEO | DIGIKEY | |
| 11 | 3 | R2,R5,R6 | 5K1 1% SMD SIZE 0805 | MURATA/YAGEO | DIGIKEY | |
| 12 | 1 | R3 | 100E 5% SMD SIZE 0805 | MURATA/YAGEO | DIGIKEY | |
| 13 | 1 | R4 | 100K 1% SMD SIZE 0805 | MURATA/YAGEO | DIGIKEY | |
| 14 | 1 | U1 | LM2907-N | TI | DIGIKEY | LM2907M-8/NOPB-ND |
| 15 | 1 | C1 | 10uF/25V SMD SIZE 1206 | MURATA/YAGEO | DIGIKEY |
Connections
Magnetic Pickup Sensor
Gerber View
Photos
Video
LM2907 Datasheet
PCB
