TACHOMETER WITH RS232 and or NMEA (RS232 compatible) FORMAT OUTPUT.
We have two interchangable sensors, optical or magnetic. See at bottom for the magnetic sensor, working with a small (delivered) magnet. See rpmsensor.pdf for more infos on the sensor.
The tachometer is a small PCB (58x19x13mm ). The optical sensor, DB9 RS232 connector and the supply wire are connected to it. This small PCB has a microcontroller (AT M8) , a CMOS/TTL to RS232 level converter (MAX232) and the supply regulator (78L05).
Output can be directly plugged in the PC RS232 Comm port and any terminal program will show the velocity rate in RPM from 28 to 13050 RPM. This covers propeller axes, engines and other applications.
The power supply requires a clean 7 to 14VDC (negative on black and positive on red wire). The board battery or a main adapter to 12VDC can be used. 5VDC can also be used after removing the voltage regulator.
The standard output Format is: $OPRPM*XXXXX at 4800B/s but other output format and baud rate can be configured on demand.
OP = Optical
RPM = Revolution Per Minute
* = Optional - , + or no Character. (See Jumper at bottom)
X = 0 - 13050 RPM. (no leading zero, so 1250 RPM = $OPRPM*1250)
CR and LF close the sentence (Checksum can be added on demand). Sentence is sent at half a second rate. The tachometer does not require any adjustment and is ready to operate; all wires are already connected.
INFRA RED TACHOMETER SENSOR (connected to the small board) Be very careful when installing the probes near a moving shaft or any moving device. Any moving mechanical part is dangerous!
The probes wires can be lengthened according to necessity. The wire thickness is of no particular significance here. Never apply any electric current to the probes and respect the 3 colored wires connection order when adding more sensor cable.
The optical probes are working with a light beam cut at intervals by the moving part attached to the rotating shaft. When working adequately, the sensor red LED will go off each time that the light beam is cuted by the blind.
Mount the probes the way that the infra red light beam is being cut at each revolution. The moving part occulting the cell on each revolution needs to have a width of at least 2,5cm (1inch) to ensure a good reading by high velocity. In fact when far from the center, one half meter or more, the blend can be about 10cm if the expected RPM rate is >5000RPM.
Do not expose or install the sensor near a strong light source like fluorescent tube, sunlight and do not place it right next to a light bulb; it would disturb the receiving cell and the reading. Install the sensor in the shadow with its connection as high as possible and keep it dry. Its two red surfaces should remain clean, even if the sensor is paint in order to prevent disturbing light breaking inside when not installed in the shadow. Sensor dim: 45x90x9mm 2xM6 or less bolts. For safety, use a piece of rubber for the blind.
Second model in IP65. In box; 98x65x40mm
Sensor optical or magnetic; L58mm 16 or 19mm diameter.
LS = Low Speed (or whatever wanted*)
RPM = Revolution Per Minute
Optional = * - , + or no or any character wanted.
X = 0 - 13050 RPM. ( so 145 RPM = $LSRPM145 )
*These very accurate tachos (1/1000) are "in system" programmable through their RS232 link. So any changes, special output string or speed, can be uploaded to them as an update with our free PC program.
See rpmsensor.pdf for more details on the sensor french/dutch/english.
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