DIGITEN 4 Digital Green LED Tachometer RPM Speed Meter + Hall Proximity Switch Magnet Sensor NPN for Lathe Conveyor Belt

This does work as expected. I figured something out though that may be super useful for someone as it was for me. I didn’t feel comfortable spinning a magnet >3k rpm on my mill spindle, so I started designing an arduino based light sensor to then bounce a signal to this tachometer based on rpm, so it becomes an IR based tachometer, I realized it was infinitely easier that doing all of that. Just grab a 5v IR obstacle sensor, and tie the output signal to the input signal of this tach. Share ground. That’s it. Now this tachometer is an IR tachometer, use reflective tape and adjust sensor to get it right. No spinning magnets, just bounce the light

Hello All! I purchased this tachometer to provide RPM information on my drill press. After reading several reviews, I thought I would do some additional measurements of the sensor for others to use in their decision making and engineering efforts. As the sensor is a hall effect device, the magnetic polarity of the supplied magnet in relationship to the sensor DOES matter. It is essential that the SOUTH pole of the magnet face the sensor. In order to determine which side of the magnet is the south pole, I used a smart phone app provided by K&J Magnetics called KJ Pole ID (iPhone version). Simply open the app and point the top of the phone towards one face of the magnet. The app will display the magnetic polarity that is currently facing the phone. Arrange the magnet such that the app displays "The SOUTH pole of the magnet is facing the phone", then mark the face of the magnet for easy identification prior to mounting.When power to the sensor is ON and no magnet is present, the sensor will output 0VDC as shown in the picture. The red LED on the bottom of the sensor will also be illuminated. When the magnetic SOUTH pole of the magnet approaches the sensor (in my test, about a quarter inch), the red LED will turn off and the output of the sensor will switch to a positive DC voltage. In my test, this voltage is proportional to the supplied DC input voltage to the sensor minus approximately 560mV (Vout_sensor = Vdc_sensor - .560).The rise time of the sensor, or the time it takes for the output of the sensor to rise from 10 percent to 90 percent of its steady value (Vout_sensor), is 114uS. This is with a 9VDC regulated DC power supply into the sensor. Please see the attached photo for additional details. The fall time (no photo attached), is much faster with a time of 160nS.During the wiring portion of the assembly, it's important to note the colorings of the wires at the display and at the sensor.The sensor color codes are as follows:Brown: +DC supply voltageBlue: GNDBlack: Sensor Output Voltage (I called this Vout_sensor in my discussion above)The tachometer display color codes are as follows:Red: +DC supply voltageBlack: GNDYellow: Sensor Input Voltage (Connect this lead to the Black lead of the sensor wiring)As mentioned by Digiten, the DC supply voltage must fall into the range of 8VDC to 15VDC (Do NOT use an AC-output power supply). As an engineer, this implies that any supply voltage below or above this range can cause unexpected operation or failure of the product. My recommendation is to use a walwart-style (plug in) regulated DC power supply with an output voltage of either 9VDC or 12VDC. When connecting the power supply to the tachometer, make certain that the output polarity of the power supply correlates to the input polarity of the tachometer.When mounting your display, I would recommend measuring the actual dimensions of your display first as mine were slightly different from the recommended cutout dimensions shown on the product page. The cutout portion of my display (the area behind the front mounting flange) measured 33.33mm by 68.26mm. The panel cutout dimension on the page has this listed at: 68x33mm. Those extra thousandths of an inch could make mounting the display a challenge depending on the supporting material.In my next review, I will compare the RPM values from this tachometer to the RPM values calculated from a high-end encoder and RPM measuring device :) In summary, this is a well made and nicely constructed tachometer for the price!

This is a nice tachometer and I’d give it 5 stars except the instructions state the “South Pole of the magnet is valid” (what that means is the South Pole faces the sensor) and they don’t mark the magnet as to poles. I know how to figure that out but it’d be nice if they labeled that.

The media could not be loaded. I bought this to install on my drill press and it’s an excellent addition. I mounted the sensor to the underside of the top body and JB weld the magnet to the pulley. It’s very accurate and the screen is bright and easy to read.

Easy to use. Just be sure to get the magnet in the right way. I had to use a 15v power supply as it wouldn't start with a 12v one. An old cordless phone power supply did the job.

I purchased 2 of these. Both popped, flashed, and smoked on initial power up. Instructions say 8 to 15 VDC input. My input voltage was 12.7 VDC, so right in the middle of the spec. I can see a small component destroyed on each circuit board. Oddly it is a different component on each. Just total junk. I am a retired instrumentation technician, so I know what I am doing when wiring things like this. I did it correctly. Naturally it has been a few months since I purchased them, so it is past the return date. My intended use was on a show garden tractor. I have already cut a hole in the finished dash for the display. What a pain in the *%#.

I bought this to show my lathe's speed. It worked well. A little problem mounting the magnet. Instructions say south pole. I used a magnetic navigational compass to determine north/south of the provided magnet. When I mounted south pole toward the sensor, it didn't work. Turned it around and it did. I epoxied the magnet so unmounting was a nuisance.Connection was simple, just be sure to follow instruction on wire colors.Ground yourself when handling electronics to keep static zero.

Used this on my Grizzly G0709 lathe as a tachometer. Works great, the display is clear and good quality and the magnetic pickup works well. I ordered a 2nd unit for my drill press. Great item!