Just finished is this NJK-5002C Hall Effect tachometer. Details coming shortly. It works like a charm. Just tape a magnet to a rotating object, press the button on the side of the tach and it displays the rpm.
As happens sometimes when working too late at night on a project, I crammed the project between 2 pieces of 13mm bamboo flooring with a cavity neatly routed out. I knew the project was working so I glued the 2 halves together. Perfect! No. I had calibrated the tach with a hand drill, but now, checking a 1725rpm bench grinder the tach reads 1938rpm instead of 1725. Fixing that is just a number change in the sketch. Only problem is I can't get to the USB connector!!! Oh well, I will pop the 2 halves apart and carefully calibrate it. Embarrassing.
Lloyd
I wish that would do it. Unfortunately (?) the sensor doesn't respond at all if the polarity is reversed. I tried on the drill and the bench grinder. Same results.
I have exposed the usb connector but when I try to connect the from the nano to the IDE, I get an error and therefore cannot reload the corrected sketch. The corrected sketch will compile but gives the error when it tries to upload.
Sketch uses 3418 bytes (11%) of program storage space. Maximum is 30720 bytes.
Global variables use 228 bytes (11%) of dynamic memory, leaving 1820 bytes for local variables. Maximum is 2048 bytes.
avrdude: ser_open(): can't set com-state for "\.\COM3"
Failed uploading: uploading error: exit status 1
I suspect (based on very limited knowledge and experience) that the communication between the nano and LCD might be interfering with the COM3 communication??
Right now I am just fumbling around and hope to eventually/accidentally find something that fixes the communication problem.
I am not sure what I did but the problem is fixed. Upload was successful and changing the calibration number in the sketch worked also.
I just fiddled in TOOLS with, board, processor, and com.
All is well.
@xfpd Thanks for the help. It's nice to have someone looking over your shoulder with friendly advice. And I have to admit, when it actually works it is a bit of a rush.
Yup, you never know what that guy will come up with. Always thinking outside the box.
I needed to do some more work on the sketch by calculating a rolling average for the RPM. When the magnet was on a small shaft rotating at high speed, the rpm reading would bounce around as the Hall Sensor changed orientation to the magnet. The RPM wasn't very stable. As I was modifying the sketch and trying to upload it, I again got the communication error with com 3, and could not get it to upload. I ended up going in the control panel on my laptop and looking at the the COM3 CH340 driver and saw that when I gave Arduino permission to update its software, it had also updated the CH340 software. Switching back to the previous version of the driver fixed the problem. I noticed that other folks had mentioned similar difficulties and the same solution.
Lloyd
Was the magnet slipping on the shaft? Can you use a smaller magnet to avoid a wide trigger arc? Can you mount the magnet farther from the shaft (on a peg) to have a flatter arc?
