Tachometers

Hi all, I've been working with the idea of building a tachometer to be fitted on my older Kubota tractor. I've set up several different versions based on projects found on the web, each with a caveat or two, so I'm seeking some input from anyone who has experience.

The first one worked fairly well using an IR transmitter/receiver through a Schmitt trigger to Uno's interrupt for counting and displayed on a 16X2 LCD display. From there I moved to using a .96" OLED display. That worked fairly well, but to be honest my old eyes would never see it from the seat of the tractor to the dash, I needed something bigger. And I'd like to incorporate a "retro" gauge look.

So now I'm playing with 2.4" tft displays and just beginning to understand their operation, with new issues there. For example. A parallel interfaced shield such as mcufriend's works well for experimentation, but uses up most of the gpio pins including the interrupt, plus the logic level translation issues. But it is one of the fastest display options. But I still need a display that will give me access to an interrupt. So then I moved to an SPI interface 2.4" display, that leaves only the issue of level translation. BUT the display transitions are much slower causing flicker.

Next I started fooling with connecting the display to an ESP 8266, using examples in the TFT_eSPI library. This produces a very fast display transition, In part by the speed of the ESP8266 and the well written examples in the library. But so far I have not seen an example of a Tachometer using an ESP 8266, and have read in some threads that the inherent calls to the wifi functions can/will disrupt the program flow times, giving inaccurate readings.

So I guess what I'm asking for is opinions as to what might be the best set up for using a SPI interfaced display for use as a tachometer. I'd love to hear opinions.

I don't know the answer but your Title is not best chosen to attract the attention of people who can help. As far as I can see your question is really about the display for a tachometer.

Maybe Help with TFT SPI display for tachometer would be better.

If you edit your Original Post you can change the Title.

...R

@Robin2 Thanks for the reply.
Well actually no the problem is not so much in displaying the information, but the best way to collect the information from the sensor, and then display it. I've ruled out using an Uno shield (display) due to the fact that the interrupt GPIO isn't available. From that point I steered toward a display with SPI interface. (I felt I might use that with an Uno, Nano, or ProMini.) That display is much slower responding, causing a great deal of flicker, so I went to an ESP8266 for a faster processor along with a faster library. But as stated I have not found a satisfactory example of using the ESP8266 in a tachometer project. Perhaps I'll just go back to displaying a numerical output.

I like the RA8875 display controller chip and the displays which go with it. Adafruit has a small selection from the range on their shop.

The RA8875 has enough memory for two copies of the screen. Ypu can display one while you are updating the other. Flicker can also be reduced by being very smart about only updating the digits which changed.

Getting a TFT to work outdoors is tricky. You will always need some kind of sunshade. If you like retro, use a Switec stepper with a real analog needle and print the analog gauge background on your printer.

I am curious where you are getting the signal for the tachometer? I have/had two different Kubota tractors and they both have/had mechanically driven tachometers.

Paul

Hi Paul, My plan is to use an IR tranmitter/receiver pair, mounted near the front pulley. To the pulley, I will place a strip of "chrome" tape from the center of pulley to the outside. On every revolution it will send a pulse, reflected from the tape. I've used this method on an old Craftsman garden tractor (Roper) with a twin cyl B&S engine successfully, using an LCD numeric display. That way there is no tapping into the system for a signal, and since my B7100 is diesel, there is no ignition pulse anyway. I was hoping to "raise the bar" with a more graphic display.

Cheers

Another option that stands up better to dirt and oil is to glue a small neodymium magnet onto the main output pulley and mount a hall effect sensor to be within range as the pulley turns.

Commercial add-on tachometer units work off the AC noise from the alternator.

Yup that'll work too. In this case I simply had the IR and reflective tape on hand. So far on the GT18 it's held up.

Getting a TFT to work outdoors is tricky. You will always need some kind of sunshade. If you like retro, use a Switec stepper with a real analog needle and print the analog gauge background on your printer.

Yes, I do realize the problem with TFT’s in the sunlight, I was also considering an epaper display to resolve that. I have to admit I hadn’t thought of a stepper, that could be a great option. Thanks for the tip.

I'm working on a similar project for an e-bike, but my max speed is 30MPH so not too worried about display refresh speeds. I do recommend the cheap and cheerful Nokia 5110 LCD matrix displays. Only black and white, but very clear to read. use about 6IOs

I have had some issues with them out the pack (the cheapest ones i could find on ebay), but generally pinching the clips down that hold the display fixes em.

I've also used the TV-out libary to display out a S-Video signal to a small LCD TV - again, black and white, but looks great for a info screen and only uses 2 ISO or 3