# PWM Dwell Meter

Okay, so I think I solved my "Tachometer Problem"... I'm using a Proximity Sensor which is triggered each revolution of the distributor drive chuck. Supplying the Proximity Sensor with a regulated 5vDC reference voltage, I SHOULD be able to simply connect the signal voltage directly to my PWM 0-5vDC meter.

So, first, does this seem logical?

Now, to the Dwell Meter. It uses the same type PWM 0-5vDC meter. It would seem to me that a couple things need to be considered. First, the microcontroller needs to calculate the degrees, within one rotation, that the circuit is closed, divided by the number of open circuit pulses within one revolution. Using the microcontroller allows me to eliminate the need for a device to manually input the number of cylinders being tested and whether the engine is a 2-cycle or 4-cycle. Second, it allows me to precisely drive the PWM meter across a scale of 0 to 50 degrees of dwell angle. To do this, it would seem that I'd have to also provide a Proximity Sensor digital input to the microcontroller. Now, the "kicker". Although the reference voltage for the Proximity Sensor is 5vDC, by insulating the distributor from the chassis ground and providing a separate ground I can sample the events as something akin to "voltage on" vs. "voltage off". Can this be INPUT as a PWM signal?

Now I'm at somewhat of a loss on how to code such a project..... Dyslexia is a beotch!

Not much. Please post a link to the datasheet of the device as well as schematics.

Arduino Controller Board = https://docs.arduino.cc/resources/datasheets/A000066-datasheet.pdf
Arduino Schematic = https://content.arduino.cc/assets/UNO-TH_Rev3e_sch.pdf

Proximity Sensor (NPN, NO, M18 3-wire) = https://www.mouser.com/datasheet/2/307/e2e_ds_e_12_4_csm446-2307609.pdf
Meters, Adafruit 3990 = https://pdf.utmel.com/r/datasheets/adafruitindustriesllc-3990-datasheets-2279.pdf

Not needed. Sorry I wasn't clear enough.

You're saying the Arduino is not needed?

That link brings up a large product catalog. Not clear at all which pages show just the model You have in mind.

Pictures of a Volt meter... No useful help.

That proximity sensor output pulses. Connecting it directly to a voltmeter can't work in my opinion. There is a constant duty cycle of pulse time and time between pulses. Okey, higher RPM produces a higher number of pulses per second....
I would go for a microcontroller measuring the RPM and then transform the numeric value to the format needed for the "display". A digital display involves no analog circuits. A controller PWM output need filtering to produce an analog signal suitable for a panel meter.

No, only that the interior of an UNO is not needed.
Your post tells about connecting a pulsing sensor to a panel meter. That was misleading information.
You connect the sensor to a controller and the controller is connected to the presentation device.

This must be a continuation of this thread:
https://forum.arduino.cc/t/tach-dwell-project/944881
How can we help? There isn't anything implausible about anything you've said. It's just that it's not clear what your request is. What I see is just some general musings about how a tach/dwell meter might be made...

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