AUTOMOTIVE BARGRAPH TACHOMETER HELP

Thread Starter

jonasbschutz

Joined Aug 24, 2022
8
HELLO ACC MEMBERS.
Im here with a question about a project of mine. im working on a tachometer for my motorcycle witch started with two ics. one frequency to voltage converter and a led driver such lm3914 that uses a reference voltage to determine how many leds will flash.
now im using just a arduino to do everything. I used a frequency generator into the motorcycle tachometer to determine the frequency of all rpm numbers (1 to 10) and used that information so the arduino know what leds will be on at the adafruit board.

I would like to know if anyone could tell me if this method of converting frequency directly indo a bar graph code on arduino is reliable.

can you tell me some pros and coms?
 

DNA Robotics

Joined Jun 13, 2014
657
It has been a while, but aren’t there enough outputs on an Uno to drive 10 LEDs directly?
Maybe even a Nano?
If not, maybe a demultipexer chip
 

eetech00

Joined Jun 8, 2013
4,056
Hardware FtoV takes the load off the arduino CPU.
I haven't used an arduino to perform ftov conversion. if you remove the hardware FtoV, and move that function to the arduino, I would be concerned with the additional load on the arduino CPU.
 

schmitt trigger

Joined Jul 12, 2010
958
In your code, include the means to perform dithering. Otherwise, the RPM steps in the bargraph will be too coarse: 1000 RPM between each.
With dithering, a pair of adjacent LEDs will glow dimly.
As an example, let’s say the engine is running at 4,500 RPM. Without dithering, only the 4th LED would light up. With dithering, the 4th and 5th LEDs would light up at half intensity, clearly indicating that your engine is running between 4 and 5,000 RPM.
 

Thread Starter

jonasbschutz

Joined Aug 24, 2022
8
Hardware FtoV takes the load off the arduino CPU.
I haven't used an arduino to perform ftov conversion. if you remove the hardware FtoV, and move that function to the arduino, I would be concerned with the additional load on the arduino CPU.
using arduino i wont need to convert to voltagem because i can use a code that takes the frequency and converts to an adafruit signal. i want to know if is there a advantage using the arduino to read the voltage signal, like is the voltaage signal more stable than the frequency?
 

eetech00

Joined Jun 8, 2013
4,056
using arduino i wont need to convert to voltagem because i can use a code that takes the frequency and converts to an adafruit signal. i want to know if is there a advantage using the arduino to read the voltage signal, like is the voltaage signal more stable than the frequency?
The voltage output of a FtoV is more stable. The frequency reflects a change in engine revolution, so the arduino would have to monitor that change and take appropriate action in "real time". Automotive RPM gauges typically resolve to 100 RPM.
 

sarahMCML

Joined May 11, 2019
421
HELLO ACC MEMBERS.
Im here with a question about a project of mine. im working on a tachometer for my motorcycle witch started with two ics. one frequency to voltage converter and a led driver such lm3914 that uses a reference voltage to determine how many leds will flash.
now im using just a arduino to do everything. I used a frequency generator into the motorcycle tachometer to determine the frequency of all rpm numbers (1 to 10) and used that information so the arduino know what leds will be on at the adafruit board.

I would like to know if anyone could tell me if this method of converting frequency directly indo a bar graph code on arduino is reliable.

can you tell me some pros and coms?
I designed one very similar back in 1982 for my motorcycle, using a LM3914. Sadly, it never got fitted to the machine, but I still have the circuit boards and the front panel and case that I made for it. The schematic though has long been lost, and it's built in such a way as to be difficult to redraw from the 2 existing boards.
What I can remember though is that I managed to get the circuit to do the first 0 to 5000 RPM using the 10 LED's in single LED mode, after which it switched to Bargraph mode to use the same LED's to go from there to 10000 RPM.
It worked well with input from a signal generator: how well it would have coped with pulses from the ignition I never found out, or even decide upon, if memory serves.
 

MisterBill2

Joined Jan 23, 2018
19,453
To go directly from a counter to a display, use I/Then statements to examine the count each count cycle. The sequence would be: end count, data to register, If data above(some value) then light segment one, next Line, If data above (next value, light segment #2, else back to the waiting location to be ready for the next reading. The code is a bit bulky but if the saved count data is over written each time the memory use will be fairly small.
 
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