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Topic: An LED bar graph tachometer (Read 4 times) previous topic - next topic


I want to build a simple LED bar graph tachometer. Maybe 10-12 LED's, green, yellow and red. Maybe an orange thrown in there  :D

The "redline" will only be 4500-5000 RPM.

Perhaps 1000rpm= 2 lit, 2000rpm= 3 lit, 2500rpm= 4 lit, etc.

I've been tinkering with practice code making led's blink and stay lit plus some sequencing so the hardware side won't be much trouble. Plus, I'm finding that I'm A LOT more into the BUILDING over the PROGRAMMING *sigh*  Hopefully this will change as I become more proficient (And less confused) by it...

I have an IR receiver and emitter set so I would like to start with using that for a trigger but I've ordered a couple of hall-effect sensors and magnets for the final build.

This will be my first project involving both input and output so it should be a good learning experience!

Any guidance would be most welcome!


Sounds like a fun project,
you should post your code so people can see how you are trying this so we can offer specific examples and help,
what kind of hall sensors did u order? There are ones that are ratiometric and you get an analog signal and there are more switch type ones that the output is considered digital( high or low)
for rpm you are best of with the digital because its alot faster to do a digital read than analog read and some math


Never to old to learn and I learn every day


I ordered 10 of these:


It seems that all the examples I can find seem to use serial output to read RPM.  I'm looking for a way to illuminate a bank of LED's based on RPM.

It's complicated (at least to me  :smiley-roll-blue:) because the output to the LED's will have time factored in.  Damned if I can find a suitable code example.

I'm leaning towards something like:

if input to pin (X) = 1000 times a minute ,  output to pin (Y) hi,
if input to pin (x) = 2000 times a minute , output to pin (Y) and (Z) hi
if input to pin (X) = 3000 times a minute , output to pin (Y) and (Z) and (A) hi

(This is just my crude example of the logic I believe would be necessary  :smiley-red:)

I'm sure there would be some additional coding for I/O when the motor slowed down or else it would just "hold" the lamps on.

It would be great to find some code already written that would allow me to just change some parameters for tuning.

The learning curve is pretty steep for me but it would be sweet to actually build something useful.


First start to read the hall sensor(s) value, calculate and write the output value to the serialmonitor. A challange enough to start with as newbie.
Use a simpel electro motor first.
When this works then start to work on the display of the RPM by leds.
Search the forum here for RPM projects.

Never to old to learn and I learn every day

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