School Help RPM counter [URGENT]

First of all I'm from portugal so sorry if I misspell something

Hello there I'm involved In a school project, and I searched the web to see if someone could help me develop a program that is basicaly a rpm counter that inputs the results into a lcd screen like this

http://www.microedeias.pt/kitmanuals/produtos/LCDazul.jpg

In my school we use Picaxe 28x2 and picaxe editor 6 as our programming software.

I already took out a sensor of a printer and figured out that it is light sensitive. So I attached white paper to a wheel with a black stripe, so when the black stripe hits the sensor it should count a rotation.

Can someone from this concept help me create a program? It would be awesome.

Thanks in advance

P.S. I know you might need the exact tension values but just work with a generic number, for example 5 volts normally, down to 1v when the black stripe crosses the sensor.

Ruben Gomes

Hi Ruben,

I'm sure people can help you. First thing, what sensor are you planning to use? There are many types. It should have a part number on it or you could maybe post a photo?

If you were at 5 volts and 1 volt, then those levels could be used as simple on/off indicators.
The "timer" variable is mentioned in Manual 2 on page 14. M2 parts have a "time" variable which counts seconds, but that's not available on the 28x2.

There are various methods of measuring speed. The "best" method will depend upon various things such as:
What speed range will you be dealing with?
How often do you ant to update the speed reading?
How quickly do you expect the speed to change?
If you can answer these questions, I suspect that you will get some responses which make sense for your particular circumstances.

The point of the project is to create something like this: http://www.e-fisioterapia.com/pt/52-284-large/pedaleira.jpg .
So it won't be super fast, just as fast as a human can pedal.
Can't the speed reading be instant? Like in a miles per hour sistem?
The speed won't change to much I guess because people will pedal consistently


Oh and the sensor I'm using Is just an ordinary printer sensor like this http://mlb-s1-p.mlstatic.com/sensor-papel-impressora-hp-c4680-178-MLB4667084756_072013-F.jpg

The sensor you have is called a "Photo interupter" it simply means it requires something to break the photo beam.

One option would be to use the "count" function in picaxe, as that allows you to count pulses over a nominated time period, for example over 1 second.
This will not allow for a instant display of speed as it requires the 1 second to read the pulses then display the data.

Or you could use the "pulsin" function where it measures the time of the pulse length, and calculate a speed from that.

I use pulsin to read the speed of a wind turbine to display rpm, and also for anemometers to read wind speed.

Personally i think your project is not very practical to just use a pedal system as per the link with no loading applied.

Perhaps you should look to something like this http://www.thebackshed.com/windmill/articles/PedalPower.asp

Although i know noone who can maintain 1000W of energy for very long, 100 - 200 watts is realistic, and perhaps 400W for a short sprint , but not human maintainable for long.

smeagol109, you need to "do the math" so you are familiar with what is involved with the PICAXE program. Remember it probably isn't as simple as "revolutions divided by time equals RPM", because with INTEGER math you have to account for OVERFLOW conditions that might occur.

Do you want to create a working prototype or just demonstrate the concept of counting during a time period and presenting the results as RPM?

I just want to demonstrate the concept of counting during a time period and presenting the results as RPM

I chose to take a diferent route and use an arduino i got this setup: http://duino4projects.com/wp-content/uploads/2013/05/Arduino-RPM-Counter.gif

the potentiometer is just to regulate the display brightness.

i just need help with the program because in my school we don't learn arduino language

smeagol109 said:

I chose to take a diferent route and use an arduino i got this setup: http://duino4projects.com/wp-content/uploads/2013/05/Arduino-RPM-Counter.gif

the potentiometer is just to regulate the display brightness.

i just need help with the program because in my school we don't learn arduino language

Click to expand...

Then perhaps contact the relevant forum?

This is the PICAXE Forum.

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smeagol109 said:

i just need help with the program because in my school we don't learn arduino language

Click to expand...

"Arduino language" is C/C++ - did you learn that?

There are comprehensive resources available on the internet for Arduino.

The upload date of that image and the website it is hosted on suggests that it came from someone else's project which will have code associated with it - is this also on that website?