Any Programmers around here?

[Prasinos]

Hey guys I have been thinking about making a dyno for my bikes and I have figured out the hardware part. I plan on using one or two 45lb plates as a flywheel and they will be spun by the back tire of a bike. I will use a mouse or a keyboard along with a cam that will click a button a number of times per revolution.

So the reason for the title.

I need a program that will record the time between clicks and possibly output them into an excel file. This way I can just use the first derivative to calculate angular velocity, the second derivative to calculate torque and the third to calculate power. It would be able to make some really nice graphs that could show the difference in power from different upgrades, I think it would be really cool.

Anyway I don't think it would be that difficult for someone that knew what they were doing. I have acess to labview, matlab, and c++. So if anyone could lend advice, or ideally write this program, I would appreciate it greatly.

[fall_down_stand_up]

Dyno would be great!!!!!I would like to know the actual output of these 2 stroke china girls....
John-John

[Prasinos]

yea im confident i can do it i just need the program if i want to have pretty graphs.

[2door]

Huh?
Derivative? Velocity? Excel file?
And I was just starting to understand the chain tensioner thing...
Tom

[TheE]

Um yeah, that wouldn't be too hard to do in good ol' fashioned C. Could export the results directly in .csv format too.

The multi-tasking of a modern OS will throw off the timing a hair, just for fair warning.

[Prasinos]

not to impose, but if i gave you my email could you make the program and send it to me? I dont want to cause you too much trouble and i dont know how complicated the code would be, but if it isnt too hard....

[TheE]

I've actually been trying to code it a bit. Turns out that getting any kind of precision timing in C is alot harder than I thought. I'll let you know if I find anything.

[Prasinos]

hmmm, yea i can only make the flywheel so heavy, if i could get to within like 50 miliseconds i think it would be enough.

[TheE]

Welp, I did a bit of researching about something called the QueryPerformanceCounter function which, as the name implies, queries a counter inside the CPU for really high-res timing. Here's my code with it so far (for Visual Studio C++):

#include "stdafx.h"
#include <windows.h>

#include <winbase.h>
#include <stdlib.h>
#include <conio.h>

int main(void)
{

	
    unsigned long int revs=0;
    LARGE_INTEGER total_time,diff_time,start_time,end_time,TICKS_PER_SECOND;
	char c=0;
	FILE *outp;

	QueryPerformanceFrequency(&TICKS_PER_SECOND);

	total_time.QuadPart=0;
	outp=fopen("output.csv","a");
	fflush(stdin);
	printf("QPC Freq: %I64d\n",TICKS_PER_SECOND.QuadPart);
	

	printf("Press any key to begin capturing.\n");
	
    
	getch();

	printf("Capturing counts to output.csv, press 'x' to quit...");

    QueryPerformanceCounter(&start_time);

	while(c!='x')
	{
		if(kbhit())
		{
		
		   QueryPerformanceCounter(&end_time);
		   diff_time.QuadPart=end_time.QuadPart-start_time.QuadPart;
		   total_time.QuadPart+=diff_time.QuadPart;
		   QueryPerformanceCounter(&start_time);
		   revs++;
		   fprintf(outp,"%ld,%I64d,%I64d,\n",revs,total_time.QuadPart,diff_time.QuadPart);
		   c=getch();
		}
		
	}

	fclose(outp);

	printf("\n\nTotal of %ld revolutions were counted!\n",revs);
	getch();

     return EXIT_SUCCESS;
}

It will tell you how many ticks per second at the beginning, and then append the results into an "output.csv" file in the same directory as the executable(will be created if it hasn't already). You can later multiply (number of ticks * (1/tick frequency)) to get the time.

I really have no idea how accurate it is, and I'm not a professional programmer by any stretch of the imagination. I'm sure someone will chime in with a better solution. Personally I prefer a microcontroller because you can manually calculate it's timing down to the nanosecond, but a general goes to war with the army he's got...

[Prasinos]

Thanks alot E, il see how this works. I get home around thanksgiving so il let you know how this all goes when i try it ou