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measuring time and distance

Flatire

Mar 16, 2020
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just noticed i should have posted in question forum....

I want to make a device to measure and compare time and distance for my 1/4 mile race car.

the way i'd like it to work is, record first 1/4mile run and store it. then on my next run,
in real time compare it to the stored run, having LEDs indicating if the current run is
faster or slower than the stored run.

I assume i'll use a pick up on the driveshaft or wheel.

Thanks for your time and input.
Tim
 

Bluejets

Oct 5, 2014
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You already have the distance @1/4 mile.

2 Microcontrollers (preferably)...Arduino of any type would cover the requirement.
Pickup sensor at the start to detect green light on-time, ideally hard wired.
Pickup sensor at the 1/4 mile mark to detect when crossing the line and shut down the timer (could be PIR sensor)
Batteries /power units both ends to operate the devices.
Wireless Tx and Rx units ...long range NRF24 units should suffice.
Some kind of display to readout the results .
16x2 LCD on I2c probably the easiest.(only 2 power and a clock and data line)
Some knowledge of all the above.

Failing that, perhaps a stopwatch glued to the wheel is the simplest I can imagine.
 

Nanren888

Nov 8, 2015
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Am I reading this right? You want real-time progress this run compared to the same distance from the prvious or reference run?
Like a bar display showing running behind, or ahead of previous?

So what's the quantity of interest? Distance versus time?
I guess your wheels spin? So distance might be a little tricky to determine accurately.
 

Nanren888

Nov 8, 2015
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So lots of lines to get a real-time readout as he goes?
Long barcode?
.
Hence my question about whether finish time is all he wants, or progress bar comparison as he races towards the end.
 

Flatire

Mar 16, 2020
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yes please..progress bar comparison as he races towards the end.

Pick up on the front wheel.
Mercury switch to start the counter
every 5 rotations 100 max

stored
1st run= 5 rotations / 1.122 seconds
10 rotations / 2.000 seconds
15 rotations / 2.752 seconds
20 rotations / 3.456 seconds
25 rotations / 4.225 seconds
compare
2nd run=5 rotations / 1.120 seconds .002 faster
10 rotations / 1.990 seconds .010 faster
15 rotations / 2.730seconds .022 faster
20 rotations / 3.456 seconds .000
25 rotations / 4.240 seconds .015 slower

Thanks!
 
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AnalogKid

Jun 10, 2015
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Taking samples based on wheel rotation means the samples are taken at fixed distances along the track. Normally a system like this would collect data at fixed time intervals, but your way will produce similar results.

Either way (fixed time interval or fixed distance), there will be an ambiguity at the start of up to 1 wheel rotation. Is this acceptable?

ak
 

Harald Kapp

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Nov 17, 2011
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Use a laser distance sensor placed at the finish line, aimed at your car.
Probably a tad expensive plus you'll have to ensure nobody looks into the laser beam.Just joking.

Either way (fixed time interval or fixed distance), there will be an ambiguity at the start of up to 1 wheel rotation. Is this acceptable?
Use multiple sensors on the wheel to increase accuracy and reduce this ambiguity.
 

Flatire

Mar 16, 2020
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Taking samples based on wheel rotation means the samples are taken at fixed distances along the track. Normally a system like this would collect data at fixed time intervals, but your way will produce similar results.

Either way (fixed time interval or fixed distance), there will be an ambiguity at the start of up to 1 wheel rotation. Is this acceptable?

ak

That being said, i'd probably take rotation samples from the drive shaft in 4 places each rotation.
Fixed time intervals if fine.
Ambiguity at start of 1 driveshaft rotation is acceptable.
Thanks!
 

Nanren888

Nov 8, 2015
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It seems you have a lot of it sorted out. Which parts are giving you trouble?
 

Flatire

Mar 16, 2020
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I'm a long time BMW auto mechanic.
i don't know how to build electronic things.

I need a schematic and parts list.
I know very little about IC's

Thanks
 

Nanren888

Nov 8, 2015
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Often, nowadays, as you have drawn, the easiest answer is a microcontroller, but this requires software rather than hardware. This is not so difficult, but a different skillset.
A purely hardware solution might be quite complicated, but microcontrollers tend to be very flexible and with many sensor modules and libraries available they are getting much easier and cheaper to use.
.So, you need time and to watch the wheel rotation sensor on the front wheels. Also need a way to reset things to tell it that you are ready to start. Some configuration to know how many sensor counts per metre, foot, mile, your unit of choice, and something to fix the scale of the how fast/slow means how many LEDs light.
Driving a few LEDs is not difficult. Counting pulses is not difficult. Depending on your sensor, you may need to debounce a little to get clean counts. You suggested a mercury switch to sense starting. Also possible.Any familiarity with microcontrollers? Many start with arduinos, accessible, cheap, many libraries, but not the only option.

Might need to add power supply to the figure. Such circuitry likes to have a well regulated power supply and usually low voltage. Also not usually a challenge.
 
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Flatire

Mar 16, 2020
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I wanted to purchase an Arduino but i got lost in all of the options.

any chance you could make me a list of items to purchase i'd really appreciate it because i'm lost in this world.

Thanks, tim
 
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Flatire

Mar 16, 2020
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i'm starting to understand what the Arduino is via Youtube and how Sketch works.
Once i get all of my hardware i'll circle back around to this forum.
Cheers!
 

Nanren888

Nov 8, 2015
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I guess there are two main ways to make the led bar display. Simple LEDs on output pins and smart LEDs.
Simple hardware using one LED per output pin will use more pins, but is conceptually simpler.
The arduino IDE comes with examples. One of them is "Blink" which shows how to blink an LED. This can be the basis of controlling as many LEDs as you have pins.

Neopixels as one variety of smart LED strip. Generally software talks to the end one and tells them what to do, so it is as if you only have to wire one of them up, rather than several. A little more xpensive than individual LEDs. Here is a page that talks about using them for various things.
https://create.arduino.cc/projecthub/robocircuits/neopixel-tutorial-1ccfb9
.
Generally many arduino sensors have software libraries to run them, so minimum coding to do.

Magnetic sensors can be reliable. Here is a page that talks about using a hall-effect sensor on an arduino.
https://maker.pro/arduino/tutorial/how-to-use-a-hall-effect-sensor-with-arduino
 

Bluejets

Oct 5, 2014
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You're not going to get accurate distance readings from within the moving vehicle without fixed external reference points.
 

Flatire

Mar 16, 2020
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This is a time slip from a drag strip.
R/T is reaction time of the driver.

E6D10F7C-BF03-4300-B65D-F80709D94EA3.jpeg
 

Nanren888

Nov 8, 2015
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You're not going to get accurate distance readings from within the moving vehicle without fixed external reference points.

As Bluejets says, it seems that you'll need something extra to get accurate distance measurement. I asked above whether the wheels spin? You suggested monitoring the front wheels. If they slip relative to the ground, you internal counter won't be tracking the true ground, so your onboard idea of distance will be wrong.
Something that you need to sort out before any of it becomes viable.
 
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