Speed Sensor- suggestions

Thread Starter

Neyolight

Joined Dec 13, 2011
54
Heya Everyone

I need to measure speed of my toy car in an experiment I just set up . Any suggestion as to what I can uses? Something simple , accurate and with PC interface?

The lower the price the better!

Thanks
 

John P

Joined Oct 14, 2008
1,808
I doubt if you can beat having the car cut 2 light beams a measured distance apart, with photosensors connected to a microcontroller which would then measure the time to travel the distance, and send the result to the PC.
 

Thread Starter

Neyolight

Joined Dec 13, 2011
54
I doubt if you can beat having the car cut 2 light beams a measured distance apart, with photosensors connected to a microcontroller which would then measure the time to travel the distance, and send the result to the PC.
That was my initial thought too, but im sure there is something simpler out there in this whole wide world to get me speed :D
 

ErnieM

Joined Apr 24, 2011
8,046
With a stopwatch what shall be the PC interface ? - My hands?:p
Well fine Mister wise guy! Just write yourself a stop watch program triggered by the parallel port pins.

Take two strips of aluminum foil and two pieces of bare wire suspended above the foil. Connect the wires by a 1K pull up to +5V. Ground the foil.

Measure out course with ruler or tape measure to determine precise distance between trip wires. As car drives over foil the wire signal goes from high to low.

Connect that mess to your PC's parallel port. If your PC doesn't have one, get a USB to port converter (and stop buggin' me). :D
 

John P

Joined Oct 14, 2008
1,808
This is the "Embedded Systems and Microcontrollers" section, so it's clear what the original poster expected. But it would be nice to find something other than a microcontroller-based solution. PC's have the reputation of being unable to measure time intervals precisely, but maybe that isn't true in the hands of an expert.

Mechanical switches rather than optical might work, but then again, would they be reliable and would they affect the motion of the car?

How about something based on a webcam tied directly to the PC? You'd be stuck with time in multiples of camera frames, but over a reasonable distance it might be OK. Surely there is free software out there to analyze the images--there's always free software on the Web.
 

GetDeviceInfo

Joined Jun 7, 2009
1,729
a long time buddy of mine, who was born in the back seat of a slot car, embarked on an ambitious project several years ago. His concept was a slot car that learned it's track and provided anticipitory control. Many a fine discussion was had over beer and slots. Thier straight track was a simple wiegh in and timer from green to light beam, with an RS232 interface. Couple fellows in the club worked over the stats to absurd levels.
 

THE_RB

Joined Feb 11, 2008
5,438
(I'm not him, but); That's where the computer brain controlling the slotcar slows down before a corner, like a real player would.

Automated (learning) slotcars are a popular lab subject in technical schools that teach microcontrollers.
 

Georacer

Joined Nov 25, 2009
5,182
They use a learning algorithm? Go faster and faster before entering each corner until they flip over?

Interesting... how do they detect flipping? Do you have any resources?
 

GetDeviceInfo

Joined Jun 7, 2009
1,729
and so insued the many colorful discussions. I'll have to give this fellow a call to see if he continues this effort. Last we discussed the project, his system basically mapped the track in power/time segments. The intial lap laid down the map upon which the system tuned. A pot on the slot guide is the basic sensor upon which the graphical map is generated. Power/time relationships are calculated with various algorithms. Many a session simply had cars running round ovals to experiment with break away dynamics, sensing break away, and recovering from onset of break away. However, locking in on the straight away power/time relationship, eased much of the corner entry problems. The main 'anticiptory' part was corner entry, and the trade offs of getting there witin an ever tightening time expectation. Filtering out the occurence of drift to recover the most resent usable segment was the outstanding issue in our last discussions.

Flipping was catastophic, for both the control system, and often the chasis. An intitial mapping lap would be required, but that was doable at any speed, without drift.
 
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