How can I measure the speed of a moving vehicle (from within the vehicle) without putting sensors on the wheels, and not hooking into the car's computer system?
Have you considered using a GPS receiver? It works pretty well measuring speed. However, this approach has some drawbacks: GSPs would have some troubles in urban canyons, under a thick forest or inside buildings.
the only working solution is doppler microwave radar.
It is easyer than you can imagine, you only need a CW source and a receiving antenna ( cone for example ). Adding source and received signal will give you a frequency in the Hz..kHz domain: easy to manage. http://hyperphysics.phy-astr.gsu.edu/hbase/sound/radar.html
- Use axis meter to measure acceleration and calculate speed .
- Measure wheel vibration and get the speed
- Use optical method (laser to road )
- Air flow meter (depends on environment wind)
Doppler microwave radar sounds interesting. I will look at that. Could the radar penetrate i.e. the bottom of the car, if I decided to put it in the car cabin?
Doppler microwave radar sounds interesting. I will look at that. Could the radar penetrate i.e. the bottom of the car, if I decided to put it in the car cabin?
How can I measure the speed of a moving vehicle (from within the vehicle) without putting sensors on the wheels, and not hooking into the car's computer system?
Forget about CW radar,it should point at a certain angle to the road (a narrow beam antenna is needed);the road is not a good radar wave scatterer;the complexity is an issue,too.
If you want an odd idea:
A microphone,when "blown by the wind",creates a noise-like output signal whose voltage is proportional to the wind speed.Drawback:if there is an adverse or a fair wind,the accuracy will be compromised.