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Topic: Detect falling object and speed (Read 1 time) previous topic - next topic

Supergiant

Hi,

My friend is working on a project whereby he needs to detect a falling object before it hits the ground and measure its velocity before it lands.

This is to be done using proximity sensors that are made out of common components (namely Cds Light sensitive resistor, photodiode and MCP6004 op-amp), a push switch button is also available.

Any ideas on how we should go about this?

I am thinking of using the push switch to detect the time the object falls, but am otherwise slightly lost.

Any help would be greatly appreciated. 

jremington

Google "photogate arduino" for lots of examples.

TomGeorge

Hi,

Opto-transistors would be more accurate and not much different in price and availability.
You may not need the opamp.

Tom... :)
Everything runs on smoke, let the smoke out, it stops running....

Delta_G

I am thinking of using the push switch to detect the time the object falls, but am otherwise slightly lost.

How will the push button detect a falling object while it is still in the air?  I guess you could let the object fall on the button thereby pressing it, but that would only detect it after it hit. 
|| | ||| | || | ||  ~Woodstock

Please do not PM with technical questions or comments.  Keep Arduino stuff out on the boards where it belongs.

JimboZA

Opto-transistors would be more accurate
And depending on the size of the object, a pre-packaged gate thingy like this with the source and the transistor in one item may do the trick.

Johannesburg hams call me: ZS6JMB on Highveld rep 145.7875 (-600 & 88.5 tone)
Dr Perry Cox: "Help me to help you, help me to help you...."
Your answer may already be here: https://forum.arduino.cc/index.php?topic=384198.0

JimboZA

I also just saw in another thread, that adafruit has these which are nicely packaged and have the source / receiver separate.

Johannesburg hams call me: ZS6JMB on Highveld rep 145.7875 (-600 & 88.5 tone)
Dr Perry Cox: "Help me to help you, help me to help you...."
Your answer may already be here: https://forum.arduino.cc/index.php?topic=384198.0

GoForSmoke

What will the object be? Include dimensions and mass.

Will it always fall how close to exactly the same?

Will it be conductive? Metal? Charged?

A metal bearing of known weight falling could induce current flow in a coil analogous to the velocity of the bearing if a magnet is also present and aligned.

A metal bearing falling through a light beam would have to fall on the same path every time. Off to the side a bit and you get some error.
1) http://gammon.com.au/blink  <-- tasking Arduino 1-2-3
2) http://gammon.com.au/serial <-- techniques howto
3) http://gammon.com.au/interrupts
Your sketch can sense ongoing process events in time.
Your sketch can make events to control it over time.

lastchancename

Regarding Optos- I doubt a Cds cell will be fast enough for many applications.

While a micro may suffice for timing - depending on the measured distance and accuracy required, you may be better using an oscillator, counter, and gating the start.stop of the counter.
10MHz clock will give you 100nS temporal resolution, say over a 100mm distance would be pretty good!
or when Using a micro directly, you need to use the on-chip hardware counter-timers.
Experienced responders have a nose for laziness, (they were beginners once)... Sure, there are trolls, chest-beaters, and pretenders - but the help you'll get here is about as good as it gets - if you try to help youself!.

GoForSmoke

They probably want you to determine how long it took to fall some measured height from a drop but that is only very very likely.

What was taught in class so far is the big clue. Half the class may not have taken notes or paid attention and has to get someone else to bail them out, tomorrows management material.

1) http://gammon.com.au/blink  <-- tasking Arduino 1-2-3
2) http://gammon.com.au/serial <-- techniques howto
3) http://gammon.com.au/interrupts
Your sketch can sense ongoing process events in time.
Your sketch can make events to control it over time.

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