Hello, I need some help deciding which technique to use to trigger a shot of a football.
This is what I want to do: A person shall shoot a football and be photographed almost immediately after the ball has touched the foot. Therefore I would like to prepare the football with some kind of sensor that triggers the shot, feeds that into an arduino which in turn triggers a small wireless switch. I already have the wireless switch, so I am only looking for the sesor side of the Arduino.
What would you suggest? Would it be good to use some sort of motion detection, or maybe better better to trigger the sound of the shot? Is there any kind of shield I could use with an Arduino Nano or such small Arduino version?
The Camera Axe includes a sound sensor that will trigger a camera when a loud noise is heard. There are an additional number of sensors (knock, light beam) with documentation that you might find useful.
I'd go with sound over motion: I think you might trigger prematurely since it would probably see the motion of the foot.
What about some kind of "tee" though.... a mat underneath the ball maybe which could have some kind of switch which is held in one position by the ball, then changes mode when the ball moves off it?
Is this a round (real ) football, or the American / Rugby / Aussie Rules oval variety? If the latter, don't they usually use a plastic stand thingy when teeing up for a shot at the posts? (I've seen that in Rugby anyway...). Might be able to put some kind of switch in there?
It is a round ball and will be held in hands before shooting. When talking about "motion detection" I was thinking of a sort of gyro put into the ball maybe, same with the sound module, because there will be several people around the set maybe making noise, thus it should somehow be isolated.
I will have a look at the "knock" solution, but I wonder if such a piezo is capable of being shot and heavily shaked over a long time. The ball will be shot 24/7 every 3-4 minutes I suppose. So the whole solution should be quite shock resistant.
What do you propose when using a gyroscope for triggering? Any suggestions?
I would believe a piezo disc would be more durable and less expensive than anything else.
You would want an accelerometer (3 axis) and not a gyroscope. You're looking for a sudden change in acceleration. A gyroscope would detect the ball's spin but that doesn't necessarily occur when kicked.
I am working on a similar project and decided to go with an accelerometer because if you want to add more functionality later you can. A good accelerometer is the ADXL335 which is really cheap on amazon but what you're doing sounds quite professional so I might go with a breakout board from sparkfun.
A problem I came accross was powering the ball and decided to go with TP4056 battery charging board (charges over usb) and a 7.4v Li Ion battery. Hope this helps!
What sort of camera are you using and, importantly, how long is there between telling it to take a picture and it actually taking the picture?
For most digital cameras the gap between pressing the button and taking the picture is so long that what you are proposing just won't work - the ball will be long gone. (Maybe a high end DSLR would be OK).
If that is a problem a solution may be to take a movie that starts before the kick and runs for a few seconds. Then pick the best still from the movie. With this approach it would probably be quite satisfactory to start the camera manually.
Another important feature may be the need for a high shutter speed.
Hello and thanks a lot for your suggestions. The response time of the cameras is not the problem, they are waiting for the trigger signal and respond very fast.
I will for sure try the piezo solution, but to be on the safe side I'd like to order a accelerator too. Now I would like to go with a very small Arduino and I wonder if I can use a accelerator with SPI or I2C. I never used that before. Also I don't know which kind of accelerometer to use, analogue or digital. Could you propose a Arduino/Accelerator combination that can be powered with a 9 Volt block battery?
@bushn: May I ask how you managed to put the stuff into the ball? Was it a real football made from lether, with air pressure inside? If so, how did you close it without loosing air and without loosing the abilty to changes batteries on the fly?
) football, or the American / Rugby / Aussie Rules oval variety? If the latter, don't they usually use a plastic stand thingy when teeing up for a shot at the posts? (I've seen that in Rugby anyway...). Might be able to put some kind of switch in there?