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Ping through fan blade

Can you use an arduino sensor to ping through a fan blade to sense the outside world? This is for my sumo robot, which will have a full body length spinner. I already have an accelerometer attached if the ping sensor can not work =/

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drewtoby's picture

Thanks for your responses! I will either stick with the accelerometer or see if I can get a sensor to ping out under the spinner, as it is not flush to the ground. Weapons have never been prohibited at this tournament, although I have a feeling that it will be next year ;) 

A LOT OF PEOPLE USE LEGO KITS FOR THEIR SUMOS!!!!!!!

I will post this robot in a few weeks. As of now I am waiting on a new lipo (the other one was old and a cell puffed out during charging).

fifer253's picture

Looking forward to seeing your bot, not many sumos are violent ;)

fifer253's picture

You might consider pushing the robot off the ring rather than trying to disable it with a full body spinner, have a look at the rules for the sumo tournement you want to enter, most prohibit BattleBot style weapons.

Receiving pulses back will be very hit and miss as the time from 'send' to 'receive' is dependant on distance, whereas the timing between blades will be fixed.  You can certainly use sychronisation for the 'send' pulse but have no way of guaranteeing getting a return pulse. 

bdk6's picture

The outgoing pulse isn't too hard, but the incoming pulse will have half removed.  So something like six inches of every foot is going to get blocked coming back in.

Chris the Carpenter's picture

I wanted to mention the sync'ed propeller thing! Arrgg!

You need an encoder, dude. You need a hall-effect sensor, a slot encoder, IR reflective sensor etc, so you can sense the exact position of the fan blades, or more to the point, one particular spot on the propeller where there is a space, and not a blade. You then simply fire your sonar when this "mark" comes around.

I suppose you should do the math on how far apart fan blades are, how fast they turn and the time it takes to fire a sonar unit. At far distances, it takes longer than you would thing to fire one of them.

drewtoby's picture

Would photoresistors work for sensing the position? I could paint the spinner black... 

Maxhirez's picture
Maybe. WWI fighter planes shot bullets through propellers. The principal is the same except you want the bullets to bounce back to you in this case. It would take a bit of work syncing up the timer to the blade. It may not be what you'd think of as an optimum solution to your situation.
flokos's picture

Just to clear something on this one since the sonar  is considered to produce some kind of  wave , the wave will not react us light an come back , a part of the wave will come back so you got a problem there , I think light will be better some laser or something .

Also light waves will mix with the sonar waves and you have to figure all that stuff which is a lot of math . 

Further more if the light wave is on the same frequency on some point of this trip tothe surfaces you are screwd and you will have some points that you wont see .

If im wrong correct me please .

Maxhirez's picture
Light waves and sound waves won't interfere with eachother without some kind of reflective or inductive physical system in between them-like a mirror on a surface that can vibrate or an amplified microphone signal modulating an lightbulb or LED.

The main problem here is that with a spinning "blade" between the ultrasonic sensor and everything in front of the robot, some of the sound wave pulses that the sensor sends out might bounce off the blade at different periods in its rotation, leading the machine to think that there is an obstacle "on" itself! The fact that light and sound both travel in waves doesn't mean they'll interfere with eachother necessarily-after all, their particles are not the same (light is photons, sound travels through gases primarily.)

You are absolutely right that there will be a lot of stuff to figure out with math though.