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will this photoelectric laser sensor work for turning off/on a 12V DC fan

will this photoelectric laser sensor work for turning off/on a 12V DC fan

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  #1  
Old 02-14-16, 02:15 PM
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will this photoelectric laser sensor work for turning off/on a 12V DC fan

Hi,
Here is my objective; when a ping pong ball rolls and reaches a certain position (a sensor will be positioned an inch or less from the ball at this point), the sensor will pick up this and turn off a 12V DC fan. The ping pong ball will then fall down a 1ft approx length tube, when it has left this tube the fan will turn on again. So I'm thinking the sensor needs to span from the top/entrance to the bottom/exit of this tube.

The product I think will work is this: M12 Through Beam Photoelectric Sensor Laser Beam X1PAIR | eBay

I'm quite the rookie in this type of electrical project. I assume the receivor part of the sensor is some how bridging the 12V DC adapter which I have used to power the fan.
Should this work?? Any suggestions or better alternatives welcomed!

Thx so much.

Richard
 
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  #2  
Old 02-14-16, 05:00 PM
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Join Date: May 2015
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It looks like it might work, but there is some needed information missing from the listing.

If you aimed the emitter down the tube and had the receiver at the other end, the receiver would sense when the ball was in the tube.

You could power the receiver from the 12 power supply you are using for the fan. You would need a 5 volt power supply for the emitter, or you could add a regulator to convert the 12 volts to 5.

To make the receiver control the fan, you would run +12 from supply to fan. The return from the fan would go to the control output of the receiver. Of course you would also need to connect 12 volt power and ground to the receiver.

But the key info missing is how much current the output of the receiver can sink when it is on. You will also need to know how much current your fan draws. The rating of the receiver has to be greater than the current the fan draws.

If the rated output current isn't sufficient, you can add a small relay (mechanical or solid state) between the fan and the receiver.

Keep in mind it will take time for the fan to stop and time for it to start again. It may not even stop by the time the ball falls out of the tube.
 
  #3  
Old 02-14-16, 06:22 PM
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Thank you Paul, generous and detailed response.

I looked up my proven power source and it provides 300mA while this ebay product shows the receivor to output 30mA. I'm thinking then it will be underpowered. You wrote 'add a small relay between the fan and receivor'.... Sounds great lol, if I knew what that meant or how to do it, where to get it etc.

The fan taking time to slow down and turn off before the ball falls is irrelevant for the project. As the ball won't fall, hence reconnect the circuit, until the fan slows down sufficiently.

Am I generally barking up the right tree on this or is there a better solution to shutting off a fan when an object blocks a 1ft gravitational pathway?

R
 
  #4  
Old 02-14-16, 07:24 PM
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Join Date: May 2015
Location: USA
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I think it's a perfectly reasonable approach! That 30ma figure is how much power the receiver uses to operate, not how much the receiver can switch. Perhaps you can ask the seller how much current the output can safely switch. While you are at it, ask them for a spec sheet; it would make things easier if they have one (and it's in English).

Here's an example relay that would work: ELK-912 SPDT Relay Board

You would connect + and common terminals to +12 volts, and - to the output of the receiver. The NC terminal would go to the fan and the other fan terminal would go to the other power supply lead. If that is too confusing, I can draw you a picture when I get a few minutes.

Good luck!
 
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