Beginner, need help please

21374 · Jul 25, 2007

hey everyone,
i am doinga project and wondering whether plc's are the riight thing to use and if so how difficult it would be to do. i will have two microwave sensors, if an object passes through the first sensor but the not the second it is counted as a miss. If it goes through the first sensor and the second it is counted as a hit. Would a plc be able to put this ina variable which a could then put onto a screen as a percenatage?

thanks

AMAZINGAHMED · Jul 25, 2007

You'll need a simple PLC as you have just 2 inputs (I assume that they are either digital inputs or analog inputs 0..10V DC). I think you can use Siemens LOGO! (6ED1 052-1CC00-0BA5)

Note: i don't know how to visualize the percentage in LOGO, but if you used a display which supports VBS then it's easy. LOGO has counters which you can count the hits and misses.

ToolGuyFred · Jul 25, 2007

AMAZINGAHMED said:
You'll need a simple PLC as you have just 2 inputs (I assume that they are either digital inputs or analog inputs 0..10V DC). I think you can use Siemens LOGO!

Before you rush out and buy a Logo or Alpha or whatever, how fast are these inputs? If you are sensing a slow-moving vehicle, no problem but if this is sensing a projectile of some sort then you may need some sort of high-speed inputs.

Are you just using the PLC as a counter or are you doing something else too?

504bloke · Jul 25, 2007

If you need high speed counting then the Logo Manual States

2 inputs can be used for counting up to 2 kHz (DC versions only).

ToolGuyFred · Jul 25, 2007

504bloke said:
If you need high speed counting then the Logo Manual States

504bloke said:
2 inputs can be used for counting up to 2 kHz (DC versions only).

Yep. That's fine if you're using one input to count misses (or hits + misses) and the other to count hits.

If the logic is not that simple then you may need interrupt inputs rather than just high speed counter inputs.

21374: If its possible to make the second sensor and not the first, is that a hit or a miss? (Or will it always make the first sensor when it makes the second?) When the second sensor is made, is the first sensor still made or has it already gone off?

MartB · Jul 25, 2007

21374 said:
hey everyone,
i am doinga project and wondering whether plc's are the riight thing to use and if so how difficult it would be to do. i will have two microwave sensors, if an object passes through the first sensor but the not the second it is counted as a miss. If it goes through the first sensor and the second it is counted as a hit. Would a plc be able to put this ina variable which a could then put onto a screen as a percenatage?

thanks

If you can disclose what your application is in a little more detail then you'll probably get a more useful answer.

At this point, it is very easy to 'assume' too much about your project to give an objective answer.

21374 · Jul 25, 2007

Thanks for your help. The project is for a basketball ring to count misses and goals, so one sensor is located at the top of the backboard to sense the ball coming in the vicinity of the ring, then the second sensor is located underneath the net to determine if the ball has passed through. The first sensor will be located so it will pick up every ball that comes in. So, if the the ball goes through the first sendor and not the second then it is a miss. Would that need high speed inputs?

milldrone · Jul 25, 2007

21374 said:
so one sensor is located at the top of the backboard to sense the ball coming in the vicinity of the ring, then the second sensor is located underneath the net to determine if the ball has passed through.

I may be wrong but if the ball passes near the net but on the outside of it will the sensor be selective enough to not give you a false signal. What if a hand from a defender is close to the net just after the ball is detected near the backboard? How fast is the microwave sensor? I'm thinking of the posiblity of just seconds before the end of a time period and the ball is heaved from beyond half court and makes a perfect swish. The speed the ball is traveling would be too fast for many types of sensors.

AMAZINGAHMED · Jul 25, 2007

21374 said:
Thanks for your help. The project is for a basketball ring to count misses and goals

If it is a school project or just for learning then it's ok but if it's something to be reliable then i don't think this solution is the best one.
milldrone suggested some situations where the system wont act as it's intended to. I'm no fan of basketball anyway

21374 · Jul 26, 2007

It wouldn't be used in a game, just at training. Maybe while practicing jump shots or freethrows. It is for school but it is a big assignment that goes for the whole year. Would PLC's be hard to program for this? Also, with the Siemens LOGO is there anyway you can run taht screen off to a bigger screen? or maybe use the data from the plc and put it onto a screen?

Beginner, need help please

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