What type of sensor??

[flyingsparks]

Hi guys. I need a sensor to put in a corn drier to detect when the grain is at a certain level to switch on a motor via contactor. What would be the best kind of sensor to use, optical? Needs to work on 240VAC and not require a PLC or such to use it. All help much appreciated.. Thanks. Chris

 

[Spark123]

Can you use some sort of weigh system?

 

[tim west]

Some form of break light beam device sounds like what you want.

 

[Spark123]

Only down side to a photocell/light beam etc will be dust.

 

[flyingsparks]

Cant use weight really, not without a serious modification to the plant! I was thinking light but dust wouldf be a problem. How about ultrasonic?

 

[Spark123]

Ultrasonic might be OK.
How about these?: http://dynatrolusa.com/products/cl-10dj.htm

 

[briwire]

Agree about the optical type. They would work, but would soon get covered in dust. You can get one from Keyence that will adjust itself automatically for a deterioration of light due to dust, but even that would need cleaning at regular intervals.

Best to go for a capacitive type proximity sensor. They look like a normal proximity sensor, but are usually a bit fatter. They will give a change of signal when a non conductive solid such as grain, plastic granules etc is present at the sensing part.

If you can't find one that accepts 240v AC you will be able to get a 24vDC one easy and adapt the circuit with a relay.

 

[flyingsparks]

Thanks, the capacitive sensors I guess are either PNP or NPN etc, and require some electronic circuit to get them to work?

 

[ricicle]

Paddle switches are ideal for this set up, I think the manufacturer you need to look at is Mowbrey or Mowbray, I will check tomorrow for you as we have several at work and there are other makes.

 

[crystal ball]

RS have a 240v Telemecanique sensor 609-0728, I always prefer 24v dc myself don't like the thought of 240v in silos etc.

I have just done a job on some converted road tankers holding granules, 4 sensors high to low, lighting LEDs on panel and alarming at low level

Used a 24vdc power supply and relays

 

[briwire]

have a look at RS on line. You might be able to get one that works on 240v. If you have to use a DC one, you will need a DC power supply and a relay that is switched by the proxy. Ypu can then do what you want to with the relay contacts.

A word of warning though, capacitive types can be tricky to set up, not like ones that detect metal. They usually have a small pot to adjust to the correct sensitivity to whatever your are detecting.

 

[ricicle]

Paddle switches are ideal for this set up, I think the manufacturer you need to look at is Mowbrey or Mowbray, I will check tomorrow for you as we have several at work and there are other makes.

Best option

 

[flyingsparks]

I found the 240V capacitive one on RS and also Farnell do it. Think I will go for this option as I dont think a paddle switch will work in the situation I have. Got a hopper with a grinding mill above a conveyer, when the conveyer has enough grain on it, (this is where my sensor will be used) the conveyer will switch on. A paddle switch will get burried, or come on as soon as grain starts pouring from the hopper.

Thanks all..