Searching for non mechanical on/off switch

[nick999]

I have a machine that drops things into a 0.5 inch clear tube. I have a switch that detects when the tube is full. (A VX-53K-1C23 on/off lever switch to be exact.) The switch turns off the dropping mechanism when full. The problem is that the mechanical lever on the switch often gets in the way. The items are very light.

I am looking to design a detection device that senses if the tube is full without using a lever. Minimal impact to the tube is preferable. Needs to take about 5 A 120-240 (AC/DC). I was thinking of a infrared or laser but could not find any out of the box for a sub 1" detection.

Any suggestions would be appreciated.

 

[Externet]

A gap optoisolator and a hack saw can separate the emitter and sensing sections to fit your clear tube. To drive a 500+ watts whatever with it; there is
solid state or not relays, to be buffered by a transistor or not.

Cut the lower 'bridge' off.

 

[shortbus=]

Cut the lower 'bridge' off.

Was going to suggest something similar. Cutting the bridge though, will that change the focus of that style opto interrupter?

I was going to suggest these(just the first link Ebay may have better prices) - https://www.amazon.com/Chamberlain-LiftMaster-Craftsman-Replacement-G801CB-P/dp/B001JDG1KU We used a similar one at work on some of our machines.

 

[nick999]

Yes. Was looking for something similar to the garage door IR sensor. A garage door unit may seem overkill for two reasons: 1. Beam would need to span less than 20 mm (less than 1 inch) across to work. 2. the part that falls through the tube is less than 9mm across, so it may not block all the IR beam. Im going to explore options for smaller scale IR sensors.

Since part of the problem is that anything in the tube causes hang-ups with the dropped items, my idea would be for something to function through the clear tube without having to cut or shape the tube in any way. I am even looking at some sort of IC that uses radar, inductive proximity sensors, laser, etc.

 

[AnalogKid]

How opaque and/or reflective are the objects?

How quickly does the circuit need to shut off the supply?

Will a mini or full sized hockey-puck style solid state relay work for the output stage?

How extreme / violent / caustic / rugged is the installed environment?

ak

 

[nick999]

1. Objects are opaque. Nickel Alloy. Light can not go through it but they are silver in color, so highly reflective.
2. Shutoff should probably be a 0.5 to 2 sec delay since objects will fly by until they stop. I am trying to essentially switch off the machine when they stop in the tube.
3. Yes, solid state relay would work just fine at the output.
4. A normal basement, room temperature.

 

[AnalogKid]

Latch off with a restart switch?
Auto-restart when the tube is cleared of objects?
Other?

ak

 

[gophert]

I would look into an inductive proximity sensor...

Inductive Proximity Sensor using TCA505 - Electronics-Lab.com

The circuit published here is an Inductive Proximity Sensor, which is used for non-contact detection of...

www.electronics-lab.com

 

[shortbus=]

The inductive switch is a good type to use, but if the tube is plastic and fairly thick you may have some problems. Here is a good link for choosing a proximity switch - https://www.controleng.com/articles/selecting-inductive-proximity-switches/

 

[rjenkinsgb]

How consistent is the weight of the items & how much change %wise does the last item in make?

A load cell system may be practical, measuring the weight of the content & feeding a comparator.

 

[nick999]

Latch off with a restart switch?
Auto-restart when the tube is cleared of objects?
Other?

ak

Should go back to "on" once the tube is cleared of objects.
"off" if the tube has a stationary object.

 

[AnalogKid]

I think an optical beam-break system is a good cross of performance, complexity, and cost. The output from the sensor drives a circuit called a missing pulse detector. As long as the beam is clear of broken quickly, the output is off. When the beam is broken long enough to be non-moving ball, the output comes on and turns off the relay.

What power sources are available to run the electronics?

ak

 

[shortbus=]

Should go back to "on" once the tube is cleared of objects.
"off" if the tube has a stationary object.

Having worked in an industry that used a lot of tube feeding type machines, one detector won't work like you think. If you only have one detector to decide when the tube is full, you will be running the feeder of and on constantly. Ours had two detectors, one for full, and another one some distance away(distance depended on the size of the product) that turned the feeder back on. This allows a better "stack weight" in the tube, which for some products keeps them from jamming in the tube.

 

[AnalogKid]

Basically, a length of tubing between two sensors is adding hysteresis to the system.

ak