Title: Lab 4-6: Filling a Grain Bin
Course: Electrical Motor Controls (Sandbox) > Section: Module 4: Control Relays and Timing Relays, 20 hr

Introduction

Background

When we fill a grain bin (or any bin with loose material), it's fed in from the top so that we can use as much of the space inside the bin as possible to store our material.

Sometimes it's a challenge to measure if the bin is full, because we also want the sensor near the top of the bin for the same reason. We don't want to stop filling unless the bin is really full, and we want the sensor to be placed somewhere where it will indicate "full" only when we've used up all the space in the bin. Because of this, the "full" sensor is often placed somewhere where it can detect material as it passes by.

But we don't want to stop the motor that is being used to fill the bin with material every time the sensor blinks. A common solution to this problem is to wait until the sensor detects material continuously for a certain period of time, say 30 seconds, before we call the bin "full". If the sensor detects material for the continuous period of time that we define, we can be pretty sure that the bin is actually full.

Assignment

Timing relays let us accomplish this, which is why you will build a circuit using a timing relay for this type of situation. Set the timing relay for 5 seconds. (In an actual grain bin, this could be set for 30 seconds or more.) As long as the bin is not currently full, then when the user presses the "Start" button, the motor starter coil energizes, which, in turn, starts the motor, running the conveyor that feeds the bin. A light illuminates telling the operator that the "Bin is Filling".

Use a normally open limit switch for our "Bin-is-Full" sensor. When the "Bin-is-Full" sensor detects material, it closes. When it closes, it powers up the timing relay coil. When the time set in the timing relay passes, the motor will stop and a light will illuminate to inform the operator that the bin is full. The motor should not stop if you "blink" the sensor—turn it on, then turn it off before the five seconds passes.

The following video will walk you through the steps of building the circuit according to the schematic below.

Instructions

1. Watch the video introduction to this lab.
2. Draw a schematic diagram, in Automation Studio or by hand, that represents a circuit that will operate as described above. Make sure your circuit works in simulation before moving on to the next step.
3. Unplug the Motor Controls trainer.
4. Build the circuit on the Motor Controls trainer.
5. Plug in and turn on the Motor Controls trainer.
6. Test the circuit.
7. The relay timer, "Bin-Is-Full" sensor, and the lights that go with their sections all work correctly to let a user know that the bin is filling and that the bin is full.

Submission

To complete this lab, submit a 30-second video following the criteria found in the rubric. If you are working with another student, each of you must record and submit your own video.

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