We all are familiar with lever.

A lever consists of two material components and two work components:

A beam or solid rod
A fulcrum or pivot point
An input force (or effort)
An output force (or load or resistance)

Here the effort is placed in static position, but the load will be slide . thus the system will work by varying the effective length of load.

What we need:

For model construction:

PVC pipe.
t shape PVC.
U shape PVC clamp to hold the PVC
a rectangular shape sheet of glass.
screw nut washer.
A clamp to add motor
small plastic container box
ball bearing
some solid balls to increase weight.
Plastic box

2. For Control moving:

lead screw
20 rpm gear motor
IR sensor
arduino
l293d motor driver ic
15 volt 500 mA smps power supply

Step 1: Construct a 3D H-shape Given in Picture

take four T shape , and some small piece of PVC pipe. Joint this PVC pipe with this T-shape

Step 2: Add Ball Bearing With a PVC Pipe

Take a small piece of PVC pipe of inner side diameter is same as the outer side diameter of ball-bearing.Add this with H-shape by adding a wooden piece.

Step 3: Add One IR (proximity Sensor) at One Side

Add 1 IR sensor as given in picture, and the IR both TX and RX should be bend to a angle 135 degree with the horizontal line of PCB. when you connect the entire component with this 3d 'H' , the IR sensor should be stay in downward at downside.

Step 4: Drill the Glass Sheet and Fix All the Item Over It

Take a scale shape glass sheet. divide in four. in 2nd portion from left side do the drill for farcum. Make drill to attach some screw to fix it with 3d H.take some wooden piece make a sliding type ring that can move easily across the glass. now fix it with a linear actuator.

Step 5: Attach the Motor

A clamp was attached previously. Attach the motor with this.

Step 6: Make the Circuit

The main working principle is based on arduino based l293D switching .The IR sensor sends signal to Arduino. the arduino switch l293d and drive as per direction.