Light gate / Photo gate

datalogging sensors


Data Harvest

Product Description

The Light gate is a digital switch-type sensor most commonly used in timing experiments. 

The Light Gate has an infrared transmitter and receiver that will detect an object passing through the ‘gate’. They can be used singly or in pairs for time, speed , velocity, acceleration and event monitoring. Designed to work seamlessly with the Data Harvest Dynamics system and timing part of the EasySense software.

Ideal for all your dynamics / mechanics / kinematics work.


1-min Drop and Bubble Counter

30-sec Linear momentum - Light gates measuring velocity

26-sec Data Harvest Dynamics track - Picket fence measuring gravity

30-sec Data Harvest 2 light gates - Acceleration

1-min Data Harvest Dynamics system - Light gates with spoked pulley 

40-sec Data Harvest - Dynamics System

Teaching applications:
  • All timing and basic dynamics work
  • Free fall
  • Proof of g
  • Diluted gravity (Galileo’s gravity from slope)


Extension and advanced ideas:
  • Time period of an oscillating body
  • Impulse (with force sensor)
  • Conservation of energy (momentum)
  • Centripetal force in a pendulum
  • Muscle fatigue


1x Light Gate
1 x Metal Rod

Download Light Gate Sensor Manual oc No.: DS054 | Issue: 4


The Light Gate is supplied with a steel mounting rod which can be screwed into the base or side of the Light Gate and clamped into a suitable holding device. A red On/Off indicator will light when the infrared beam is blocked. When used in a non-Timing mode e.g. Graph, the Light Gate can be used to mark an event on a graph and the length of the interrupt can be used to determine velocity.

  • Infrared source: Peak at 880nm
  • Response time: Less than 5 microseconds
  • Timing Resolution: 10s

Muscle fatigue (Light gates) (Biology (14-18) eBook)
A simple but fun activity to show tiring in muscle systems



Dynamic friction (Physics (11-14) eBook)
How does friction affect the motion of an object? can you measure it?

Measuring speed on a runway (Physics (11-14) eBook)
Introductory activity to show how timing cards and light gates are used for calculation of speed / velocity.

Average speed / velocity (Physics (11-14) eBook)
Light gates are used to measure the time form A to B, the students calculate velocity. Good trainer for the basic calculation of velocity.

How does the angle of a slope affect velocity? (Physics (11-14) eBook)
This activity is an introduction to the use of a single Light gate to measure speed. The investigation can be analysed at a number of levels. Able students will be expected to create a mathematical relationship between the angle of the slope and the velocity

Manual calculation of acceleration (Physics (11-14) eBook)
Acceleration is the change in velocity over time. Use light gates to collect the data and then manually calculate the acceleration.

Streamlining (Physics (11-14) eBook)
Air resistance is a force that pushes against objects when they are moving through the air. It is a kind of frictional force because it tries to slow objects down. It is also called drag, streamlining attempts to reduce drag. the practical uses a more dense medium than air to help vis
ualise the effect of streamlining. Light gates measure the time between two points.

Speed / velocity of a cart on dynamics ramp (using the motion sensor) (Physics (14-18) Motion & Forces eBook)
In this experiment, you will measure the speed of the cart, after starting it moving at different points along the track.

How does the angle of a slope affect velocity. (Physics (14-18) Motion & Forces eBook)
Create a mathematical relationship between the angle of slope and the speed / velocity / Acceleration. 

Does the mass of a cart change its velocity? (Physics (14-18) Motion & Forces eBook)
In many respects this is a “trick” investigation. The mass on the cart should not have any effect on the speed of the cart, Galilleo and dropped objects at Pisa proves this!

Average velocity and speed (Physics (14-18) Motion & Forces eBook)
In this experiment, the students will measure the speed between two points. They should be encouraged to make the connection between the time passed and distance travelled. Data is additionally collected to show the initial and the final velocity of the cart, Acceleration could be introduced. 

Calculated acceleration (Physics (14-18) Motion & Forces eBook)
Acceleration is the change in velocity over time.This practical exercise uses light gates to collect velocity data, the student then plugs the numbers into the acceleration equation to calculate.

Acceleration from a single intterupt card, software (Physics (14-18) Motion & Forces eBook)
Uses a single interrupt card and two light gates to calculate acceleration, The software does the calculation freeing time up to investigate acceleration 

Acceleration calculated from a double interrupt card (Physics (14-18) Motion & Forces eBook)
A double interrupt card produces two velocity values at a singge light gate. The software calculates acceleration at a point (the light gate), tow acceleration values can be found.

Acceleration at two points on a slope (Physics (14-18) Motion & Forces eBook)
Acceleration is the change in velocity over time. In this investigation the students will run a cart down an incline and let the software calculate and display the acceleration at 2 places. 

Measuring the velocity of a cart with light gates. (Physics (14-18) Motion & Forces eBook)
If the light gates show the time they are in the "off" state students can extract the data to produce velocity and acceleration. Once mastered the method will allow multiple light gates to be used or or other sensors (e.g. force) to be used with timing practicals. 

Motion on a slope Spoked Pulley (Physics (14-18) Motion & Forces eBook)
Use the spoked pulley attachment to produce a time distance graph with a light gate. Convert distance data to velocity or acceleration at a "click". Use gradient tool to show relationship between time distance and velocity or time velocity and acceleration

Period of a pendulum vs length (alternative using Rotary motion sensor) (Physics (14-18) Motion & Forces eBook)
An alternative to measuring the period of a pendulum. Simple apparatus to record the "swing" directly. 

Pendulum, period and amplitude (Physics (14-18) Motion & Forces eBook)
Alternative method to study the relationship between amplitude and period in pendulum. Uses a light gate to time the period.

Measure gravity from a cart moving on a slope (diluted gravity) (Physics (14-18) Motion & Forces eBook)
Galileo realised that objects of different mass fall, under gravity, with the same acceleration. This is a re working of his experiments where he diluted gravity to compensate for poor timing apparatus. 

Heavy and light masses falling (Physics (14-18) Motion & Forces eBook)
Classic study, does mass change how quickly something falls? 

Picket fence (multiple stripe interrupt card) and acceleration due to gravity. (Physics (14-18) Motion & Forces eBook)
The purpose of this experiment is to measure the acceleration due to gravity by measuring the time of fall of a “picket fence” dropped through a Light Gate. Data collected can show the relationship between distance-time, velocity and acceleration. 

Balanced forces (Physics (14-18) Motion & Forces eBook)
Motion takes place because the forces acting on the object are unbalanced. What happens to the motion of a cart when the forces are balanced and unbalanced?

Newton's second Law (Using two light gates and average acceleration A to B) (Physics (14-18) Motion & Forces eBook)
A pair of light gates are used to find the average acceleration from A to B in this classic study of Newton's second law. 

Newton's second law (using a single light gate and a double interrupt card) (Physics (14-18) Motion & Forces eBook)
Classic study of Newton's second law using a light gate and a double interrupt card to find the acceleration at A.

 Newtons Second Law Spoked Pulley (Physics (14-18) Motion & Forces eBook)
The condition for staying still or moving with a uniform velocity is that there is no resultant force acting on a body. Common experience tells us that objects at rest do not move unless a force is applied to them. The force that produces motion is the ..

Atwood's machines Newtons second law. (Physics (14-18) Motion & Forces eBook)
Atwood’s machine provides a simple and economical way of testing Newton’s 2nd Law. It is two masses hanging either side of a free running pulley. The accelerating force is the difference between the weights of the two masses. Using a light gate and a spoked pulley wheel.

Atwood's Machine Newtons second law (Physics (14-18) Motion & Forces eBook)
Atwood’s machine provides a simple and economical way of testing Newton’s 2nd Law. It is two masses hanging either side of a free running pulley. The accelerating force is the difference between the weights of the two masses.

Conservation of linear momentum (two light gates). (Physics (14-18) Motion & Forces eBook)
Light gates will be used to measure the velocity of carts before and after they collide. The total momentum before and after the collision can then be calculated and compared. 

Conservation of linear momentum (Software calculates) (Physics (14-18) Motion & Forces eBook)
Use two light gates to find the velocity, energy and momentum of carts before and after collision. The software uses a built in function to calculate the values, freeing time for investigation

Explosions and recoil (Physics (14-18) Motion & Forces eBook)
Magnets are used to repel two carts.momentum, impulse are calculated and compared. 

 Impulse and crumple zones (Physics (14-18) Motion & Forces eBook)
A practical to measure impulse and to apply knowledge practically to make a safer car or better train buffers.

Why 30 mph? (Physics (14-18) Motion & Forces eBook)
This is a supplemental piece of work to go with the impulse investigation. It attempts to give a reason for the crumple zones by considering the forces that would act upon a pedestrian in vehicle – pedestrian collision, and how the forces could be attenuated.

Bungee jump - impulse and change in momentum. (Physics (14-18) Motion & Forces eBook)
Extension of simple monitor of forces in bungee jump. Addition of a light gate gives the additional information to calculate velocity and impulse.

Centripetal force in a pendulum. (Physics (14-18) Motion & Forces eBook)
This experiment measures the centripetal force acting on the bob of a pendulum, and the speed of the bob. The force in the pendulum is measured continuously, and the speed of the bob is measured as it passes through the mid point of the oscillation.

Lenz's Law (velocity of magnet vs induced current) (Physics (14-18) : Electricity & Heat eBook)
investigates the relationship between the speed of the moving magnet and the induced current in a coil.




Who won (Science in Sport (11-18) eBook)
In this experiment, the students will measure the speed between two points, the start and the finish. It is a model of how timing and speed sensors work and can be used in sport. 

Muscle fatigue (light gates) (Science in Sport (11-18) eBook)
Muscle fatigue is a big problem for any spotsperson. How do we recognise it? 

Reducing impact (Science in Sport (11-18) eBook)
The investigation allows the students to measure the forces in an impact and design solutions to reduce the maximum force and extend the time the force is present, both desirable outcomes if you are to reduce damage or potential for damage. 

Reducing the impact (accelerometer) (Science in Sport (11-18) eBook)
The investigation allows the students to measure the forces in an impact and design solutions to reduce the maximum force and extend the time the force is present. Good for understanding the need for the correct foot ware landing platform etc.

Making the landing safe (Science in Sport (11-18) eBook)
A mini project to design a landing surface that keeps the athlete safe after landing from a height or at speed.

Streamlining - reducing air / water friction (Science in Sport (11-18) eBook)
Measuring air resistance can be difficult in a class or laboratory, fortunately the same drag is experienced when objects move through liquids (e.g. water). Water is much denser than air, so the effects of drag are magnified. a chance to play around with how shape can reduce friction

Can I improve my putting (Science in Sport (11-18) eBook)
Practice your technique against a "best profile" get the muscle memory developed. Model of how technology can act as the third coach. 

Can I measure my performance (Science in Sport (11-18) eBook)
Can you record what you are doing for later analysis? 




Why 30 mph (Science At Work (11-16) eBook)
An exercise to show how energy and speed are linked. That difference between 30 and 35 mph really is the differnce between life and death. 

Make a safe car (Science At Work (11-16) eBook)
This is an activity to involve the students in making a safer car, and understanding the role of the modern cars crumple zones. 

HK$ 620.00