What can be used instead of LDR or What is an alternative of LDR?

 We can use Phototransistor as an alternative for LDR.  A phototransistor can respond much more quickly than an LDR.  that's why if we used phototransistor Instead of using LDR we can get a very less response time.  and the size of a phototransistor is not that big,  or you can say it is very similar in physical size to an LDR. If you are doing a project where you have to take light intensity as an input,  then a phototransistor is the perfect replacement for  LDR.

What is an alternative for a LDR
The best alternative for an LDR

Through the following paragraphs, we will come to know about what is an LDR,  why we use it, and also its physical properties.  Then we will discuss what is a phototransistor and its physical properties.  then we also discuss why a phototransistor is a perfect replacement for an LDR.  I hope throughout this post all of your doubts will be cleared.  and you will able to take a perfect decision to choose a component for a replacement for an LDR.

What is an LDR? 

 LDR is a cadmium sulfate photocell,  which is called a light dependent resistor.  it can react in a different way in different intensities of light. As it is a register and it is photosensitive,  that's why and a leader is called a photoresistor. LDR is a passive electric component. Its resistance can very upon the intensity of light. 

Physical property of LDR 

LDR is made of high resistance semiconductor that can absorb the photon particles that comes from the light.  And based upon the amount of the photon particles and their frequency the semiconductor material gives the necessary amount of energy to the bound electron particles so that they can jump into the conduction band. That's why in the darkness where the earlier cannot receive any kind of photon particles,  it shows a higher amount of resistance.  On the opposite as the intensity of light increases,  the resistance of the LDR gradually decreases. 

Uses of LDR

LDRs are available in different shapes and colors in the market. Especially in alarm clock,  light sensitive devices,  street light switching devices, and in some many other applications, we can use LDR.  as an LDR can increase or decrease its resistance depending upon the intensity of light,  it is used in several applications to turn ON and OFF a circuit depending upon the ambient light.

Is there any sensor that can be used instead of LDR?

Yes, we can use a phototransistor instead of LDR. And the applications of the phototransistor is quite similar to an LDR. we can use this phototransistor in any type of Arduino projects,  and it will give us a very less response time than an LDR.  that's why using a phototransistor instead of an LDR is quite beneficial. Do the principle used in LDR and phototransistors are different,  but their results are quite similar. 

What is a phototransistor?

 The phototransistor is a semiconductor device that reacts with the intensity of the available light.  it has the ability to sense the intensity of light, Which means it can also collect the photon particles from the light.  according to the intensity of the light,  a phototransistor can alter the flow of current between the emitter and collector of the transistor. A phototransistor is more sensitive than a photodiode. But it is slower than a photodiode and it has also less response time than an LDR.  That's why considering several good properties of a phototransistor we can say that it a phototransistor is a perfect replacement for an LDR.

Physical property of a phototransistor

 The phototransistor is a bipolar junction transistor for the BJT type transistor. When the photon particles from light Strikes with the semiconductor device,  freeze the electrons and holes.  and this causes the flow of current through the phototransistor.  the phototransistor has three terminals.  so the main difference between the LDR and a phototransistor is that the LDR is a two Terminal electronic device whereas the phototransistor is a three terminal electronic device. 

Applications of phototransistor

 phototransistors are very easy to apply and it is also very beneficial than other photosensitive components. that's why phototransistors have several types of applications and is being used in several circuits. 

  • We can use a phototransistor in a light controlled circuit.  
  • Phototransistors are also used in accounting systems where we have to count the amount of reflected light or reflected infrared.
  • The transistors are also used in security systems.
  • They are also used in encoders where black and white stripes rotate in a disc and it is used to measure the direction of the rotating disc. 


I hope throughout this post you have gained a depth of knowledge about the light detecting resistor and phototransistors. And we have also discussed why phototransistors are better than a light detecting resistor or LDR. If you know any more details about this you can also comment down below this post.  or if you have any query you can also let us know about that.  we will try to reply as soon as possible. I hope this post has helped you.  If you found this helpful then you can also share this post with your friends.