Automatic Lamp Dimmer Circuit using Triac

Share on FacebookShare on Google+Tweet about this on TwitterShare on RedditShare on StumbleUponPin on Pinterest
automatic-lamp-dimmer-circuit-triac-electronics
Automatic Lamp Dimmer Circuit using Triac

Lamp dimmers circuit can be found through out the internet since these kind of circuits are have a great significance in real time.  Here is a similar circuit which was used to control a AC lamp connected to it based on the light present in the environment. To summarize, this will make the lamp glow brighter in the absence of light and in the presence of light the lamp will glow dim or will be turned off. Lets move into the working of this above lamp dimmer circuit.

WORKING OF AUTOMATIC LAMP DIMMER CIRCUIT:

Triac and LDR holds the significant place in the working of this lamp dimmer. Here LDR (Light Dependent resistor) was used as a light sensor which offers high resistance to the current flow in the absence of light and low resistance when light incident on it. A Triac (Triode for Alternating Current) is a semi conductor device commonly used for switching and power control of AC systems. Triac can be switched On by either negative or positive gate pulse regardless of the polarity of the AC supply input. 

triac-symbol-diagram
Triac

When there is no light in the environment LDR shows high resistance thereby the voltage across the gate terminal of the triac will be high. This makes the Triac to drive the lamp connected to it and the light will glow brighter when there is complete dark. When light intensity was high the LDR shows low resistance therefore the voltage across it will be less or zero. This makes the lamp switch off when the light intensity in the environment was high. The Triac will dim the lamp gradually when there is a increase in light intensity and make the lamp brighter when there is decrease in light intensity.

NOTE:

– AC 220V, 5Watt Incandescent light bulb should be used with this circuit.

– The above circuit can only handle only low loads so never use high loads than the specifications mentioned in the diagram.

– Never touch the circuit or you will be electrocuted.

Related Designs and Schematics

Share on FacebookShare on Google+Tweet about this on TwitterShare on RedditShare on StumbleUponPin on Pinterest
The following two tabs change content below.

Frank Donald

Junior Network Engineer at Tata Communications
Frank Donald is an Electronics and Communication Engineer who is very passionate about his subject. Reading, Surfing and Blogging are the things he loves.

Ask your query

8 Comments on "Automatic Lamp Dimmer Circuit using Triac"

Notify of
avatar
Sort by:   newest | oldest | most voted
NDS
Guest

What is the wattage of the 3.3M resistor ?

Mohamed
Guest

What about using higher lamp watt value? . and is the ldr can stand this high ac voltage? .

Anonymous
Guest

Hello ,

Ldr’s works this way : in light they gives few resistance and in dark they gives very high resistance.
An Ldr can be used to dim the lights when in light or when in dark or vice versa – it’s a matter to how the Ldr is
connected in the circuit – ok

Frank Donald
Guest

Sorry for the wrong information and now the article is updated, thanks for pointing out the mistake

Anonymous
Guest

Guys i see the LDR found in the market shows high resistance in the absence of light. I believe this circuit need a resistor which should work like a conductor on absence of light. I am not able to find such kind of LDR . Any advice please? –

Anonymous
Guest

Guys i see the LDR i found in the market is shows high resistance in the absence of light. I believe this circuit need a resistor which should work like a conductor on absence of light. I am not able to such kind of LDR . Any advice please?

Frank Donald
Guest

Your point is correct , sorry for the wrong information now the article is updated.

wpDiscuz