555 PWM LED dimmer circuit diagram

Here are 555 PWM LED dimmer circuit diagram for dimmer a lamp or control speed of a DC motor. I suggest these circuit by using the principle of PWM (pulse width modulation) form.

Like TL494 PWM Speed motor controller. But sometime it may hard to find and inexpensive. Is may it better? If we use a NE555 is very cheap and popular.

These DC Dimmer circuits have a lot of useful. For instance, the Lamps, Light bulbs, LED,  DC motor controller, Coils, etc. And we can use up to 20 watts.

Basic DC Dimmer by Rheostat

A simple DC dimmer circuit that we see commonly, always use a variable resistor is adjuster voltage to load high-low as we need.

We must use the high power variable resistors only, which always called “rheostat resistors”

dimmer using rheostat resistors

Figure 1 The simple dimmer using rheostat resistors

But the disadvantage of the circuit is so expensive and some power consumption loss in heat form. So, this way is so low performance.

Then, we found the best way that cheaper and high performance. It is PWM Controller as above. To briefly provide an output voltage with very high frequencies.

This dimmer with on/off time range of waveform to load, Not cause a loss of energy in the form of heat anymore.

How circuit works

For really application circuit as shown in Figure 2. We will see that IC1-NE555 is a frequency generator to feed the transistor output. Which it serves as switch on-off voltage to a lamp in that frequency.

555 PWM DC Dimmer circuit

Figure 2: 555 PWM DC Dimmer circuit using NE555 and Darlington transistors

The output frequency of the circuit will depend on the value of R3, R2, VR2, and capacitor-C1. And, the time period on/off will depend on adjusting VR2.

From the value setting. We can adjust the time range:

On: Off rate Up to 100: 1.

Which we will provide to the load voltage of nearly 100%. That is the light bulb will be fully light. Or, if the DC motor will speed fastest, as well.

In the event that needs to the dimmer light. Also, we can adjust:

On: off range up to 1: 20

The output from pin 3 of IC1 will be fed through R4 to base Q1. It causes Q1 to turn on-off the voltage to a lamp as an input signal.

Then, see:

The working of transistors as above will cause the voltage drops across between emitter-collector between 0.7V to 1V.

And this is a loss of some power. But it very least when compared with the old circuit that uses the rheostat resistors.

What is more? Here is a function of other parts in the circuit.

  • The Diode-D1 acts as a booster of time range on-off wide up.
  • The potentiometer-VR1 acts as the adjuster the output voltage lowest as you want.
  • The capacitor-C3, C4 and L1 acts as reducing the noise signal from the circuit don’t interfere with other electrical circuits.
  • For L1, we can make it up by using copper wire No. 20 SWG winding on ferrite cores about 50 times.

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How to build

We can assemble the parts on the PCB as shown in Figures 3 See Positioning device based circuits correctly As Figure 4.

Keep the output transistor, It is tall and hot. So need to hold on a larger-size heat-sink.


Figure 3 the Actual-size,Single-sided PCB layout


Figure 4 the components-layout

When assembling the components as a done circuit, then adjust VR2 until the lamp a few glow up softly, next adjust until go out lowest light, and later adjust VR1 again to really low light.

The components list

IC1: NE555N LM555, Timer IC
Q1: TIP120_transistors
D1: 1N4148_75V 150mA Diodes
0.25W, 5% Resistors
R1: 1M
R2: 10K
R3: 47K
R4: 2.2K
VR1: 4.7M (preset) Trimpot
VR2: 470K__Trimpot
C1, C2: 0.01uF 50V_Ceramic
C3, C4: 2.2uF 50V_NP
L1: 150 uH _inductor.

What is more? Let’s see DC spot Lighting Dimmer using 555.

Spot Lamp DC dimmer circuit using 555

This is simple low voltage DC Dimmer Circuit. It can adjust the brightness of a maximum 12V 100W Power Spot Lamp from 5% to 95%.

In the circuit use IC-555 as free-running multivibrator to drive both power PNP transistor,  to control the lamp with PWM mode.  And, using a few other components. Which easily buy in most of the local markets.

Working of the circuit

Spot Lamp DC dimmer circuit using LM555-TIP2955

Spot Lamp DC dimmer circuit using LM555-TIP2955

In the circuit, we use IC-LM555 is free-running Astable Multivibrator mode. Which these components R2, R3, VR1, D1, D2, and C1 determine the frequency output pin 3.

Then, the circuit can change the duty Cycle by adjusting VR1-potentiometer and R3. They also control a brightness level as you want.

Next, the output oscillator will limit load current, the lamp ON and OFF at a rate duty cycle of the multivibrator.

After that, the current flows to the base of Q1-TIP2955 and Q2-MJ2955 to drive the load.

We should install Q1, Q2 with the suitable heat sink. When the circuit operates in full power. The Q2 is too heat. It may damage.

The D3-general silicon diode protects a oscillator feedback. Which it can damage this circuit.

For a load of this circuit, you can use 10A 12V, power all lamps, or the strip lights LED, or high power LEDs.

The LED1 is a power on display. The R1-series resistor to limit current in save value for LED1.

‘Keep reading: 555 Pulse Generator circuits’ »

Parts you will need

IC1: IC-555 Standard Timer Single
Q1: TIP2955 15 A, 60 V PNP Bipolar Power Transistor
Q2: MJ2955 15 A, 60 V PNP Bipolar Power Transistor
D1, D2: 1N4148 75V 150mA Diodes
D3:  1N4002 100V 1A Diodes
R1: 560 ohms 0.25W Resistors
R2: 1K 0.25W Resistors
R3: 1K-100K 0.25W Resistors
R4, R5: 680 ohms 0.25W Resistors
VR1: 100K Potentiometer
C1: 0.027uF 50V Ceramic Capacitor

In addition, you can see other circuits. That also use for all power LAMP.

‘Keep reading: 12V-24 PWM motor controller’ »

How to learn electronics with simple ways

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This Post Has 13 Comments

  1. #Spot Lamp DC dimmer circuit using LM555-TIP2955

    A limiting resistor(>47Ω) in the collector of T1 must be employed. Otherwise, soon Q1 and probably Q2 will be history.

  2. Hi
    That Is a Vary Good Circuit.Thankyou

  3. Realy you are fantastic website that i see to now

  4. Hiiiiiiiiiiii
    thank you.
    your web are very good.

  5. Hi,م.مصطفى المصرى
    Thanks for your feedback.

  6. Hey I appliciated much the diagrams helps me much can I have more for how to make free power using altarnator and more about radiant power.

    #Spot Lamp DC dimmer circuit using LM555-TIP2955

  7. pls. how can i order parts

  8. I need variable Capacitor 1-100 µf or executive the enclosed circuit

  9. I wonder, the circuit should handle 100W load (9A) and the V+ is connected with an 1A fuse. How come??

    #Spot Lamp DC dimmer circuit using LM555-TIP2955

    1. Hello, Alexander Sergeyev
      Yes, It may be wrong. You should the fuse rating follow load current.

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