This is circuit for dimmer a lamp or controll speed of a DC motor. I used to suggests these circuit by use principle most PWM (PWM Control Speed Motor 12V By TL494) form.
But TL494 is not cheap and hard to buy we use NE555 beter very cheap and popular.
This circuit have a lot of useful such as the DC dimmer , DC motor controller, etc.
Which can use up to 20 watts.
The working principle of circuit
A simple DC dimmer circuit that we see commonly, always use a variable resistors is adjuster voltage to load high-low as we need.
We must use the high power variable resistors only, which always called “rheostat resistors”
Figure 1 The simple dimmer using rheostat resistors
But disadvantage of circuits that use it, is very expensive and some power consumption in heat form, therefore, this way so low performance.
Then, we found best way that cheaper and high performance. By briefly provide a output voltage with very high frequencies.
This dimmer with on/off time range of wavefrom to load, Not cause a loss of energy in the form of heat anymore.
For really application circuit as show in Figure 2 will see that IC1-NE555 will acts as frequency generator for feed to the transistor output. Which serves as switch cut off voltage to a lamp.
Figure 2 the circuit diagram of PWM DC motor controller with NE555 and darlington transistors
The frequency value of circuit will depends on value of R3, R2, VR2 and capacitor-C1. Which time on/off, that will depends on adjusting of VR2.
For the value that can adjust time rang on : off up to 100 : 1 . Which will be provided to the load voltage nearly 100%, that is the bulb will fully light. Or if the motor will speed fastest, as well.
In the event that need to dimmer light, we can adjust on : off range up to 1 : 20
The output from pin 3 of IC1 will be fed through R4 to base TR1, making TR1 turn on-off the voltage to lamp as look of input signal.
The working of transistors as above will cause the voltage,to drop across between emitter – collector during 0.7V – 1V, and This was a loss of power to some part. But it very least when compare with the old circuit that use the rheostat resistors.
– The Diode-D1 acts as 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 do it with We can make up your own using wire No. 20 SWG winding on ferrite cores for about 50 times.
How to builds
We can assemble the parts on the PCB as shown in Figures 3 Positioning device based circuits correctly. As Figure 4 For the output transistor that tall , need to hold on larger-size heat-sink.
Figure 3 the Actual-size,Single-sided PCB layout
Figure 4 the components-layout
When assemble the components as 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 ___timer IC
D1_________1N4148_75V 150mA Diodes
R1_________1M ____1/4 watts 5%
R2_________10K____1/4 watts 5%
R3_________47K____1/4 watts 5%
R4_________2.2K____1/4 watts 5%
VR1________4.7M (preset) Trimpot
C1, C2______0.01uF 50V___Ceramic capacitors
C3, C4______2.2uF 50V__NP
L1_________150 uH ___inductor
Note: You can buy here: