V_circuit.png' alt='Zero Crossing Triac Driver Circuit' title='Zero Crossing Triac Driver Circuit' />PWM Motor Soft Start Circuit. The post explains an effective PWM motor soft start circuit which can be used for enabling heavy motors with a soft start and thus prevent the equipment from drawing dangerous high currents. High wattage motors such pump motors or other forms of heavy industrial motors tend to draw huge current during their initial power switch ON, which in turn impacts the associated fuses and switches adversely causing these to either blow of or degrade overtime. In order to remedy the situation a soft start circuit becomes highly imperative. In a few of my previous articles we discussed regarding a related topic, which you may learn comprehensively through the following posts Soft start circuit for pump motors. Soft start circuit for refrigerators. Although the above designs are quite useful, these may be considered slightly low tech with their approach. In this article well see how the process may be implemented using a much sophisticated PWM based motor soft start controller circuit. The idea here is to apply a gradually incrementing PWM to a motor each time its switched ON, this action allows the motor to attain a linearly increasing speed from zero to maximum within a stipulated period of time, which may be adjustable. Referring to the figure above, the production of the linearly incrementing PWM is achieved with the help of two 5. IC, configured in their standard PWM mode. I have already discussed the concept elaborately in one of my earlier articles explaining how to use IC 5. PWM. As may be witnessed in the diagram, the configuration employs two 5. ICs, IC1 being wired like as astable, while IC2 as a comparator. IC1 generates the required clock signals at a given frequency determined by the values of R1 and C2 which is applied to pin2 of the IC2. IC2 utilizes the clock signal to generate triangle waves across its pin7, so that these may be compared with the potential available at its control voltage pin5. Pin5 acquires the required control voltage via an NPN emitter follower stage made with the help of T2 and the associated components. When power is switched ON, T2 is fed with a ramping or a gradually increasing voltage at its base via R9, and due to the proportionate charging of C5. This ramping potential is appropriately duplicated across the emitter of T2 with respect to the supply voltage at its collector, meaning the base data is converted into a gradually increasing potential ranging from zero to almost the supply voltage level. Mantech Electronics is an Electronic Component, Test and Measurement, Tool and Power Product Importer, Supplier and Distributor. Products are available from any one. In this post we learn through two examples how to build a simple light dimmer switch circuit for controlling light intensity with pot, using the principle of triac. Skip to Bottom. OA91A NTE109 Glass Germanium Diode OA95 NTE109 Glass Germanium Diode OA95 NTE177 General Purpose Silicon Rectifier. This FM transmitter circuit is a quite fun project for electronics beginners, so heres a circuit with the 2SC9018 transistor. It uses the 2SC9018 high frequency. The lighting industry must overcome differences in lamp load, lack of standards, and legacy wiring problems to optimally pair a phasecut dimmer with an LED lamp. DIY%20PICS/ZC-schema.gif' alt='Zero Crossing Triac Driver Circuit' title='Zero Crossing Triac Driver Circuit' />This ramping voltage at pin5 of IC 2 is instantly compared with available triangle wave across pin7 of IC2, which is translated into a linearly incrementing PWM at pin3 of IC2. The linearly incrementing process of the PWMs goes on until C5 is fully charged and the base of T2 attains a stable voltage  level. The above design takes care of the PWM generation each time power is switched ON. In order to implement the PWM motor soft start circuit effect, the output from pin3 of IC2 is required to be applied to a triac power driver circuit, as shown below The above image shows how the switch ON soft start PWM control may be implemented on heavy motors for the intended purpose. In the image above we see how triac driver isolators with zero crossing detector can be employed for driving the motors with the linearly incrementing PWMs for executing a soft start effect. The above concept effectively takes care of the start ON overcurrent situating on single phase motors. However in case a 3 phase motor is used, the following idea can be used for implementing the proposed 3 phase soft start on motors. HfZaM.png' alt='Zero Crossing Triac Driver Circuit' title='Zero Crossing Triac Driver Circuit' />Simple Light Dimmer Switch Circuit. In this post we learn through two examples how to build a simple light dimmer switch circuit for controlling light intensity with pot, using the principle of triac phase chopping. Introduction. We have already seen in many of my earlier articles how triacs are used in electronic circuits for switching AC loads. Triacs are basically devices which are able to switch ON a particular connected load in response to an external DC trigger. Though these may be incorporated for complete switch ON and complete switch OFF procedures of a load, the device is also popularly applied for regulating an AC, such that the output to the load may be reduced to any desired value. For example triacs are very commonly used dimmer switch applications where the circuit is designed to make the device switch in such a manner that it conducts only for a particular section of the AC sine wave and remains cut OFF during the remaining parts of the sine wave. This result is an corresponding output AC which has an average RMS value much lower than the actual input AC. The connected load also responds to this lower value AC and is thus controlled to that particular consumption or resultant output. This is what exactly happens inside electrical dimmer switches which are normally used for controlling ceiling fan and incandescent lights. Simple and the Best Triac Dimmer Switch Circuit. Zero Crossing Triac Driver Circuit' title='Zero Crossing Triac Driver Circuit' />The circuit diagram shown above is an classic example of a light dimmer switch, where a triac has been utilized for controlling the intensity of light. Nokia C2 00 Opera Mini. When AC mains is fed to the above circuit, as per the setting of the pot, C2 charges fully after a particular delay providing the necessary firing voltage to the diac. The diac conducts and triggers the triac into conduction, however this also discharges the capacitor whose charge reduces below the diacs firing voltage. Due to this the diac stops conducting and so does the triac. This happens for each cycle of the mains AC sine wave signal, which cuts it into discrete sections, resulting in well tailored lower voltage output. The setting of the pot sets the charge and the discharge timing of C2 which in turn decides for how long the triac remains in a conducting mode for the AC sine signals. You might be interested to know why C1 is placed in the circuit, because the circuit would work even without it. Its true, C1 is actually not required if the connected load is a resistive load like an incandescent lamp etc. However if the load is an inductive type, the inclusion of C1 becomes very crucial. Inductive loads have a bad habit of returning a part of the stored energy in the winding, back into the supply rails. This situation can choke up C2 which then becomes unable to charge properly for initiating the next subsequent triggering. C1 in this situation helps C2 to maintain is cycle by providing bursts of small voltages even after C2 has completely discharged, and thus maintains the correct switching rate of the triac. Triac dimmer circuits have the property of generating a lot of RF disturbances in the air while operating and therefore an RC network becomes imperative with these dimmer switches for reducing the RF generations. The above circuit is shown without the feature and therefore will generate a lot of RF which might disturb sophisticated electronic audio systems. Improved Triac Dimmer Circuit. The light dimmer switch circuit illustrated below incorporate the necessary precautions for subsiding the above issue. This enhanced light dimmer circuit also makes it more favorable with high inductive loads such as motors, grinders etc. C2, C3, R3 which allows the diac to be fired with consistent short burst of voltage instead of a abruptly switching pulses, which in turn allows the triac to be fired with smoother transitions, causing minimum transients and spikes. Parts List for the above enhanced fan dimmer circuit. C1 0. 1u4. 00. VC2, C3 0. V,R1 1. 5K,R2 3. K,R3 3. K,R4 1. Ohms,VR1 2. K, or 4. 70. K linear. Diac DB3,Triac BT1.