12/22/21, 9:36 PM 110V/220V Light Dimmer Circuit with Active Reset (/) Advertisement Home (https://www.electroschematics.com/) » Lights (https://www.electroschematics.com/category/lights/) » TRIAC Dimmer with Active Reset (https://www.electroschematics.com/wp-content/uploads/2014/04/Triac-light-DimmerActive-Reset-Schematic.jpg?fit=1136%2C544) TRIAC Dimmer with Active Reset JIM KEITH (HTTPS://WWW.ELECTROSCHEMATICS.COM/AUTHOR/J-KEITH/) light dimmers (/tag/light-dimmer) This light dimmer control has active timing capacitor reset or AC line zero- crossing synchronization. The 13 additional components are garden variety and cost less than $2. Performance at the low end is exceptionally smooth and snap-free –better even than the TRIAC Dimmer Avoids Snap-ON version that uses a passive reset technique. This is a superset of the aforementioned control, so refer to that web page for additional information. https://www.electroschematics.com/triac-dimmer-active-reset/ 1/12 12/22/21, 9:36 PM 110V/220V Light Dimmer Circuit with Active Reset Schematic of the Light Dimmer Circuit (https://w ww.electroschematics.com/wp-content/uploads/2014/04/Triac-light-Dimmer-Active-R eset-Schematic.jpg) Bill of materials ww.electroschematics.com/wp-content/uploads/2014/04/96-Dimmer-BOM.jpg) Bill of materials file triac dimmer with active reset bom.xls (https://www.electroschematics.com/wpcontent/uploads/2014/04/TRIAC-Dimmer-With-Active-Reset-BOM.rar) The object of line-crossing reset One of the shortcomings of the DIAC trigger diode circuit is that the timing capacitor (C1) does not automatically discharge to zero volts when it triggers. In fact, the residual voltage is an unknown variable that is a function of the DIAC turn-off properties, aging and perhaps temperature. DIAC turn-off properties are not tightly controlled or specified. Eliminating this residual voltage greatly https://www.electroschematics.com/triac-dimmer-active-reset/ 2/12 12/22/21, 9:36 PM 110V/220V Light Dimmer Circuit with Active Reset stabilizes the timing circuit and improves the low end performance. The zero- crossing reset circuit senses when the line voltage is at zero and at that instant, it fully discharges the timing capacitor –all within about 200uS. (/) How it works The way Q2 & Q4 are connected, they can only discharge the timing capacitor (C1). On the other hand, the timing capacitor charges only via the timing potentiometer circuit. To enable it to function in either polarity (opposing halfcycles), two circuits are required. The positive discharge circuit uses NPN transistors, while the negative discharge circuit uses PNP. The line synchronization signal comes through R6 to the bases of transistors Q1 & Q3. C4 attenuates any potential noise at this node. At zero volts, both Q1 & Q3 are turned off –at that point, they can no longer short out the base drive to Q2 & Q4 respectively. R-C network consisting of R7 & C3 provide an alternating power supply bias voltage that turns on either Q2 or Q4. C3 provides phase shift so that the voltage is near maximum at zero-crossing –the polarity is subsequently for each half-cycle. Fixed voltage sources could also do this, but it would add yet more components –this is a simple and effective solution, and worked immediately upon circuit completion –did not even have to diddle with circuit values for circuit optimization other than to add noise filter C4. Limitation Since line voltage must be brought into the control via a 3rd lead, it is not suitable for two-wire applications without rewiring. Oscillographs https://www.electroschematics.com/triac-dimmer-active-reset/ 3/12 12/22/21, 9:36 PM 110V/220V Light Dimmer Circuit with Active Reset (/) (https://www.ele ctroschematics.com/wp-content/uploads/2014/04/96-Oscillograph-1.jpg?resize=505%2C 408) Observe that at AC line zero-crossing, the timing capacitor discharges very quickly. Nothing else is happening here because the potentiometer is set at maximum resistance. https://www.electroschematics.com/triac-dimmer-active-reset/ 4/12 12/22/21, 9:36 PM 110V/220V Light Dimmer Circuit with Active Reset (/) (https://www.ele ctroschematics.com/wp-content/uploads/2014/04/96-Oscillograph-2.jpg?resize=505%2 C408) In this oscillograph, observe that the DIAC is firing. Observe trace 4 that is monitoring Q1 & Q3 base inputs. Trace 3 is the phase shifted bias voltage signal –observe that the voltage is near maximum at zero crossings. Trace 2 is the DIAC output signal. Compare with the oscillographs in the previously published circuit. https://www.electroschematics.com/triac-dimmer-active-reset/ 5/12 12/22/21, 9:36 PM 110V/220V Light Dimmer Circuit with Active Reset (/) (https://www.ele ctroschematics.com/wp-content/uploads/2014/04/96-Oscillograph-3.jpg?resize=505%2 C408) This shows operation at a low conduction angle. (https://www.ele ctroschematics.com/wp-content/uploads/2014/04/96-Oscillograph-4.jpg?resize=505%2 C408) https://www.electroschematics.com/triac-dimmer-active-reset/ 6/12 12/22/21, 9:36 PM 110V/220V Light Dimmer Circuit with Active Reset This shows operation at mid-range. Light Dimmer Photos (/) (https://www.electroschematics.com/wpcontent/uploads/2014/04/96-Bench-Setup.jpg) (https://www.electroschematics.com/wpcontent/uploads/2014/04/96-Getting-Started.jpg) (https://www.electroschematics.com/wpcontent/uploads/2014/04/96-Protoboard.jpg) Isolation transformer Observe that I used an isolation transformer during the testing phase to prevent damage to test equipment and reduce shock hazard. Of course, in normal applications it is connected directly to the AC line. Conclusions Although somewhat complicated, performance is exceptional. At the very least, this makes a great experiment that deals with some issues of line voltage synchronization. Share this: Tweet Share 0 Share More Previous (https://www.electroschematics.com/triacTRIAC Dimmer Avoids Snap-ON lamp-dimmer-snap-on/) https://www.electroschematics.com/triac-dimmer-active-reset/ 7/12 12/22/21, 9:36 PM 110V/220V Light Dimmer Circuit with Active Reset Next Piezo Trigger Switch Circuit (https://www.electroschematics.com/piezo(/) trigger-switch/) Related Tutorials No related posts. Recent posts Simple Sports Timer v1 (https://www.electroschematics.com/sports-timer/) Arduino & MAX9814 – Getting Started! (https://www.electroschematics.com/arduinomax9814-getting-started/) BT-168 Battery Tester Review and Teardown (https://www.electroschematics.com/bt-168battery-tester/) Arduino Joystick Shield – Revised Primer (https://www.electroschematics.com/arduinojoystick/) DS18B20 Explained (https://www.electroschematics.com/ds18b20/) One Comments Join the conversation! You must be logged in (https://www.electroschematics.com/log-in/) to post a comment. Check this checkbox to get notifications of followup comments via e-mail. You can also subscribe (https://www.electroschematics.com/commentsubscriptions/? srp=10139&srk=49917252f13a91d5fee07d5bb551175c&sra=s&srsrc=f) without commenting. tiago_cazahotmail-com https://www.electroschematics.com/triac-dimmer-active-reset/ 8/12 12/22/21, 9:36 PM 110V/220V Light Dimmer Circuit with Active Reset Would this circuit work to dim an AC led driver? Also it’s possible to replace the pot R1 with a PWM circuit to change the duty cycle from an MCU 3.3v/5v? (/) Posted on January 02nd 2021 | 11:45 am (https://www.electroschematics.com/triac-dimmer-active-reset/#comment1903711) Log in to Reply (https://www.electroschematics.com/wp-login.php? redirect_to=https%3A%2F%2Fwww.electroschematics.com%2Ftriac-dimmer-active-reset%2F) (https://www.datasheets.com/en? utm_source=electroschematics.com&utm_medium=DS_Widget) LOOKING FOR DATASHEETS? Enter Part Number Login Email Password Remember Me Log In Register (https://www.electroschematics.com/register) | Lost your password? (https://www.electroschematics.com/lostpassword) Latest Article Comments https://www.electroschematics.com/triac-dimmer-active-reset/ 9/12 12/22/21, 9:36 PM 110V/220V Light Dimmer Circuit with Active Reset The Mighty ESP-01... (https://www.electroschematics.com/the-mighty-esp-01adapter/#li-comment-1903850) "kiranshashi: As a 3.3V microcontroller, logic-high (H) (/) means 3.3v. Thanks! Further read:" The Mighty ESP-01... (https://www.electroschematics.com/the-mighty-esp-01adapter/#li-comment-1903849) "You wrote .. "...During the normal (usual) mode, the status of GPIO0 and GPIO2 will be" Water Switch Sensor... (https://www.electroschematics.com/water-switch-sensorcircuit/#li-comment-1903848) "I think what the Dr. is trying to say is it is unstable if it isn't connected so a micro-level" DS18B20... 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All Rights Reserved. Contact Us (https://aspencore.com/contact-us/) About Us (https://aspencore.com/) Privacy Policy (https://aspencore.com/privacy-policy) Terms of Use (https://aspencore.com/terms-of-use) Site Map (/sitemap.xml) https://www.electroschematics.com/triac-dimmer-active-reset/ 12/12 12/23/21, 9:52 PM LIght Dimmer Circuit Using DIAC And TRIAC LIght Dimmer Circuit Using DIAC And TRIAC 1. 1. Light Dimmer Circuit Prepared by :- Parth D. Patel (140110109039) Jay j. Patel (140110109034) Batch : C109 Basic Electronics OEP 2. 2. The Circuit Diagram 3. 3. The Components Used : Resistors : - 100 Ω - 2Watt - 4.7 kΩ - 0.5 Watt - 1 MΩ - 0.5Wat Capacitors : - 0.1 μF – 400 V - 0.1 μF – 400 V - 0.1 μF – 400 V TRIAC : TLC 223B DIAC : DB3 Variable Resistance : 500 kΩ 4. 4. The Working Of Circuit • A light dimmer works by essentially chopping parts out of the AC voltage. This allows only parts of the waveform to pass to the lamp. The brightness of the lamp is determined by the power transferred to it, so the more the waveform is chopped, the more it dims. • Mains power is comprised of an alternating current that flows in one direction and then in the other, along the cable, at the rate of 50 or 60 cycles per second (known as Hertz). • By chopping the waveform at the zerocrossing point, smooth dimming can be achieved without the lamp flickering. 5. 5. • The mains sine wave, and a phase-controlled waveform. The Alternating Current Wave form The choped waveform at zero point where smooth dimming is achived 6. 6. The Imperative Components 7. 7. The DIAC • The DIAC is a full-wave or bi-directional semiconductor switch that can be turned on in both forward and reverse polarities. • The DIAC gains its name from the contraction of the words DIode Alternating Current. • The DIAC is widely used to assist even triggering of a TRIAC when used in AC switches. DIACs are mainly used in dimmer applications and also in starter circuits for florescent lamps. 8. 8. Operation : • The DIAC conducts a break-over voltage. When the device excceds thr break over voltage , it enters the region of negative dynamic resistance. • The diode remains in its conduction state untill the current through it drops below what is termed the holding current. • Below the holding current , the DIAC reverts to its hhigh resistance. • Its behaviousr is bi-directional and therefore its operation occurs on both halves on AC Cycle. 9. 9. The TRIAC • The TRIAC is a three terminal semiconductor device for controlling current. It gains its name from the term TRIode for Alternating Current. • It is effectively a development of the SCR or thyristor, but unlike the thyristor which is only able to conduct in one direction, the TRIAC is a bidirectional device. • The TRIAC is an ideal device to use for AC switching applications because it can control the current flow over both halves of an alternating cycle. 10. 10. Opreation : • It can be imagined from the circuit symbol that the TRIAC consists of two thyristors back to back but with a common gate terminal, and the cathode of one thyristor connected to the anode of the other, and vice versa. • When the voltage on the MT1 is positive with regard to MT2 and a positive gate voltage is applied, one of the SCRs conducts. When the voltage is reversed and a negative voltage is applied to the gate, the other SCR conducts. This is provided that there is sufficient voltage across the device to enable a minimum holding current to flow. 11. 11. Thank You https://www.slideshare.net/ShivamPatel25/light-dimmer-circuit-using-diac-and-triac 1/1
