Kerim
Member
It happens that I still have many 5A/600V triacs. So, I had the idea to use them sometimes in driving power relays (coil 24V DC, 220R) on AC mains (nominal 220V, 50Hz) instead of using SMPS units.
If the mains voltage and frequency are constant, a simple fixed triac dimmer with a diode-bridge could be the solution. But I had to assume that the mains voltage may vary from 100V to 290V, for example. Also, its frequency (period) may not be exactly 50Hz (20ms).
The attached schematic shows how the triac phase delay (dly) has to change with the mains voltage (Vrms) to get around 24V on the relay coil (220R, 3.2H). The step/resolution of the phase delay is fixed (52us), it is related to the MCU assembly code I wrote to generate the gate pulses that turn on a relay.
Note: The gate sensitivity of a triac is better (in 4 quadrants) if the direction of the current gate is out of it (negative).
For instance, I try to pass my time by sharing some of my works around here. My private business (designing and producing products related to electronics for the local consumers since more than 40 years) is almost halted lately due to various world’s regulations, besides the strong earthquake that hit my city about 3 weeks ago (some predicted another one on March 6).
Wish you all to be safe and happy,
Kerim
If the mains voltage and frequency are constant, a simple fixed triac dimmer with a diode-bridge could be the solution. But I had to assume that the mains voltage may vary from 100V to 290V, for example. Also, its frequency (period) may not be exactly 50Hz (20ms).
The attached schematic shows how the triac phase delay (dly) has to change with the mains voltage (Vrms) to get around 24V on the relay coil (220R, 3.2H). The step/resolution of the phase delay is fixed (52us), it is related to the MCU assembly code I wrote to generate the gate pulses that turn on a relay.
Note: The gate sensitivity of a triac is better (in 4 quadrants) if the direction of the current gate is out of it (negative).
For instance, I try to pass my time by sharing some of my works around here. My private business (designing and producing products related to electronics for the local consumers since more than 40 years) is almost halted lately due to various world’s regulations, besides the strong earthquake that hit my city about 3 weeks ago (some predicted another one on March 6).
Wish you all to be safe and happy,
Kerim
