thyristor full rectifier from a 16f877 with 24 volt pw 50 Hz.

First of all can you give some more details?

I assumed that you have 24VAC, which you want to rectify with 4 thyritors, and all logic will be in PIC mcu:

1. First you have to get information about synhronisation with AC voltage - use RB0 as with external interrupt defined (use 2 resistors to made voltage divider, from 24VDC to RB0, some diodes ...)
2. than in code when you get interrupt, sinusoidal voltage has pass zero voltage (if you need really exact calculation, when you get interrupt voltage must be at least 2-3V, so zero crossing happend a little time before), this is start point for all regulations and calculations of trigger angle.
3. use 4 output pins (maybe 2 is enough) and via MOC3020 (opto-triac, MOC302x) trigger gates of thyristors.

Thats it.


Mr.Cube

There is possibility to avoid using of mcu. In that case you need ic TCA785, this ic speciality is driving thyristor/triac.

Take a look, I upload and datasheet.

Re: explen
hello please how can connect tca785with pic16f877

Click to expand...

If you want to use TCA785, you don't need mcu, you can make everything with hardware.

Look examples in datasheet.
Pin1 = V-
Pin5 = sinhronisation with AC voltage you want to regulate
Pin6 = inhibit, put it to V+ via 10k
Pin9 = 22k +trimer 100kOhm (pin9 & pin10 are used to make triangle voltage, when you change resistor on pin9, you change amplitude of triange voltage)
Pin10 = 47nF
pin11 = regulating voltage 0-10VDC, 0VDC max output voltage (thyristors work as much as they can), 10VDC min or zero output voltage
pin12 = 1n (with this pin you define how long will be your impuls to thyristor gate) If pin 12 is connected to ground, pulses with a duration between trigger point and 180° will result.
pin13 = V+
pin14&15 = trigger pins for thyristors
pin16 = V+

There are several examples in datasheet, so you can see some applications. You can find some applications using google.

If you really want to use PIC mcu, than PWM out can be used to generate control voltage (pin11), but in that case you have to trim trimer 100k to have triangle voltage with 5 volts amplitude (because triangle voltage and control voltage are compared inside chip....).

I use TCA785 a lot, I made several 3 phase regulators with this chip and must say it's working very nice.


Mr.Cube