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AC Rectified - DC Mosfet dimmer - Hints please
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bingo600:
I was thinking about using this AC rectified DC-dimmer

http://www.instructables.com/id/AC-PWM-Dimmer-for-Arduino/



BrianHG writes here


--- Quote from: BrianHG on February 28, 2017, 01:20:54 pm --- Now, I have a method using a power mosfet and AC-DC bridge rectifier, but, it's something like a 10 component solution and you need to switch the optocoupler on only during the 0 crossing phase of the AC & you also need both access to the hot and neutral.

--- End quote ---

Would that apply to this construction (switching of the opto during zero cross) ?

I mean it's not AC anymore , but "unfiltered DC"

/Bingo

bingo600:

I'll be dimming 2 x 40w - lightbulbs (The big ballon ones with golden glow)


I have gotten both some

Mosfets : STB10NK60Z - http://www.st.com/resource/en/datasheet/stb10nk60z.pdf

And some

IGBT's : SGP10N60  - https://www.digchip.com/datasheets/parts/datasheet/216/SGP10N60-pdf.php

100uF will be - NIPPON CHEMI CON series KMX 100uF 400V super LONG LIFE capacitors 105'C

And i have some 4N25 Optos in the drawer.


The author says the IGBT's are probably the best for this , but Mosfets are ok.

I don't have much experience with Mosfets or IGBT's , but i do with mains (no worries there).

MCU would be a ESP8266 , where i'll adapt the opto resistor to 3.3v


Can anyone see problems with the circuit , besides missing a fuse ?

/Bingo
bingo600:
The ESP8266 is going to need 3.3v anyways , so if i get a 230->12v PSy , and a DC-DC switcher for the 12 -> 3.3v

Could i get rid of the Capacitive PSU , i mean the 100uF cap & diode.

And put the 12v psu in use for driving the Fet/IGBT ?

I'll loose the galvanic isolation , but the IF is going to be wireless via the ESP , so i'm not too worried.
Unless the "shared ground "Unsmooted 400v DC Ground" , and 12v DC-DC converter ground would intefere.


Any hint for what to modify ?
I mean i suppose i still need to have a pullup in the FET gate , as the opto is the "pulldown"

Do i need some 400v cap on the "mains (load) DC" ? - For smoothing ?
As i see it on the existing schmatic , there isn't any on the one in the picture, due to the diode.

A few hints would be appreciated.

/Bingo
Benta:
That circuit has so many dumb things, it's difficult to know where to start (is "instructables" really like that? I've never visited them).

First: if you switch off your Arduino, the lamps will be lit always.

If you decide that the "always on" functionality is OK, then:

There's absolutely NO reason to use a 400 V cap. The cap will work just a well connected to the junction of R4/R5, so a 25 V type is enough.

D5 is unnecessary.

Reduce R5 to 5k6

Place a resistor between R4/R5 and the 4N35

Use a high-voltage resistor for R4, eg, VR68 from Vishay.

That's just a start...


bingo600:

--- Quote from: Benta on March 02, 2017, 08:16:42 pm ---That circuit has so many dumb things, it's difficult to know where to start (is "instructables" really like that? I've never visited them).

--- End quote ---

Thanx for the comments
I knew about the PWM source must be always on


Author mentions this circuit (other creator) , and says it has some bad design faults , explains on Instructables page


He modified it , and says this is better



Unfortunately i'm an "Analog noob" , and "have to trust" the designers , that's why i asked for some hints (review)

It will be in my summerhous , and i don't want a fire  :scared:

/Bingo
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