Hi power,Three phase dimmer

[vertebro]

Hi everybody from Buenos Aires,Argentina!!
Well...what I would like to do is a 3 channel flash curing unit ,based on the dimmer designed by Giorgos Lazaridis,heres the link:
http://www.pcbheaven.com/circuitpages/Voltage_Controlled_AC_Light_Dimmer/ I will post pictures of the full proyect including
building,painting and metal fabrication of the unit till its fully done.
Ive already build it and it works excellent!.I control the power with a potentiometer.
i will attach a scan with the basic concept and requirements of the proyect,since it needs some adaptations and mods,I will be happy reading your advices!!!
This circuit Ac source must be three phase (220v x3 + neutral) due to the amps handled
Each channel has three infrarred lamps of 1500w each that means, 4500w per channel
Im using Triac BTA41-800B
You have to be able to select what channel to use :1, 2 0r  3 channels at once with three little switches on control panel
the 3 channels must be controled with just one potentiometer on control panel
It needs to have a timer (with ci 555 would be nice) with a potentiometer on control panel too.a 0 to 15 seconds timer its fine.
A start input (and test button) from a magnetic sensor to activate the cycle.Its going to do hundreds of cycles per day.
THANKS A LOT!

[kam]

13.5 KWatts is BIG! That 555 dimmer works really that good? This chip never cease to amaze me...

I'm looking forward to see your work! I'll feature it in the home page when its done!

[vertebro]

Sure,that would be great! Coul you give me some hints how to add two more optocouplers to the original circuit?

[vertebro]

Please I need some help,Ive got to get this working as soon as possible Im working on the mechanics already,but I still need some help to get the electronics mods ,
questions:
how can I attach two more channels? (two more MOC3020)
how can add a start button.(without taking the 9volt source out?)
how can turn  on and off each channel,where should i put the 3 switches?
will i have some kind of conflict since I use 3 phases,but only one dimmer ?
should i put some RC circuit between A1 and a2 on the triacs to avoid peaks of current?
for timer I would use a separate commercial unit that i bought already,wich has double relay outputs
Common,Normal Open and Normal Clossed.how do i attach it to the circuit of the link,

CHECK THE PICTURE ATTACHED ANY COMMENTS WILL BE WELCOMED!!!

[cheerio]

how can I attach two more channels? (two more MOC3020)
if all channels are dimmed together you can use some AND-Gates. 1 Input gets the pwm signal and the other one will be one of your switches.

how can add a start button.(without taking the 9volt source out?)
just use a gpio pin of the mcu as an input. if the start button is pushed the mcu starts the pwm signal. if you switch it off it will kill the signal. you got to code that part ofc.

how can turn  on and off each channel,where should i put the 3 switches?
if all channels are dimmed together you can use some AND-Gates. 1 Input gets the pwm signal and the other one will be one of your switches.
you put the switches between the AND gate of the channel and vcc.

will i have some kind of conflict since I use 3 phases,but only one dimmer ?
you don't, because in fact each triac is a dimmer by itself
only thing that might result in different brightness of the lamps is when the AC phases are shifted (zerocrossing at different times)
dunno if that would be much noticable. as the moc opto will do the zerocrossing check there will be no harm to the triac.

should i put some RC circuit between A1 and a2 on the triacs to avoid peaks of current?
not sure. just hook up some measurement gear and check it out. if you do not have the gear than use the RC filter because-> better safe than sorry

@kam:
plz verify what i wrote. i am not so experienced with that stuff.

[vertebro]

thank a lot Kam!
I would rather not to use mcus i wanna keep it simple,the more analogical,the better!
good idea about the AND gates,any suggestion on wiring one of those?
would you have any drawing to update?

[cheerio]

you wire them up like in the schem i attached. i did not have the opto isolator symbol in the tool. so imagine the opto is inside the triac ^^
pwm is generated by the 555. i think you can stop the pwm signal by pulling the reset (pin 4) low. don't know if the output goes to 0V then. just try it

[vertebro]

Ok,this is the original circuit diagram,that i have working,with one AND gate added (blue lines),is this conection correct?

[cheerio]

If the AND gate can supply enough current (they usually do) you can remove T3 and R10. Pin 3 of the 555 can be connected to one input of the gate and the output of the gate can be connected to r11 (instead of the vcc connection of r11)

If you want to use T3 then you need to connect Pin 3 of the 555 to one input of the AND gate and the gate-output to R10 (instead of T3). You need the Base resistor always connected directly to a Bipolar transistor.


If the output signal of the 555 is not 0V with Reset pulled low, then you can turn the vcc supply of the 555 off (with another switch). That should turn off the lamps.

[vertebro]

cheerio,could it be possible that someone said that T3 is working as an inverter?
If im correct ,to get 1 on the output of Gate AND it needs two positives inputs,one from the channel switch connected to vcc(enables the channel)and the other from pin 3,since that output are pulses and not a constant Vcc,will i have a stable output?


If the output signal of the 555 is not 0V with Reset pulled low, then you can turn the vcc supply of the 555 off (with another switch). That should turn off the lamps.
Yes,i will try switching #4 pin of the 555,(reset)between Vcc and Ground to stop 555 oscillating(here is when the output relay contacts of the timer unit comes into play  ,if that doesnt work,then i cut Vcc to 555 with the timmer relay.

Another question,how can i add two more optocouplers and triacs,( one 220v phase per channel)
is the output signal strong enough to handle them? wher shoul i connect them? Thanks for your answer!

[cheerio]

If im correct ,to get 1 on the output of Gate AND it needs two positives inputs,one from the channel switch connected to vcc(enables the channel)and the other from pin 3,since that output are pulses and not a constant Vcc,will i have a stable output?

yes the output of the gate is 1 if both input signals are 1. one signal (the switch) is always 1 if it is switched on. the other signal is the pwm signal. that way the ouputsignal will match the pwm signal. Just check the datasheets of the AND Gate to make sure it can handle the frequency. it will handle it most likely


you are right. T3 acts as an inverter. But must the signal be inverted?

you can put the additional Triacs (and optos) in parallel on the DC side and also on the AC side. I do not think it that you have to worry about overloading on the AC side (you fused it anyway, did you?)
on the DC side you have to check if the Opto Diode current (summed up) does not exceed the curretn source (the AND Gate). If the Forward Voltage is <VCC/3 (assuming 3 optos) you can put them all in series.  This way you only need 1 current limiting resistor and they need only the current of 1 opto.

i do not know if my description confuses you. just ask me if anything is not clear to you. A drawing always helps ^^

[cheerio]

i just tested smth. if the AC Lines you use are phase shifted you need a zerocrossing detection and a 555 for each channel. you can then select each channel by turning on/off the channels 555 by a switch.

what i tested has yet to be confirmed by further tests. i give you feedback in a few days.

[cheerio]

you have to make sure the AC lines of the channels are not phase shifted. otherwise you will need a 555 timer + zerocross detection for each channel. you do not need the AND gates anymore if this is the case. you just switch the channel on/off by switching the 555 on/off

[vertebro]

im not quite sure,about phase shifted,what i can tell you is that each phase vary 120 electrical degrees one from another ,is that phase shifted?
if so ,what could happen if i use just one 555 with 3 optos and triacs? what would be the results?
i attached a pdf talking about three phase in my country ,is written in spanish,but no need translation
for the images! Take care!

[cheerio]

i do not see any pdf. but yes the 120° variation is what i mean with phase shifted. What will happen if you use just one 555(and a single  zerocrossing) is that 1 line will dim as you want it to. but the others will be brighter or dimmer compered to the line where the zerocorssing detection is hooked up to.