Dimmer

[sougata]

Hi,

Understood. The only problem is that I don't have 16F84 ready. However it should work. Do you have a PIC18F452 ready? This is where I am most comfortable. I also have 16F676, 16F73, 16F619 handy. BTW you don't need five PICs.

Regards

Sougata

[Ioannis]

I have not done this but may be my idea could help.

Using Interrupts, when there is pulse from zero-crossing detector, you could succeed in your house keeping, timing that is.

Entering the ISR, the relevant registers would increment or decrement according the flags you have set in your main program. So there is accurate timing to fire every SCR even 5 or more since the ISR would be triggered every 10ms.

Ioannis

[sougata]

Hi Everybody,

It is possible to trigger n numbers of SCRs within the 10ms(50Hz) time frame. My DMX Dimmer handles 48 of them. There I use a bubble sort algo and actually different interrupt sources. One for syncing the timer with ac, one for firing, listening to USART, fader read and so on. All this handled by two PICs 18F452 @ 40MHZ. The second one is mainly for the download and running of pattern or randomizing them.

I am working on a simplified version using a PIC16F84A (Yes I found one) and trying to acheive a 100% PBP code using the On-Interrupt function. I have no idea about the latency till I get my code running tomorrow and checking on scope. Even the asm interrupt would be quite easy.

You see with a clock frequency of 8MHz--> 2MHz(Fosc/4) / 128 (prescale) / 100 (reset every 10miliseconds), the timer0 would count 156 (50Hz) or 130(60Hz max). Compare this constantly in a loop with preset or increasing / decreasing values and fire the appropriate port.On interrupt

1. Clear all outputs
2. Reset Timer0
3. Return

Thats it. It will be done before the new cycle begins!!!!!!!!!2MIPS

I am working on a two channel version and let you all guys out there juice it up.

BTW most of the PICs have an inbuilt Schmidt Trigger on input ports so the interfacing is pretty easy. I use a couple of resistors a diode bridge and an optocoupler to derive the zero cross sync. It is accurate without any phase latency (as in the case of transformer based).Direct AC feed through high value resistor is also possible and practical but the circuit becomes live and is not recommended for experimenters.(I use it in my remote controlled fan/light dimmer to keep costs under control. It retails for about 18USD!!!!)

The toughest part is possibly randomizing the paterns or using pschychedelic effect with beat detection within the scope of the chosen processor (clock code space, instruction set).

We are having Diwali (the festival of lights) and a holiday to work with a fun project. The entire town is having myriads of lighting displays so why not doing one for the forum. Happy Diwaly to guys out there.

It is midnight now and I can get my hands on the PIC only tomorrow when I get the lunch break. So till then....

Bye!!

Regards

Sougata

[BMIelektonik]

Hello everybody
What happend here , did the the project stall

RGDS
BG

[sougata]

Sorry guys,

I could not keep up to my commitments. I lost a very near and dear friend. Give me a couple of days, I will get back with something working.

Regards

[mister_e]

A previous thread ==> http://www.picbasic.co.uk/forum/showthread.php?t=1026

Schematic + code (Dimmer.zip) ==> http://www.melabs.com/resources/samples.htm#submitted

Maybe not exactly what you need but should be enough to start

[sougata]

Sorry guys although I did a testing for a single channel version, I couldn't test the five channel one. I am posting the circuit and the code. I request the PIC gurus to have a look at the code and point the flaws. Please do read the notes.doc file for important information.

Regards

Sougata