Dimmer

[Reven]

Can someone help me?
I build the circuit from (Dimmer.zip) ==> http://www.melabs.com/resources/samples.htm#submitted,
and I have this problem:
If I press the increase button (<500ms) ,the lamp go on,full and if I press the decrease button, the lamp go off (normal).
If I try to decrease the intensity from full on, or increase the intensity from off state, the lamp it fllash fast without decreasing/increasing brightness, until the lamp go on or off.
On GP4 I have 50hz, and value at the pin GP2 while press the buttons, increment/decrement pulses by 500 uSec,until the maximum/minimum value, everything look ok.

Any Help?

Thanks!

[Ioannis]

Have you adapted the program for the 50Hz line freq?

Ioannis

[Reven]

If you mean the maxdelay value, yes.

But if you conect osciloscope and take a look at the pulses from the pic output and the 50Hz at the same time, you will see that the maxdelay value is only for the maximum brightness.

[mister_e]

Looks like a bad signal level to me...

What is the voltage of your transformer?
What are your R3 and R4 value?

Try decrease R3 and post your results.

[Reven]

This is the osciloscope measures from the GP4 (AcLine input), and from GP2 (Output to TRIAC).
I use tranformer 8Vac, R3=4k7 and R4=10k.

Look the pictures from 0 to 4. Is from value off to on through 3 steps.


But the lamp still flashing...

[HenrikOlsson]

Reven,
I've not used that circuit or code you are reffering to but by just looking at your waveforms it seems that the triac is triggered at the same phase angle in case 1, 2, 3 & 4.

The triac only needs a short pulse on the gate and will then hold itself 'on' untill the AC-line crosses zero, at which point it will turn 'off'. That short pulse should be delayed a certain amount of time from the zero crossing.

On your scope pics the triac seems to be triggered exactly 1div from the zero crossing in all cases except full on and full off.

/Henrik Olsson.

[Acetronics2]

Hi, reven

Henrik is right ...

Here, the pulse length is not the thing to be variable.

but you must vary the time between zero voltage detection and triac gate firing ...

Long time = weak light
short time = full light

remember once the triac is turned on it stays turned ON until current becomes null.


Alain

Here, you had programmed a ... DC Dimmer !!!