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unstable performance

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hhhsssmmm

New Member
Hello

I have a PIC18F2420 running at 20MHz ceramic. Compiler used is C18.

I have successfully developed a PIC controlled 2 channel AC (230V/50Hz) Halogen lamp dimmer via transformer coupled. I use an opto (MOC3020) and TRIAC BTB16600BW (snubberless) to control my lamps via the PIC. For the dimming the PIC controls the phase angle on 230V AC on each channel independently. The PIC dimmer works great and I have no exccessive heating issues either. I can control the dimming of Electronic and Simple transformer such as.....

1) Halogen lamps via simple transfromer coupled (230/12)
2) Halogen lamps via Electronic transformers (dimmable by leading or trailing edge)....(230/12)

I can have the following connection arrangement on each of the channels and the PIC dimmer works perfectly.....

1) Simple transformer on CH1 and Electronic transformer on CH2
2) Electronic transformer on CH1 and Simple transformer on CH2
3) Simple transformer on CH1 and Simple transformer on CH2
4) Only CH1 in operation with Electronic or Simple transformer
5) Only CH2 in operation with Electronic or Simple transformer


.....BUT there is one problem.

If I connect two electronic transformers on each channel, then thats where I seem to be getting unstable dimming performance and my Halogen lamps flicker. It happens when any one channel is start to dimmed and has effect on the other channel.

Please can someone help me to solve this mystry?

Haseeb
 

SPDCHK

Member
Is it just me, but what is the difference between an Electronic Transformer (230/12) and a Simple Transformer (230/12)?

I assume (230/12) means 230V Primary to 12V secondary.
 

hhhsssmmm

New Member
simple transformer is the traditional wire wound (conventional type) where there is also the advantage of electrical isolation from the HT (High Tension 230V) to the LT (Low Tension 12V).

Electronic transformer is the same thing what a simple transformer does....meaning step down the voltage. It does this via electronically. However there is no electrical isolation as is with simple transformer.

So can you help?

Haseeb
 

picbits

Well-Known Member
Try putting a small low wattage bulb (240V 5-10 Watt) on the 240v section in parallel with one of the transformers and see what happens.
 

hhhsssmmm

New Member
you are asking me to place a resistive ballast across the inductive load.....

please note that I have already tried this and YES this works very nicely....

My dimming unit will be standalone unit with two 230v channels where you can connect any of the items that i have mentioned in my first post. This entire dimming unit will be inside an enclosure box where heat dissipation is an issue. So having a light bulb in side the box is a very bad idea due to heat issues and plus its just a cheap fix.....

please can you suggest anyother means of remedy for this problem.

thank you
haseeb
 

picbits

Well-Known Member
Have you tried an RC snubber ? You can buy mains rated ones for not too much money.

I had to do this with the washing machine controller I built years ago. If I just connected the water inlet solenoids to the Triac, weird things happened. If I used the snubber (or light bulb) in parallel everything worked nicely.
 

picbits

Well-Known Member
P.s. I wasn't suggesting putting the light bulb in your box/project, it just clarifies that it will work with a resistive load in the circuit.
 
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