555 timer TRIAC flasher

[Athosworld]

I made this circuit that is just an astable 555 powered by a capacitive dropper with the output connected to the gate of a MAC97A6 triac. The load (a dimmable LED lamp) does flash, but it never fully turns off, how can I solve this? The triac gate voltage and current seem to be fine.

 

[rjenkinsgb]

You are mixing up voltages within the bridge rectifier DC output, and the AC neutral.

The negative from the bridge is either near (0.6V) the neutral voltage - or near the reduced live voltage - on alternate half cycles.

You generally cannot mix connections between AC and DC sides when using a non-isolated supply.

You could use an opto-triac trigger (eg. MOC 3000 series) to trigger a triac in the AC side from the DC side without cross connecting the two.

ps. It looks like there is no current limit resistor feeding the gate?

 

[Galgso]

You can get a neutral-referenced (or live-referenced) capacitive dropper if you are willing to use a half-wave rectifier (i.e. a single diode) rather than a full bridge. That way you don't need an opto-isolator or an optically-triggered triac. You will however need a larger filter capacitor.

Also I've attached an application note that I've used before, you may find it useful.