Proper way to drive mains incandescent bulbs with LM3914

Hi
I would like to know how to replace the led's on the outputs of a LM3914 bar graph display to switch ten mains powered (220V) bulbs.
I was thinking of using SCR's? TRIAC's or something.
Any schematics would be helpful. Thank you!!

You need some insulation so I think you should go for opto triacs, they usually are quite low power, depending on what you want to drive you could use an opto triac driving a proper beefy triac. May I ask what is your application for this?

JS

they won't respond as fast as LEDs

diydidi said:

Hi
I would like to know how to replace the led's on the outputs of a LM3914 bar graph display to switch ten mains powered (220V) bulbs.
I was thinking of using SCR's? TRIAC's or something.
Any schematics would be helpful. Thank you!!

Click to expand...

I would use an opto-triac, to drive a power triac.

The opto-triac (like MOC 3023) has a LED for input that can connect directly to the LM3914... the isolated output triac  is a 1A peak current part and 300mW dissipation so too wimpy to drive an incandescent lamp directly, so use that small triac to trigger a larger power triac. (like T-1619T-6I). This power triac is 16A so probably bigger than you need.

Circuit is pretty simple drive gate of power triac with a small resistor in series.

Obviously be careful about mains wiring (240V in So. Africa). The MOC is rated for 400V so should be safe at 240VAC. The triac is rated for 600V so OK.

http://groupdiy.com/index.php?topic=59542.msg756096#msg756096 see the schematic here for how I connected opto to triac... (note the schematic symbol is not accurate for the MOC.

JR

Why not simply use a solid state relay (SSR).
Many types to choose from.
e.g. https://www.sparkfun.com/products/10636
Four pins. Two for the LED, and two for the "relay contact".
Connect the SSR LED in series with the existing 3914 LEDs, so you have both displays.
Leo..

Thank guys!!!

try it but you will have a lot of failure, bulb are not designed to be lighted so intensively

The OP didn't say how long this has to work. Incandescent bulbs will not be happy toggled on/off too many times. Perhaps LED lighting would be more on/off friendly if this has to work in some permanent application.

@LeeYoo the SSR is just an opto-isolator and output triac built into a single more expensive building block.

JR

didi, I hope you get this working, and then upload a video to youtube so we can all see the results!  8)

Also, concerning the on/off lifetime of incandescents, maybe the LM3916 would be easier on the bulbs (but maybe you don't want RMS and prefer peak for some reason.. I'm just assuming you're going for a DJ light show or Star Trek effects in the studio)