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4hv.org :: Forums :: General Science and Electronics
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Mains constant current LED driver wont turn 'off'

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Avi
Tue Jan 06 2015, 03:04AM Print
Avi Registered Member #580 Joined: Mon Mar 12 2007, 03:17PM
Location: Melbourne, Australia
Posts: 410
When using a mains constant current LED driver in series with a solid state relay, when 'off' the LEDS keep flashing. What method should be used to stop this from happening?
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Dr. Slack
Tue Jan 06 2015, 09:23AM
Dr. Slack Registered Member #72 Joined: Thu Feb 09 2006, 08:29AM
Location: UK St. Albans
Posts: 1659
Use a real coil'n'contacts relay, which has an off current much nearer to zero, than an SSR, whose off current is clearly enough to keep your load active.

Either that, or parallel a heavier load, like a light bulb, with your constant current LED driver input, to load the SSR's off current to below the driver's minimum working voltage. A bulb would be the ideal load for this, as cold, its resistance is an order of magnitude lower than hot, so it will load better when cold, and waste less when hot.
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Avi
Tue Jan 06 2015, 10:57AM
Avi Registered Member #580 Joined: Mon Mar 12 2007, 03:17PM
Location: Melbourne, Australia
Posts: 410
what about putting a resistor that draws 1/4 watt with mains voltage across it? (about 250k?). would that do anything?
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dexter
Tue Jan 06 2015, 12:11PM
dexter Registered Member #42796 Joined: Mon Jan 13 2014, 06:34PM
Location:
Posts: 195
Avi wrote ...

what about putting a resistor that draws 1/4 watt with mains voltage across it? (about 250k?). would that do anything?

it all depends of how much current if flowing through the SSR in the OFF state
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Avi
Tue Jan 06 2015, 05:08PM
Avi Registered Member #580 Joined: Mon Mar 12 2007, 03:17PM
Location: Melbourne, Australia
Posts: 410
is there a standard practice for such issues? a parallel resistor? capacitor? something else? a different method entirely?
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Sulaiman
Tue Jan 06 2015, 09:26PM
Sulaiman Registered Member #162 Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140
'normally' the led + resistor would be an indicator
across the actual load,
which would be of low enough resistance
to ensure that the L.E.D. does not illuminate.

Why use an SSR to drive just an LED?
Try it with your intended main load and the LED will not light.
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BigBad
Tue Jan 06 2015, 09:58PM
BigBad Registered Member #2529 Joined: Thu Dec 10 2009, 02:43AM
Location:
Posts: 600
It's probably the current through the snubber capacitor is enough to turn the LED on. I would think that a resistor in series with the LED driver circuit would knock the volts low enough to switch it off more reliably; perhaps 100k or so; it forms an RC circuit with the snubber which would be about 1e-6F, so you want the roll off to be well below the mains frequency, so that would be about 1.6 hz, sounds OK unless I've stuffed the maths up (quite possibly).
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Avi
Thu Jan 08 2015, 03:44AM
Avi Registered Member #580 Joined: Mon Mar 12 2007, 03:17PM
Location: Melbourne, Australia
Posts: 410
Sulaiman wrote ...

why use an SSR to drive just an LED?
There is a reed switch, switching the SSR, switching the constant current driver, to a string of LEDs.

Apparently there is a concern about the "wasted electricity" caused by the flashing LEDs, or by the solution put in place to stop the flashing which would use even more.
I then showed its less than 1 watt and cant even measure it and that the low voltage control transformer uses 1w constantly.
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Sulaiman
Thu Jan 08 2015, 09:46AM
Sulaiman Registered Member #162 Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140
You could use an opto-triac without zero-crossing switching
for low leakage, e.g. MOC3051 Link2

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BigBad
Fri Jan 09 2015, 01:43AM
BigBad Registered Member #2529 Joined: Thu Dec 10 2009, 02:43AM
Location:
Posts: 600
If you're using a snubber cap with the SSR then you may be able to replace it with a faster TRIAC with better dv/dt characteristics and ditch the snubber entirely.

What size of "on" current are we talking?
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