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Solid state relay flashing.

Pommie

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I have this SSR controlling four 230V 10W LED bulbs. With the inputs open circuit or both grounded the bulbs flash about once per second. Anyone come across this before? Any and all suggestions welcome.

Mike.
 

gophert

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That's why I prefer bare LEDs - is it the lamp flashing or the relay falsely triggering?
Can you post a schematic or a photo?

Do you actually ground the inputs or did you do that through code?

Is there a static charge issue?
 

Pommie

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I noticed, after I posted above, that only one bulb was flashing. Removing that bulb caused a second to start flashing. I figured it had to be due to some minute leakage current so added a 100k resistor in parallel with the bulbs. Voila, all working as expected.

First time using a SSR and wonder if it's normal to get leakage current like this?

Gophert, I grounded one via code but then disconnected both. I'm now fairly convinced that it was a pesky leakage current.

Mike.
 

kubeek

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The datasheet says that the maximum off-state current is 5mA. That is enough to hurt when touched, so no wonder it slowly charges the cap in the led bulbs and lets them start for a brief moment.
 

Pommie

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Looks like I got lucky. If the full 5mA was leaking then my 100k (1/8W) resistor would be totally inadequate.

Mike.
 

Reloadron

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Happens all the time and has shown up in this forum a few times. The cause is a leakage current inherent to the SSR. Without going into great detail one option is to place a resistor across the load (LED) so when off the LED remains off. One of my front porch lights has a LDR so even if left On at night, come daylight, it turns off. I replaced the incandescent lamp with a 120 VAC LED. Neighbor calls me asking why one of my front porch lights is blinking. :)

In a nutshell if you take a hammer to the LED bulb you will find a small circuit board. On that board is a capacitor with several other components. The leakage through the SSR slowly charges that capacitor until the charge voltage reaches a point where the LED turns on. When that happens the cap discharges through the LED and then the cycle repeats.

Anyway what you are seeing is common and normal when using a SSR with an AC Voltage LED bulb.

Ron
 

kubeek

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Lot of people just use an X rated 400V foil cap parallel to one of the bulbs, 470nF should be more than enough. No energy wasted there, but some discharge resistor in the Megs would be a nice touch to add.
 

gophert

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Most Helpful Member
If you'd be controlling a 0.5HP motor or a 500 watt bulb with that relay, you'd never notice a problem. This pops up when you select a relay for a relay suitable for 700 watts for a 30 watt load.

A properly sized relay would have had only 10uA of leakage current (max) ... and half the price.


 
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