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View Full Version : Problem with LED light bulb and solid state relay



Moskog
02-27-2012, 07:19 PM
I bought a few solid state relays (http://www.ebay.com/itm/N-SSR-25A-Solid-State-Relay-3-32V-DC-24-380V-AC-Control-/180763037741?pt=LH_DefaultDomain_0&hash=item2a1651102d) from ebay some time ago,
(http://www.ebay.com/itm/N-SSR-25A-Solid-State-Relay-3-32V-DC-24-380V-AC-Control-/180763037741?pt=LH_DefaultDomain_0&hash=item2a1651102d)

My plan was to use these relays to control some 7,5W LED (dimable) lightbulbs from a BS2. So I took away the old light sensor and replaced it with one of those relays. The lightbulb did shine bright but when I turned off the relay the bulb started to blink. Never stopping. I replaced the light bulb with an old fasion 40W bulb and also tried an 11W energy smart light bulb. No problem. I also tried a smaller 2W LED lamp and that one could not be switced off at all.

So now I wonder, is it the low Watts that is the problem or is it the LED technology itself that has this effect on the relays?

What other kinds of solid state relays could be recommended for this kind of lightbulbs (LED 230V 7,5W) and driven by a BS2 (12V)?

tonyp12
02-27-2012, 07:35 PM
Sounds like some leakage from the 230v side comes over to the 5v input pin if the bulb uses to little of power.
How do you connect the 5v pin to the BS2?, tro to connect a 4.7k-10k resistor to gnd on this signal pin (called a pull-down resistor)
You could just wire it between the two terminals on the solid state relay inputs side.

Franklin
02-27-2012, 07:52 PM
Some relays require a certain amount of load resistance to turn off the transistor or other device switching the load. As mentioned this may not be enough.

Moskog
02-28-2012, 10:47 AM
tonyp12, pulldown doesn't help. I did also short the input terminals but light still blink.

Franklin, guess you are right.

I could not find information on the datasheet (http://www.fotek.com.tw/pdf/etc_34.pdf) on minimum load but maybe it is the output leak current (3mA) that is enough to turn on or at least blink the lamp. 230V x 0.003A = 0,7W. Lamp is 7,5W, could that make sense?

tonyp12
02-28-2012, 03:08 PM
Pull-down resistor on the 230v side, not really a good idea as it will waste energy and get hot.
But try a 470k ohm between the terminals.

These solid state are for heavy-duty, you could/should use a much lighter version for LED lights.
Or make your own, though high volt warnings.

Peter KG6LSE
02-28-2012, 03:36 PM
SImple issue .
\
Considering that most LED and CFLs are running on a Switch mode supply of some kind ..

there is never a true Zero Crosing event to have I and V {E} = 0 ..

Most AC SSRs are based often on Thyristors Like SCRs and TRIACs .

They dont like non linear loads ( bad power factor PF )

You need to get some that are MOSFET or IGBT. but AC .

I had the Same issue with my LEDs and a dimmer ..


Post Edit ... What frankln said is spot on .. SCRs need to Cross a lower threshold to shut off ....


Peter..

Circuitsoft
02-28-2012, 04:52 PM
Pre-rectify your AC input, and use this:
PS2535-1-A (http://search.digikey.com/us/en/products/PS2535-1-A/PS2535-1-A-ND/2601900)

It'll drive 120mA to the output if you put more than 30mA into it (it'll take up to 50mA and would probably work with 10mA), and can handle 350V, so 230V rectified shouldn't be a problem.

Otherwise, try TLP3023 (http://search.digikey.com/us/en/products/TLP3023(S,F)/TLP3023(SF)-ND/871276). It'll take 100ma, needs far less gate drive, and should still have a small enough leakage to not activate the LED light.