Why are the led chips flashing? Switched off. At the dimmer.

[Jaymee1]

Hi. Folks. Im having a go at replacing two cob chips. Ive replaced with 50w 3500k white.
The chip in the unit was a multi array chip. That was burnt out by over heating..as one of the cooling fans wasnt connected.. ive since connected it back up and both are working. But the chips ive installed are flashing with the dimmer switched to off. The dimmer was working fine before i removed the chips. The unit says 435w on the back. But i dont know if thats what it draws at the wall. The unit has 5 Cc drivers. All the same. Says 60-80 v at 680ma.
Have i hooked it up wrong or do i have the wrong chips.
Is the flashing caused by under powering them? And why do some leds have a resistor?

 

[Lucien Nunes]

Flashing when off suggests that the drivers are momentarily starting up on the accumulated leakage through the dimmer or its RFI suppression network. It's not clear how that would be influenced by changing the LEDs but if the ones you fitted have a different forward voltage (i.e. different number of chips in series in each package) then the drivers might behave differently. E.g. if you replace an array with a single LED the voltage will be much lower and the driver might now be working out of spec.

 

[Rockingit]

Could be residual energy in the smoothing circuit of the power supply that's taking some time to discharge and as Lucien said the replacement led's could have different characteristics with a lower resistance than the originals which is why they're reacting to it.

 

[happysteve]

Companies like Varilight have dummy loads available for this sort of thing:

Link to LEDFix PDF

 

[Jaymee1]

Flashing when off suggests that the drivers are momentarily starting up on the accumulated leakage through the dimmer or its RFI suppression network. It's not clear how that would be influenced by changing the LEDs but if the ones you fitted have a different forward voltage (i.e. different number of chips in series in each package) then the drivers might behave differently. E.g. if you replace an array with a single LED the voltage will be much lower and the driver might now be working out of spec.

Thankyou for the detailed answer. I now understand the forward voltage of the two types of leds are different. I really thought matching a wattage would have been enough.
can i measure the FV of the Array ?to match a led? . How do i match a chip to the driver? Its a CC 60-80V @680MA.
The array has 30 individual chips.
Ok does this mean . That these drivers were produced just to run these Arrays ? Only?

 

[Lucien Nunes]

30 chips x approx. 3.5V per chip = 105V so they can't all be in series as this is more than the 80V maximum available from the driver. Two strings of 15 in series-parallel gives 52.5V x 340mA per string with a minimum of 7.5V to be dropped in current balancing resistors (to help the two strings share the current equally) to make up the 60V minimum. You should be able to measure this with an ordinary DC voltage range on a multimeter.

 

[Jaymee1]

30 chips x approx. 3.5V per chip = 105V so they can't all be in series as this is more than the 80V maximum available from the driver. Two strings of 15 in series-parallel gives 52.5V x 340mA per string with a minimum of 7.5V to be dropped in current balancing resistors (to help the two strings share the current equally) to make up the 60V minimum. You should be able to measure this with an ordinary DC voltage range on a multimeter.

This is becoming a rabbit hole of epic proportion ?
I did put a meter on the chip before i removed it. To test the drivers output and the function of the dimmer.
Could you please link me to a chip suitable for the driver.. ?
I bought these ones from vocopsa.com
Your help is greatly appreciated
? TIA

 

[Jaymee1]

This is becoming a rabbit hole of epic proportion ?
I did put a meter on the chip before i removed it. To test the drivers output and the function of the dimmer.
Could you please link me to a chip suitable for the driver.. ?
I bought these ones from vocopsa.com
Your help is greatly appreciated
? TIA

https://www.ledsales.com.au/index.php?main_page=product_info&cPath=148_188_314&products_id=2313
Could someone tell me if this chip will be run by a CC driver 60-80v@680ma .
Its ratings are 50w 30-36v @1500ma
Is that doable? With a resistor?
Lucien?

 

[telectrix]

no you need a driver supplying > 36V (but not much over) with a current capacity of > 1500mA.