LEDs flashing. Any guesses why?

[MorganAtlanta]

I just built a little 8 LED array for my UAS test. I plugged them into the driver and they worked fine for a minute or so, then they started flashing on and off (all together) with a variable period of roughly one second. Any ideas what would cause this? I used an inexpensive Chinese 20W driver, supposedly giving 20-36 volts at 600mA constant current with 6 660nm and 2 455 nm "3 watt" LEDs. I'm afraid I got a bum driver, as the LEDs seem fine when I test them with a different power supply.

[kerry]

You dont have enough LED's on the driver.

[MorganAtlanta]

I think you are right... I just measured the voltage drop and it is only 19V, which is under the ratings on the driver.

[kerry]

Add a LED or two and you will have a solid lit array.

[MorganAtlanta]

I don't think I can fit another. I'll have to hit Radioshack and pick up a couple resistors.

[MorganAtlanta]

I've already got 8 on a 6" x 4" heatsink...

[kerry]

I tried the resistors but they get so HOT!!! Even with just a few ohms.

[MorganAtlanta]

Well, I took the easy route and just added three more 660nm LEDs. I figure if I'm going to burn energy, I might as well make light instead of heat. That's way more light than I wanted given the small screen, but it should fix the flashing problem, and I can always shorten the period.