Building my first COB with a question...

Hello Rollitup guys and gals!

WOW I have learned a lot here from reading a ton of the DIY threads and I want to start by saying how much I appreciate this forum. I even got some advice here a couple months ago on another thread before I commenced ordering parts.

It was a close contest between Vero's and Cree's. I am going to run both, but chose to start with Vero's. My first build uses a heatsink I recovered off an old (music) PA system, two of the Vero29 5K's, and some cheap and cheesy power supplies I "happened upon" on fleabay while I was scoping better ones like the HLG MW's.

I took a cell phone charger (states its 9v but measured higher, and at enough mA), removed it from its shell and mounted it to the re-purposed oddball terminal blocks I also recovered. This one ain't very pretty, but I wanted to do a "proof of concept", see it working. And of course it has raised at least one question. Here are pix of the build as it went together: The question is afterward.
raw heatsink: re-used some holes, drilled others, filed the burrs off etc.



...wet sanded with 1000 grit after scribing the locations and drilling the mount holes...

Drilled and tapped (before the final sanding...)


test mounting the vero's


The terminal block is thermoplastic...I bolted it to the side of an outside fin. Then zip tied the supply and the fan power and soldered 'em up.


...my understanding is, these should be wired in series, not parallel. Feel free to correct me if I am wrong. Wired in parallel, they both light up. Wired in series - they don't. When I wire just one COB - it (of course) lights up, and there I measure 1.75 amps of current. Being a constant current driver I will guess that the 3000 mA (3A) rating on the label is way high (duh, its chinese) but it seems like 1.75 should be enough to drive 2 in series. What am I missing (besides my mind), and what would happen if I run them in parallel (damage the COB's, the supply or both?) Not really sure...I'm fair at electronics but this tech is new to me.

Thanks for looking....hopefully other noobs can benefit from this too.

Forgot to add the pic showing my fans mounted, and the suspension chains....

Your driver reads output 21- 38V
Single Vero needs 34.20V to 40 Volts depending on current..
In series you need 2ce this voltage, which clearly your driver will not provide.

When you run them in parallel the voltage required does not double, so your setup works in parallel.

Usually recommendation is to wire them in series. In parallel if one cob fails, more current goes into remaining cobs.
However give your driver is 3000ma max, it will not fry out the 2nd cob if one fails as max for vero 29 in 4000ma.

Edit: You are seeing only 1.75 amps because driver voltage in low enough. You need close to 40V for over 2000ma operation. i suggest new power supply for led
Just curious..how much amps when both in parallel. Is it same as when single cob 1.75a?

robincnn said:

Just curious..how much amps when both in parallel. Is it same as when single cob 1.75a?

Click to expand...

Amperage
is doubled in this case

Abiqua said:

Amperage
is doubled in this case

Click to expand...

i agree double current parallel.
sorry i was not clear.
The driver puts 1.75 amps in single vero due to max voltage limitation.
i think in parallel Vf will be a little less so i was expecting between 1.75 - 2 amp in parallel.

I suspect the 3A driver may actually be a 1.75A driver (surprisingly low even for a generic driver). So if you run one Vero29 you will get 1.75A @ 37V but if you add a second (in parallel) you will get ~.85A and 35.5V each COB.

Running in series would not be an option unless you had at least a ~75V driver .

These drivers will put out 2.55A but they are $40 ea and you would need a pair
HLN-80H-36A

Thanks all! I tried to order a MW LPF-90D-48 from TRC but they told me next day they did NOT have the stock they said, would be three weeks so I cancelled.

Yep they're cheapo's...but I can get three of 'em for 45 bucks (PLUS the guy includes a Chinese 100 watt COB per supply). I did it because I already had the Vero's and wanted to do a head-to-head compare. I still plan to get some MW's though, or some from Fasttech.

Robinn, I haven't measured the current in parallel but now I'm curious. I'll do that and post first thing tomorrow just for the data point.

You sure can tell which Chinese vendors want return business vs. those that just want that one sale...these were packed really poorly and I am even thinking because they are so cheap I might strip off the back sealant and see if there is an internal adjustment to crank up the Vf...

Current across each when measured in parallel config is .89 amps per. COB (pretty much what Supra said )

These will get me started, and that's excellent data for future ID of the correct meanwell. I will measure the current again when I run them long enough to stabilize at running temp, and hopefully have an IR temp gun to measure temp. by then. Thanks all!