Running multiple COB's in a row
- Thread starter spazatak
- Start date
epicfail
Well-Known Member
I'm not sure how MrFlux has his hooked up exactly (parallel?) but you can use a driver like the Meanwell HLG-185H-Cxxxx which would allow you to hook up 4-7 cxa3070's at 700mA or 3-5@1050mA in series. When using a driver like this you are introducing high voltage (up to 286v@700mA) into your system which could be dangerous and even fatal to anyone not educated in how to work with it. On the other hand using 1 low voltage driver per cob is much safer as our skin can resist electricity to a certain point.
Positivity uses the high voltage inventronics divers to power his cobs with some reds in series i believe.
So though it might look nicer with less drivers, I'm not sure I could recommend the average DIY hobbyist do this. You are not going to kill yourself if you mess something up with low voltage.
Positivity uses the high voltage inventronics divers to power his cobs with some reds in series i believe.
So though it might look nicer with less drivers, I'm not sure I could recommend the average DIY hobbyist do this. You are not going to kill yourself if you mess something up with low voltage.
spazatak
Well-Known Member
GroErr
Well-Known Member
Hi guys, I'm just in the early stage of spec'ing out whether I want to bother with a DIY build. I think the one-one ratio is probably easier/safer. BUT, it would be nice if there were a power supply that could handle say 4x 3070/50W COB's safely, just neater and easier imo. I'm thinking something like the Meanwell HBG-240-48, or HBG-240-60 could handle 4x50W 3070's well, and safely. Other than the voltage warning, any reason this would not be a good idea?
CaliWorthington
Well-Known Member
You can use single low-voltage DC drivers for each COB and just run multiple cables and/or multipair to each heatsink.
spazatak
Well-Known Member
yeah I like those bars that flux has.
Would be great to have four bars with 3 50 watters on each or a combination similar but dont trust myself with electricity...
Positivity
Well-Known Member
Ive questioned my decision to use high voltage drivers multiple times.
I wouldn't have if it was my first project. You need to build a few successful low voltage ones first. If your getting shocked building those you have no business using the high voltage drivers.
With that said..I've built a few and taken apart every light I've bought. My connections are better...my wire management is better..my tool selection is better..I've got a lot better all around since I started.
I'm still trying to learn as much as possible..not 100% confident as I'm not a trained electrician. But I take every precaution I can.
I do the same with low voltage..just good practice I think.
And it's another reason I'm considering casing every light I build in the future. It will cost more...but will give ample room for immaculate wire routing and securing.
I wouldn't have if it was my first project. You need to build a few successful low voltage ones first. If your getting shocked building those you have no business using the high voltage drivers.
With that said..I've built a few and taken apart every light I've bought. My connections are better...my wire management is better..my tool selection is better..I've got a lot better all around since I started.
I'm still trying to learn as much as possible..not 100% confident as I'm not a trained electrician. But I take every precaution I can.
I do the same with low voltage..just good practice I think.
And it's another reason I'm considering casing every light I build in the future. It will cost more...but will give ample room for immaculate wire routing and securing.
epicfail
Well-Known Member
To be honest I don't really understand how MrFlux has his lights hooked up, it confuses me as i am new to this. I'm not sure how he is able to run 5 stings of 5 vero10's on 1 driver, 25 cobs total. The vero10 have a typical Vf of 26.7v, so 25x26.7v = 667.5v and the driver he is using is only capable of 143v@1400mA. I know it has something to do with the whole parallel string thing, im going to have to do more reading.
The HLG-185H-C1400 can handle 3 3070's at 1.4mA. The HBG-240-48 and HBG-240-60 are 48v and 60v drivers, if there is a way to hook these up I don't know how to do it and would like to learn.
I'm not sure you can use those drivers as they are not constant current. You need to add up the voltage of all the cobs in your string and get a driver that can handle that amount voltage. cxa30** have a typical voltage of 37v so 4x37=148v.
The HLG-185H-C1400 can handle 3 3070's at 1.4mA. The HBG-240-48 and HBG-240-60 are 48v and 60v drivers, if there is a way to hook these up I don't know how to do it and would like to learn.
Positivity
Well-Known Member
5 strings I think..
5 x 26.7= 133.5v....as long as each string doesn't go over the voltage. Constant voltage not constant current. Just need to stay within the wattage specs and fuses I think in case a cob goes out and the voltage jumps
Nice way of doing it
5 x 26.7= 133.5v....as long as each string doesn't go over the voltage. Constant voltage not constant current. Just need to stay within the wattage specs and fuses I think in case a cob goes out and the voltage jumps
Nice way of doing it
churchhaze
Well-Known Member
I understand what mrflux is doing and considering it myself.
You would only get 667.5V if it was 1 string of 25. When you put strings in parallel, they will all have the same voltage going across them.
It's the current that gets divided between the 5 strings. Mrflux also says that he measures the forward voltage of each vero at its desired current , and matches them that way.
either way, there's no such thing as over voltage with a DC supply (except for transients and unstable supplies which overshoot nominal values(ring)). If the driver is at 10V, the string will drop 10V.
You would only get 667.5V if it was 1 string of 25. When you put strings in parallel, they will all have the same voltage going across them.
It's the current that gets divided between the 5 strings. Mrflux also says that he measures the forward voltage of each vero at its desired current , and matches them that way.
either way, there's no such thing as over voltage with a DC supply (except for transients and unstable supplies which overshoot nominal values(ring)). If the driver is at 10V, the string will drop 10V.
Last edited:
Positivity
Well-Known Member
That's right...read about that way a while ago. The current going up and harming the other leds always scared me off
Greengenes707
Well-Known Member
The affordable driver I got that are being recommended...are pretty small and could defiantly be put into a bank or sorts...illumitex and bml come to mind. Then rust run simple smaller gauge wire out to the cobs/holders.
churchhaze
Well-Known Member
Only if the 2 have perfectly matched V to I characteristic curves. It's possible one cxa3070 could drop a few more milivolts than the other at 700mA, which would cause more current to flow down one than the other if put in parallel..
churchhaze
Well-Known Member
Thing of it like splitting a pipe , running the 2 new pipes in parallel with 1 way valves in them. You can be sure the flow of the 2 pipes combined is equal to the flow of the original pipe, but the valves must have equal resistance or more water will take the easier path. In this situation, it's somewhat challenging to balance the flow between the 2 valves.
If you instead put the 1 way valves in series, the problem is a lot simpler. You know the flow throughout the pipe is the same, so the flow through the 2 valves will be the same. Since we're using constant flow pumps rather than constant pressure pumps, it shouldn't matter how much pressure each valve drops. The pump will increase or decrease its pressure to ensure a constant flow.
If you instead put the 1 way valves in series, the problem is a lot simpler. You know the flow throughout the pipe is the same, so the flow through the 2 valves will be the same. Since we're using constant flow pumps rather than constant pressure pumps, it shouldn't matter how much pressure each valve drops. The pump will increase or decrease its pressure to ensure a constant flow.
Last edited:
alesh
Well-Known Member
Great metonymy. The challenging thing there is the fact that more water flows through the valve, the more it opens.
UKpeanuts
Well-Known Member
Thanks Church, I can relate that analogy well to VI
My driver can only output a max of 40V (ish) and if I read correctly then putting 2 cxa's in series require 36V + 36V = 72V output driver.
If I wired them up in series both cobs would drop ~ 20V.... and.....
a) They wouldn't work at all
b) They would work.
Im not to sure of my self... (hence Im asking)
What do you foresee as the pitfulls of running 1 cob @ say 650mA and 1 @750mA. part from the resulting difference in output and Tc I can't see many issues?(which is why I ask)
Kind Regards, UKP>
My driver can only output a max of 40V (ish) and if I read correctly then putting 2 cxa's in series require 36V + 36V = 72V output driver.
If I wired them up in series both cobs would drop ~ 20V.... and.....
a) They wouldn't work at all
b) They would work.
Im not to sure of my self... (hence Im asking)
What do you foresee as the pitfulls of running 1 cob @ say 650mA and 1 @750mA. part from the resulting difference in output and Tc I can't see many issues?(which is why I ask)
Kind Regards, UKP>
churchhaze
Well-Known Member
If you put 2 cxa3070 in series on a 40V supply, you are right. They would each drop about 20V. According to the characteristic curve at 20V, current will be extremely low.
The pitfalls of running one at 650mA and the other at 750mA is nothing other than being uneven. You have a point. Even if 1 chip got 100% of the current (1400mA), it would still work fine assuming it's designed to handle the heat.
The pitfalls of running one at 650mA and the other at 750mA is nothing other than being uneven. You have a point. Even if 1 chip got 100% of the current (1400mA), it would still work fine assuming it's designed to handle the heat.
UKpeanuts
Well-Known Member
Okay thanks, of course it's always reassuring to clarify with someone!
I made massive mistake in my initial post. not quite sure how. ..
I've got 2 3070s and 2 drivers. 1x1400mA & 1x1200mA dim. after I purchased them I had to alter my box size.... smaller
.
New footprint is 470mm x 450mm. I figured the 2 lights on separate drivers might be overkill in that space and so it prompted my question about running both of them from the 1400mA driver.
On a similar note I have some thoughts about the dimming driver;
if the output is dimmed using a DC PWM style (I think) doesn't this just mean that its switching the supply at a high frequency, does this high switching freq. have any negative effects on the LED attached?
many thanks, UKP
I made massive mistake in my initial post. not quite sure how. ..
I've got 2 3070s and 2 drivers. 1x1400mA & 1x1200mA dim. after I purchased them I had to alter my box size.... smaller
. New footprint is 470mm x 450mm. I figured the 2 lights on separate drivers might be overkill in that space and so it prompted my question about running both of them from the 1400mA driver.
On a similar note I have some thoughts about the dimming driver;
if the output is dimmed using a DC PWM style (I think) doesn't this just mean that its switching the supply at a high frequency, does this high switching freq. have any negative effects on the LED attached?
many thanks, UKP