scubado Posted October 11, 2010 Share Posted October 11, 2010 Here's the senario, hope it makes sense to you. I have two large octogon flower beds with WRGB leds. The whites I have individual channels for each side, the colors are tied together for one channel each color. I have two computer power supplies hooked up to my DC brd, one for 1-8 and the other for 9-16. The positive feed for one flowerbed is from 1-8 and the positive feed for the other is from 9-16. Here's the problem, when I plug in 1-8 power supply, the fan on the other power supply is on, this tells me the supplies are somehow wired parralel and not separate like they should be. The hazard is this, The supplies put out 12V 4A each, if a channel has a short, the supply should shut off no harm done. But sinse these are in parallel I have 8A to fry the crap out of a mosfet. I have fixed the short and repaired the board and added 4A fuses to the power supplies, but still have 8A potential to fry something. One supply can't handle both flowerbeds if I have more than two colors on.Some additional clarity, the flowerbeds are parallel, what one does the other is the same. the negative side from both beds are tied together, the positive is tied to gether on each bed but not connected between the beds.Feel free to fire away or ask additional questions... Link to comment Share on other sites More sharing options...
Guest guest Posted October 11, 2010 Share Posted October 11, 2010 Don't quote me on this, but from my experiences with power supplies, you'd need to keep them both completely seperate, that is nothing tied together between them, I think as long as they are tied together at the negatives, this problem will continue until you seperate each negative to each independent power supply, just like the positives are independent to each power supply unit. As it is, it sounds as you have themn tied together in a series/parallel type of circuit, and I would think they'd both need to be completely independent of each other to prevent the possible issue you may have. Link to comment Share on other sites More sharing options...
Guest guest Posted October 11, 2010 Share Posted October 11, 2010 scubado wrote: Here's the senario, hope it makes sense to you. I have two large octogon flower beds with WRGB leds. The whites I have individual channels for each side, the colors are tied together for one channel each color. I have two computer power supplies hooked up to my DC brd, one for 1-8 and the other for 9-16. The positive feed for one flowerbed is from 1-8 and the positive feed for the other is from 9-16. Here's the problem, when I plug in 1-8 power supply, the fan on the other power supply is on, this tells me the supplies are somehow wired parralel and not separate like they should be. The hazard is this, The supplies put out 12V 4A each, if a channel has a short, the supply should shut off no harm done. But sinse these are in parallel I have 8A to fry the crap out of a mosfet. I have fixed the short and repaired the board and added 4A fuses to the power supplies, but still have 8A potential to fry something. One supply can't handle both flowerbeds if I have more than two colors on.Some additional clarity, the flowerbeds are parallel, what one does the other is the same. the negative side from both beds are tied together, the positive is tied to gether on each bed but not connected between the beds.Feel free to fire away or ask additional questions...So the first question would be..why not one supply to handle the load for both...not sure your current requirements, but sounds like 15-20A will suffice...probably less.As far as what is happening, I would assume it is the fact that while your supplies are 2 separate units, the fact your returns are all tied together is what is causing you the grief.I think you either need to go with one supply, or split the beds completely. Link to comment Share on other sites More sharing options...
Geoff Harvey Posted October 11, 2010 Share Posted October 11, 2010 The DC board has a common +ve; all the +ve outputs and the +ve supplies are common for the entire board (both sides). The board controls by switching the negatives. With the wiring as described (common -ves), I would be surprised that you get any control.I do use separate power supplies on some DC boards, but it is essential to ensure that each of the negatives is ceparately connected to the light strings. Using 2 supplies on each side of the board will work, just ensure that you wire them and the LEDs as if they were different voltages. I would NEVER connect supplies in parallel as it is difficult to predict how they will load share.Regards Geoff Link to comment Share on other sites More sharing options...
Guest guest Posted October 11, 2010 Share Posted October 11, 2010 Geoff Harvey wrote: The DC board has a common +ve; all the +ve outputs and the +ve supplies are common for the entire board (both sides). The board controls by switching the negatives. With the wiring as described (common -ves), I would be surprised that you get any control.I do use separate power supplies on some DC boards, but it is essential to ensure that each of the negatives is ceparately connected to the light strings. Using 2 supplies on each side of the board will work, just ensure that you wire them and the LEDs as if they were different voltages. I would NEVER connect supplies in parallel as it is difficult to predict how they will load share.Regards GeoffGood point..forgot it was switching the returns.. Link to comment Share on other sites More sharing options...
scubado Posted October 11, 2010 Author Share Posted October 11, 2010 Let me see if I can make this a little clearer. All the positives from one bed are connected together and powered from one supply. All the positives from the other bed are tied together and supposed to be running off the other supply. The two banks of 8 are supposed to be separate hense two fuses on the board and two inputs. ALL the negatives for red are tied together and on one channel and the same for green and blue. The white negatives are each side together, in other words, side 1 from both beds are together and on one channel. The whites can chase around, but the other colors cannot until I get more cards next year. Yes I can put in a bigger supply, but if there's a short somewhere it will fry the mosfet unless I put a fuse on every channel.What I don't get is how the one supply is feeding into the other.Another observation sinse the lights are running at night now, I currently have only one supply running right now. The bed that gets the direct power is much brighter than the one getting the bleed through power. Link to comment Share on other sites More sharing options...
-klb- Posted October 11, 2010 Share Posted October 11, 2010 So you have your positives, per bed tied together, and as long as they are on 1-8, or 9-16, that is fine.But I am not clear on how you have your negatives tied together. Is it all red, from both beds? If so , that may be how it is cross feeding. Link to comment Share on other sites More sharing options...
Geoff Harvey Posted October 11, 2010 Share Posted October 11, 2010 There was an error in my earlier post as it's been a while since I initially tested various circuit configurations. On the DC board, the +ve supplies are NOT tied together as previously stated, it is the -ve supplies on the board that are common. On each bank of the board, the +ve supply and all +ve outputs are common, but separate from the other bank. The -ve outputs are all individually switched, but the two -ve supply inputs are common.I originally checked this aspect a couple of years back when I was looking to connect a multi-colour multi channel string with each colour separately controlled. These strings had +ve commons, but required different overall voltages. After investigation, I decided the use of 2 banks with separate voltages was not possible because the -ve supplies were connected on the DC board, but the +ves were all connected at the string common.I'm fairly sure that this is where your cross feed occurs.Regards Geoff Link to comment Share on other sites More sharing options...
cmoore60 Posted October 12, 2010 Share Posted October 12, 2010 Sounds like some type of a sketch will be needed to actually see what you have connected. Sketch does not have to be perfect, but should be accurate.I work in an environment where we do run redundant supplies and they are often tied together. Granted this is for fail safe operations and the supplies have a very touchy crowbar to take them off line should a short occur.There is no harm in connecting either the positive OR the negative side of the supplies together. Sounds like by the description you have un intentionally tied both together.Draw out the circuit accurately and I would not be surprised if you find the error.Chuck Link to comment Share on other sites More sharing options...
rmturner54 Posted October 12, 2010 Share Posted October 12, 2010 The CMB16D , dc boards are a common anode configuration. Meaning the postive outputs are shared and the negative outputs are controlled.So if you wanted to hook up a RGB device you could use a 4 conductor cable instead of 3 each 2 conductor cables.One wire would be for the positives and each of the remaining 3 wires to each color.I use a lot of 4 conductor in my display, it saves cable runs. I USE A SINGLE POWER SUPPLY FOR MY DC DOARDS Link to comment Share on other sites More sharing options...
scubado Posted October 12, 2010 Author Share Posted October 12, 2010 rmturner54 wrote: The CMB16D , dc boards are a common anode configuration. Meaning the postive outputs are shared and the negative outputs are controlled.So if you wanted to hook up a RGB device you could use a 4 conductor cable instead of 3 each 2 conductor cables.One wire would be for the positives and each of the remaining 3 wires to each color.I use a lot of 4 conductor in my display, it saves cable runs. I USE A SINGLE POWER SUPPLY FOR MY DC DOARDSDo you use fuses on your channels for protection?I am using 5 conductor thermostat wire, four color, one common. I think what I'm going to do is fuse the common positive lines and remove the 4A fuses from the power supplies. I need to see if I have bigger supplies, I still haven't tried the high powered leds yet, trying to get past this hurdle first. Link to comment Share on other sites More sharing options...
rmturner54 Posted October 12, 2010 Share Posted October 12, 2010 No I dont use fuses on each output, just the fuse protection from the power supply. Link to comment Share on other sites More sharing options...
scubado Posted October 12, 2010 Author Share Posted October 12, 2010 rmturner54 wrote: The CMB16D , dc boards are a common anode configuration. Meaning the postive outputs are shared and the negative outputs are controlled.So if you wanted to hook up a RGB device you could use a 4 conductor cable instead of 3 each 2 conductor cables.One wire would be for the positives and each of the remaining 3 wires to each color.I use a lot of 4 conductor in my display, it saves cable runs. I USE A SINGLE POWER SUPPLY FOR MY DC DOARDSDo you use fuses to protect your channels?I use five conductor 18awg thermostat wire, four color, one common.I think what I'm going to do is, remove the fuses from the power supplies (the ones I added) and install the fuses on the positive feeds. I did a quick search and I found I have a bigger power supply to use. I haven't tried my high powered leds yet, trying to get past this hurdle first. Link to comment Share on other sites More sharing options...
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