EmmienLightFan Posted February 13, 2015 Share Posted February 13, 2015 I have loads of DC LEDs that I would like to include in my show, so I brought a 24 Channel RGB/Non-RGB DMX Dimmer (24v). It is rated at 3amps per channel and 5-24v. The first one I received, wet (Capaciter blew) but now I have the replacement. It works fine on some DC incandecent lights (It works really well) but the first set of leds I connected come on really dim, and get dimmer as it goes along the string, and theres nothing by about half way. The same happens when I connect my icicles directly to the power supply. (Power supply: 24v 2.7a, Blue LED rating: 24v 12va, Icicles rating: 24v 18va)I have bypassed a flasher on the icicles, but the blue ones are intact, but with a different power supply. I even connected the power supply to some lights with the flasher (Using a female to two wires adapter) and nothing happened at all. I don't want to keep fiddling and testing as I will most likely break something. I'm confused. Link to comment Share on other sites More sharing options...
Max-Paul Posted February 14, 2015 Share Posted February 14, 2015 Ok, there is no need for a capacitor in a LED string that is using a D.C. source of power. And just to review, LED are polarity sensitive in a D.C. Power source environment. So if they dont light swap the leads on the terminals (LED not power supply). As for why the lights are dimming and totally out half way through the string. Sounds like a voltage and resistance issue. What is the voltage out of the controller where the leads are attached to the channel terminals? How long are the leads from controller to the first LED lamp? What gauge is this wire? What is the voltage at first LED lamp? Link to comment Share on other sites More sharing options...
EmmienLightFan Posted February 14, 2015 Author Share Posted February 14, 2015 The leads on the icicles are short. About 10 inches to the first bulb. The blue leds have the original cable cut where the power supply would be, about 5 meters. Link to comment Share on other sites More sharing options...
EmmienLightFan Posted February 14, 2015 Author Share Posted February 14, 2015 Here is some pictures. Read the comments/descriptions to understand what is going on/what it is. (Click the i in the circle at the top when viewing a picture)https://drive.google.com/folderview?id=0B6dCx7Jc8zNnfkxlc3d2dHNRZ2VwNElxLWVtcmRtMEduNXg1ekVOTVVBS1hURHFQSDJVU1E&usp=sharingIf you need to know anything more, just ask. Link to comment Share on other sites More sharing options...
Max-Paul Posted February 16, 2015 Share Posted February 16, 2015 You show 3 different power supplies. So, which one are you using in this application? It appears that this string has several sections to it. each consisting of about 9 LED per section. But looks like the string needing about .4A per string. The one power supply is 3VA which is another way of saying wattage. 3 watts @ 24VDC means that you are only supplying .012A So if your using the one in the wall with the two wires in screw terminals. Remove it and use the rectangle one that is rated at 2.5 Amps as I remember it. Oh and so your going to be 5 meters between lights and controller. What size wire are you going to use? to be on the safe side, go no smaller than 22 ga. Link to comment Share on other sites More sharing options...
EmmienLightFan Posted February 16, 2015 Author Share Posted February 16, 2015 The one in the wall is the one that came with the lights. The rectangle one I purchased later to use with the dimmer with several strings of lights connected. It is brighter with the original one rated at 3 watts, although this new power supply is 65 watts. (2.7 amps) I have not decided how long the wires between lights would be. I think it will be about 5 meters. I have not added any wire or taken it away, that's the amount that came with it.I don't know how the lights can be brighter with a less powerful power supply. The same thing happens with some icicle lights. They are bright with their original power supply, and dull with this new one. Could there be something special in the power supplies? Link to comment Share on other sites More sharing options...
Steven Posted February 19, 2015 Share Posted February 19, 2015 I suspect that the original power supply is AC, not DC. It's rated in "VA", which is almost never used with DC (because with DC, it's the same as W). Link to comment Share on other sites More sharing options...
Max-Paul Posted February 19, 2015 Share Posted February 19, 2015 The one in the wall is the one that came with the lights. The rectangle one I purchased later to use with the dimmer with several strings of lights connected. It is brighter with the original one rated at 3 watts, although this new power supply is 65 watts. (2.7 amps) I have not decided how long the wires between lights would be. I think it will be about 5 meters. I have not added any wire or taken it away, that's the amount that came with it.I don't know how the lights can be brighter with a less powerful power supply. The same thing happens with some icicle lights. They are bright with their original power supply, and dull with this new one. Could there be something special in the power supplies?As Steven points out. The power cube in the wall is A.C. (thanks Steven I missed about it being A.C.). Ok A.C. Voltage is actually the RMS (root mean square) of D.C. voltage. Let me use some numbers that I can work with in my head. 10VDC is 10 volts. While 10VAC is got a peak voltage of 14 volts. Thus they look brighter. When I make a LED string for special purposes. I keep this peak voltage in my mind and if I want to design a string of LEDs to operate on 10VDC but really going to use them on an AC circuit. I will measure the AC to be 7 volts knowing the peaks will be at 10 volts. Link to comment Share on other sites More sharing options...
EmmienLightFan Posted February 20, 2015 Author Share Posted February 20, 2015 (edited) My dimmer is DC only, so how can I get them to work? The dimmer can only do 12-24 volts. Would it be safe to move half of the stuff from my CMB24 and put it on this, and use the dimmer for the stuff that was on there, and then find a more powerful AC powersupply (How much exactly?) and use it on the CMB24? Or could I just get an AC power supply and use it withnthe CMB24? Edited February 20, 2015 by EmmienLightFan Link to comment Share on other sites More sharing options...
Steven Posted February 21, 2015 Share Posted February 21, 2015 No, the CMB24 does not work with AC. You have several options:As Max-Paul mentioned, you can run LEDs that were designed for 24VAC with a higher DC voltage. The CMB24 card works up to 30VDC, so you could get a 30VDC power supply and try that. However, due to the non-linear nature of LEDs, we can't know the exact DC voltage that will get you full brightness while not reducing life time. It is possible, with some modifications, to use a CTB16PC board with low-voltage AC. Someone on this forum used one with 12VAC landscape lights. The part you have to modify is the power supply for the electronics, because the on-board transformer is designed for mains voltage (120 or 240 VAC). To test this idea, you can remove the jumpers between the left and right sides of the board, power the right side with mains as usual, and power the left side with low voltage AC. If you only need on/off, you could plug the original power supply into a channel on a CTB16PC board, and just turn the mains voltage on and off (dimming will usually destroy the power supply). You could also use the DC board to power relays that can switch the lights on and off. Link to comment Share on other sites More sharing options...
EmmienLightFan Posted February 21, 2015 Author Share Posted February 21, 2015 I have one CTB16PC and it is full with incans, but if I had to I could buy another, but shipping to the UK when it is not much coming is not worth it (Adds about another third of the cost) I thought the CMB24D can do 60v.I can get one of those changeable bench power supplies and try different voltages (My current one only does up to 24v). Could I test the original power supply with a multimeter for DC only? Would it work or could it break it? Link to comment Share on other sites More sharing options...
Steven Posted February 21, 2015 Share Posted February 21, 2015 I have one CTB16PC and it is full with incans, but if I had to I could buy another, but shipping to the UK when it is not much coming is not worth it (Adds about another third of the cost)I suggested to try it as a test only. If it works, then maybe you can add it to a future bigger purchase, or find someone locally who will sell or loan one. I thought the CMB24D can do 60v.The data sheet says 5v to 30v, but you shouldn't need more than 30. I can get one of those changeable bench power supplies and try different voltages (My current one only does up to 24v).That sounds like an excellent idea. Could I test the original power supply with a multimeter for DC only? Would it work or could it break it?The original power supply is 24VAC. Measuring its exact voltage won't help, because the response from the lights is different between AC and DC, and you can't use AC with the CMB24D. Link to comment Share on other sites More sharing options...
EmmienLightFan Posted February 23, 2015 Author Share Posted February 23, 2015 I think I will get a variable bench power supply and use one side of my CMB24, and put the lights that were on it on the DMX controller I was planning on using for the other lights. Unfortunately, as I am one of two LOR users in the UK (The other is at the other end of the country), it is really expensive to get another CTB16PC. Thank you very much for your help, Steven and Max-Paul! I was really confused and would definitely have broken something if it wasn't for you!!! Link to comment Share on other sites More sharing options...
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