DSC with Passive Hub

[deplanche]

Not sure why this popped into my head, but it did, so I will ask.

If I were to put 5V into a 4 port passive hub with a DSC connected to it, would I be able to run a set of 5V RGB lights? 

There is nothing on the 4 port passive hub to worry about, so I think that would be fine.  I think it would just be a question of if the "brains" of the DSC would be getting enough power to function.  I think we usually have to get it down to 5V or 3.3V anyway, so seems like it could be a possibility.  But if is expecting 12V to get down to the lower voltage, it might not work. 

[JonB256]

Simple answer - No.

The Smart String controllers are designed for the 3-wire TM1804 and TM1809 pixel control chips. (Data, +12v and Common) They are all 12vdc (at least, from the Wiki and Ray Wu, they're only 12vdc).

The Dumb String controllers also assume you are using 12vdc strings because the controllers uses regulators to power the PIC based on 12vdc input.

Everything is designed for 12 volts.

Too much work to modify. Would be easier to just use controllers designed for 5vdc.

[tbone321]

The hub will not care burt the controllers will.  You would also have to remove the 5V regulator from the controller and jump the input directly to the output and making these modifications kinda goes against the purpose and desires of the creator of both the site and the equipment.  There is also no way to know how the controller would operate with this mod and if things didn't work as expected, you would be on your own to figure out why and how to correct it.  This is why changes like this are not liked or really allowed.  If everyone start making willi-nille changes to the equipment, it quickly becomes jut about impossible for the group to support it.  We went with 12V for a reason and that was to eliminate the need to have multiple power injection points in the strings which is typically required for 5V strings of any real length. 

[deplanche]

I wasn't planning on any modifications to any of the equipment.  I don't have enough knowledge to try to do that and not be afraid I would light my house on fire.

I was thinking more along the lines of the MR16's, which were originally designed for a specific input voltage (I think 12V), but will work with a range of voltages (7-24V).  But it sounds like that is not the case here.

Thanks.

[n1ist]

We seem to confusing smart and dumb strings here.  The original question was about dumb strings.  The DSC takes the input voltage and uses it three ways: To power the LED strings, to generate 5V for the level shifter chip, and to generate 3.3V for the PIC.  The 5V regulator needs at least 7V to work correctly so you can't run an unmodified DSC on 5V.


Since the DSC uses low-side switching, I would power the DSC as usual with 12V from a passive or active hub, and to use a separate 5V supply (or the 5V output if you are using a PC supply) to power the LEDs.  Just connect 5V to the LED's common anode (+ terminal) and don't connect that lead to the DSC.
If you are using a separate 5V supply, connect it's negative terminal to the ground terminal that the pigtail is connected to.

/mike

[tbone321]

LOL, I didn't even think about the 5V output on the PC supply.