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    Low Voltage Power Transforming Distribution

    1) What do I need to transform 24vac to 24vdc. I have a Qubino Flush Relay with the Temp Probe I need to power using the Furnace 24vac.
    2) I don't know much about Din Rail, but I'm thinking I need to at least look into putting all this in a small Alarm Panel type enclosure, and possibly have another stepdown 24vac or the 24vdc to 5vdc needed to power a tablet.
    3) My thermostats get power from the furnace, and maybe having this panel powered by a separate 120v to always be powering the tstat. Can you power the thermostat while still using the internal relay for actuating the furnace? I think so, and this would be one step away from an actual relay instead of an actual tstat. Would having a second hot lead on the hot post cause issues? Only if second source is from the second phase right? I'm very ifffy on power..
    Edit: I think I would simply disconnect the common hot from the furnace. The tstat would energize the heat or cool wires accordingly. Correct?
    Last edited by tome10; March 22, 2018, 07:47 PM.

    #2
    1) You need a bridge rectifier to convert AC to DC, they come in all shapes and sizes for the current you need. However because of the voltage drop across a bridge (effectively two diodes) then at the DC side you would get something like 24V - 1.4V = 22.6V DC depending on the particular rectifiers properties - you might need to thing about something else but in the last bit you say powering a furnace with AC - do you need to go DC to AC instead? That becomes unfortunately a bit more complicated and it might be worth thinking along the lines of having two power supplies and switching one from the other.

    2) DIN rail transformers are all over the internet and you can buy the rail alone to mount into your own enclosures or screw to a wall. You will likely find 24V to 5V drop down circuits somewhere or you can buy blank DIN enclosures and put your own converter in.

    3) I'm not sure on that one I am afraid without having a bit more of an idea of the internal workings, furnaces as such are not all that common here.

    Comment


      #3
      Surely the Qubino's tolerances would allow for 22vdc.
      I don't need to power the furnace, the furnace is 120, but I'm torn about using the furnaces 24vac distribution for the thermostats, or bring my own power at the distribution box. I can foresee possible reasons for cutting power to the furnace.

      Comment


        #4
        I’m not clear on exactly what you want to accomplish, maybe you could describe what you trying to do.

        With regard to the first question, Adam is partially correct. If you put a bridge rectifier on the 24VAC supply, you will end up with DC, but it will be very noisy (electrically), with quite a bit of ripple. You would need to filter it with a capacitor to get rid of the ripple. A 1000uf 40V would probably work. After that your 24VAC (assuming it is actually 24V) will be about 31-32VDC. This is because AC voltage is measured by RMS. This RMS calculation is to provide the effective voltage, not the peak voltage. A sine wave for 24VAC will be about +34V at the 90 degree point in its phase and -34V at its 270 degree point. The bridge will invert the negative phase, providing a DC with a 120HZ ripple. After the loss in the bridge and filtering the ripple, the resulting DC voltage should be around 32V.

        You might be better off using a separate power supply for the Qubino. Something like this.

        The 24V transformer in the furnace should be able to power several thermostats and I don’t see the harm in them being powered off with the furnace should you need to for maintenance. The rest of the time the furnace should be powered.
        HS4 Pro, 4.2.19.0 Windows 10 pro, Supermicro LP Xeon

        Comment


          #5
          I'm trying to figure out the best way to power multiple devices with different power requirements in one location with minimus footprint enclosure. The obvious line voltage to the 'voltage illiterate' would be the 24v from the furnace, but I'm not finding any kind of 24vac to 24vdc conversion Dinrail module for the next highest requirement which is the Qubino. it appears all the line voltage Dinrail stuff is 120 anyways. I searched for 24v bridge rectifier +Dinrail and didn't find anything. So it appears I would have to run 120 into the panel?

          Tstat=24vac
          Qubino=24-30vdc. (this can be powered by 120 supposedly, but it is pretty small, it doesn't look safe to power via 120.
          Led Light Strip(Future)=12vdc
          Tablet=5vdc

          Comment


            #6
            Originally posted by tome10 View Post
            I'm trying to figure out the best way to power multiple devices with different power requirements in one location with minimus footprint enclosure. The obvious line voltage to the 'voltage illiterate' would be the 24v from the furnace, but I'm not finding any kind of 24vac to 24vdc conversion Dinrail module for the next highest requirement which is the Qubino. it appears all the line voltage Dinrail stuff is 120 anyways. I searched for 24v bridge rectifier +Dinrail and didn't find anything. So it appears I would have to run 120 into the panel?

            Tstat=24vac
            Qubino=24-30vdc. (this can be powered by 120 supposedly, but it is pretty small, it doesn't look safe to power via 120.
            Led Light Strip(Future)=12vdc
            Tablet=5vdc
            I power my Qubino modules from 240V so I wouldn't worry about 120V, they will be just fine.

            If small footprint was essential then a multi output PSU might be something to research, this is just a random company I found on Google but they are available all over the .net - http://www.allpsu.co.uk/Data_Sheets/..._qu/QP-200.pdf

            So you can have 24/12/5V output in one unit with a 120V input, the issue still of difficulty is the 24VAC - I don't know enough about the insides to know whether or not it truly needs AC or not.

            Comment


              #7

              Comment


                #8
                Here is a wide range DC input to 5vdc output. I assume you have to pay attention to what your line amperage is in some fashion. 48v POE seem to have low Amperage ratings. I found a 48vdc wall wart that had a 600ma rating. Say I wanted to run two tablets on the 5v output of this. I guess your going to gain some amperage with the stepdown from 48v, and the 5v 3amp rating would be accurate, but I also assume if you line feed with 24v you would not achieve 3amp. To emphasize; I assume the 48vdc @ 600ma into this converter will power a 1amp tablet, and an arduino running a short led @5v also? Thoughts?

                https://www.alliedelec.com/tracopowe...5-dc/70062693/

                Comment


                  #9
                  Originally posted by tome10 View Post
                  Here is a wide range DC input to 5vdc output. I assume you have to pay attention to what your line amperage is in some fashion. 48v POE seem to have low Amperage ratings. I found a 48vdc wall wart that had a 600ma rating. Say I wanted to run two tablets on the 5v output of this. I guess your going to gain some amperage with the stepdown from 48v, and the 5v 3amp rating would be accurate, but I also assume if you line feed with 24v you would not achieve 3amp. To emphasize; I assume the 48vdc @ 600ma into this converter will power a 1amp tablet, and an arduino running a short led @5v also? Thoughts?

                  https://www.alliedelec.com/tracopowe...5-dc/70062693/


                  For that price you could get 3 different voltages for the one you posted. Try Amazon US

                  And if you were ever to have a large project and trying save money or being green check these out : http://www.kiatronics.com/interface-modules.html

                  You use them to get 4 outputs from each 5V,12V or 24V input at 1AMP constant from the ones mentioned above! (1 = 4 outputs at 1amp constant)



                  Eman.
                  TinkerLand : Life's Choices,"No One Size Fits All"

                  Comment


                    #10

                    Comment


                      #11
                      Can you read again what @rprade posted? He clearly stated the disadvantages of reconverting power "back to front"===> bad idea!
                      Now that aside, you at post #8 are looking a power supply worth $77 and me at post #9 advising you that you can get three different voltage power supplies out of that price. Avoid the conversion and power the units separately!

                      Leave PoE to the Network devices e.g cameras and the like and you could get something this : WT-AF-5v10w for the tablet.




                      Eman.
                      TinkerLand : Life's Choices,"No One Size Fits All"

                      Comment


                        #12
                        There are a lot of things going on in this thread.

                        For clarification, POE is a standard for providing Power Over Ethernet for network connected devices. There is some specific handshaking required prior to the voltage being available at the connected device. It is really only a good solution for network connected devices, other powered devices would be better served by a conventional power supply.

                        For my system I evaluated the voltages I needed and provided them. I needed 24VAC for my thermostats and zone valve motors, 12VDC for RGB lighting and 5VDC for most everything else. I chose to provide a 24V transformer, a 12VDC power supply a 5V DC-DC converter off of the 12V power supply.

                        My 24VAC transformer just supplies thermostats valves and 1 relay. I chose to go with standalone power supplies for the DC requirements because they are cheap, efficient, stable and reliable.

                        A 12V power supply like this would be fine.

                        Click image for larger version

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                        I used a 10A supply, because it is distributed to several places in the house.

                        The DC-DC converters are inexpensive and reliable. I used this one. They can provide a 5V 3A output from a 12-24V DC source. Remembering that these converters are roughly 80-85% efficient, it is easy to calculate that a 5V 3A output requires approximately 1.5A at 12V for a supply.

                        Click image for larger version

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                        for about $20 you have two voltages at plenty of current. You can mount the AC to DC power supply and one or more DC-DC converters in an enclosure. If you note on the DC-DC converters, they can provide 5V at 3, 5 or 10 amps and 12V at 5 amps. I have used these for years and never had a failure. If you need 24V for LED lighting, you can go with a 24V supply as a primary supply and DC-DC converters for 12V (if needed) and 5V.
                        HS4 Pro, 4.2.19.0 Windows 10 pro, Supermicro LP Xeon

                        Comment


                          #13
                          Originally posted by rprade View Post
                          There are a lot of things going on in this thread.

                          For clarification, POE is a standard for providing Power Over Ethernet for network connected devices. There is some specific handshaking required prior to the voltage being available at the connected device. It is really only a good solution for network connected devices, other powered devices would be better served by a conventional power supply.

                          For my system I evaluated the voltages I needed and provided them. I needed 24VAC for my thermostats and zone valve motors, 12VDC for RGB lighting and 5VDC for most everything else. I chose to provide a 24V transformer, a 12VDC power supply a 5V DC-DC converter off of the 12V power supply.

                          My 24VAC transformer just supplies thermostats valves and 1 relay. I chose to go with standalone power supplies for the DC requirements because they are cheap, efficient, stable and reliable.

                          A 12V power supply like this would be fine.

                          [ATTACH]68671[/ATTACH]

                          I used a 10A supply, because it is distributed to several places in the house.

                          The DC-DC converters are inexpensive and reliable. I used this one. They can provide a 5V 3A output from a 12-24V DC source. Remembering that these converters are roughly 80-85% efficient, it is easy to calculate that a 5V 3A output requires approximately 1.5A at 12V for a supply.

                          [ATTACH]68672[/ATTACH]

                          for about $20 you have two voltages at plenty of current. You can mount the AC to DC power supply and one or more DC-DC converters in an enclosure. If you note on the DC-DC converters, they can provide 5V at 3, 5 or 10 amps and 12V at 5 amps. I have used these for years and never had a failure. If you need 24V for LED lighting, you can go with a 24V supply as a primary supply and DC-DC converters for 12V (if needed) and 5V.
                          Sweet! Randy,

                          This one is one to treasure! Good insight and explanation! Bookmarked!




                          Eman.
                          TinkerLand : Life's Choices,"No One Size Fits All"

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