Building a DHT End Node

[papa]

Building a DHT End Node (on a prototyping shield) with DHT temp/humidity sensor, push button, & relay control of AC devices

Also see the Oct 17, 6:10pm post below for a "Simple DHT End Node" with just a DHT Sensor built not on a shield, but on an Arduino compatible.

See this Building an RFM69 Home Automation Network (Beginners ??) thread on how to build & program a necessary Gateway & also program this DHT End node.

Parts needed for each DHT end node: You need a Buono Uno Arduino compatible switched to 3.3 volt mode. (Or you could instead use a regular Arduino Uno compatible hacked to 3.3 volt operation like this.) You also need an Arduino prototyping shield with 2 push buttons AND with soldering strips in the middle originally intended for mounting Integrated Circuit packages (pics in a post below show its top & bottom). You also need:  a BC547 transistor, a DHT11 temperature / humidity sensor, a SSR-10DA (DC to AC) solid state relay, a supply of 22 gauge insulated wire (at least red, black, & yellow) plus tools & solder to assemble the above.  For a DS18 temperature sensor, you also need a 4.7 kilo ohms resistor. Some resistors (like for the DHT sensor) were eliminated via what I documented in thread Simplify End Node w Arduino internal pullup resistors.  Somewhat optional but recommended: more colors of wire & heat shrink tubing.

You also need enough break away header strips (including sockets you will "waste" in between the following sections) to create four 3-socket header sections, one 4-socket header section, & one 5-socket header section.  Here's a source for Break Away Female Headers (.1" spacing).  These have female sockets on top & male pins for installation on the bottom. To use: Count how many female sockets you need, then pull the male pin beneath the next socket. Score (cut a small groove) around all sides of that "wasted" socket middle. Put 1 set of pliers on each side of the scoring. Gently twist to break the strip at the scoring.  A slightly different method is here though I recommend trimming against something hard & flat, not one's thumb. My favorite method now is using a coping saw to cut a groove on one or both sides of the "wasted" socket then use my hands to break along the grooves.  (Without damaging a wanted socket, be sure to trim off ALL of the wasted socket (or it could get in your way).

This post continues with assembling a DHT End node on a Prototype Shield chosen & adapted for extra 3.3 volt connections. The Shield is then plugged on top of an Arduino compatible in 3.3 volt mode.

     Prepare a DHT11 Temperature / Humidity sensor to plug into the shield you are creating.  Immediately below is the sensor's "hashed" front with the connecting pins labelled.  Vcc is power & NC means "not connected."

      (Click on the images for a larger view.)

     The pins are too short & too thin for our purposes.  Cut 22 gauge insulated wires about 1.5 inches long:  one red for 3.3 volt power, one yellow for data, & one black for Gnd. From each wire, strip insulation from one end for soldering to a DHT11 pin.  From each wire, strip the other end, so the tip will bottom out in a female header socket & the insulation will be next to the top of the socket.

     << Solder the wires to the pins like this, using the Helping Hand method for "when wire leads are too short or thin" in a Sept 28, 2015 post.  Then cut some heat shrink tubing (match colors?) to slide over the bare wire / pin joint.  Use gentle heat to shrink the tubing.  Set this piece aside to be installed later.

      Prepare a RFM69 Wireless transceiver to plug into the Shield you are building:

Here is my RFM69HC mini-board.  The hole labels on your board may be in similar locations or different.  What's important is matching each RFM69 to the correct Arduino connection.  One wire is crimped to the MOSI solder hole.  The detached wire has one end stripped to crimp on a solder hole.  Its other end is stripped to insert into an Arduino Shield socket.
  

Revised 12/7/2016:  From my research, the 1/4 wave ANT or ANA (antenna) wire for 868 or 915 MHz can be about 3 inches (80mm), about 6.5 inches (165 mm) for 433 MHz. (After soldering, you may leave the antenna straight or wind it around a pencil into a coil).  This page shows a 433MHz antenna that is some coiled & some straight.

  If components will be installed below the RFM69 radio (like the transistor for the relay below), I suggest you make the RFM69 & its plugged wires a little "roof" about 1 inch above the top of the Shield.  To prepare the RFM69 radio for this, cut the following (color coded?) wires: 4 wires 1.5 inches long (GND, MISO, MOSI, NSS); two wires 1 5/8 inches long (3.3v & SCK), & one wire 2.25 inches long (DIO0).  (If components will NOT be installed below the RFM69 radio, keep the antenna length as indicated above for your radio frequency, but the other wires may be about 1/4 inch shorter.)

As the End Node schematic indicates, SCK connects Arduino D13, MISO to D12, MOSI to D11, NSS to D10 (different from Gateway), DIO0 to D2, 3.3v to a source of Arduino 3.3 volts, & one RFM69 GND to an Arduino GND.  My RFM69 has 3 GND solder holes to choose from, & my Shield has 3 Arduino GND sockets.

     As much as possible, plan for the most possible RFM69 wires to be on the same side as the Arduino connection they need.  Using those wiring/inserting locations & having the radio above the Shield, cut each wire to be able to bend, reach, & insert into its connection socket.  For all wires, strip one end just long enough to insert into its RFM69 solder hole & crimp back over the hole.  For all wires, except ANT (ANA), strip the wire's other end to insert totally into a socket & remaining insulation stops just at the top of the socket.

     See this post about using a Helping Hands method to hold the RFM69 board & wires steady so you can solder one side of the board at a time.  Remember a piece of cardboard to protect RFM69 components from the Helping Hand alligator clip.  Also see the Sep 28, 2015 at 6:52pm post about checking the quality of your soldering with multimeter, etc.  Set the wired RFM69 transceiver board aside to install later.  RFM69 solder holes are very close together. Soldering them gets easier with practice.

[papa]

Preparing a Solid State Relay to control AC devices via an End Node.

(Click on the images for a larger view.)

      DC to AC Solid State Relay (SSR) before preparation

      Template for end cap to insulate SSR's mains voltage terminals

      SSR prepared with AC & DC connections & protective end cap

You will modify & attach an grounded extension cord (3 male prongs) to a solid state relay. (I use short extension cords, 6-8 inches, but you can use larger ones.) Near the middle of the extension cord, carefully slit about 2 inches of the outside insultation & see the 3 wires inside. Avoid using the ground wire (green?). Aim to use the hot wire (black, first choice) or neutral wire (white?). Cut this wire in the middle. Strip enough of each cut end to fit under an SSR terminal plate & snug the insulation's edge against the plate's edge. Twist the ends' wire strands to be compact. Set the extension cord aside for the moment.

Caution: You will be connecting dangerous mains voltage to your solid state relay (SSR) so you need some protective insulation for that. You can buy a clear plastic cap on eBay or like me, you can make it as follows....

We are making a TIGHT end cap to fit over the mains terminals. On light cardboard (cereal box, toilet paper tube), draw the cap's lines according to the dimensions listed on the template above (drawing is NOT to scale). Cut the line where you see "C". Lightly score the lines where you see "F" to help make neater folds.

So your markings will not show at the end, fold "in" toward the side with markings. Be sure you are capping the AC side of the relay. Position the SSR laying on its shiny metal back with the "Fotek ... SSR" label upside down." (The high voltage AC screw terminals will be toward you.)  You will install the cap on that AC side that is closest to you.

Have a hot glue gun heated. With your cap markings facing up, put section 1 under & against the SSR's metal back. To form 4 sides of the end cap, in the following order, fold these sections against the SSR: 2, 3, 4, 5, & 6. Section 6 should overlap sections 3 & 4. Positioning the sections to form a TIGHT 4-sided box, hot glue section 6 to overlap sections 3 & 4. Hold the glued area long enough to set.

Retrieve the modified extension cord.

Puncture holes thru sections 6, 3, & 4 so the stripped ends & a little insulation of the extension cord wire can snugly pass thru the puncture holes. Loosen the terminal screws. Thru each hole, insert a stripped wire end to fit its insulation snugly against the edge of each terminal screw plate. This should leave only insulated wire extending out from section 6. After inserting each stripped wire end under its terminal plate, tighten its terminal screw.

Do not proceed until you are certain the stripped ends are secure under the terminal plate AND only insulation extends from section 6.

Once the preceding step is completed, you may complete the cap: Have a hot glue gun heated. Fold section 7 over the mains AC terminals & secure it in place by folding & hot gluing sections 8 & 9 to section 7.

For safer shock protection, coat the cardboard cover with shellac, varnish, or liquid electrical tape.  Even better, in a project box, enclose the node including the relay.

This should complete the mains output side of the SSR. On the SSR's DC input side loosen the terminal screws. Under the positive (+) terminal plate, insert a stripped end of a red 24-22 gauge insulated wire (as long as you think you'll need to be able to connect to your Home Automation End Node & the wall socket for the extension cord). Under the negative (-) terminal plate, insert a stripped end of a black wire. Strip the other ends of the red & black wires to bottom out in an Arduino socket with the insulation snugged next to the socket.  Set the prepared SSR aside for now.

[papa]

 Starting from the beginning to create a DHT End Node on a 3.3 volt friendly prototyping shield.

Introduction: To build a node, on top an Arduino compatible, I plug a double-sided prototype shield made for 20 pin integrated circuits (IC) seen below. As is, besides the usual Arduino header sockets, it has 5 more power sockets (FIVE volts, not 3.3), & 5 more ground sockets. The push button at the board's corner can restart the attached Arduino. In the middle of & outside the IC area are 2 each power (5v) & ground strips. For each IC pin is a strip of 3 holes. I solder female headers on some IC pin strips (in the strip rows labeled A5 & A6 below) to create plug in connections (like when one connects a node button to a resistor & power. See that below).  See a below post for pics of the final assembly.

You may want to review soldering techniques described starting at this Sep 28, 2015 post & the break away header techniques at this Oct 10, 2015 post. The aim is to help stabilize components to be soldered, sufficiently solder components (enough for a good connection, not getting solder on nearby locations), & to assemble things in an order to provide the most possible working space on the shield. An Arduino compatible & a plug in prototyping shield have 3 GND sockets & only one each of these sockets: 3.3 volts, D0-D13. However, for what the DHT End Node schematic requires, those Arduino connections are not necessarily enough or in a convenient location. Soldering break away headers on the shield's soldering strips will increase access to needed Arduino connections. Now to continue the assembly.

In the following text & pics, labels starting with “A” or “B” are ones I added to indicate places on the Prototype Shield. Labels like “D8” refer to an Arduino digital connection labeled such on the Arduino compatible & on the Prototype Shield.

Female header sockets A1 & power strip A2 will be changed from 5 volts to 3.3 volts. To first remove those from 5 volt, cut the trace labelled B1 on the shield's bottom. Completing the 3.3 volt connection will be described in the next post starting at item 6a). Five volts will still available at the 5v Arduino socket AND the horizontal 5v strip at the middle of the IC pin strips.

For nodes I sometimes solder resistors, but otherwise plug RFM69 wires (8), transistor, Solid State Relay wires, & jumpers into the Arduino shield sockets & my add-on female headers. I add enough solder to enlarge thin component leads so they insert securely into a socket.

       Prototype Shield, Top View (labeled by Papa)
           I've bought these online like at eBay, a few US sources, several China sources.


     (Click on the images for a larger view.)
              ^^  Prototype Shield, Bottom View (labeled by Papa)

       Updated 1/29/2017
             ^^Adapted Schematic for DHT End Node with push button & connections for a solid state relay

The following instructions updated 1/28/2017 are somewhat simpler than a previous version. A pullup resistor is handled in the software instead of a physical resistor being soldered in. It's based on what I documented my thread Simplify End Node w Arduino internal pullup resistors.

When assembly is complete, the Prototype Shield push button labeled A4 (near the Arduino RST & 3v sockets) can be used as the DHT End Node button, a switch on the node to toggle the solid state relay on & off. The button's pins near the board edge are already connected to ground (GND). This is how I assemble for the button & leave room to add the DHT11 sensor & connections to a solid state relay:

1) Put the pins of a 3 socket break away female header thru the top of the A7 strip somewhat opposite the D8 socket. Use cellophane tape to hold it in place. (The breakaway header is shorter than the Arduino female headers, so fit a 1.5 inch square piece of cardboard between the Arduino female headers & on top the breakaway header. Carefully turn over the shield so the tape & the cardboard against a table surface holds the header pins completely thru the A7 strip.) To the bottom of the A7 strip, solder only the 2 header pins within B12's brown rectangle. That is, do NOT solder the pin at B4 & do solder the other 2 header pins coming thru that strip.

2) Strip the end of some insulated 24 gauge solid wire (yellow?), insert it from bottom of the A3 solder hole, & solder it carefully from the top. Make the wire long enough to curve around the A14 IC strip & reach B4, the one header pin you did not solder yet. Do NOT insert or solder the wire’s other end yet. (When soldering, you may melt insulation near solder points. Before soldering this & other wires, I recommend you put 2 short pieces of heat shrink tubing at the wire's middle where soldering is less likely to shrink tubing too soon. Then after soldering both ends of the wire, you can move the tubing close to the two solder points & shrink with a little heat to prevent short circuits.)

3) Position the wire coming from the A3 solder hole so it touches only the B4 unsoldered header pin. Carefully solder these together. Move the heat shrink tubing to both ends of the wire & shrink with moderate heat. Make a short insulated 22 gauge jumper wire with right-angled bared ends to go from the Shield's Arduino D8 socket (on the shield's top) to a socket on the header which is soldered to A7. Clip off pieces of wire & resistor leads that extend from where they are soldered. Save the clipped off pieces for using later in the project.

Via the jumper between D8/A9 & a female socket soldered to the A7 strip, the DHT End Node Arduino sketch should be able to read when the A4 button is pushed.

Below, the next posts about the End Node's Prototype Shield will finish the increase of 3.3 volt connections. It will also add the DHT11 temp/humidity sensor & a solid state relay for controlling AC devices.

[papa]

Continued:  Building a DHT End Node with DHT temp/humidity sensor, push button, & relay control of AC devices
(Click on the images for a larger view.)

       Simplified 1/29/2017 via what I documented in my thread Simplify End Node w Arduino internal pullup resistors.
          ^^ Schematic to guide creating a full DHT End Node with relay control of AC devices

      Top of Prototyping Shield used (labels added by Papa) Updated 12/14/2017.

      Bottom of Prototyping Shield (labels added by Papa)

4a) In the following text & above pics, labels starting with “A” or “B” are ones I added to indicate places on the Prototype Shield. Labels like “D8” refer to an Arduino digital connection labeled such on the Arduino compatible & on the Prototype Shield.

4b) Introduction:  You may want to review soldering techniques described at this Sep 28, 2015 post & the break away header techniques at this Oct 10, 2015 post.  The aim is to help stabilize components to be soldered, sufficiently solder components (enough for a good connection, not getting solder on nearby locations), & to assemble things in an order to provide the most possible working space on the shield.  An Arduino compatible & a plug in prototyping shield have 3 GND sockets & only one each of these sockets: 3.3 volts, D0-D13.  However, for what the DHT End Node schematic requires, those Arduino connections are not necessarily enough or in a convenient location.  Soldering break away headers on the shield's soldering strips will increase access to needed Arduino connections.  Now to continue the assembly.  See a below post for pics of the final assembly.

4c) Updated, 12/14/2017: If using a DS18 temperature sensor, via the shield’s top, insert the sensor’s 4.7 kilo ohm pull-up resistor thru the power strip hole at A10. Gently holding the resistor against the hole, turn the board over. Bend the resistor lead at a right angle to hold it in place, solder the resistor to the hole, trim off & save the extra lead wire. Steps 4c) & 5) are not needed for the DHT sensor, via what I documented in my thread Simplify End Node w Arduino internal pullup resistors.

5) Updated 12/14/2017: If using a DS18 temperature sensor, turn the shield back to the top. Slide a little heat shrink tube (red?) onto the 4.7k resistor’s still free lead wire. Leaving that resistor sort of vertical, curve its free wire & insert it thru the A12 hole. Turn the shield to the bottom. While keeping the resistor sort of vertical on the top, on the bottom, gently bend the free resistor wire at a right angle to hold it in place, but do NOT solder or snip it yet.

6a) Turn shield back to the top. Prepare 3 break away headers with 3 sockets each & 1 header with 4 sockets. Insert a 3 hole header’s pins into the solder holes to cover the A11 strip (dark blue rectangle). Into each of the A14 & A15 strips (pink rectangles), insert a 3 socket header. Into the A16 yellow rectangle, insert the 4 socket header which will reach one GND solder hole.  Do NOT solder headers until step 9.

6b) Prepare a break away header with 5 sockets. Into the A9 red rectangle on the shield's top, insert the 5 socket header.

6c) IF you need more than one 5 volt socket (as for a cooking controller), insert some female headers into the A21 5 volt strip. << New, 12/14/2017

7) Hold the new, still loose headers in place with strips of cellophane tape that cross at right angles. Put a piece of cardboard inside the “frame” of the original Arduino headers so that it covers the new socket headers. Turn shield to the bottom side so tape, cardboard, gravity, & table top pressure hold the new socket headers securely in their solder holes & ready to solder. To make it easiest, I recommend you do the soldering for each header in the order I describe.

8) [Deleted step)

9) To their strip holes, solder ONLY the 2 header pins enclosed by B6’s pink rectangle. Against the 2 header pins exiting the B7 yellow rectangle, put a left over piece of resistor wire. Pressing your hot soldering tip against them, solder each of the 2 junctions of leftover resistor wire, header pin, & solder hole. This will connect all 4 of the A16 (B6/B7) header sockets to Arduino GND.

10a) To their strip holes, solder ONLY the 2 header pins enclosed by B8’s orange rectangle. Against the 3 header pins exiting the B9 red rectangle, put a left over piece of resistor wire. Pressing your hot soldering tip against them, solder each of the 3 junctions of resistor wire, header pin, & solder hole.

10b) IF using a DS18 temperature sensor, to their strip holes, solder ONLY the 2 header pins enclosed by B10’s green rectangle. From step 5, the 4.7 kilo ohm resistor's wire should emerge from the A12 hole's bottom. Put the resistor wire against the header pin at B11.  Solder together the wire, the pin & the B11 solder hole. Trim excess wire.

11) Prepare a short red jumper wire with insulated area to bridge between the new A19 socket & the existing A13 Arduino 3.3 volt socket AND stripped right angle ends that will just bottom out in the sockets. Now all the A9 sockets will have 3.3 volts.

12) Strip an end of your supply of red wire & insert it from the shield’s top into the B2 solder hole. Holding the insulation against the hole, turn to the shield’s bottom, bend the stripped end to hold it. On the bottom, carefully solder the wire only to B2, & snip off extra wire extending from the solder. Back to the shield’s top, cut enough of the red wire to reach from B2 to an A9 socket. Slip a little heat shrink tubing (red?) next to B2 on the red wire & shrink the tubing with gentle heat. Next make sure the red wire’s free end is stripped enough to bottom out in a socket & bent at a right angle. Insert the free end into an A9 socket. Now all the A1 sockets & all the A2 solder strip holes will provide 3.3 volts.

13a) Updated 1/28/2017:  Insert a DHT sensor’s data wire (yellow?) into the Arduino D4 header socket. Insert DHT’s vcc wire (red?) into the A17 socket source of 3.3 volts. Insert DHT’s gnd wire (black?) into a GND socket. The DHT sensor should now be installed.

13b) IF using a DS18 temperature sensor, put a (yellow?) jumper wire between the Arduino D3 socket & the closest A11 socket. Insert the sensor's data wire (yellow?) into another A11 socket. Insert the DS18’s vcc wire (red?) into the A17 socket source of 3.3 volts. Insert the DS18’s gnd wire (black?) into a GND socket. The DS18 temperature sensor should now be installed.

14) Shorten both ends of a 2.2 kilo ohm resistor so when each end is bent at a right angle & bottomed out in header sockets, the ends will connect the Arduino D9 socket (relay actuator) with the closest A15 header socket. You may need to add a little solder to each resistor end so they fit tightly in the sockets.  Or on each end, fold over a socket length of resistor lead & crimp the bend.

15) To each of a BC547 transistor’s pins, add a little solder so they fit tightly in sockets. Follow the following carefully so you do not fry your transistor. Hold the shield, top up, so the buttons are on the opposite side from you. Hold the BC547 so the rounded side is toward you. With that orientation of the shield & BC547, insert the transistor pins into the X, Y, & Z sockets.

16) When you have the solid state relay (SSR) prepared (see above), you will use a black wire to connect the SSR’s DC negative input (-) with an A14 socket. Use a red wire to connect the SSR’s DC positive input (+) with the A20 Arduino 5 volt socket. Now on the first & later odd times), when the button is pushed or a virtual switch on a browser-held user interface is clicked, the end node sketch will send 3.3 volts to the transistor base thru D9 & resistor which will allow the transistor’s collector & emitter to send 5 volts (& more current than available at 3.3 volts) to the SSR’s DC input. This allows AC current to flow through that side of the SSR & thru an AC device plugged into the extension cord. On the even times that button or virtual switch are “pushed,” the sketch will turn off D9 & thus turn off AC thru the relay.

17) As the DHT End Node schematic indicates, insert the stripped RFM69 wires into the appropriate shield's Arduino connections:  Connect SCK to D13, MISO to D12, MOSI to D11, NSS to D10, & DIO0 to D2.  Connect the RFM69 GND you wired to the shield's closest source of an Arduino GND. Connect the RFM69's 3.3v wire to a source of Arduino 3.3 volts (I suggest in the new A9 header).

18) Make sure the Arduino compatible is switched to 3.3 volt mode & maybe recheck to make sure the above connections were done correctly.

19) When your prototyping shield is built, insert the shield into the Arduino compatible switched to (mostly) 3.3 volt mode, but do NOT force this. That could crack things on either unit & cause frustrating malfunctions. If necessary, bend the long pins slightly to make the mounting relatively easy.

20) Appropriately customize a computourist style sketch for programing a full DHT End Node (see below) & upload it to the node's Arduino compatible.  Powered, the node should be ready to connect & work with the Gateway & with a computer's running MQTT service & OpenHAB.

[papa]

Final product:  A DHT End Node assembled on a prototyping shield.

Maybe along with the above details, the following pics will give you some idea of what we are working toward.  Notes:  The wires on the RFM69 transceiver can be shorter, just enough to clear the BC547 transistor underneath.  The RFM69's antenna wire can be coiled instead of straight.  The DHT11 sensor's wires can also be shorter.  (Click on the images for a larger view.)

     
                 ^^ Completed DHT End node, from the top (mounted on Arduino compatible)

     
               ^^ Completed DHT End node, close view from the top (NOT mounted on Arduino compatible)

   
             ^^ Completed DHT End node, from the bottom (NOT mounted on Arduino compatible)

[papa]

What if you (as lhw455 did in his Newbie... thread) say, "Papa, I just want a (somewhat) simple end node that just reads /reports the DHT11 sensor & skips the prototyping shield, the push button, & the relay. How can I do that?"

        Here's what I proposed to lhw455 (& updated on 1/29/2017):

This (maybe) somewhat simpler approach still requires an Arduino compatible (like a Buono Uno) switched to 3.3 volt mode, a wired RFM69 transceiver, & a wired DHT sensor AND some more: The Buono does have enough GND sockets for RFM69 GND & DHT11 GND, but it only has ONE 3.3 volt socket when two are needed (one for RFM69 & one for DHT11).  Also the DHT sensor needs connection to 3.3v & GND. I eliminated a resistor via what I documented in my thread Simplify End Node w Arduino internal pullup resistors.

Here are two ways (A or B) you might accomplish "a simple temp/humidity node: I guess it would be simpler (while less robust) than a full blown DHT End Node shield, but would still have challenges.

            For BOTH A & B, you must connect (solder? male-female Dupont cable?) wires to the DHT's vcc, data, & gnd pins.

A) You might make a "starter" version of my DHT End Node on a shield & then you could add more functions later. I numbered the steps at the Oct. 15 3:36pm Success... post. At that post, do these numbered steps: 4a & 4b, 6b, 7, 10, 11, 12, 17, 18, 19, & 20. Take the DHT sensor as wired just above & plug the DHT vcc wire to one of the new sockets connected to the shield's 3.3 volt socket, plug the data wire into the shield's D4 socket, & the GND to a shield GND socket.

OR B) To build a "simple" DHT node on mostly a Buono Uno... You could use a 3 socket break away header where you solder one piece of wire (a snipped resistor lead works) across all the bottom pins) like this ...
        << like this. Then ... connect one wire from the Arduino 3.3 volt socket to one socket of the adapted break away header. That makes 3.3 volts available to the break away header's other two sockets where you can plug the DHT vcc wire & the RFM69 3.3v wire. With the DHT sensor as wired above, plug the DHT vcc wire to one of the new sockets connected to the shield's 3.3 volt socket, plug the data wire into the shield's D4 socket, & plug the GND wire to a shield GND socket. Caution: Situate that break away header (with insulation on those bottom soldered pins or hanging of the side of the Buono OR BOTH) so its 3.3 volts don't ground & short out.

       << (click on this for a larger view)
                ^^ A simplified schematic for a "Simplified Version" of the DHT End Node (just a DHT sensor.  NO button or LED or relay)

    From this post, download the latest choose_nodes sketch (Dec. 18, 2018 or later) to program this simplified DHT End Node.

               Necessary customization of the sketch, then upload:

The following #define lines should be UNcommented (no // at their beginning):   #define HT & one of the following, #define FAHR or #define CELS.

Give a unique NODEID to this node.  (between 5 & 255)
Use the same ENCRYPTKEY as you did when programming the gateway
UNcomment #define DEBUG to see debugging info on the Arduino IDE Serial Monitor

UNcomment only one of the three #define FREQUENCY lines, according to your RFM69 radio's frequency
UNcomment #define IS_RFM69HW only if your RFM69 radio has H in its part #