Make the Halloween sign turn itself on at sunset

Find the right pins in the D1 Mini bag

Each D1 Mini came with a few small black plastic strips. These are header pins. Soldered to the D1 Mini, they let it plug into the breadboard.

• You need two strips of 8 pins, one for each long edge of the D1 Mini.
• If a strip is longer than 8 pins, count 8 and snap it between pins 8 and 9 with pliers.
• The D1 Mini has 8 holes along each long edge. That's where these pins go.

Learn how the breadboard is wired inside

Lay the breadboard flat in front of you, long side left to right, and turn it so column 1 is on your left. Each hole has a name: a letter for the row (a–j) and a number for the column, like a5. Both are printed along the edges.

This is the one idea that makes the rest work: two things are connected when they're plugged into the same numbered column, on the same side of the center gap.

Solder the pins to the D1 Mini, using the breadboard as a jig

You'll solder the pins while they sit in the breadboard. That keeps them straight, and it leaves the D1 Mini in exactly the spot the rest of this guide uses.

1. Push the long ends of one strip into holes b5 through b12 (8 holes in a row). Push until the black plastic sits flat on the breadboard.
2. Push the second strip into holes i5 through i12. There are 9 hole spaces between the two strips, counting the center gap, which matches the D1 Mini's width. (These two rows are the same whichever way your board is printed.)
3. Hold the D1 Mini with the silver ESP-12F can and the printed pin names facing up and the USB socket pointing left, toward column 1.
4. Lower it onto the strips so the short pin tips come up through all 16 holes along its edges. It rests on the black plastic.
5. Check the corners: 3V3 should be top-left (far side, near the USB end) and 5V bottom-left. If not, lift it off and turn it around.
6. Solder one corner pin, check the board sits flat, then solder the opposite corner. Then do the other 14. Touch the iron to the pin and the ring of copper around it for 2 seconds, feed in solder, then pull both away.
7. Look at every joint: 16 shiny cones, and no solder bridging two neighboring pins.
8. Leave it in the breadboard. It's now in its final position.

Install Tasmota on the D1 Mini

Tasmota is free firmware for ESP8266 boards. It has built-in timers that run at sunset, so you don't have to write any code.

1. Plug the D1 Mini into your Mac with the micro-USB cable.
2. In Chrome, open tasmota.github.io/install.
3. Choose Tasmota (english) and click Connect. Pick the port that appears, usually named USB Serial or wchusbserial….
4. Tick Erase device, then click Install. It takes about a minute.
5. When it finishes, the installer offers Configure Wi-Fi. Choose your home network and type its password.
6. Click Visit Device. A Tasmota page opens at an address like http://192.168.1.57. Bookmark it.

Tell Tasmota which pin drives the lights

1. On the device page, click Configuration → Module (newer versions call it Configure Module).
2. Set Module type to Generic (18), click Save and wait for it to restart.
3. Open Module again. Next to D1 GPIO5, choose Relay and number 1. Click Save.
4. The main page now has a big Toggle button and shows ON/OFF. Nothing is wired to it yet, so nothing visible happens.

GPIO5 (labelled D1 on the board) is used because it stays off while the board starts up, so the sign won't flash on every reboot.

Set your location, clock and schedule

On the main page click Consoles → Console. Paste each line below into the box at the bottom and press Enter, one line at a time.

DeviceName Halloween Sign

Latitude 42.33

Longitude -83.05

Timezone 99

TimeDst 0,2,3,1,2,-240

TimeStd 0,1,11,1,2,-300

Timer1 {"Enable":1,"Mode":2,"Time":"00:00","Window":0,"Days":"1111111","Repeat":1,"Output":1,"Action":1}

Timer2 {"Enable":1,"Mode":0,"Time":"00:00","Window":0,"Days":"1111111","Repeat":1,"Output":1,"Action":0}

Timers 1

Status 7

Open the sign and remove the batteries for good

1. Unscrew the back panel: the brown MDF board that holds the battery box and LED string.
2. Take out both AA batteries.
3. Slide the sign's switch to ON and leave it there. It's in series with the LEDs, so from now on it works as a manual master switch.

Find the box's + and − terminals

Look into the empty battery compartment. At one end, a metal strip joins a spring to a flat plate: that's the bridge between the two cells, so leave it alone. At the other end are a spring and a flat plate that aren't joined. Those are the two terminals you'll solder to.

Solder a lead to each terminal

1. Take a red and a blue male-to-male jumper wire and cut each one in half. Keep the half with the pin end; each lead is about 10 cm.
2. Strip 5 mm from each cut end and twist the strands. Tin the ends: melt a little solder into them.
3. Scrape the solder spot on each contact with a knife or sandpaper until it's shiny. Battery contacts are plated steel and won't take solder otherwise. Flux helps a lot.
4. Solder red → the + flat plate and blue → the − spring. Solder to the back face of the contact, or to its tab if one pokes out behind the end wall, so the wire doesn't block the compartment.
5. Work quickly, 2–3 seconds per joint, so the plastic doesn't melt. Route both leads out of the box toward where the D1 Mini will sit.

Do a quick polarity test, with no transistor yet

Unplug USB. The leads from step 7 have a metal pin on the end: push it straight down into the hole until it stops, about 5 mm. A gentle tug shouldn't pull it out.

1. Push the red lead's pin into a5 (j5). That's the free hole directly above the pin labelled 3V3, just outside the D1 Mini's edge.
2. Push the blue lead's pin into j6 (a6). That's the free hole directly below the pin labelled G.
3. Plug in USB. All 10 LEDs should light at normal brightness.
4. Unplug USB and pull the blue lead out of j6 (a6). Leave the red lead in a5 (j5); that's where it stays.

If nothing lights, check the sign's switch is ON, then swap the two leads. A few seconds of reversed 3.3 V won't harm the LEDs. If they light only after swapping, you mixed up + and − in step 7. Re-solder them, or remember from now on that your "red" lead is the one that goes to 3V3.

Identify the transistor and the resistor

The ELEGOO kit keeps transistors and resistors in labelled compartments. Read the printing on the transistor's flat face to be sure which one you have.

Plug in the transistor

Unplug USB before every change on the breadboard. Build in this order, one part per step, and compare with each picture before going on.

1. Hold the transistor with its legs pointing down and its flat, printed face pointing away from you, toward the center gap and the far edge. You're now looking at its rounded back.
2. Seen from this side, the legs are reversed from the step 9 picture. From your left they're C, B, E.
3. Spread the legs slightly so they line up with three neighboring holes.
4. Push the legs into g18 (d18), g19 (d19) and g20 (d20): left leg (C) in column 18, middle (B) in 19, right (E) in 20. Check the flat face still points away from you.
5. Push down until about 5 mm of leg shows above the board.

Plug in the 1 kΩ resistor

1. Bend both resistor legs straight down at a right angle, about 3 mm from the body. It doesn't matter which end goes where.
2. Push one leg into j10 (a10). That's the free hole directly below the D1 Mini's D1 pin (not D2, not D4).
3. Push the other leg into j19 (a19), in column 19 like the transistor's middle (B) leg.
4. The resistor lies along row j, just above the holes between its ends. That's fine: it only connects where its two legs go in.

Add the black ground jumper

1. Take one black male-to-male jumper wire from the kit. It has a pin on both ends. Any color works, but black means ground.
2. Push one end into j6 (a6), the free hole directly below the G pin.
3. Push the other end into j20 (a20), in column 20 like the transistor's right (E) leg.
4. Let the wire loop around the outside of the resistor. If it touches the resistor, that's fine: wires only connect at their ends.

Check the red lead from the sign

1. The red battery lead should still be in a5 (j5) from step 8, the free hole directly above 3V3. If you took it out, put it back there.
2. It goes into the main board area, not the long red rail along the edge.

Plug in the blue lead from the sign

1. Push the blue battery lead's pin into f18 (e18). That's in column 18, like the transistor's left (C) leg, in the hole between the transistor and the center gap.
2. Don't put it in column 6 (G) as you did for the test in step 8. It now goes through the transistor.

Check every connection before powering up

Go down this list and touch each part as you check it. It takes 30 seconds and catches most mistakes.

• Nothing is plugged into the long rails along the edges.
• The transistor's three legs aren't touching each other.
• The sign's switch is ON and there are no batteries in it.

If your D1 Mini's printed pin names don't match the drawings, trust the pin names: each wire goes into the free hole in the same column as 3V3, G or D1.

Test it

1. Plug in USB and wait about 10 seconds for the board to join Wi-Fi.
2. Open the device page and click Toggle. The sign should light, and go dark when you click again.
3. Or type Power1 1 and Power1 0 in the Console.

Not working? See Troubleshooting at the end.

Solder the final circuit

You can use the same D1 Mini and solder wires onto its header pins, trimmed short. Or take a fresh one without headers, repeat steps 2–4 to set it up, and solder the wires straight into its holes, which ends up smaller.

1. Prepare the transistor. Bend the outer legs (E and C) outward so they can't touch the middle leg or each other.
2. Resistor to base. Twist one leg of the 1 kΩ resistor around the tip of the middle (B) leg. Solder, trim the excess and cover the joint with tape or heat-shrink.
3. Ground. Solder a black wire about 8 cm long from the D1 Mini's G pad to the E leg.
4. Signal. Solder a yellow wire from the D1 pad to the free end of the resistor.
5. 3.3 V. Cut the pin off the red battery lead, strip it and solder it to the 3V3 pad.
6. LED return. Cut the pin off the blue battery lead, strip it and solder it to the C leg.
7. Insulate. Cover every bare joint, then wrap the transistor and resistor together in a few turns of tape. Nothing bare should be able to touch anything else.
8. Re-test before mounting: plug in USB and click Toggle, as in step 11.

Mount it and bring the cable out

1. Stick the D1 Mini to the MDF with hot glue or foam tape, close to the battery box. Keep the silver ESP-12F end clear of anything metal so Wi-Fi reception stays good.
2. Tuck the taped transistor bundle beside it and dab it in place with hot glue.
3. File a notch in the bottom edge of the panel, or drill a ½ in. hole. A micro-USB plug fits through ½ in.
4. Thread the cable through and plug it in. Leave a little slack, then hot-glue or zip-tie the cable to the panel. The D1 Mini's USB socket is fragile, and a tug on the cable could rip it off.
5. Screw the back panel on. Check the sign's switch is still ON.

Plug it in and confirm the schedule

1. Plug the cable into the wall charger where the sign will live.
2. Open the device page and click Toggle once to confirm the sign still works, then set it back to OFF.
3. In the Console, run Status 7 once more. The Sunset value is when the sign will light tonight.
4. Run Timers to confirm both timers are enabled.

That's it. The sign now lights at sunset and goes dark at midnight every day, with no batteries to replace.