In this instructable, I will show you how to convert virtually any broken toy drone that had remotely controllable lights into a versatile pair of devices. The first device made from the old remote controller detects something using a sensor module (motion, light, uv rays, metal, magnets, flames, smoke, gasses, obstacles, tilting, bumping, contact, temperature, water), and sends a command to turn the lights on the second device - the drone receiver board, ON or OFF.

Here's the magic; Instead of toggling the old LED lights on or off, we will be swapping the lights with the control pin on a relay module. This way, we can switch larger, separated circuits ON and OFF such as A/C appliances, alarm bells, lamps, strobing alarms, etc... The sky is the limit!

The process works in a toggle switch fashion somewhat similar to "The Clapper" hand clap controlled power outlet. The first sensor detection triggers the relay ON, and the second sensor detection instance triggers it back OFF again. "Clap ON. Clap OFF."

Unlike the Clapper wall outlet, we can use sensors that detect things other than sound.

Additionally, with a relay, you can control two devices with one being normally ON and the other being normally OFF until the sensor detects something as seen in the embedded video.

Many of the cheap sensors available have a little screw on them which you can rotate to set the threshold before the sensor trips up.

I plan to use this rig as a remote alarm notifier system for a chicken coop. When the coop door is left open too late in the evening, or their water dispenser runs dry, or they run out of food, or they lay some eggs, I'll be notified!

Maybe I'll use it to automate some of the coop too!

Step 1: Parts Needed

You will need the following parts:

multimeter which can measure DC voltage and continuity.
broken drone with remotely controllable lights built in.
broken drone's remote controller.
alkaline batteries for your drone's controller - These might be AAA or AA cells.
old rechargeable drone battery.
old drone's charger
solder
soldering iron
hot glue sticks & hot glue gun
a plastic card (old gift card, piece of water bottle, whatever)
scissors
2 relay modules 5 volts
sensor module rated for 5v power with a digital output which is either LOW or HIGH depending on the detection status. search
voltage step-down module buck converter
jumper wire cables dupont f-f plugs
wire strippers
electrical tape
header pins male type

Get the sensor module with whatever type of sensing you want to detect. For example motion detection sensor module:

Step 2: Crack Open the Controller

Using a screwdriver, carefully open up the remote to find the points where the battery casing goes to the main circuit board inside. Look for the red wire and the black wire coming from batteries.

Also note where the button that controls the drone's LEDs is located.

Step 3: Solder Extensions to the Button

Preheat your soldering iron, then solder some wires to the soldered points where the button attaches to the board. Don't remove the button, just solder in parallel.

Step 4: Solder Extensions to the Battery Casing

Solder a wire to each of the points where the battery casing heads to the main board in parallel.

As a bonus thing if you want to do so, you can solder two more wires to the same point then to a wall wart power supply which is the same voltage as the total of the alkaline batteries. That way you can use zero batteries and just plug this device into the wall outlet power supply. This is especially practical because when the receiver loses connection to the remote controller, the relay would power itself ON, OR possibly flash ON then OFF then ON again repeatedly. You could use this to your advantage as a low battery alarm or out of range alarm for the pair.

Step 5: Solder the Voltage Step Down Module

Solder the voltage step down converter module V in + pin to the positive wire your has just soldered coming from the battery casing.

Solder the voltage step down converter module V in - pin to the ground wire you soldered coming from the battery casing.

Solder some header pins onto the output contacts on the step down module.

You should make sure you you didn't wire it in the incorrect polarity using the multimeter. It will say the voltage with a minus sign if the polarity is wrong. The black wire is the ground negative wire usually.

Step 6: Tune the Voltage Step Down Module

Using a screwdriver and the meter, turn the little screw on the step down converter module output pins until it is around 5 volts.

You could lock the screw with glue if you want to.

Step 7: Insulate the Controller Board With a Plastic Card

I decided to pack the 1st relay module and step down module in a port which was already built in to my remote controller. In order to protect the internal circuit board from shorting out by touching the other modules, I separated them by hot gluing an electrically insulating plastic card between them.

Step 8: Wire Up the Sensor - Remote Controller Circuit

Wire up your sensor to the relay and step down module as described in the diagram picture.

The sensor causes the relay to conduct, which shorts the button and simulates a button press on the light control button.

Like I said earlier, many sensor modules come with a threshold adjustment screw which you can use to tune the sensitivity of the trigger.

Step 9: Crack Open the Drone

Open up the toy drone and remove the main board.

Step 10: Add Connectors to the Receiver Board

Determine which pins on the receiver board were formerly connected to a LED light, and using the multimeter figure out the polarity.

Solder or jam a header pin into the pin that used to go to the LED positive side (anode), and hot glue it in place securely.

Jam or solder some header pins in parallel to the battery connector, and glue them in place too.

I added more pins in hopes of using two of the pins which used to power a motor to send a control signal to a switching device (MOSFET) which can modulate the speed or dimming of a heavy duty DC fan or lamp. That portion would not use the sensor, but would instead use the receiver gyroscope sensor and control sticks on the remote controller.

I was unable to detect a speed/dimming signal coming out of the old motor pins, so for now this instructable does not show how to do pulse width modulation dimming with a MOSFET. If I figure that part out, I will be sure to update this instructable!