What is Raindrop PLC? - A simple way to Home Automation


Home automation is (as you already might know)  any kind of equipment which enables automated or remote control to equipment in your home. So home automation can control indoor and outdoor lights, control and supervise kitchen appliances, open windows and blinds, water the garden, open and close garage door and do many other things, as seen below.

Home Automation example


There are lots of specialized devices doing function or two and unfortunately, usually they are not compatible with each other. Another problem is that most of units on the market are parts of large and expensive subsystem. Imagine that we have already electrical operator for window and just need electronic device to do it remotely, and we got offer for new window with all inside. That would mean we must call house builder to install it, connect cables and so on... Price can easily multiply in process.. Is there a solution for that problem?


Concept of Raindrop PLC

Imagine we want to do Home Automation in simple and cost effective way. Great thing would be to use one single, universal type of electronic device, and use equipment bought in first computer shop for everything else. Then, it would be nice if end user can do some small modifications of system by himself and revert back if things do not work as expected. What kind of device that should be?


We can try to put wish list for such device:

  • It plugs easily in home network. Not only we could use ubiquitous Ethernet and WiFi, but we can communicate with devices everywhere in the world.

  • It would be nice if device have simple web server, with customizable GUI written in HTML. That way, every device with browser can control it. PCs, Tablets and Mobiles use several Operating Systems, but simple Web page will look same on all of them, using any browser.

  • Outputs should drive lights, motors, solenoids and large relays. Easily drive LED and halogen lamps, (with light effects) start sauna from ski field, open yard gate without remote (by mobile).

  • Inputs for light, temperature and other measurements would be very useful. For example: Start lamp when gets dark in the room

  • Some kind of programmable automation depending on timers, sensors and commands sounds like good idea. Imagine: Send command now to start watering garden at 10PM and end at midnight.


Result would be something like this: A Raindrop PLC

Raindrop PLC:


Essentially, a Raindrop PLC is set of very smart switches on one side, Web Server for remote control on the other and Automation Logic in the middle. Automation scripts and Web site are on SD Memory Card so it could be replaced easily with updated value, without affecting main Firmware of Controller. Of course, we can forget about automation and use only default Web age. In that case we can forget complicated things and just pull out our (or borrowed) mobile phone, or approach first PC and control devices at our home. Then you open user interface in Web Browser and control devices. Easy.



Two examples of GUI. First is simple slider, second use control buttons on picture.


But, why such simple device does not exist on market? Well, it does exist... almost. Geek can use Raspberry Pi or Arduino  to build such system. But what they build probably won't be multi-purpose, flexible devices for masses. Custom devices also take lots of time to assemble and adjust and they cost more then my design would if made in quantity.

Right now, ordinary people can choose between switches with IR remote (no feedback and you must be in room) or complex and expensive systems made by other companies who usually want to make users dependent. I am aiming on simple and open device, while maintaining necessary degree of safety. Take a look more about Raindrop PLC usage and implementation.


Usage of Raindrop PLC

Raindrop PLC is designed to be used in number of applications. Here are described just a few of them, to give you an idea of it's versatility. In a nutshell, Raindrop PLC have 6 independent power-regulated outputs, giving 6-40VDC, up to 5A. There Analogue and Digital Inputs (8 each), internal Timers and Web control via Html GUI. Controller can be monitored and controlled via Home Network from PC, Tablet or Mobile Phone with standard browser. Proprietary applications can be used, but they are not necessary.


Light Control

Raindrop PLC as light controller can drive 6 branches with one or more lamps in each of them and power regulation works on LED diodes, Halogen or old Incandescent lamps, while lamps unsuitable for Dimmers can be operated in On/Off mode. Switches, Dimmers, Light Sensors and Movement detectors ca be connected on Inputs and combined with Timers and used in automated operation. Power can be derived from unregulated batteries, for example car accumulators, making it practical for vehicles, boats, summer cottages or emergency lighting.

Light Control


Multi-Colour LED Reflector

Special kind of light are multi-coloured LED lamps, such as “mood” lamps or stage and light-show reflectors. Raindrop PLC can be used for those types of applications a well. It can run RGB (Red -Green – Blue) light with possible addition of White to make RGBW light too. Two bidirectional channels can be used to drive direction motors which will point reflector in desired direction. All controls can be organized to be used with Web interface or by simple manual control using dimmers and switches.

Multi-Colour LED Reflector


Window operators

One of most common applications in Home Automation is automated opening and closing of windows, skylights and blinds. Raindrop PLC is capable of bi-directional drive of two DC motors so can open and close two windows, skylights or blinds, including any combination.

Window operators


Agricultural or garden watering

This application is shown as an example of more complex automated system. It represents watering system of large field. Each Raindrop PLC can open and close two water dams or large valves with motor drive. Relays can be used to drive big pumps (small water pump can be driven directly), and solenoid valves can be driven directly by Raindrop PLC. Inputs can be used for level sensors (as shown) and also humidity, pressure or temperature. All can be monitored and controlled either on PC screen or on farmer's mobile phone.

Agricultural or garden watering


Other use cases:

These are just few example what Raindrop PLC can. It is hard to count all possible applications where it can be used such as:

Use it to turn on sauna from ski field.

Control house heating.

Check and pump bilges on your boat, and warn you if something is wrong.

Perfect to monitor your battery powered cottage and turn off equipment when needed.

Can drive your solar water heater and rotate solar panel like sunflower to catch most energy.


Use it as Embedded board and module.

One whole new area is possible with this device: It can be used as companion board for PC, tablet, Raspberry Pi or Beagle Board either through standard software, or by developing special applications. Even though Ethernet is preferred communication channel (since it has galvanic separation) Board has USB and communicate that way with other devices.


Hardware Implementation


After couple versions of functional prototype, here is first version of pre-production prototype. This PCB is very close in appearance to market device. It's size is 160*100mm, so it fits in number of standard industrial boxes, and is possible to have even own box made by order. Product is designed to stand on desk or get mounted on DIN-rail in electrical cabinet. On the front side are inputs, Ethernet, USB and SD card. On the back side are outputs and power connector.

Raindrop PLC Board


Prototype in a box

Here is prototype fitted in standard industrial box, cut to size. Here is Front View, or upper side if installed on rail. Inputs left, Ethernet and USB right and SD card in the middle.

Front View


Here is Back View, or lower side if installed on rail. Output connectors are on the right, power supply on the left.

Back View


As we can see, all connectors are easy to connect and disconnect cables. Current connectors are used in computers and lighting applications. In future is possible model suitable for industrial environments with strong vibrations.



Raindrop PLC have small Web server as a part of firmware so device can be controlled directly from Web browser, and Web controls can be used in combination with automation. End user or system integrator can create own custom Web GUI using standard technologies, only must include header to communicate with Embedded software. Otherwise, user is free to customize GUI according to own needs and desires. Mind you, examples down there are just that – examples. Expect to get those, or better with your Raindrop PLC and tutorial how to do them yourself.


Plain Data IO

This GUI is used for simplest communication between host PC or Linux board. All inputs and outputs on raindrop PLC are on one web page. Instead of browser, proprietary application might be used for communication.

Plain Data IO


Light Control

Simple control for general purpose (light) channels. We can disable logic or web (slider) part in brightness control. In most cases, brightness is regulated using slider.

Light Control


Motor Control

Similar control, but slider allows operation of bi-directional drive, so DC motor can turn either way.  Slider regulates power (speed).

Motor Control


Multicolour Light Control

For multicolour (RGB LED lights we can use brightness control on each channel.

Multicolour Light Control


Multicolour Control with Picker

Alternatively, we can use picker to set colour of RGB lamp.

Multicolour Control with Picker


Floor plan Light Control

Using floor plan with On/Off button (or slider) on place of each lamp simplifies light control.

Floor plan Light Control


Image Light Control

Alternatively, we can take a photo with lamps and set controls on it.

Image Light Control


Image Motor Control

Garage and Gate drive system can use GUI control with  photo of garage and gate. Clicking next it closes it and slide across opens it, for example. Hear, click on upper buttons open and on lower closes, in addition to slider control.

Image Motor Control


Automation subsystem of Raindrop PLC

Yes, there is automation “engine” of Raindrop PLC and if you look at videos you can see it in action. It is programmable and end user can modify it too without special programming skills or expensive tools. I will tell more after successful campaign, when becomes certain Raindrop PLC goes to market.


Campaign and production:

Plan is to produce it and put on market. I am looking for investor(s) and plan soon to start Crowd Funding campaign. Please check for updates. Serious offers and advices are welcome.



All 4 edited together:



Consisting of 4 components:



Motor Driving:


Driving Colour LEDs:


Driving White LEDS







Contact us at

mmat042 (at)gmail.com