This gadget steps up the game from leaving a light on at home when you’re out. Place it near a window to make it look like somebody’s at home watching TV.
Update: Looks like somebody had this idea before me and made a product out of it. Just Google Fake TV. In fact, you can also buy a clone of this from AliExpress – again, just search for ‘fake tv’ in AliExpress. The Chinese versions can be had for about $12 in your hand and that includes a power supply (no doubt of somewhat dubious quality and safety standards). So what follows is a fun project, but it’s easier and possibly cheaper to buy direct from China.
The idea of leaving a light on at home while you’re out is to give the burglar an uneasy feeling that somebody’s at home and it might be worth trying the next house along instead. A TV on at night plays a constantly-changing light-show against your window which really does say I’m at home and I’m awake. Of course, you could leave a real TV on but that’s an eco-disaster since TV’s consume 50W at best and hundreds at worst. Plus you might not want to be burning your TV in for days on end if you’re not at home.
Why not use some of these neopixel RGB LED’s and a microcontroller to simulate the same effect? With just a few eurodollars, an hour of build time and a power budget of 5W absolute maximum, it sounds like a winner.
I used a Digispark for this project since the system is neither demanding in terms of processing nor I/O connectivity. Digspark’s have a USB connector for power input from one of those bazillion USB mobile chargers you now possess. I found a female micro USB to female USB A type socket adaptor on AliExpress (that cost about the same as the DigiSpark).
The light-dependent resistor (LDR) lets the device save power during daylight hours. I fitted a little black tube around the LDR so that you don’t get the LEDs feeding the LDR. Which would be bad. In any case I added some hysteresis to the software to avoid oscillating between day and night modes.
I built using some of my favourite prototyping board. It’s not stripboard (Veroboard) so you have to solder your own wires but it’s cheap, pre-cut to commonly-used sizes. I get mine from eBay – search for ‘prototype PCB’. I had to file down the end of the board so as to not foul the USB connector on the Digispark.
The resistor and capacitor for the neopixel WS2812B LEDs part of the circuit are on the back of the board.
I turned the little black tube for the LDR of plastic on the lathe. It occurred to me while I was making it that I probably had several tens of metres of spare black irrigation tube from which I could have snipped off a centimetre in a heartbeat. There we are, it works.
I could imagine several variations on building this. You could use any kind of Arduino with pretty much the same source code – just need to change the pin assignments. You could use fewer LEDs and increase the value of LED_BRIGHT in the code. Or just increase LED_BRIGHT. Bear in mind that these LEDs eat about 0.5W each at full brightness (in RGB ‘white’ colour). The LDR is optional. Obviously you’d need to trim the code if you left off the LDR. If you’re only going to use this for two weeks a year while you’re away on holiday, the environmental impact of manufacturing and shipping the LDR probably outweighs the tiny electricity savings of switching off the LEDs during the day.
The source code is on GitHub with an Apache license.
You want to make it look like you’re watching TV without the skanky thief knowing that you’re hoodwinking them. So the gadget needs to throw indirect light such that you see the illumination from outside the house, but not the LEDs themselves. An upstairs window would be good, assuming that they don’t have line of sight view to see that nobody’s in the room. Alternatively a diffuse curtain or closed Venetian blind could work.
With 4 LEDs in the string and the first version of the code where I have the LEDs’ R, G or B values at 120 maximum, I’m using about 0.5W of power or less.
You could combine this with a basic, mains-powered radio for maximum effect, although that might be an issue if you share walls with neighbours who might not appreciate a radio blaring 24/7.
From AliExpress: DigiSpark (about $1.50 delivered), Light Dependent Resistor (LDR) (cents, delivered)
From eBay: neopixel WS2812B LED modules (a few euros for ten, delivered), USB power lead (USB extension cable), prototype board
From the parts bin: 1k and 470 Ω resistors, wire, electrolytic capacitor
A case would be nice. Perhaps something 3D printed that lets you clip on to furniture / curtain rail.
The code could do with some more sophistication for creating more entropy in the ‘picture’. Take care with this since you’ll note that the light coming off from your TV is mostly white-ish most of the time. Plus, there’s not a lot of point in this gadget spending lots of time with dim LEDs.
A Bluetooth Low Energy (BLE) module could be used to automatically sense whether you’re home / in the room with your mobile and therefore automatically switch off the LEDs. Alternatively you could integrate this with a home automation system via WiFi using one of the cheap, low-ish power ESP8266 modules.
If you make this project and anything bad happens, don’t blame me. You’re doing this at your own risk, etc. For example, if some strung-out low-life steals all your stuff while you had this gadget running, blame the burglar, not me.