CUSTOM SENSORS | Radical Tech Tutorials

#130 A Few DIY Radar Sensors

Testing the current (multimeter was used for accurate uA measurments)

One sensor that’s been incredibly useful to me is the radar sensor. Over the past few years I’ve made quite a few different versions with great results and many improvements especially in power consumption. One of the most useful features is the ability to place wood or plastic over the entire sensor effectively covering the entire unit from sight. This allows the device to be placed covertly in very effective positions. The biggest issue is ensuring the alarm signal can be transmitted from these locations and that’s where LoRa technology comes into play.

My first wireless Radar prototype used a 12V 23A battery and used a lot of power

RF 2.4GHZ and 433MHz,Wifi and LoRa are some of the most well known and common low bandwidth digital wireless communication methods, of course we could use a classic analogue radio to send digital square wave signals like the very early alarm systems but that tends to make the device a power hog and increases the size of the device however more power can also have great pros like increasing the transmission and, having less interference affecting the signal and even some level of immunity to jammers.

My second radar sensor rechargeable uses less current and made use of deep sleep but still not good enough for me…

However I always focus on low power and low current applications I want my sensors to do the job in remote areas with solar power or hefty batteries running them for years without breaking the bank.

During my journey I started with basic breadboard projects moved to more permanent perfboard and strip board projects and eventually started creating fully fledged PCBs for these devices. I encountered various problems like matching antennas to increase the transmission effectiveness, waterproofing and powering the devices with solar and batteries, the effect the blazing hot African sun has on enclosures outside for years, consuming the least amount of current and running the microcontrollers in the most effective configuration suited to their purpose and I can go on.. there’s always something new to learn and I bet there will be even more advancements in Radar technology assuming solar flares or nuclear war or maybe even aliens don’t destroy our electronic and electrical technologies. we have our ancestors to thank for creating and sharing this power with us over the many many decades and hopefully we will eventually evolve to colonize the stars… well ahem I guess that’s a bit ironic coming from a South African but ideas are stronger than any country government or religion I can only hope we keep moving forward.

Front view of my 3rd radar sensor uses 100uA when in deep sleep mode and about 600uA when running and around 10mA when TXing for about 1.2s. Uses HC7333 regulator and a rechargeable LiPo battery. SYN1115 used to TX ASK alerts. Rd-04 Module Ai-Thinker *X-band* radar is used.

#105 Custom integration sensors with custom receiver

V1.0 breadboard prototype with DIY EEPROM module

V1.0 stripboard soldered prototype with USB and Lipo battery

Testing 2x custom sensors (1x ATTINY85 and 1x ATTINY412) with 433 RF modules

Recently I wanted to integrate the RoboGuard system with some custom sensors on my farming property.

This motivated me to study the hardware and RF protocols used by the RoboGuard

I would like to also account for multiple RoboGuard transmitters scattered over the property each RoboGuard device has 2x pir sensors and sends an alarm signal once both are triggered.

They also send a heartbeat ping every 15min.

They have a range of roughly 400m from transmitter RoboGuard to receiver HQ.

Now the RoboGuard system uses 433.92Mhz to send signals to the HQ however the HQ can only add up to 8 paired RoboGuards.

Once you reach this limit you will need to purchase more RoboGuard units.

For example if you had 12 RoboGuards, 2 HQ units would be required but if you wanted an HQ that can store more than 8 you would be out of luck.

luckily I had made my own custom RoboGuard receiver and was able to add my own DIY sensors to the RoboGuard device ecosystem

The protocol used is 433.92 ASK and each RoboGuard has 3 signals

alarm
tamper/learn
heartbeat ping

Testing penetration behind galvanised shed (using CY33 module)

Now my receiver needs to store the received device learn UID and this is done via EEPROM on my board

Now my custom device receives all signals just like the RoboGuard HQ.

Next is communicating with the TAK Server.

I could swap the 328P for an ESP8266 which allows WiFi connectivity to the internet

This then allows the device to connect wirelessly.

It still receives RF data from the RoboGuards and just ports these signals over the internet

In future I will make a device with an integrated WiFi connection but In this case all I wanted was more zones and an affordable extra device to keep in my laboratory permanently with the capability to receive 433mhz signals walking around the premises. If need be

Overall my unit contains

A speaker
6 push buttons
2000mAH Lipo battery
built in charger
ability to add clients 12 RoboGuards (more depending on EEPROM size)
433 MHz superheterodyne receiver only
logic to handle all these features

More info + datasheets and schematics etc. on my GitHub here

Radical Tech Tutorials

Tag Archives: CUSTOM SENSORS

RADAR SENSORS

ROBOGUARD INTEGRATION

Passionate about technology!