Tag Archives: 433.92MHZ

ATTiny, Experimental, Programming, Radio, Uncategorised

RADAR SENSORS

Leave a comment

#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.
Back view

Electronics, Experimental

COMMON RF MODULES IN SOUTH AFRICA

Leave a comment

#109 Types of 433Mhz RF modules in ZA

FS1000A module at 5v no attenuator just using antenna.

Recently I have been using wireless technologies for a few projects.

While looking for a balance between price, functionality and disposability I decided to focus on the 433Mhz RF modules.

These use a free spectrum and have been around for a long time. There’s is a few different types and kinds, with LORA being kind of new and better in almost every way but this comes at a high price compared with the standard 433 RF modules.

So I purchased a few receivers and transmitters from electronics suppliers located in South Africa.

All my tests consisted of running the 4 receivers at 5v and a single 17.3cm straight LAN cable strand as an antenna. The signal sent was a 23bit ASK signal with a pulse length of 1200ms.

All 3 transmitters were tested at 3.3v with a single 17.3cm straight LAN cable strand as an antenna.

The transmitters testes were the FS1000A, CYT1 and the WL102-341.

The crude module actually has more power and range at 5V but I am using them at 3.3v for super low power applications so In this case the module loses.

The Tests were done on farm land.

All transmitters could trigger the receivers at 400m line of sight but only a few could penetrate foliage and a galvanised steel shed.

I only needed MAX 400m which is why I stopped there but some sources claim up to 600m – 800m + for these superheterodyne modules. Not as good as LoRa but for the price what reason do I need not to use them?

*Sidenote Using RF or LoRa in conjunction with a 2.4G Wifi module like the ESP32 or even 3G/4G modules can create multi dimensional divers systems. where we are leveraging the long range and penetration + power output of 433Mhz and 868Mhz but also allowing packets of data to connect over the internet to be stored on a server for data analysis and the creation of graphs to make the data more visually appealing.

Currently I do have some pilot devices and hope to one day make some good quality sensors in 3 different tiers:

  1. Cheap and disposable sensors
  2. Affordable long term sensors
  3. High end sensors

These will be focused on use within rural outdoor areas and I will have a version with Gerber files and schematics etc. available for anyone to download and make for themselves. However the more refined version with a nice enclosure and style will be sold commercially since I do want to be paid for my work.

Back to the modules..

The transmitters that support 5v could penetrate a little better sometimes.

The position of the transmitter/receiver could also greatly affect the received signal especially at range.

Also during summer and during rain the signal was worse with the foliage and water most likely absorbing and/or reflecting the signal

All receivers were superheterodyne with a crystal and I did not use any counterpoise though it would help in some circumstances it makes the receiver unpractical and large.

From worst to best

Some people may wonder why I am using these modules instead of the fashionable LoRa modules. This is simply due to cost and availability.

Designing a good circuit cost time and money. Inserting said circuit into an extremely hostile environment like for example.. rural South Africa is an even more costly exercise…

I have had devices damaged by the sun, damaged by water, damaged by ants, damaged by cows, damaged by some kind of rabid animal (assuming jackal) The list goes on.

AND I have not even mentioned the human element… devices damaged by criminals some even STOLEN… for what? You telling me that criminal is sitting in the bush conspiring to reverse engineer my simple circuit and RF protocol and some how will be able to defeat Microchips code protection? I highly doubt it but it is possible…

So now I hope you can understand why these cheap modules do work and are very useful + inexpensive for my purposes.

I also have LoRa versions but for now I only use those when distance and extreme sensitivity is needed.

Electronics, Experimental, Programming

ROBOGUARD INTEGRATION

2 Comments

#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.

Testing EEPROM data storage.

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

Front of the 433 Transmitter
Back of the 433 Transmitter

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