Electronics, ESP8266, Experimental

RADIO REPEATER MONITOR

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#132 Designing a Radio Repeater Monitoring PCB

3D model of the PCB

About a year ago I realized the need for a dedicated repeater monitor that’s isolated from my clubs ham radio repeater equipment. E.G (power supply VOTER and Radio equipment). Having a dedicated monitoring PCB with a few extra complimentary features like remote control switching and reading/triggering capabilities would be very useful for largely remote and isolated places, also I get to test out and make some cool stuff.

PCB design

So I convinced myself to make the RRM V1.0 radio repeater monitor based around the well known and beloved ESP8266. Well what about the ESP32 you may ask? Yes I have made a new and improved version with asynchronous reporting and many other hardware improvements however I intend to sell that as a commercial product and thus I will not be giving away to many details for free but for a small fee you too could have one in your hands so now hopefully you see my simple strategy.

Soldered PCB

Though I designed this board for monitoring repeaters it can also be used to measure current temperature and control inputs and outputs for a number of other appliances like monitoring the current, temperature and input outputs of a vehicle. With the WiFi capability the device can be connected to as an Access Point as well for mobile operations, of course connections to the internet through WiFi is required to send the sensor and peripheral data to the server so that reports and nice colourful charts can display the data in a useful logical manner.

Here you can watch a YouTube video where I discuss the design at our Ham radio bimonthly meeting a few months ago

I decided to make a version 1 SMD PCB with large 1206 components as a prototype just to see that everything works correctly. I chose KiCad as my design software and got to work.

My requirements were:

  • 1206 SMT Parts
  • Current Measurement
  • Internet Capability
  • Reed In Detect
  • Digital Input
  • Digital Output
  • Voltage In Detect
  • Battery Back Up
  • Temperature Sensors
  • High Resolution ADS1115 ADC
  • IO Expander
  • OLED Screen
  • Reset Button
  • Control Button
  • M3 sized Screws
  • USB-C
  • Buzzer
  • Notification LEDs
3D back of PCB

So I got down to work and created a prototype around the an ESP8266 module. Note: although this module has been around for a while there’s a lot of different variants available however the EPS32 will be used in my commercial version as it has much better performance and features as well as long term support.

Designing the PCB took a few weeks of fulltime checking and double checking and then triple checking XD. Then eventually I send the PCBs to be manufactured. I soldered everything myself and confirmed everything was working correctly. Next I just experimented a bit with different components, led colours and temp sensors etc.

Bare PCB

Now I was ready to Install the module for tests at my local repeater site. We have WiFi and power at the site so I was able to connect all the hardware up and make things look neat.

Everything worked well and has been for over a year now so the project is a success I just need to monitor it long term.

Electronics, Experimental

FLUX DANGERS

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#131 Flux causing strange IC behaviour

Low solids runny liquid flux is the best

When I ran out of my professional electronics flux I decided to try and use some off the shelf flux from the local construction store.

The flux was quite thick and seemed to work quite well when soldering parts but after cooling down some time later it forms a gunky wax that is conductive and causes all kinds of interference(Guess how I know) and worst of all it gets under IC’s and is almost impossible to remove entirely without de-soldering cleaning and then re soldering while using a very runny flux.

I tried cleaning with paint thinners and alcohol multiple times but in the end I had to remove the whole IC and clean it thoroughly

Even after multiple cleans you can still see the stubborn flux gunk on the pins as soon as i desoldered the IC
Side view of the gunk shorting out pins (Very difficult to remove when the IC is soldered on the PCB even after multiple washes and scrubs)

When the flux dries it can cause a few issues: gunk up of the pins and getting trapped under the IC

Backside is also gunky
This flux caused electrical issues on my IC’s pins…
ATTiny, Experimental, Programming, Radio, Uncategorised

RADAR SENSORS

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#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

ATTiny, Electronics, Experimental

DIY ROBOREMOTE REMOTE

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#129 Building a DIY Robo remote

My prototype using a LAN cable breakout enclosure made it small and nifty.

A few years ago while using many wireless systems on a large remote property I had the problem of testing the signals in varies areas before installing my hardware like: Roboguards or my own custom devices that have the ability to communicate with the RoboGuard ecosystem.

Front view of the PCB. It fits perfectly into an ABS enclosure.

So I decided to create a dedicated remote that uses the ASK protocol used with these devices. This makes my life so much easier because it allows me to test multiple requirements at once.

I’m able to test:

  • Signal strength in the area
  • 433 modules I want to use
  • Antennas I want to use
  • The transmission logic I want to use
  • Different ASK protocols

All this with a wireless, rechargeable and easily customizable package. At the moment this is not a commercial product however I have many other devices that work with the Roboguard ecosystem that have commercial applications.

Back view of the PCB. This was made around the ATtiny212 MCU and the SYN1115 transmitter.

Electronics, Experimental

DIY ENEGIZER

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#128 making a simple energizer

Since I’ve been living in a rural area for the past few years I’ve had to come up with some affordable solutions to problems unique to my situation. One of these problems is keeping animals out of certain areas with methods that wont cause permanent harm but will definitely be effective. So the logical solution was to use electricity in the form of electro shocks. I searched for commercial solutions and found a few but they were a bit overkill/overpriced and of course not very hacker friendly… so I decided to make my own which I can always scale up with microcontrollers/relays/monitoring and all those nice to have features but for this one I wanted it to be plain old dumb without any programming required.

So I did my research and came up with a suitable schematic found the correct parts and settled on the good old 555 timer. Designed a very small PCB and got it manufactured a voila the idea became a reality and after a few tests it works perfectly fine.

Now the shock is created by the collapsing fields of the ignition coil I used for the project. I got the most basic simple coil that is driven by a suitable N-FET at a frequency and strength that I can fine adjust via a potentiometer on the PCB. The whole system runs on a 12V battery and consumes very little current.

I took inspiration for this device and modified and created my own flavour. Like everything in life no one can do everything by themselves so I would like to credit the source which got me started here.

With that being said I had a lot of fun making this device and it’s been working well I was also able to adjust the voltage to a very humane jolt so smaller animals know not to enter the area but also don’t get fatally hurt.

Experimental, Radio

DUAL BAND ANTENNA FIX

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#127 Fixing a Faulty Handheld Antenna

A while ago I purchased a few hand held radio antennas from a reputable source. Unfortunately one of them had a great SWR for 2m but a terrible SWR for 70cm. So I began investigating this and started to take apart the antenna to find out more. Just as a side note: I would not recommend this for beginners or businesses (if you have a faulty product immediately contact the seller and get a replacement or refund)

So during my autopsy of the antenna I was able to determine a few things. Firstly the plastic connectors in the middle of the antenna is supposed to have a loaded coil but there was just a crimped thinner antenna wire. Second on opening up the base of the antenna I was surprised to find out that they had a metal enclosing case which was nice.

Then looking at the SMA connection to the antenna I was pleased to see a base tunning coil and capacitor, this is a good sign. potentially meaning the antenna is a “GOOD COPY” of whatever the original antenna was. the antenna has zero markings but we can take a guess that its a good copy of the Diamond RH951

Finally I found the culprit.. the capacitor on the coil seemed to be destroyed.. after de-soldering it and testing it turned out to be a faulty part. So in order to fix the antenna I soldered another cap with a close enough value.. (13pf instead of 12pf) and sure enough after putting everything back together a gluing it the antenna worked perfectly but did have a slight frequency shift when Compared to the others I had purchased.

still this is a mission success the antenna works perfectly in both bands and I’ve been using it for over a year with both bands and no issues.

Radio

ALLSTAR NODE

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#126 Creating An Allstar Node

Display prototype on an actual Bread Board 🙂

In my previous article I was focused on the RTCM and the VOTER PCB which are used with repeaters. however I found out you could make a node instead for personal use. So basically a node is a radio connected through a sound card to a raspberry pi acting as an Allstar server.

You setup and connect this to the internet and you have a home made personal gateway to the Allstar servers. now you can listen or chat with anyone on the Allstar network

With that being said I was very interested in making my own version but I wanted it to use LiPo battery power for portability and a solar panel as power intake. I wanted a complete stand alone unit that could be setup once and placed somewhere and almost forgotten just remembered for maintenance and check ups.

I also wanted clean audio which could be a whole article in itself but for this write up I’ll be brief.

Testing out different filters and super capacitors
Eventually settled on a case with very short wires

I got the initial setup working using a UHF only Analog radio connected to a CM108 sound card that is plugged into a raspberry pi 2w with an OTG adapter. (it’s very important to keep all the wires as short as possible to prevent them from becoming antennas!!)
This was connected to a 5V step up converter and charger in 1 module. Now the radio needs max around 4.2V so I had to add an additional stepdown converter to accommodate this.

CM108 FOB

Everyting worked well and the system was portable but there was a very annoying whine. with some filtering I was able to reduce this significantly and the setup was almost done.

One annoying issue was that when the 5vstep up converter switched from main to battery power there was a very brief short delay where power to the raspberry pi could be lost casing a brownout and reboot of the pi. The solution was to add super capacitors in parallel with the supply to keep the volts flowing during this dip in power.

Also using a linear voltage regulator with a high ripple rejection circuit helped reduce the audio whine and noise

Over all this was a fun success of a project I will be creating a permanent case for my DIY version and I will be creating my own custom Nodes with a professional PCB for sale in future!

COS wires location on the radio
RX, PTT and GND solder areas

Experimental, Radio

ALLSTAR VOTER

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#125 Creating a DIY VOTER

Unpopulated VOTER PCB from the factory

VOTER (Voice Observing Time Extension for Radio) 

For a while now I have been involved with some troubleshooting at my radio clubs repeater site closest to me.
we have had a few issues where our equipment gets damaged from lightning water and rats.

We’ve tried to mitigate these problems however the reality is that it more of a manage the symptoms situation rather than solve the problem situation.

With this in mind we have had some damaged RTCM devices, the RTCM (radio thin client module)
is connected to the internet and to the repeater. It has an IP address and forwards the voice data to other sites or nodes that have the Allstar system setup. It’s basically like a small VOIP system that can adjust squelch and do simulcasting but the repeater site can choose what settings to enable or disable.

In our case its just connecting the Voice data to the internet so that club members can chat with other repeater/node users over a greater distance through the internet.

E.G: talking to someone in Durban is not possible using VHF at the altitude where I am situated, due to the terrain, large mountains and a hefty over 100Km+ distance away VHF will have a really hard time. Also with all the solar whether these days… I would expect diminishing results.

But… with an RTCM connected to a repeater or a Node, I can now communicate over that distance using Analog VHF radio to the RTCM over the internet and then through the repeater or node on the other side in this case in Durban.

Checking and adding components to the PCB

So now the big issue I had was that RTCM devices will be just under 10K south African ZAR from America for 1 with shipping and all the tax applied it’s very expensive and I wish money was no object but the truth is our club is not super financially inclined due to many reasons a lot of them out of our control.

This prompted me to investigate on an alternative and I found a few but I chose the original 2011 VOTER PCB which allows us to do the same thing basically just on the prototype board.

Of course this rises some concerns like:

  • THT components used
  • Parts are all PDIP and most have to be substituted
  • No case provided
  • A larger size
Back of the PCB while I was populating it

But… in my case weighing up the pros and cons there’s no major issue using this VOTER version.

So I got a few professionally made, read the datasheets for all the IC’s and purchased the available parts.
I also substituted the parts no longer available and integrated them with some small modifications.
(I will create my own PCB based on this in the future for better availability and usability)

Overall It took me around 3 month just to read all the datasheet and to get familiar with they systems bootloader and firmware of the VOTER PCB not to mention learn about the Allstar system as I had not really been educated on it. Though it was worth it and the research paid off in the end.

I was able to learn fast and I can say that I was happy with this project and the VOTER boards turned out great!!

Front of PCB while I was populating it.

Electronics, Experimental

CUSTOM UPDI PCB

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#124 Making a Custom Programmer

Fake CH340N IC on the left real on the right

While looking for a good example PCB project I decided upon a simple UPDI programmer PCB for the well known new ATtiny ICs.
I had a few prerequisites I wanted to satisfy for the project.

  • Design must work but also have room for improvement
  • small SMD PCB design
  • BOM list and prices
  • simple schematic using KiCad
  • 1206 component size sop-8 IC size
  • USB-C
  • 2 sided PCB
  • all standard sizes for PCB manufacture
  • PCB panel example
Front
Back

I wanted the project to cover many of the basic and intermediate PCB manufacturing practices of course the IC is not very sophisticated and there is no impedance matching or equal length traces etc. However it shows how designing, quick and affordable manufacturing can be achieved in South Africa. Designing for manufacturing, thinking of the capabilities of the manufacturer and keeping best practices in mind at least to the best of my knowledge at that specific time.

In the project I keep things as standard as I can using metric measurements and easy milling panel design for the panel (no fancy curved edges or designs) although many interesting looking designs can be made surprisingly simple, it takes experience plus CAD artistic intuition. That being said I wanted this to be a simple and practical example I could use for teaching references later.

Getting to the component choices for a small UPDI programmer I chose the CH340N IC. It needs very little external components and has an internal crystal. Small and lightweight and perfect for my UPDI project. It is missing other pins like the reset pin but in my case this was not an issue. Always double check your IC datasheets and capabilities.

KiCad modal front
KiCad modal back

On that note I did receive some FAKE CH340N ICs and I tested them. They only worked on lower baud rates and adding LED indicator resistors to the TX and RX made them unstable. Unfortunately in this day and age fake ICs are very common you need to recognize them and weigh the balance between using them or not. Sometimes there’s a “good fake” so as a maker I may use this test projects or make throwaway projects but the characteristics of the IC are now different so any calculations are incorrect… so it’s a balancing act that no-one can escape. For production always use IC’s from the original manufacturer the stores are easily found online and it’s worth it in the end.

Simple schematic

All other components are very basic 1206 (easy to solder) SMD capacitors, resistors, TX/RX LEDs, power indication led, a diode 16-pin USB-c connector with 5k1 sense resistors keep the PCB copper balanced on both sides also saves etching chemicals for the manufacturer I also added some example fiducials and the copper stops 1mm from the edge of the PCB creating a small protection layer all around.

Since there is a USB-C connector I chose not to include any ESD or fuse but I would add these components to a commercial variant.

Also this v1.0 has the TX/RX LEDs on the wrong indication pins. I would change them to the USB side instead.

Overall I think it’s a good introductory example showing a simple design including some errors and fixes.

Panel front
Panel back
KiCad panel back
UPDI_programmerDownload

Electronics, Experimental

IO EXPANDERS

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#123 Looking at some common IO expanders

What to do when you are using n 8-pin MCU to to the job of a 16pin ore even a 20pin MCU? Well it depends.. but if all you are doing is using IO’s to switch for example relays or similar tasks where the amount of IO’s is important, and not the capabilities of the IOs then you may be able so save costs by purchasing an IO expander instead of an abundantly pin gifted MCU.

These come in all shapes and package sizes and don’t increase the project size too much. Also I tend to use I2C much more then SPI but IO expanders can support both these packages.

Examples like the PCF8574, MCP23017, 74LVC595 and the MCP23S17 which uses SPI if you want to use that instead. The expanders support interrupts but always double check the datasheet before purchasing!

Something similar but not an expander more of a multiplexer IC is the MC14051B Analog Multiplexer/Demultiplexer this is quite common and affordable at least in South Africa and allows analogue pins to be expanded instead of digital.

Some Links to shops in South Africa that sell these expanders:

PCF8574

MCP23017

74LVC595

  • not common in South Africa

MCP23S17

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