HN50
-
Posts
138 -
Joined
-
Last visited
Content Type
Profiles
Forums
Gallery
Events
Blogs
Everything posted by HN50
-
Hi, Thanks for reading, our posts crossed! Dave
-
I checked the data again today and compared the signal to the times I turned things on and off. As far as I can see they had no affect on the signal which I am pleased about however as can be seen in the chart below something else appears to have happened... There is a huge jump in signal after I changed the SD card that lasted for several hours. I don't quite know what has happened there but I left the radio running, unplugged the Arduino, changed the SD card before turning the Arduino back on. That elevated reading kicked off again later and has carried on into today; I can still see the 5 AM jump as well as the maintenance window 8-9, but the overall signal seems to be between 0.7 and 0.8 volts. I am wondering if that jump in signal is due to the Arduino, I have been having a look around and I may need to add in a decoupling capacitor between the Arduino ground and the pin I am using for the voltage divider. It makes me wonder if the funny readings on the 15th and 16th were also caused by this(?). I decided to turn everything off at 11:48 for an hour or so and turned it back on at 13:15 but I am tempted to just leave it running for the week. I am working again from tomorrow and won't have a chance to do any more today. Next weekend I will build another veroboard chassis that the Arduino/SD reader/RTC/power leads plug in to and add a capacitor, if that works I will then retrofit the capacitor to the other board to keep them synchronized. It also means with a second chassis I will be able to leave my production system running in the roof until I have tested changes and am ready to deploy them. Dear Lord, that sounds like I am back at work already..!
-
Over the course of yesterday evening I spent time turning off and on lights, chargers, computer and so on in order to try and replicate some of the (massive) interference and strange readings I had recorded in previous days. My thinking was that I could at least identify and perhaps mitigate them, so today I went and pulled out the data to analyse. The full day is below. Immediately I was a baffled (can't see the affects I had hoped for) but also pleased as it is starting to look like the type of plot I would like to see, plus I can still see the null during the maintenance window. I went back to my log of what I did when and plotted it onto the data. As before I was trying to replicate some of the anomalies I had seen on the 15th and 16th, but when I look at the plot I don't really see any obvious impact. I have not run this via any statistical analysis but certainly by eyeballing it my tests have not had the effect I had wanted. So... I have been turning things on and off again earlier in the day today in the hope that I will be able to see some impact, but I am beginning to wonder if something odd was happening to my setup on the 15th and 16th. I am also leaving them on for longer. What I have pulled out for the 18th already looks similar. I have remembered that the RTC has an inbuilt temperature sensor so I will tweak the Arduino code. The instructions mention that temperature can affect tuning so it won't hurt to log it anyway. Anyway, more things to think about!
-
I have had the radio logging since Monday and was interested to see what had been happening, so today I went up into the roof and pulled the data out. To my surprise/relief it has been logging data all that time. The overall pattern looks like; Hmmm, seems a bit noisy but there do appear to be patterns in there and not just a load of random noise. The plot for 14/04/2020 looks like; That abrupt drop in signal between 8 and 9 AM is very useful as that is the maintenance window when DHO38 gets switched off. So that is visual confirmation I am tuned to the correct frequency. There is a rise/dip/rise around dawn, but later in the day it all goes a bit pattern less. 15/04/2020 and 16/04/2020 don't show the expected diurnal pattern (though I can see the maintenance interruption on 15th) Finally 17th to ~13:00. Again it has a similar dawn profile to 14th and also shows the maintenance window. I have been in touch with UKRAA and the problem looks likes noise from appliances round the house swamping the signal from DHO38 - LED lights, computers etc. So I have been turning stuff off at particular times to see if I can work out who the culprits are. So my timings are; 17/04/2020 16:45 - Turned off everything upstairs at mains (LED lights/pc/phone chargers/toothbrush chargers) 17:00 - Turned off boiler for 15 minutes (not at mains) 17:15 - Unplugged my laptop for 15 minutes 17:30 - Turned on oven at 17:30 18:00 - Turned off mains alarm clock I will then start turning stuff back on sequentially to see what happens...
-
I did a bit more work today and built a circuit board that the Arduino plugs into. This gets rid of all the jump leads in the breadboard and gives slightly more secure attachment of wires. I tested it for a few hours and it does indeed run in the same manner as the breadboard circuit; I didn’t want to set it running only to find it does not work. I don’t have a case for it yet as it is a prototype and I may need to make further changes to the circuit. Next I set about tuning the antenna. I wrote a sketch that shows the voltage coming out the radio every second and began adjusting the capacitance in the tuner - it gradually began to increase and I spent a while trying to find the maximum. The signal is a little noisy (!!! sounds familiar from previous VLF experiments), however from a functional point of view the Arduino is now logging data coming out the radio. I am going to leave it in my roof for a few days to see what gets recorded and go from there. Quite pleased with progress so far, not least as I have something beyond the breadboard stage!
-
Today I set about getting the Arduino to read the voltage from the radio. I have built a home brew version from an Instructables page (YABBAS - ‘Yet Another Bare Bones Arduino on Stripboard ) and got it onto the breadboard. I have set it to run using the internal voltage reference of 1.1V and added a voltage divider to drop the maximum output from the radio down to 1.1V as well. My thinking (happy to be proven wrong) is that at 10 bit each increment will then be equivalent to approximately 1 mV rather than 5mV if I had been using the full 5V range. I got this working and then wired up the SD card and RTC. It now goes into hibernation, gets awoken by an interrupt from the clock, resets the alarm to go off in a minute’s time, takes a voltage measurement, writes this and the time to the SD card and then goes back to sleep. Which looks like this on the serial monitor; Next step might be to get a veroboard circuit built for a more permanent set up. Not least as my sausage fingers keep knocking out the jump leads.
-
I carried on with the antenna today for a few hours. I found an old project box and screwed that to the antenna base and with a few wires connected up the tuner with bnc male socket. Things were going well up to this point so I switched on the oscilloscope and started measuring. Unfortunately the oscilloscope is 9V (JYEtech), it worked for a while but then stopped at which point I realised the transformer was still on 12V. So I may no longer have an oscilloscope(!). To get round this I got out my LCR meter and measured the inductance of the antenna with tuner and extension cable added. I then found an online resonant frequency calculator and put in 23.4kHz and it fired back 2.269nF. I then used the LCR meter to set the tuner. I don’t know how accurate this is but I can tweak it if needs be once the antenna is connected and logging. So the next task will be to get the Arduino measuring the output voltage from the radio.
-
It has been a bit of a while since my last post but I finally got back to doing some more work on this. The first task has been has been to tune the radio. I have opted for Rhauderfehn (23.4kHz) as I understand there is a maintenance window each day when it gets turned off and which helps work out if you are tuned correctly. I worked my way through the UKRAA instructions and it wasn’t as difficult as I expected, just a bit fiddly. The instructions say the trimmer resistors have a maximum of 15 turns, but I found mine were 30. I mailed UKRAA about this though and they got back really quickly. Anyway the photo below is the outcome of this. It does not look much but that 1.23V took a few hours..! I am using the 2.5V output so there is some headroom for the signal to vary when a flare happens. So I think the radio is tuned. Next was to tune the antenna. I am going to use the one I built in another thread but have assembled my own tuning unit (inspired by the UKRAA one). My creation isn’t a thing of beauty but it gives a range between 135pF to 4.2nF. The dip switches allow you to increase the capacitance and there is a variable capacitor for finer tuning. The white capacitors are 1nF, the blues 0.1nF A few more things to solder but then I can get it connected to the antenna and start up the oscilloscope. Looks like tomorrow is taken care of!
-
It had been a bit difficult to get much time lately to finish the innards, but a bit of work today and the radio is done. I tested the output of the 5v output with my multimeter and it is measuring 0.43/0.42V. I don’t know if that signifies something is wrong, but I also wonder if as I don’t have an antenna plugged in there will be very little signal in anyway. The 12V regulator sits underneath the pencil line on the lid so I might cut several air holes. But for the time being the radio is built. Next I will have to try tuning it.
-
I found a length of old extension cable so split it down into the individual wires with a view to using them in this radio. Power in and out are wired up, as is the power LED. Antenna BNC socket is connected too. I had a bit of an accident with the black analogue out socket (broke it), so have ordered another and will sort next weekend. Red one is soldered and screwed in place. So after that I have just been using the multimeter to check voltages and connections, the voltage out is about 14.8V which will easily power the Arduino - the home brew one I made has a 5V switching regulator that can take up to 36V. I had hoped to get it all done this weekend but I am pleased with progress.
-
My attempts at SID monitoring have been languishing for a while due to radio problems, though I have been getting to grips with Arduino and even had a go at building my own. In order to move things along I went to the UKRAA stand at Astrofest and bought the VLF radio kit, their signal generator and the 15V power supply. Last weekend I soldered the board. It wasn’t too difficult following their instructions which are pretty clear. The only fiddly bit was soldering on an SMD capacitor but they also give you a through-hole one as well. Initial tests suggest it is working but I will have a better idea when it is all connected. This weekend I have been working on the housing and hopefully tomorrow get the leads soldered. From left to right will be led power, 15V in, 15V out, antenna in, then analogue -ve and +ve (can be 5V or 2.5V). I am building it as-is, so the first iteration will have the radio running off mains power and in turn the radio will power the Arduino. That seems a bit backwards but I would just like to get logging data. For the time being it will write to an SD card, but the Arduino MKR 1010 looks rather good and comes with WiFi and encryption. That though, is a long way off..! Anyway, this shows progress so far.
-
Hi HB, Firstly apologies, I only just saw that you posted on this thread. I have been away from the site looking at programming with Arduinos and building my own, so the VLF has taken a bit of a back seat for the moment. So I hope a late reply isn’t too late to be of use. The potentiometers are both 10k. I think though I had a dual gang 20k kicking around and wired it up in parallel. With regards the inductors, they were definitely both 0.1H. Without wanting to sound cheap but I get my components from eBay :). If you search; Radial Ferrite Choke Inductor 10uH to 100mH That returns several vendors (I am not connected to any). There are a few bbb-4 schematics out there and one lists them as being 82mH instead if that is easier to source. That isn’t me in the text. Once again, hope this isn’t too late to be of use. Otherwise, thanks for the post and glad some of the stuff has been of use. Dave
-
Hi, Thanks for the post. Unfortunately, a whole load of non astronomy things have gotten in the way of my work on this since (Gulp! Can’t believe it...) last November. I had been having a bit of trouble building a band pass filter to tune to a single station. It should be a case of a high pass and a low pass in series, but I think that something was not quite right with my workings, and I was investigating a different radio entirely. Anyway I am hoping to get back on to this soon, and if nothing else I have a hankering to build a table top VLF radio. Out of interest, what range of frequencies can the Arduino frequency counter detect? Dave
-
Thank you Alan. Working with Arduino is rather fun, it feels a bit like old school programming when getting it to interact with home brew electronics. Dave
-
Another slightly underwhelming update approaching, but I am feeling a bit chuffed. I have been learning how to program an Arduino ('Exploring Arduino' by Jeremy Blum) and have been able to; 1) Detect a varying voltage (used a spare potentiometer) 2) Get time from a real time clock 3) Log results from #1 and #2 to an SD card every minute 4) Use a transistor as a switch to turn on an LED My thinking is that if I can master all the above I have the basic ingredients for my logging module. Today I have been trying to get #4 modified to turn a radio on and off; the bit in the red box below is the transistor switch (2N3904 transistor). I gather these can take a maximum of 200mA - the radio seems to draw 150mA so I think it might be okay. Anyway, I got the radio hooked up to spectrum lab and several weeks of work/frowning gave me this; The radio comes on at ~57.75 seconds, is on for a second, then goes off. Hahahahaha! A little underwhelming, but baby-steps and all that. Next I will try tinkering with the radio output so that it goes into the Arduino and gets logged, though at the moment I am trying to get the new version radio laid out and the narrow band filter working. Dave
-
Hi Alan, Thank you. It has been quite a slow piece of work but I have enjoyed it. Dave
-
After a bit of work today the potentiometers got sorted. Well, they took 10 minutes to change, the following 2.5 hours was me trying to work out why the radio had stopped working. In the end I traced to it a loose connection caused by me tugging on one of the leads. I had plans to make a nice insulated shoe for the circuit and battery to sit in, but in the end I opted to use silicone sealant and glue them in place. Further down the line I am going to redesign the circuit so that the potentiometers are soldered directly to the veroboard, but I am happy enough for this version to have flying leads all over the place. Anyway, this is the latest pdf after some post build changes; BBB-4 VLF radio with headphone amplifier.pdf I have compared the physical size versus the first one I made, and I think the boards are comparable in size, looking at it now I just needed the larger case be able to handle two potentiometers (left pot is gain, right pot is on/off and volume). So if the amplifier was given a fixed gain, it would be possible to squeeze it into the smaller case. I also have fired up SpectrumLab in my back garden to see if me messing about with filters has made a difference (the BBB-4 with the filters certainly sounds more pleasant than the unfiltered Peanut Butter VLF radio). First screen capture is the unfiltered peanut butter radio; Mains hum is very obvious right at the bottom of the plot, and it really overpowers all but the loudest sferics when listening. The BBB-4 with high pass filter attenuates a lot of this (little signal below 1kHz). There are still harmonics, but they are not as loud. Gain is set to minimum. From a visualisation point of view the filters do not seem to make much of a difference, but for ease of listening they do. Both plots show sferics (vertical lines), VLF transmitters (solid horizontal lines), and I think the intermittent horizontal lines are Russian Alpha transmissions. So, all in all I am quite pleased. I have a few ideas for how I want to improve the layout in future versions, but for the moment I will leave it as is. The next stage is to clear the prototyping board as I want to put together a version of this radio that is tuned to just one of the VLF transmitters. That way I can see if I can get the variation in voltage logged by an Arduino datalogger and use that for SID detection. So the radio and filter will be posted eventually here, but I might start a separate Arduino data logger thread. Hope you enjoyed the post. Dave
-
After more than a lot of frowning the radio is now 90% working (I wired the capacitors up wrong so both controls work backwards). I have also had to spend more than a bit of time debugging the circuit as I now realise the board had several important ommissions and would not work. Mainly the +9v line to the op amp was going to the wrong leg. A little reminder to myself of what happens when I rush or don’t pay attention. But then again I have had voltmeter out comparing values to the prototype and also checking connectivity so it has been useful practice. I have a few days off this week so I will sort the potentiometers and insulate the underside of the board. And maybe make that second headphone socket do something. That case looks huge!
-
This is today’s work, about 3 hours of soldering. I think once again I have made the layout too snug (the inductors were a bit of a squeeze to get on), but otherwise so far I am pleased. Will stop now as I am starting to make mistakes, but the next job is getting the flying leads on to the potentiometers and battery holder.
-
It has been a bit of a while getting the layout done, but I am starting to assemble the new circuit. Have got the circuit board cut out and cut rails as per plan. So I will get soldering tomorrow. Not the most exciting of updates, but after a bit of a break due to work it is nice to see the build progressing again. I am also keen to get the prototyping board cleared as I have started tinkering with an Arduino and have bought a data logging shield.
-
I am still working on converting the schematics into a layout on StripboardCAD, but in the meantime I went out into the South Downs and a slightly more radio quiet location to try listening and recording with the prototype. There is significantly less mains hum, though you can hear a little interference from longwave (I think) radio in the form of faint garbled speech. However the low pass 24kHz filter is helping to remove some of that. I played around with the gain on the radio and spectrogram, but the above is certainly better than in my back garden. Tweaking the settings more and I could see quite a few more VLF transmitters (horizontal lines) from about 12kHz up; I heard lots of sferics but no tweaks or whistlers, though I don't think midday is a good time to listen. The iPhone can be a bit temperamental in knowing when the the radio is plugged in, but my first version will be headphones only so I am not too fussed about solving this now. Anyway, back to getting that circuit layout complete.
-
I have been playing around again with SpectrumView and I found that it does have a gain control in settings, so by adjusting it you can display a fainter signal better, as below; I tried running it out the headphone amplifier again, however one thing I have found is that the plot does/can become a bit erratic (overload/feedback? - limit of my electronics knowledge) as below; So maybe it might be better to run any recordings from the second transistor as per the original BBB-4 design and have a dedicated radio for this (another project!). I have also found that I can either run the headphones or the microphone at any one time. Again, probably a simple fix for someone with electronics knowledge but at this stage I am just happy to have a functioning radio. Given that this is intended as an audio project I have decided that the first iteration will just have a socket for headphones. For the moment I have gone as far as I want with the prototyping, so I will fire up StripboardCAD and start laying out the circuit. Dave
-
I had a play this morning by rewiring the 4 pole socket to run from the second transistor rather than from the lm386 audio amplifier. The BBB-4 is designed to plug into a recorder or laptop directly, however the visual settings on the iPhone spectrogram are basic and you can't alter the colour distribution to handle a weaker signal. Anyway I wanted to see what the difference looked like; Versus the plot from yesterday out the headphone amplifier; I am sure this would not be a problem in SpectrumLab, but for the purposes of what I am trying to achieve I prefer the second. So I think I will have the socket(s) out the headphone amplifier. Dave
-
I have added a 4 pole socket to the test bed so that I can try and get the radio plugged into my iPhone and working with a (free-ish) app called SpectrumView. I like SpectrumLab but getting out the laptop every time is a bit of a faff. So I added the socket at the bottom corner; Black lead is earth, red microphone, white left and right headphones. I am waiting for the silicone sealant to dry, however I very gingerly plugged it in and tried it in the garden... The vertical lines are sferics. There is a lot of hum from the mains, and I believe I can see three military transmitters at approx 18kHz, 19kHz and 22kHz but never the less I can now record to my phone. I will try and take it somewhere more radio quiet in the South Downs as the small screen makes seeing stuff harder with the a/c hum, but otherwise I am quite pleased. Just realised that the phone was not in aeroplane mode, I will try that as well next time. At the moment the socket won't work with the headphones, however I am thinking of having two sockets on the finished thing; one for headphones, the other for recording. If I play some more it might be possible to have a single socket do both. Dave
-
I have been working away and now have a functioning prototype. I took the schematic for the bbb-4 receiver; http://www.auroralchorus.com/bbb4rx3.htm and married it to a headphone amplifier; http://www.circuitbasics.com/build-a-great-sounding-audio-amplifier-with-bass-boost-from-the-lm386/ Which has given me something that looks like the following; Looks ugly but does work. The lower potentiometer is volume control, the upper is gain control. I have also been playing around with an online filter designer and have added in a 230Hz high pass filter (try and take the edge off mains hum) and a 23kHz low pass (filter out long wave radio; without it you can hear voices ). As I mentioned earlier, I can't believe how much easier the test board makes things, as particularly with filters you can easily switch them in and out while the radio is working to hear the difference. Next is to (once and for all) get it working with a spectrum analyser on my iPhone. I have bought specially some 4 pole headphone sockets, so will hopefully get one working on the test board first. Dave
