2 years since my last blog post. Time to rectify that…
2 years since my last blog post. Time to rectify that…
So I had some (limited) success with my astrophotography last night. It was a clear night for an hour or so and I managed to get the settings for raspistill tweaked to capture some night stars. I grabbed a couple of hundred shots and then converted those into a short video.
The settings I used for raspistill were:
raspistill -bm -tl 1000 -v -set -ISO 800 -awb off -awbg 1,1 -t 21600000 -ss 6000000 -o %06d.jpg
This created a bunch of .jpg files, but skipped tons of frames, so the numbering sequence was way out of kilter (000001.jpg, 000048.jpg, 000073.jpg etc). To fix that, and get them into a proper sequence I used a little script as follows:
I=0 for F in 0*.jpg; do echo "$F" `printf image_%06d.jpg $I` mv "$F" `printf image_%06d.jpg $I` 2>/dev/null || true I=$((I + 1)) done
Then, to convert the individual jpgs into an mp4 movie I used avconv in the libav-tools package as follows:
avconv -i image_%03d.jpg -r 5 -vf scale=1280:720 -vcodec libx264 -r 5 star-trail-$(date "+%Y%m%d-%H%M%S").mp4
I’ve been looking at using my Raspberry Pi NoIR Camera for Astrophotography recently…
A decent shot of the Milky Way is the objective. A decent time-lapse video of a clear sky through the night is a secondary goal. The Pi NoIR camera may be a bit limited as it only has up to around 6 seconds of exposure. This limitation can be countered with ‘stacking’ (if I understand it correctly).
There is a great resource here that dives into the detail of how best to shoot astrophotography. It covers some great guides as to what equipment, what settings etc.
There are some interesting points around settings used for the Pi Camera with raspistill to get ‘star trails’ in this project. Those settings are a good starting point.
There is a lot of trial and error involved in shooting this kind of stuff. Capturing a bunch of frames, stacking and seeing how they look, rinse, repeat.
To hopefully remove a lot of that trial and error, I’ve used this github project. It has some really useful features:
So, tonight’s plan is to get things set up outside, find the optimal settings, then kick off a time-lapse run.
If I get a chance I’ll also look out my little IR LED module and see how things look with that.
For a while now I’ve been meaning to put together a board with a few IR LEDs for a Pi NoIR Camera…
The Pi NoIR camera is an add on for the Raspberry Pi that uses the CSI-2 camera interface on the Pi. It’s just like a normal camera except it has no IR filter (hence NoIR).
This means it can capture in the IR range as well as the visible light range of the spectrum. This is good for dark or nighttime shots where you can ‘light up’ the scene with IR light (that is not visible to the human eye) instead of ‘normal’ visible (white) light.
The Pi NoIR Camera itself does not come with any IR light source. So for nighttime photography is pretty useless on it’s own.
The IR LEDs for a Pi NoIR Camera circuit is pretty simple to build. A few IR LEDs (I got some from Amazon that draw about 20mA and drop somewhere between 1.2 to 1.4 volts) and some resistors. Each LED needs it’s own current limiting resistor (this question gives a good explanation of why). You could just run the LEDs and resistors from a +5v and ground connection directly. However I wanted the LEDs to be switchable by a GPIO pin. As I planned to use 4 LEDs I’d need to be switching ~80mA so I’d need a transistor. The transistor would be driven from a GPIO pin so I’d need a resistor there too.
The circuit I put together look like this:
Calculating the resistor values was pretty easy.
IR LED current limiting resistors
We know the LEDs draw up to 20mA (0.02 A) and drop between 1.2 and 1.4 volts. We want to drive them close to 20mA to get maximum brightness from them.
5v – 1.3v (average) = 3.7v / 0.02 A = 185 Ohms. So I selected 220 Ohms to be on the safe side.
Transistor base resistor
We want the current on the base to be limited to a reasonable value so that we’re not pulling too much from the GPIO pin.
With an HFE of around 100, a 2N2222 only needs about 1mA to drive 100mA through the load. I may add more LEDs in the future, so I opted for something that would give me ~4mA at the base.
3.3v – 0.6v = 2.7v / 0.004 A = 675 Ohms. So I opted for 560 Ohms which will give around 4.8mA.
I soldered this all up on some veroboard with 3 header pins to connect up the +5v, Gnd and GPIO pin:
Next, I connected it up to my Raspberry Pi (GPIO pin 23) and set that GPIO to an output and high. Switched off the lights. Took a raspistill image on my other Pi (with the NoIR camera connected) and you can see it works :
So, the little IR LEDs for a Pi NoIR Camera project was completed in an hour or so. Next up will be something a bit more complex (for me) – trying some outdoor, nighttime photography…
I’ve been playing around with getting a Raspberry Pi with a RDA5708 FM Radio module working.
I bought 2 of them from ebay for around £7. They took around 2 weeks to arrive (from China).
Wiring them up is pretty simple. They are controlled via I2C, so only need SDA, SCL and power (3v3 and Gnd). Audio out is via a standard 3.5mm headphone socket and it has pin holes for a 3 pin header providing Left, Right and Ground.
It took me a little while to get things going and working out the correct command sequences to send it. When that was cracked it was pretty much plain sailing. The resulting audio is fine (for a small radio). The headphones also act as a decent antenna for radio reception, so no need for connecting an antenna for testing.
I will post a fuller tutorial later but getting it working boiled down to 3 steps:
There is a bunch more to do in terms of measuring signal strength, scanning frequencies etc. That said, for quickness, the 3 steps above will get you listening to your favourite station. Some of these modules also have RDS capabilitiy but I do not think the particular version I got has this. It may have and I just don’t yet know how to turn it on – more experimenting required.
will be posted to GitHub in the next few days is on GitHub
I have a project in progress where I’m replacing the ‘guts’ of a vintage Roberts Rambler II Radio (from the 70’s) with this module.
After one too many times of forgetting to shutdown my (headless) Raspberry Pi before shutting down my PC/laptop (and resorting to just pulling the power plug), I decided I needed a button to shut it down gracefully – a ‘Raspberry Pi Shutdown Button’…
There’s lots of solutions around for this, but I decided to re-invent the wheel (as usual)…
This is a fairly simple project, with a little bit of easy soldering required. I had all the bits I needed laying around in various component boxes. It’s not a lot and is likely to cost less than £1 for one. However, typically, you can’t buy these items in ones, they come in quantities of twenty or fifty. Even so the total cost should be much less than £10 and you’ll have a bunch of useful parts left over.
Here’s the list of what you’ll need (with links to buy the components if you don’t have them):
First we work out which legs of the button are shorted when the button is pushed. Using the multi-meter determine which two pins get shorted together when the button is pushed. There will be two sets of 2 pins that get shorted (as the button has four legs). We only need one set, so the other two legs we simply break off (bending them back and forward multiple times works well).
The jumper wire gets folded in half and cut in two at the middle point, so that we have two bits of similar lengths, each with the female connector on one end. The other end we strip two or three millimeters of insulation from. As an aside, I like to use yellow or white for these kind of things as Red, Green, Black all make me think ‘power supply lines’.
For the thinner piece (2mm diameter) of tubing, we cut it in half (so each piece is around 20mm long). For the thicker piece (6mm diameter), we cut it into two lengths, one is 1/3 and the other is 2/3 (so for a 40mm long piece, one of the cut pieces would be about 13mm long and the other 27mm long). Lengths do not have to be accurate – these figures are just a guide (we can be a bit ‘rustic’).
Now we should have something like the image below.
I usually find myself staring at some left heat shrink after I’ve finished soldering. Then realize that I forgot to put it on, and have to redo it all. So, make sure you put the heat shrink on first. You want to (in order):
The soldering involved is really easy. Essentially you want one wire connected to each leg of the button. It doesn’t matter which way around it is.
All that is left on the hardware side is to shrink the tubing. You need to push the two thinner pieces (one on each wire) as far as possible towards the button legs. Try to ensure that there is no bare wire or bare leg visible. Now shrink both of those so that they hold tight. Next push the thicker tubing over the two bits you just shrunk. It doesn’t have to go all the way. It is more just to hold the wires together. Now shrink that too.
Now the final shorter, thicker bit of tubing I push over the two connectors (it should be a fairly tight fit). This just makes it easier to insert the connector as one unit rather than as two separate wires.
Great the hardware is now done. You can place the connector onto P1 connector pins 20 (Ground) and 22 (GPIO 25) and we can write the software that monitors the button and does the shutdown.
So, our button is connected between GPIO 25 and ground. We’ll want our software to:
I’m going to do this in a simple bash script. I’m also going to make sure the script runs when the Raspberry Pi boots.
To set and monitor the GPIO pins we’re going to use the ‘gpio’ utility that ships with Raspbian Jesse.
We’re going to check every second to see if the pin is low. If it is we’re going to check again in another 5 seconds that it is still low. If that is the case then we are going to shutdown (and halt).
We’ll keep it user friendly by issuing a terminal message to all users when the shutdown happens.
Here is the code for the script (shutdown.sh)
# Raspberry Pi Shutdown Button Script
# Wait for a minute – to let everything settle.
# Set up GPIO pin 25 as input and pull-up
gpio -g mode 25 in
gpio -g mode 25 up
# wait for pin to go low
while [ true ]
if [ “$(gpio -g read 25)” == ‘0’ ]
echo “Hold button to shutdown Pi…”
if [ “$(gpio -g read 25)” == “0” ]
echo “Raspberry Pi Shutting Down!”
sudo halt &
When you have written the script make sure you make it executable:
chmod +x shutdown.sh
To ensure it runs on every boot you need to edit your /etc/rc.local file, so in terminal type:
sudo nano /etc/rc.local
and add the following to the end of the file, but before the final ‘exit 0’ line:
# Raspberry Pi Shutdown Button Monitor Script
printf “Starting Raspberry Pi Shutdown Button Monitor Script”
sudo /home/pi/shutdown.sh &
That’s us done. You now have a button that you can hold for ~5 seconds and it will cleanly shutdown your Raspberry Pi.
If you want to make things a little neater you can use some hot glue to secure your button to the case you are using. I glued mine to the end of the case, above the micro USB power connector. All it needed was a small dab for the base of the button and a small dab for the wires to hold it straight. There is less chance of it being mistakenly pressed when glued there, and it’s out the way. It looks pretty clean there too.
Our kitchen radio finally gave up the ghost a few days ago. I suspect it is just the power supply, and at some point I’ll crack it open and see if it is salvageable. However, it was a good opportunity for another little side project – A Vintage Pi Radio.
I just won an auction for one of these vintage transistor radios on eBay.
… which prompted me to order a couple of FM Stereo decoder modules (with a convenient I2C interface for control) and begin shaping ideas for a Raspberry Pi Zero vintage radio project. There’s plenty of info and datasheets around for the RDA5802 IC that these modules are based on, so it shouldn’t be too much trouble to get it up and running. I also have a bunch (5) of the little 3W+3W 5volt amplifiers from my previous (first version) of the Raspberry Pi Outdoor Music Player project (which, by the way is also getting a cool new chassis).
Combined cost was less than £10, so less than £15 all in, including a Raspberry Pi Zero. Watch this space for more details
This project, a Raspberry Pi Outdoor Music Player had been germinating in my mind for a while. We’d had a few BBQs and found that running an extension outside to plug the iPod and speaker system into was a bit of a pain.
I had seen a whole bunch of MP3 players housed in old / up-cycled ammo boxes, and I wanted something similar. The thing I wasn’t too keen on was most of them only had play/pause and fwd/back buttons. I wanted something that I could play music on, have playlists and stream internet radio on. So the requirements list was shaping up a bit like this:
Whilst an ammo box is rugged and cool, I wasn’t too sure how a Wi-Fi adapter would fare trying to get a decent signal from inside a metal box. So, something else was needed, something rugged and non metal. Looking around the garage I spied some old plastic boxes that housed power tools. One of those would be ideal. I chose a Bosch Cordless Drill/Driver box that was empty anyway. If I hacked it about, it wouldn’t be a big loss if anything went wrong and I had to bin it.
This was a ‘no brainer’ (pun intended) – I would use a Raspberry Pi. I had a spare Model B+ (with 2 USB ports), so I could attach a Wi-Fi USB dongle and a USB memory stick to hold a local music library. That also allows me to change / improve the software as needed, and it can play from the local library, stream from the garage server, or Google Play Music, and the GPIO pins would allow me to drive a LCD display to show track information etc. if I chose to do that in the future. The Raspberry Pi also has an audio out jack, so driving the amp / speakers wouldn’t be an issue.
For software I decided to go with MPD (Music Player Daemon). This is fairly ubiquitous in Raspberry Pi Music Systems, and rightly so. It gets the job done well, has a ton of clients across all platforms and is easy to get installed working. For the front end I found ympd which is a great application, single file, self contained that you run and it acts as a web server (so no apache, nginx, lighttp needed) listening on a port of your choice. The UI has a nice clean functional look too.The only issue is that it doesn’t (yet) do playlist management/creation (I’ll be looking into adding that later).
The audio output from the Raspberry Pi itself is fine for headphones, but is not really good enough to drive a set of speakers directly. So, I wanted to feed a stereo audio amplifier from the Pi and have the amplifier drive the speakers. Initially I went with a 12 volt 15watt amplifier module, but after a few problems with this (see below), I swapped to one of these 5 volt stereo 3W=3W watt amplifier modules.
For the speakers I needed something that fitted into the space available in the plastic case, and that would fit into a flat area on the outer part of the case. I found some 4 inch 4 Ohm speakers from Maplin, for the princely sum of £2.99 each. They were a perfect fit for the space I had available in the box. If you can’t get them from Maplin they you can try these from Amazon.
I originally planned to use some spare LiPo batteries that I had laying around. I had 2200mAh 3S batteries available that would provide around 11-13 volts. After having audio noise problems (see build below) trying to use a DC-DC (buck) converter to get this down to 5 volts for the Raspberry Pi, I abandoned this and reverted to an Anker 20,600mAh portable battery pack that I had anyway. I normally carry this portable charger around with me, and when needed in the Raspberry Pi Outdoor Music Player I just plug it in and we’re ready to go. I may have to buy one to keep in the box rather than swapping it around every time.
I put this project together in 3 stages, each of around 1 hour.
The first part of this was to cut out cardboard templates for the speakers – this allowed me to place them on the case and see where the best fit was. When I was happy with the position I then marked it and cut the holes. For the cutting I started each with a holes drilled all the way around, then did the rest with a Stanley knife / box cutter.
Next was the internal case mods. This will vary depending on the case you use. For me the plastic risers and dividers inside were thin enough to cut with the Stanley knife, so it was a quick job. Just find suitable spaces for the Raspberry Pi, the amp, the battery and cut those to the size required. You’ll also want to cut out some routing for the power and audio cables. I routed these around the outside of the box, but whatever suits you best.
Note: Initially I mounted the 15W amp on it’s side, screwed into one of the dividers (see image below), but the 3W+3W (smaller) amp had an adjustable pot on it and was designed to be mount through the chassis.
The final product looked like this:
This stage required a little soldering. Basically I took a 3.5mm audio cable I had laying around and cut off one end. I then found the right connections for Ground, Left Audio and Right Audio and soldered those to a 3 pin header socket I had. This was then connected to the 3 pin header on the amp board. The output of the amp board is a + and – audio signal for each channel. I used 2 pin cables to plug into the headers on the board, cut off the other ends and soldered the cables directly to the speaker + and – tabs.
For Raspberry Pi power I ran a USB to micro USB cable from the battery to the Raspberry Pi (just as you normally would). For the power to the amp board, I first considered hacking about another USB to micro USB cable. Then I remembered I had some little micro USB socket boards that I’d bought in bulk some time ago. I plugged in the second USB to micro USB cable to that board and soldered the +5V and Ground connections from that board to the amp board.
Everything was now connected – time to start on the software side.
This is still a (kind of) work in progress stage. To get the first version working I installed mpd and the command line client (mpc) on the Raspberry Pi:
sudo apt-get install mpd mpc
Next I used the command line client to add a stream (Heart Radio) and told it to play:
mpc add http://media-ice.musicradio.com/HeartBerkshireMP3
Not much happened at first, but I turned up the volume on the amp board (using the on board potentiometer) and then it worked well, so I knew I had things connected and working correctly.
So far so good, but I didn’t want to be SSHing into the Raspberry Pi to add or change songs. I also wanted to get a local cache of all my music on there. A 64GB USB stick would easily hold my music collection with room to grow. So, I copied all music from my home server to the USB stick and inserted it into a USB socket. You could also simply copy all your music onto the Raspberry Pi SD card itself (assuming you have enough spare storage). The default location that MPD looks for music files is /var/lib/mpd/music so best to copy your files there.
If you go the USB route then you have to tell mpd where the base folder is for your music. This is done in the config file, so a few more commands at the terminal:
sudo nano /etc/mpd.conf
Now find the line with the setting music_directory and edit the path to your USB drive. On my machine that was /mnt/usb/music. You may have to restart the mpd daemon after this, to do so:
sudo service mpd restart
There are simple instructions on the website to get this installed and running. Essentially, download it, extract it and run it.
I wanted it to be run automatically so I moved the app :
mv ympd /usr/bin
… and the made it automatically start with :
sudo crontab –e
… then added
@reboot /usr/bin/ympd –webport 90
to a new line at the end of the file and saved/exited.
With all that set up you should be able to use a browser to navigate to your Raspberry Pi. I gave mine a hostname of musicpi, so I simply browse to http://musicpi.local. From the web interface you can control everything you need to. Of course, there are a ton of other clients available for mpd if you would rather control it directly from your mobile etc.
It is probably worth noting that initially (with the 15W audio amp) I had a lot of noise and distortion. The amp I had chosen needed a 12v source, so I had used a 12v power supply and fed the amp as well as a DC-DC (buck) convertor to step the voltage down to 5V for the Raspberry Pi. I believe the buck converter is very noisy (switching) and this was causing the problem. As soon as I switched to the 5v amp the noise vanished. Bonus for only having a single supply voltage too.
Overall, I’m really happy with the Raspberry Pi Outdoor Music Player Project result. A few spare (laying around) parts, combined with a cheap amp and speakers and a few hours of integrating it all together and I have a pretty cool music box. There are a few enhancements in the works for this too:
If you build one, or found this useful please comment below and leave a link for me to check out your project.
Finally completed the V1 Pi Outdoor Music Player. This is an old power tool case modified to mount/contain:
Sound is loud enough for a family BBQ and decent quality. The stereo amp has a volume control to allow adjustment. The wifi dongle (and ympd) allow the music and playlists to be controlled via a phone or tablet.
A full write up on the project will be coming shortly…The full project write up can be found here