30 Replies Latest reply on Feb 28, 2020 7:48 AM by marco'polo

    Building a Pi WiFi radio receiver controlled by vintage aircraft instruments. Some pointers, please ?

    marco'polo

      Hello, new to this forum, I am seeking some help to get started in the right direction with this project.

       

      My goal is to build a WiFi radio receiver with speakers operated by RP and controlled by vintage aircraft cockpit instruments, probably a Pi3+ (?). It needs to look nice and be original.

       

      Here's an example of the radio part, with credits to Bob Rathbone

      https://bobrathbone.com/raspberrypi/pi_internet_radio.html

      There are exquisite instructions and manuals by him on how to build the radio part of this project so that is not my question.

       

      Here's the twist and where I need to help getting started. I have 5 of these 80s analog, precise, unused instrument controllers. I would like to incorporate these to replace the stock rotary dials and control channel and volume. It would look cool, be original, but.... I don't know how to use the controller to feed inputs to the RP.

       

      Idea1: In the back there is a 37 pinout D-bus terminal. The most elegant would be to buy some female 37 pin board converter and find a way to feed the input to the RP, perhaps via the GPIO of the RP. I don't have a mapping of each pin's purpose, the closest I could find is in the pic below.

      Does anyone have an idea how to discover the use of each pin and how to turn that into a listening variable input into a program on the RP ?

       

      Idea2: If all else fails, there may be a brute force method of removing the backplate and gluing some rotary knob controller directly onto the disc. Might function but not elegant.

       

      Expanding the project, I could even add some electric dial powered instruments/gauges to show volume level setting by feeding the right input back to the instrument.

       

       

       

      I would greatly appreciate if anyone could give me some general steps and ideas to follow especially for idea 1 above. THANKS!

        • Re: Building a Pi WiFi radio receiver controlled by vintage aircraft instruments. Some pointers, please ?
          michaelkellett

          Do you have a schematic for the actual controllers you own ?

           

          The schematic in the picture doesn't look right - it shows a different front panel.

           

          Then you need to apply power to the controller and monitor what happens on the pins while you play with the controls (informed by the schematic).

           

          You'll need an interface to the Pi and it may be necessary to run the controller with Pi unfriendly voltages.

           

          First step is to get the right schematic (and manual if possible) and post it complete in fully legible form here.

           

          If you can't get a schematic it may be possible to reverse engineer the controller or maybe easier to rewire it . It always seems wrong to wreck these ancient parts by re-wiring - I'd go to some lengths to preserve it in original state.

           

          Where are you (if in the UK I might be interested in having a look at one of the controllers).

           

          MK

          1 of 1 people found this helpful
          • Re: Building a Pi WiFi radio receiver controlled by vintage aircraft instruments. Some pointers, please ?
            DAB

            Interesting project, but very challenging.

             

            Just looking over the basic schematic you showed, I am pretty sure the control units are just the switch housing.

            These are not the actual radio sets. That actually works to your advantage.

            You can interface to the wires on the connectors to generate switch connections you can pass on to the RPi, using suitable level controls, and then use an SDR stick with the RPI to do the actual radio bits.

             

            Please be aware that this is a challenging project. It will take a fair amount of hardware and a lot of software knowledge to bring off.

             

            DAB

            2 of 2 people found this helpful
              • Re: Building a Pi WiFi radio receiver controlled by vintage aircraft instruments. Some pointers, please ?
                marco'polo

                Many thanks for your perspective DAB. What was I thinking when I thought I would post this in the beginner project section :-)

                Yes you are correct this device (the 585b controller) is only the UI to select the frequency.

                 

                For those interested to know more on this, an ADF (automatic direction finder) is a flight navigation instrument that will point an arrow to the source of an emitting beam. These types of ADF systems have 3 parts :

                1- Input frequency selector, where the pilot chose the frequency of the beam to be located

                2- The actual beam receiver which is a big black box connected to an antenna on the fuselage

                3- and an indicator that looks very much like this

                In fact if I am lucky enough to move this project ahead and look for more unnecessary complication, I might want to an indicator in to show something else associated to the WiFi radio. But that's one for the next step...For right now it seems I am over my head, but I'll persist with the help of the great contributors on this forum.

                3 of 3 people found this helpful
              • Re: Building a Pi WiFi radio receiver controlled by vintage aircraft instruments. Some pointers, please ?
                phoenixcomm

                marco First, Let me assure you this is not rocket science! You have the pin-out, or you can generate one your self, DVM to ground. and then probe. The good news is your print. above looks ok, So. Take a deep breath. I believe your pinouts show the tuning frequencies. What you have is only a Radio Head, ie each head has its own black box, radio. So for your indicated frequency "820Khz pins 12 and 6 will be connected via ground.  now with that said the BFO switch is SPST.  Then the function switch test/ADF/ant/off is just a rotary switch. All of this can be handled by Arduino. Now you have to send you selected frequency to your radio (pi whatever). since this is a Fixed system your and your Radio Heading will not work.  unless you just want to point to the radio station from where you are.

                I am working on a project Nexgen. I have a motto: 1) Do not harm to the equipment. 2) see rule 1, rules  3 -9 see rule 1. rule 10 ) for vacuum drivin stuff you will have to convert to small stepper! Another one is my fuel gauge there are no docs and everybody says property. Which leads me to rule 11)  Abuse it if you must!

                NexGen Flight Simulator

                3 of 3 people found this helpful
                • Re: Building a Pi WiFi radio receiver controlled by vintage aircraft instruments. Some pointers, please ?
                  phoenixcomm

                  marco Back to your idea #1. DO NOT CUT UP YOUR HEADS! I will direct you to one of my older blogs Audio Panels Ins and Outs cutting up your heads is a disaster!!  Lots of Soldering for nothing! You can buy a DB-37F on eBay for 4-5 buck hey don't want to build cables buy a National Instruments Compact FieldPoint Cables, DB37M - DB37F, L-com E119932-J and cut the male end off, they are like 9 bucks. Me most of my connectors are circular Bendix connectors and then can cost more than $50 each. Personally I use old printer cables! They're really cheap! DB-25 <> Pertec Connector, so I cut off the Pertec Connector this gives me about 6' of cable between my instrument and its controller (Arduino) terminated with the DB-25F.   So to terminate to the instrument or radio head I use the original connectors mate (solder-cup).

                  #2 Your Pi should just do the heavy lifting. You can use Arduino Megas for tunning and then run CAN bus between them! Just remember that you will have to write a protocol (software) to translate the Radio Head to Arduino for decoding. And then put that into a format that the Pi can understand.

                  1 of 1 people found this helpful
                  • Re: Building a Pi WiFi radio receiver controlled by vintage aircraft instruments. Some pointers, please ?
                    marco'polo

                    All right, thanks to all the inputs. I have now received the ADF controller and here is a video presentation of it.

                     

                     

                     

                    And here are some close-ups of the device:

                      • Re: Building a Pi WiFi radio receiver controlled by vintage aircraft instruments. Some pointers, please ?
                        phoenixcomm

                        marco Marco just one small note:  What have are dumb radio HEADS. You must have a controller to decode the frequency and the position of the switches. This can be done with an Arduino Mega and its output can go to your PI.

                        outer1000800400200100
                        Center402010
                        Iner1248
                        1
                        2
                        3
                        4
                        5
                        6
                        7
                        8
                        9
                        0

                        7The easiest way to build a small spreadsheet and you are in the NYC area and you know that you can get a good fix on WABC 770KHz.

                        Therefore when the outer band is set to 7  signals 400, 200, 100 with the inner band which is also tuned to 7 400, 200, 100 will be low via common to the ground and all the outputs pulled up.

                        I hope I have helped.

                        Cris

                        1 of 1 people found this helpful
                          • Re: Building a Pi WiFi radio receiver controlled by vintage aircraft instruments. Some pointers, please ?
                            marco'polo

                            phoenixcomm YES you have helped ! THANK YOU ! I posted my msg by mistake before I finished the edit, and you already replied with the question I was going to ask :-)   ...which was, how to feed this analog input into something to transform it into a variable for software. I am quite the beginner at this, I think I will figure out the software part, but the analog side is entirely new to me.

                             

                            I fully understand that I will need to play with the device and its Arduino Mega decoder to map a bijective function between the position of each dial and the output frequency.

                             

                            That said, I am not building an FM/AM radio receiver, I am building an internet radio receiver. Basically I plan to use the big dial (pos 2 ->17) to select a webradio stream URL, and mid+small dial to adjust volume.... All that will take place in the RPi, so we don't need to concern ourselves with that for now. Let's say, the intermediate step would be to bring on a screen the same number as the frequency dial position. I use the device as input just for fun, it just won't be a frequency.

                             

                            So with that I will follow your advice and buy an ARDUINO MEGA and I will NOT cut the heads. No guillotine. I will also get a DB38 female breakout board like you suggested before.

                             

                            So, I'll need to get on a crash course to learn Arduino, I have never touched one. There are plenty of resources, but do you have a recommended reading/resource to get started in connecting the pins to the proper MEGA I/Os ? In particular can you tell me if the MEGA can be the power source for the ADF or do I need another dc-power source ? If so, do you have a reco ? I'm afraid to fry things with uneducated trials.

                             

                            I received 5 of these ADF units in a ebay package deal. If you Chris or any other contributor have an interest in one unit, I'd be happy to ship it to you (in the US).

                             

                            Thanks again,

                            m.

                             

                            Below is a map of the pin switches from what I could make out visually.It may not be perfectly exact, some tiny wires are hard to follow.

                              • Re: Building a Pi WiFi radio receiver controlled by vintage aircraft instruments. Some pointers, please ?
                                phoenixcomm

                                marco marco do you know C? and don't worry about audio at this moment.  you will three arrays here is how it would look if it where 7.

                                the table is initialized as Outer[1][10] = {{7},{H, L, L, L, H}} // so you are going to iterate over table 0 to 9 in a for loop now you have to put some if(x) in there.

                                 

                                function Outer () {

                                  for(int n; int < 10; n++) {

                                        if ( Outer[7]  =  400) {

                                             if ( Outer[7] = 200 ) {

                                                if (Outer)[7] = 100  ) {

                                                    return 7; }}}

                                  }}

                                  • Re: Building a Pi WiFi radio receiver controlled by vintage aircraft instruments. Some pointers, please ?
                                    michaelkellett

                                    Hello Marco & CH,

                                     

                                    You don't need to bother with an Arduino unless you want. You can use port extenders on your RPi.

                                     

                                    Here is an example:

                                     

                                    https://www.abelectronics.co.uk/p/54/io-pi-plus

                                     

                                    This is a 32 bit IO board, you might be OK with a 16 bit board but this is the first one I found. There are lots available, choose on that uses the MCP3017 chip and has its own software libraries.

                                     

                                    You can connect this to your switch box (CH calls them HEADS). If the schematic you have is anything like your switch box then there are some diodes in the box so the polarity of the common is important. You'll need pull up resistors on the inputs and to connect the frequency common to 0V.

                                     

                                    If you go this route the RPi can do all the work in Python.

                                     

                                    MK

                                    2 of 2 people found this helpful
                                      • Re: Building a Pi WiFi radio receiver controlled by vintage aircraft instruments. Some pointers, please ?
                                        phoenixcomm

                                        michaelkellett  Micheal your Pi will busy doing its radio thing, and not much else yes you could use an I2c port expander, but then you're going to let it churn to get the frequency. Marco says he wants multiple heads. It is far easier to use a Megas to offload that crap.  In this way the when the proper head is selected you will have the frequency. Now about the audio and lights normally dial lights are only turned on when your unit is ON since this most likely you will need a small relay as well they can be picked up on eBay. And saying that implies you will monitor the position of the switch.   

                                         

                                        BTW Michael, you said "your switch box (CH calls them HEADS)" I did not come up with the term. It is used by both the military and the avionics folks the term head describes a  dumb box display or switches in an aircraft's cockpit, while its box (like your Pi) would be downstairs in the avionics bay.

                              • Re: Building a Pi WiFi radio receiver controlled by vintage aircraft instruments. Some pointers, please ?
                                jc2048

                                In case you're not clear about the schematic, the frequency switches encode negative-logic BCD [Binary Coded Decimal].

                                 

                                One slight disadvantage with the scheme that the original designer used is that, on the setting for '7', there are two diodes in series on a couple of the outputs, so the drop across them is going to be a fair bit more than where there is just one diode, and the corresponding low-level will then be higher. You might want to measure that voltage level with a meter and then take a view as to whether you were happy with it for whatever logic it was going to be connected to.

                                1 of 1 people found this helpful