Introduction: Smartphone WIRED Connection to Old Opel Tape Player, Headset Functions, Mic!

Hey guys, here's another project I made, that I am proud of!

I drive a really old 1994 Opel Astra F, with a Blaupunkt SC 202C car radio, and I wanted a wired, handsfree connection to play music, and more. After a lot of searching, I came across THIS INSTRUCTABLE, a great guide that explained exactly how to make my connections and gave me the courage to do it. But I wanted to control my phone also, being used to the control I have on my Android headset.

So my project is partially an implementation of the previous Instructable for my car, but also shows how to integrate the functions and mic of the headset into your car for a fully controllable, on the cheap car handsfree wired system!

So here you will learn how to:

- turn your Opel radio into an amplifier for your phone's headset signal

- use an old headset and buttons to have Play/Pause, Next track, Home Button (Google Now/Assistant) functions at your fingertips in any old car!

Step 1: You Need:

- about 1/2 hrs to read and comprehend the original INSTRUCTABLE; it will explain concepts that I will glance over in this one.

- about 2 hours for taking apart the radio, making the connections, etc

- about 1 hour taking apart the console and putting it back again

- about 1 hour figuring out how and where you want your buttons.


- Soldering iron, flux and beginner skills

- an old smartphone, TRRS headset, no button necessary, must have mic

- Buy two push buttons from an electronics store, one a toggle (on/off) and the second a momentary. When buying them, find some that will fit nicely with your car's dashboard. One will be the switch from radio to phone, and the other will be the Home button.

- You will need some other household tools, like screwdrivers, wire strippers, cutter, drilling machine.

Step 2: Remove the Car Radio


... However, for me this was not necessary, since it was not coded. I already knew that, because I had to take out my car battery for a day or so, and the radio came back on with no problem, presets and memory intact. Yeah, good old stuff!

To remove it is really easy on these old models, if you use the right tools. For me those were some gardening sticks my wife uses, the fit the holes and did the job perfectly. Alternatively, use wires or premade tools that you can find on the web really cheap. Or get a mechanic to take it out.

Step 3: Take It Apart!

Take off the upper and lover covers. There are no screws here. Just find the space between covers and push them apart.

Once you do that, identify the 4 black screws keeping the tape player in place. Unscrew them, and put it aside, connected just by the wires.

Step 4: Identifying Stuff Inside :o

OK, so for me this was the scary part too. But I got it done, finding some old schematic, with help from friends and drawing on the photos taken. But hey, you do not need to go through this! So here it goes:

In this first picture, The rectangles mark your general areas of interest. The Casette signal Amplifier is the Integrated Circuit in the bigger rectangle, and the connections from the tape player are your second area of interest. If you are curious, you also have the schematics of the IC, colorized :D If not, move on! What you will do is on the back side of the circuit.

Step 5: Identifying Stuff on the Back

Well, here is what you need. I already marked for you the following:

- the L and R audio outputs from the IC

- The ground

- what lead you need to interrupt to cut power from the IC

- where you need to solder the wires for the switch radio/tape (in our case radio/phone)

- another pair of leads to solder together

IMPORTANT! I will take out the entire tape player! I do not need it, and as such have no use for it. If you want to keep it, it will be a little tricky. You will need to think your own switch, keeping in mind that for tape player:

- pins 5 and 6 identify that a tape has been inserted

- pins 3 &4 probably identify when a tape has reached end

- the IC must be powered to function. If you power it with the phone on, noise will appear!

Anyway, second picture with real photos of where to cut and solder.

Step 6: Soldering Part One

Now it is time to build! I used some audio wire I had hanging around. Soldered the audio inputs, then guided the wire inside the player.

Step 7: So, Why the Headphones?

Here is why. At this point we have the audio inputs, so if you just want to listen to music in your car, then it's enough. But I wanted more. And that can be given us by an old 3.5mm headphone, TRRS. Google it!

Here's what it does:

The TRRS has LR channels, a Ground channel and a Mic+ channel. The original circuit board in that old headphone will also have some condensers between the Mic ground and the speakers ground, to reduce interference. The regular button on the headphones, that we will recreate, produces a short between the main Ground channel and the Mic + and produces an event, a hook, for Android (or iPhone I guess) to do various things. If you want to know what, well google it!

(Speaking of iPhone, I think you can also use this setup for it, but the headphones for it have a different configuration, with ground and Mic+ switched)

So what do we do with it?

  1. Firstly, we need the jack. If the jack and the cable are in good conditions, then we can use the entire cable up to the inline mic for what we need. If not, then we need to buy a new 4 pin jack, maybe even 4 wire audio cable.
  2. Crack the mic case open. Inside it it has a small circuit, with a mic
    soldered on. Unsolder the mic, but be careful: do not overheat it too much or u will damage it! & Mark on the mic where is the Mic + input!
  3. Since I do not know what headphones you will be using, I recommend you use a circuit meter to figure out if the config of the wires corresponds to that above. If they are switched, unsolder them an resolder in the correct position!
  4. If you have a button on it too, unsolder that as well. You could use it leads to solder the new wire for the button, but as well use the wire connections as they are soldered to the board.
  5. Resolder the wires you need: Home button, Mic, speakers (the ones you soldered the previous part). I ended up doing it a little different than the image, and I just used a 3 wire cable, soldered to main Ground, Mic ground, Mic +, to get outside the player rack, and then it got split into 2 wires.
  6. If possible, after you check your connections, isolate this board, or drown it in hot glue, like I did!

Step 8: And That Part You Said Will Be Easy :D

Well, now we get to the previously mentioned position/ aesthetical considerations.

Where will you put the radio/phone switch? I chose to use the rewind button of the player, and simply anchored behind it a regular cheapo pushbutton with some hobby board.

How will you get the wires out of the player? Well, you can use the tape player door, or drill a 10mm hole in the back of the player and the rack (there already is a 4mm hole there) and pull the wires through that.

Speaking of, if you do not want to have a bunch of wires hanging, you will want to take off the dashboard and run them behind it. Here are the how to's:

Where will you put your Home button? I chose to place it centrally. Not a great button, but hey, I can change it whenever! (you will need a short button for this position, 10-12 mm in length)

Where will you put the mic? I chose to put it in the steering wheel cover, and the sound is OK. I drilled 3 small holes, and I encased the mic in some rubber foam.

See? I was being generous about it being only an hour...

Step 9: Here It Is in Action!

The audio is indeed great. Even better than radio, and better levels.

The mic works OK, people hear me ok, Google recognizes what I say easily.

In call there is no feedback loop, the voice of the person is heard OK on the speakers, and I can control the volume though the Radio.

Step 10: Thanks!

Thanks to claudiopolis who gave me the know how.

Thanks to Instructables, for being such a great platform. Knowledge is power, Sharing is caring and All the best things are free!

Thanks to my electronic savvy friends that I pestered with questions, so thanks Gabi and Mihai!

Thank you all for reading this far!