A while ago I bought a Blaupunkt Frankfurt US to replace the modern stereo in my car. I contacted a couple of people who made bluetooth adapters and waited months for a reply. After a while I thought it can't be that hard to make my own...
The Frankfurt has a 6 pin din plug on the back for attaching tape decks etc. Pin 1 is output from the tuner, pin 2 is input to the amplifier and pin 4 is unswitched 12V. There’s a white cap in it by default which bridges pins 1 and 2. A Bluetooth adapter can easily be added without any modification as long as it can pass through an aux signal.
I scoured AliExpress for suitable Bluetooth modules with an Aux in, Line out and microphone for hands free that would run on 12v. I bought about 6 of them as they're only $5-15 each and there's almost no information on their features other than a picture. The best one I found is an LN-BT02:
https://www.aliexpress.com/item/3268...5da34c4dmPHfEJ
This one turns on and passes through the Aux input by default. When you start playing music it switches to that. When you stop the music it switches back to Aux. The hands free seems to work but I have pretty low expectations on the quality. There's some buttons but I don't plan on hooking them up, just control it from the phone.
I also bought some 6 pin DIN plugs from AliExpress and wired one up to the bluetooth adapter. My Frankfurt is mono so this is wired for that. I assume the stereo units have a plug with more pins and a similar cable can be made.
blaupunkt.bluetooth.png
I've tested it on the bench and it works great. Next step is to 3d print a case and install it in the car. I'll update on that later.
The Frankfurt has a 6 pin din plug on the back for attaching tape decks etc. Pin 1 is output from the tuner, pin 2 is input to the amplifier and pin 4 is unswitched 12V. There’s a white cap in it by default which bridges pins 1 and 2. A Bluetooth adapter can easily be added without any modification as long as it can pass through an aux signal.
I scoured AliExpress for suitable Bluetooth modules with an Aux in, Line out and microphone for hands free that would run on 12v. I bought about 6 of them as they're only $5-15 each and there's almost no information on their features other than a picture. The best one I found is an LN-BT02:
https://www.aliexpress.com/item/3268...5da34c4dmPHfEJ
This one turns on and passes through the Aux input by default. When you start playing music it switches to that. When you stop the music it switches back to Aux. The hands free seems to work but I have pretty low expectations on the quality. There's some buttons but I don't plan on hooking them up, just control it from the phone.
I also bought some 6 pin DIN plugs from AliExpress and wired one up to the bluetooth adapter. My Frankfurt is mono so this is wired for that. I assume the stereo units have a plug with more pins and a similar cable can be made.
blaupunkt.bluetooth.png
I've tested it on the bench and it works great. Next step is to 3d print a case and install it in the car. I'll update on that later.
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