borzech

Okay, folks, I wanted to add aux-in port to my Lexus, but I didn't wanted to use relays and empty cd disk, neither use cassette adapter because of quality. It has to have "clean look". I wanted to sactifice tape, cause I don't use it, but my Lex is so quiet, I could hear electric mechanism from the radio.

Pioneer made the system very sophisticated. It's a quite hard to "fool" the mechanism, while the electric motor is disconnected. Both reels have opto couplers to read reel movement. So I made oscillator based on Velleman mk102 kit, but instead of LED, I used opto darlington couples 4n33 (pin 1-Anode, 2-Cathode).

I disconnected motor and connected the oscillator supply instead, ground is metal chassis. On the cassette board there are 6 soldering points between 2 pcbs. We need 3 from right: FRS, GND, RRS. Both emitters (pin 4) from 4n33 I connected to GND, I disconnected orginal FRS and RRS sensors and connected the collectors subsequentely (pin 5) on 4n33.

To connect the audio input - it was much easier. I just disconnected the original cassette pre-amp and connected wires.

It takes patience to adust the correct frequency of oscillator to fool the mechanism. Be aware the frequency changes slighty with different voltage supply, so check with engine off and on before you put all together, but voltage stabilizer is not necessary.

All you can see on the pictures. I hope all knows I can't take any responsibility for someone mistakes to copy my idea. But if you want to copy / improve this - feel free and put it on comments.
Quality is very good. It cost me not even $10 and it's worth every single penny.

little correction: Today I drove a little and notice it's very vurneable to voltage fluctuations, causing frequency fluctuations. So I'll add voltage stabilizer like lm7812 or simmilar to fix it.

PureDrifter

iTrader: (10)

this is an amazingly complex idea you have so it makes me wonder...
EE major or ?

Trancerush

Great idea, nice write-up.
You must be a BMW technician...

borzech

:PureDrifter
I would lie if I would say I know nothing about electronics.

:Trancerush
You know me I fix BMW, but I drive Lexus.

:all
Do anyone have any idea how to make multi aux in? I need 3 so far. One for Ipod, second one for HD radio and third one for bluetooth. I thought I can use IC MAX311, but, maybe anyone has better idea?

If anyone has questions/improvements of my idea - feel free to post. Let's make our babies better!

PureDrifter

iTrader: (10)

i actually contemplated something like this a few years back when i was making my aux in mod, but decided it was beyond the capabilities of 80-90% of CL members, and that i wanted something with equal quality but a simpler execution. your solution is very elegant but much more involved. props for getting it done though.

borzech

I just finished my another project finally with my wheels. Now I'll go back to improve the sound. Will keep posted. I need to make multi aux-in and to switching I want to use eject button. So still the radio looks exactly as orginal, no plugs, wires attached, everything hidden, but with modern features.