Lexus RX Steering Wheel Buttons

Is there any way to connect the volume button and other button wiring of a Lexus RX Steering Wheel to an Arduino for PC keyboard or PC keypress controls?

How do I figure out which wire is ground, and which wire is for each button?

Do I need resistors?

I included pictures.






Yes, maybe.

For the Arduino, get a Pro Micro (don’t confuse with Pro Mini).

Draw a schematic of each board showing each switch, resistor and led, by tracing the pcb tracks, and post that. The resistor values should be read as, eg. “912” means 91 followed by 2 zeroes, ie. 9100 or 9.1K ohms. You can ignore those “TP” markings, they are test points and dont affect the circuits. Where a track ends in a small hole, these are “vias” to allow the track to continue to the other side of the pcb. Those “S” shapes are the switches. A piece of conductive rubber on the back of the buttons connects the tracks.

You may not need to use that cable. Ordinary female to male dupont wires might plug into those 7 & 8-way sockets.

PaulRB:
Yes, maybe.

For the Arduino, get a Pro Micro (don’t confuse with Pro Mini).

Draw a schematic of each board showing each switch, resistor and led, by tracing the pcb tracks, and post that. The resistor values should be read as, eg. “912” means 91 followed by 2 zeroes, ie. 9100 or 9.1K ohms. You can ignore those “TP” markings, they are test points and dont affect the circuits. Where a track ends in a small hole, these are “vias” to allow the track to continue to the other side of the pcb. Those “S” shapes are the switches. A piece of conductive rubber on the back of the buttons connects the tracks.

You may not need to use that cable. Ordinary female to male dupont wires might plug into those 7 & 8-way sockets.

Wow, thanks for the detailed reply PaulRB. I have learned a lot of information from your post. I will try to draw up a schematic, but it will take me quite some time. I am a total noob.

Just in case, I am including more pictures.

Another clue: the leds have a "k" printed next to them to indicate which side is the cathode (negative) side.

PaulRB:
Another clue: the leds have a "k" printed next to them to indicate which side is the cathode (negative) side.

Thanks for all the clues. I am using Fritzing to make the schematic. I am actually trying to redraw the PCB directly as I see it in the original picture I took. The original picture is much higher definition. Fritzing automatically makes a schematic and breadboard view. Even though I am using this approach, it does get complicated to trace the PCB circuit. For now, I will try to complete the left side with the volume button just to see if I am drawing it correctly.

Are the left and right side circuits connected together because the original cable does connect three wires between both sides?

Also, can a resistor begin with 0089 or is this likely a 6800 resistor?

androidftw:
Also, can a resistor begin with 0089 or is this likely a 6800 resistor?

That's 680 ohms. 680 with no added zeroes! I suppose that could be written 681. I don't know why it is written 6800. Maybe it indicates a higher precision.

androidftw:
Fritzing automatically makes a schematic

No it doesn't. It makes a pretty but largely meaningless pattern. It is nothing like a schematic and therefore useless for the purpose. Including it when asking for help will achieve little I'm afraid.

This is what a schematic looks like:

PaulRB:
That's 680 ohms. 680 with no added zeroes! I suppose that could be written 681. I don't know why it is written 6800. Maybe it indicates a higher precision.

Exactly what I thought. Thanks for the clarification. I just wanted to make sure I wasn't reading the value upside down.

AJLElectronics:
No it doesn't. It makes a pretty but largely meaningless pattern. It is nothing like a schematic and therefore useless for the purpose.

Thanks for letting me know this about Fritzing. Yes, I was afraid that Fritzing was too simple. Unfortunately, I feel that my schematics knowledge is at that level currently. My overall electronics knowledge could also use an improvement. If I was to draw the schematic by hand, it would most likely appear the same way like on Fritzing. I am having trouble just redrawing the PCB at this point. When I look at the PCB, it looks like a relatively simple circuit if I am not mistaken so I don't know where my confusion is coming from.

AJLElectronics:
No it doesn't.

Yes it does.

It may not be the best or most complete schematic editor around, but it's fine for beginners, and can introduce them to the concept and symbols used.

Many schematic editors are part of a larger tool package which also includes a pcb layout editor. Often, the schematic editor and pcb layout editor are linked and can help the designer enourmously by detecting any inconsistencies in the components and connectons between the two "views" of the same circuit. Eagle, for example, is like this.

Fritzing is no different, but it also has a third view, the "breadboard view". This is the view that it is famous/infamous for. A Fritzing project can have all 3 views and spot errors and inconsistencies between all 3, which could make it very usefull for absolute beginner projects.

My criticism of Fritzing is the poor "workflow". Projects should always start with a schematic, then assist the user as they lay out their prototype on breadboard or stripboard as the next step, spotting connection errors, missing connections etc compared to the schematic. During prototyping, it can help the user keep changes and corrections made in the breadboard in sync with the schematic and vice versa. Once the prototype is working, the last stage would be to design the pcb, maintaining consistency with the 2 other views. Unfortunately, many users never explore beyond the breadboard view, and often even call that a "schematic".

PaulRB:
Yes it does.

Thanks for your input. I will try to organize the resulting schematic into a more readable view. For now, I still need to finish redrawing the PCB. And, I need to review the circuit to make sure everything is in place.

If this doesn't work out, I will just resort to placing normal Arduino buttons underneath the real steering wheel buttons.

PaulRB:
Yes it does.

It may not be the best or most complete schematic editor around, but it's fine for beginners, and can introduce them to the concept and symbols used.

Except that is akin to learning Esperanto when you should be learning Mandarin to start with. There is little commonality between a circuit diagram and Fritzing, the use of the latter is just trying to dumb it down to "Lego" building blocks and the user learns nothing useful. Then when they are looking for help and support, those daft pictures are presented which we have to try to follow.

Each to their own, but I tend to skip past posts where those things are used as evidence.

AJLElectronics:
Except that is akin to learning Esperanto when you should

Would the original schematic manual help? I looked at the available manuals, and I came to the conclusion that the brown wire is ground, for example. Is this correct?

There is no standard for low Voltage wiring, so you need to look at other ideas and formulate your own.

Brown is the German idea of "GND" but in the UK, black is used typically. We use red for a positive low Voltage, although in electronics the conventions have become red for 5V+, Yellow for 12V+ and one I can't recall for the negative rail.

Mains power in Europe is Brown, black or grey for phase, blue for neutral, and green/yellow for earth.

It also depends what wire colours you have in stock, but try to be consistenet as it makes it so much easier to debug a prototype.

AJLElectronics:
There is little commonality between a circuit diagram and Fritzing

I guess you didn' t read what I put in post #10. It was rather long.

Here is a schematic drawn with Fritzing


and here is the breadboard layout

Two views of the same circuit, you can flip from one to the other. Changes made in one are immediately reflected in the other, although they might need neatening up a bit.

So I am guessing the original schematics don't address the original harness pinout issue of this topic? I still need to make my own schematic?

AJLElectronics:
Except that is akin to learning Esperanto when you should be learning Mandarin to start with. There is little commonality between a circuit diagram and Fritzing, the use of the latter is just trying to dumb it down to "Lego" building blocks and the user learns nothing useful. Then when they are looking for help and support, those daft pictures are presented which we have to try to follow.

Each to their own, but I tend to skip past posts where those things are used as evidence.

Best description of Fritzing that I've seen.

androidftw:
So I am guessing the original schematics don't address the original harness pinout issue of this topic? I still need to make my own schematic?

Oh, you mean the link in post #16? Seams to be for the entire vehicle. Did you find schematics for the 2 pcb you want to use? Please post those. If they are detaile enough, you may not need to make your own.

PaulRB:
Yes it does.

It may not be the best or most complete schematic editor around, but it's fine for beginners, and can introduce them to the concept and symbols used.

Many schematic editors are part of a larger tool package which also includes a pcb layout editor. Often, the schematic editor and pcb layout editor are linked and can help the designer enourmously by detecting any inconsistencies in the components and connectons between the two "views" of the same circuit. Eagle, for example, is like this.

Fritzing is no different, but it also has a third view, the "breadboard view". This is the view that it is famous/infamous for. A Fritzing project can have all 3 views and spot errors and inconsistencies between all 3, which could make it very usefull for absolute beginner projects.

My criticism of Fritzing is the poor "workflow". Projects should always start with a schematic, then assist the user as they lay out their prototype on breadboard or stripboard as the next step, spotting connection errors, missing connections etc compared to the schematic. During prototyping, it can help the user keep changes and corrections made in the breadboard in sync with the schematic and vice versa. Once the prototype is working, the last stage would be to design the pcb, maintaining consistency with the 2 other views. Unfortunately, many users never explore beyond the breadboard view, and often even call that a "schematic".

And this is the best description I've seen.
While it's far from the best program for the task, the real problem is noob's posting the breadboard view instead of the schematic view and that's simply because that's what they understand better.