Silly assumption?? | Posts 16+

It might just be a silly guess. I have a working interface. It works on 2 PCs and a laptop. TESTED. There are no problems anywhere. Maybe it's because (I don't know how it is for you), but the COM port speeds are set incorrectly in the Device Manager. I have something like 926,000 baud, which is the maximum. Maybe yours is set too slow? Sometimes, computers and cars behave in a somewhat strange way }.

Have a nice day.

DeathAngel69

Hello.
I've experimented with some settings regarding the baud rate, but nothing has changed.
I'm trying to disable COM 2 in the BIOS today.
I cannot translate this because it consists only of question marks.
But, as I said, the settings on the desktop and the laptop are identical.






A6, AEL.

Hello Oliver,

It is conceivable that the electrical characteristics of the interface may differ between desktop computers and laptops. So far, I have only encountered the opposite situation, where some serial laptop interfaces had driver circuits that were poorly designed.
If your adapter works on a different desktop, then maybe you should double-check the component values again.
If your modem is working, then the interface shouldn't be the problem.
Could the behavior possibly be related to potential differences caused by different grounding between the desktop computer (power plug with grounding) and the laptop (battery, switching power supply with Europlug without grounding)?
Try, as a test, placing your desktop computer in your car, disconnecting the plug from the power cord, and replacing it with one that doesn't have a grounding wire (the yellow-green wire). Don't forget to connect the monitor to a separate power source. For a quick test, you can also simply disconnect the monitor's power cable and VGA connector; this will allow you to see if you were able to communicate with the control unit.
If possible, you should carefully examine your adapter.
I don't have the circuit diagram memorized. Could it be that there are inputs with undefined potentials floating around in the vicinity of the optocouplers/transistors?

Best regards, Rainer.

Hi.
I found the error.
By chance.
So:
When the diagnostic tool is connected to the vehicle via the adapter (engine off, ignition on), the adapter is detected.
The adapter is not being detected by the desktop PC when connected to the vehicle (engine off, ignition on).
But: Once the motor is running, it works perfectly fine with the desktop PCs.
Why???
It doesn't really matter, as long as it works.
Thank you all for your good and helpful tips.
Best regards, Olli.

It could be due to the voltage. With the engine running, the on-board voltage is higher, and since the adapter draws power from that source, it could potentially affect the voltage of the serial interface.

The notebook, being built with low voltage components, is likely less sensitive than the larger computer.

Best regards,

Jan.

Okay, that sounds good, I'll check it out today.
Maybe I'm 'lucky,' and things will turn out for me like they did for Oliver!

I've only used desktop computers with it so far.
Let's see what happens.

So, I used my notebook today, but I'm still getting the same error: 'Adapter not found' .

I've noticed the following: I have 4 contacts (2; ground, K, L) on the car. There are 12 volts measured logically between 12+ and ground. If I 'plug in' the adapter (I insert the bare wires), the voltage is only +2 V.

Is this normal, or should I start looking for my mistake there (I've already gone through the circuit diagram countless times...)

Thank you for the responses.

You should double-check that.

Pin 16 is directly connected to 12V, protected only by a fuse.

CU Gremlin.

btw: what kind of car do you have?

I have a Passat 35i 1Z, model year 1994.

The 12 volts are already present, but when my adapter is connected, the voltage drops to 2V (and a certain amount of current, around 500mA, flows).

If the voltage drops to 2V even during normal operation, it's no surprise that the program reports 'Adapter not found.'
If 500mA is flowing into the adapter, something is wrong.
Please double-check the wiring diagram on the OBD side.

DocSnydor wrote:

...there's also a certain current flowing, around 500 mA

That's quite a lot, or? Before something serious happens to you, I would carefully examine the circuit.

Best regards, Rainer.

Did you use an electrolytic capacitor for the smoothing capacitor (1uF) located in the lower right corner of the schematic? Then it might get hot if it's connected with the wrong polarity (due to voltage drop!)?

Hello,

Oops, but having an incorrectly placed electrolytic capacitor would be a problem. Once, a surge of voltage damaged one of these components for me, and it shot off and hit my leg. The component was about 2cm x 1cm in size and left a nasty bruise. It could have been noticeable, so be careful!

Best regards, Rainer.

Hi,
I just took some measurements (unfortunately, only on the 1552, as the OBD2 adapter is currently borrowed). Even the 1552, with its (LED) backlight and dedicated processor, only requires 280mA (at approximately 12V).
If the voltage drops to 2V and a current of 0.5A is still flowing, then...
You are getting dangerously close to a short circuit.
If in doubt, first remove one leg from the ELKO connector and see if the current decreases. Otherwise, please double-check everything again.

Thank you for your helpful tips. I've reviewed everything again and can't find any errors. What I've also noticed is that there is no voltage across the capacitor...
Well, but now it's over, I'm fed up with this crap, I should just take a big hammer and smash it into powder, at least I can use it to spread on the road in the winter...

I'm going to buy a ready-made product now.
So, once again, thank you to everyone who tried to help.

Ciao.
David.

Hi,
The capacitor is connected (or should be) directly to the 12V.
How did you connect the adapter with the OBD2 connector to the car?