Ulf's Circuit Diagram: Questions & Answers

Hi!

So, just to get it out of the way, I'm completely clueless when it comes to electronics, so please don't bombard me with criticism right away!
Regarding Ulf's schematic diagram 2.2, what alternative optocouplers can be used? I have three CNY17-1s on hand; can those be used instead? And are VR1 and VR2 adjustment potentiometers, or am I mistaken?

Sure, no problem! Here's the translation:

'Thank you in advance!!!'

Hi.

Regarding the selection of optocouplers, I wanted to make the circuit as robust and reliable as possible.
If your components don't have an extremely poor coupling factor (roughly the ratio between diode current and output current), it should work.

VR 1 and VR 2 are adjustment controls (trim pots), correct.

However, I would advise people without basic knowledge of electronics against building it themselves.
Even in relatively simple circuits, there are countless ways to introduce errors, and troubleshooting these issues remotely (via forums or email) becomes virtually impossible.

'I'm going crazy!! I finally bought the PC 817, soldered everything together, but now when I try to test it, LED 2 is lighting up instead of LED 3. I've been searching for this error all day, but I just can't find it. Can anyone help me? This is unbelievable; I've checked the circuit diagram at least 10 times, and everything seems correct!'

Thank you.

Hi.

cf. the last sentence of my previous post .

The best thing to do is find someone who knows about electronics, give them your adapter and the instructions, and maybe even tip them well...

Yesterday, I went through everything with an electrical engineering student, and he also couldn't find any errors.

Hello,
The test is simple:
You'll need a 12V power supply, a rectangular wave generator with 10 Vpp, and an oscilloscope (which your electrical engineering student probably has). Then you can trace the three signal lines and find your error.

Hi there,

I have nothing against students, but if I were you, I would rather look for a practitioner than a theorist .
Good luck...

Eike.

Hi,

I can only agree with Eike. Out of my approximately 40 fellow students (electrical engineering), maybe 3 or 4 would be able to do something like that.

Have fun searching!

Quote:

So, now, if I want to run the test, instead of LED 3 lighting up, LED 2 lights up for me.

Hi.

Please check if there is a solder bridge between pin 3 and pin 4 of the PC interface (or their corresponding connections on the circuit board). There shouldn't be one there.

Besides that, of course, there are countless other possibilities for errors .

So, there is no bridge between pins 3 and 4. But I just noticed that first, LED3 briefly lights up, and then LED2 stays on permanently!

ckone wrote:

So, there is no bridge between pins 3 and 4. But I just noticed that first, LED3 briefly lights up, and then LED2 stays on permanently!

Hi.

The mistake with bridge 3-4 would have been a more obvious and "typical" error.

However, all that remains is to measure where the power for LED 2 is coming from, as it shouldn't be receiving any power.
Probably some kind of bridge between resistor R19 and resistor R3, which could naturally exist anywhere where traces connected to R19 and R3 are present.

Okay, I simulated the circuit with a software program, and everything seems to be working perfectly. However, LED3 still isn't lighting up on my actual setup. I measured the voltage at the left R5 resistor, and it's 12V on both sides. According to the simulation, it should be 12V and 2.63V. I'm seeing the same phenomenon with the right R5 resistor and VR1. I've already tried replacing the resistors. Could this be due to my power supply?

Connect the positive terminal of the power supply (cathode D6) to DTR pin 4. Then, short pins 3 and 4 of component OK3. If the LED turns on, then the secondary circuit OK3 is working correctly.
Then, connect 12V to resistor R19 and ground via resistor R15 (100 ohms). Bridge the CE pin of component T3. If the LED then lights up, the driver circuit OK3 is working correctly.
Then you should read the forum post titled 'VAG-COM Adapter Status 3: not found, not ready.'

Thank you for your answer first!
I followed the steps you described, and in both cases, LED3 is lit up, so both circuits seem to be working correctly. What could be the problem now? Could it be the transistor T3?

ckone wrote:

Thank you for your answer first! I followed the steps you described, and both times LED3 is lit up, so both circles are okay. What could be the problem now? Is it the transistor T3?

Hi.

As I mentioned before, LED 2 should not light up "on its own" without voltage being applied to the TXD pin.

So, I'm going to figure out where the voltage is coming from, eliminate the error, and then that thing will probably work .

Oops! I forgot to post. Now neither LED2 nor LED3 are lit.