How can I convert the square wave signal of the car turn signal into a level that does not change much?

liuzhiying666

How can I convert the square wave signal of the car turn signal into a level that does not change much? [Copy link]

 

The problem now is that the signal keeps changing and affects the circuit, so I want to use the simplest method to turn it into a level that does not change much, about 10V will do, but the integration circuit does not seem to work, is there any other way?

maychang

"The integrator circuit doesn't seem to work." How does it "not work"? What are the results of your experiment?

ienglgge

The level does not change much, so should it be changed? What is the external input signal like and what does it need to be converted into?

liuzhiying666

ienglgge posted on 2018-8-9 14:39 The level does not change much, so should it be changed? What is the external input signal like, and what should it be converted into?

It means that it becomes basically a high level and will not go low, otherwise the screen will flicker.

philipchiu

Are you trying to get power from the turn signal?

liuzhiying666

philipchiu posted on 2018-8-10 08:02 Do you want to get power from the turn signal?

When turning, the signal is triggered (12V enters the 5V voltage regulator tube and is sent to the chip for detection). Now we have found that the cause is that when it is triggered, the GND will have a spike, which will cause horizontal stripes on the screen image.

topwon

First use buffer isolation, and then use RC filtering to convert it into a DC level.

liuzhiying666

topwon posted on 2018-8-10 10:48 First buffer and isolate, then use RC to filter to DC level.

What is there to do buffer isolation, capacitor plus inductor?

liuzhiying666

I found the reason, but I don't know why. Adding a large capacitor in front of the circuit changed the waveform (the circled waveform in the figure), which easily caused a spike on GND. After removing it, it was normal (the waveform above the circle). I don't know what the reason is.

gmchen

liuzhiying666 posted on 2018-8-13 15:55 I found the reason, but I don't know why. It is that adding a large capacitor in front of the circuit changes the waveform (the circled waveform in the figure), which is easy to cause spikes on GND...

Is the large capacitor you are talking about the 10uF capacitor C3? If so, it means that at the moment when the square wave input signal rises, a large current flows through this capacitor, or in other words, at the moment this capacitor is equivalent to a short circuit.

liuzhiying666

gmchen posted on 2018-8-17 00:21 Is the large capacitor you mentioned the 10uF capacitor C3? If so, it means that at the moment when the square wave input signal rises, a large current flows through this capacitor...

Yes, it is much better to remove it, but the effect is still not very good. Later, the effect of using an optocoupler is much better. Now the impact will be greater when the camera is turned on in low light infrared