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Topic: Problem with using a PN2222 Transistor as a switch for a CSR8645 Bluetooth board (Read 962 times) previous topic - next topic

Grumpy_Mike

Ok, the traces seem to have changed a lot since you first posted hem. They are now very noisy. Any idea why the traces have gone wrong?

Tristan9497

i think i must have been zoomed in on the noisy part of the signal which than more or less looks like a rectangular signal.


Grumpy_Mike

OK but in that case the noisy part is a signal that you are picking up for some reason. Is the scope grounded to the same point as the signals? It almost seems like it is not.

Tristan9497

well i thought it was, since i connected the GND part of the Probe to the GND of my Laboratory PSU i can try to connect the GND port on the oscilloscope with that aswell. And take a look at the signals again. Thanks for your Help

Tristan9497

i've just taken a look at it again and everyting was connected to the same GND. The GND port of the oscilloscope is directly wired with those of the probes. So even after i connected it again there wasn't any difference in the signal. They still have the same amound of noise.

Grumpy_Mike

Thanks for testing this again. I must admit I am puzzled by this. Not at all what I was expecting.

Tristan9497


Thanks for testing this again.
Sure
This is way beyond my knowledge in electronics, im glad you are trying to help me out.
If you want to try something out or me to measure something just tell me :)

Tristan9497

Small Update:
I've got it to work using a NPN Transistor.
I thought about your statement that with a NPN Transistor you typicaly switch something to GND.
So my Idea was how about adding a large resistor between the E port of the transistor and GND. I attached a drawing with the resistors i picked by pure luck. Maybe this makes sense maybe not xD

Now i am on to the next problem with the other ports of my CSR module gonna check their voltage soon.

Grumpy_Mike

It would help if those rails in the diagram were marked with +5V and ground.
By convention ground is at the bottom of the diagram and the + at the top.

Tristan9497

uhm if you mean the drawing i've attached in the last message i marked tha rails at the top with +12V and GND.
But you're definatly right with placing the GND on the bottom of the schematic the next time

Grumpy_Mike

OK I was on my iPad when I downloaded that image and it cut off the bottom of the picture.
As it was posted sideways an iPad always tries to rotate it so it continues to be on its side.

It is a bit of an unconventional circuit but I can see why it would just about work.

Tristan9497

Ok final Update:

Thanks for all of you for helping me wih this Problem
I have figured out the schematic and will attach it to this post for everyone interested in it or struggeling with a similar problem.

Grumpy_Mike

Thanks for rounding it off with a report and schematic. I wish more people would do that. Have a Karma point.

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