Phototransistor switching freqeuncy

Thread Starter

Alasttt

Joined May 13, 2015
68
To flip your signal. You can go back to something like we started with. It was just easier to get you on the same reference as everyone else (me) is used to seeing an NPN in a switching circuit.

View attachment 98308
Its flipped thank you for your help
flipped.PNG

I still need to make it look more square, as Im going to read this into a microcontroller and they need clear 1s and 0s.
 

dl324

Joined Mar 30, 2015
16,846
Its flipped thank you for your help

I still need to make it look more square, as Im going to read this into a microcontroller and they need clear 1s and 0s.
Switch the output back to the collector and use a Schmitt inverter to clean it up.
 

GopherT

Joined Nov 23, 2012
8,009
Its flipped thank you for your help
View attachment 98312

I still need to make it look more square, as Im going to read this into a microcontroller and they need clear 1s and 0s.
I asked about the tektronix scope quality. You may just have a crappy scope. Or, you may need to turn up the sampling frequency on the scope you have (if there is such an adjustment).
 

dl324

Joined Mar 30, 2015
16,846
Inexpensive, and possibly even some espensive, DSO's don't handle the type of waveform you're viewing well. To "clean up" the waveform, you need to do more averaging. If you do enough averaging, the information you're transmitting will be lost...

If the data was invariant, a DSO might do well...
 

GopherT

Joined Nov 23, 2012
8,009
Really?, In your opinion a microcontroller can distinguish between a 1 and a 0 in a wave that round and pointy ?. Im planning on an atmega328p. If so then I dont need to bother cleaning it
You might need a stronger signal unless you can set the high/low threshold in software or with an external reference.
 

Thread Starter

Alasttt

Joined May 13, 2015
68
How do you get this image to look so "digitized". It seems like a fairly high resolution scope (for a 4 kHz signal). I would think the steps should be un-noticable. But, I have never used digital scopes.
Im zooming in to the wave if that answers your question ?. digi.PNG
Thats the data unzoomed. and zoomed in looks like the previous post
 

Thread Starter

Alasttt

Joined May 13, 2015
68
You might need a stronger signal unless you can set the high/low threshold in software or with an external reference.
I can set the threshold its at 2.56 anyway so this will suffice, I though the uC needs a really square wave at the moment it looks like this avr read.PNG

I dont feel confident that the uC can operate on this, but then again that's just an assumption
 

GopherT

Joined Nov 23, 2012
8,009
I can set the threshold its at 2.56 anyway so this will suffice, I though the uC needs a really square wave at the moment it looks like this View attachment 98316

I dont feel confident that the uC can operate on this, but then again that's just an assumption
If each peak crosses the 2.56 v threshold, the micro will see the differences.

What type of signal generator do you have that makes such a bad signal like this to turn on the IR LED?

image.jpg
 

Thread Starter

Alasttt

Joined May 13, 2015
68
If each peak crosses the 2.56 v threshold, the micro will see the differences.

What type of signal generator do you have that makes such a bad signal like this to turn on the IR LED?

View attachment 98317
Ok, I will see where I get, Just out of interest, may a low pass filter or a schmitt trigger make the wave more sqaure?.
That is not the signal driving the IR LED the pic below is the one.Data.PNG

It is not from a signal generator, I have manually generated it using an arduino, high (delay), low (delay) etc. A signal generator isnt appropriate for my data set
 

Thread Starter

Alasttt

Joined May 13, 2015
68
So, are you picking differing delays each time or why not a nice clean, consistent square wave?
Yeah exactly I need different delays at different times. Also weirdly increasing the distance between the IR and transistor makes the wave more square!. It has less pk-pk but that its expected.
apart.PNG

I could always use an amplifier to amplify it. Id rather have the above and have to amplify it as opposed to having the rounded one from before. Assuming the amplifier does not distort it !
 
Top