$10 O-Scope revisited

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rexnanet
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Re: $10 O-Scope revisited

Post by rexnanet » Thu Mar 23, 2017 12:07 pm

Hi mausi_mick,

Why are you using negative supply rails?
MCP6S is only positive supply if I recall. I'm going to add VCC/2 on an input amplifier so that it can accept negative voltage and be already in the ADC voltage range.
Might have a few drawbacks but it's simpler in other aspects.

mausi_mick
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Re: $10 O-Scope revisited

Post by mausi_mick » Thu Mar 23, 2017 3:16 pm

rexnanet,

I know it, it must be easier, but I tried to copy the reducer from DSO150 only with little changes:
Separate switch for AC/DC and C for max 230-50V AC, in the first stage bigger distances between the components and in the divider 2 resistance for one ( because of the electric strength :lol: ) .

A video with the preamp in action is here:

https://www.youtube.com/watch?v=sLfzLB7 ... e=youtu.be

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rexnanet
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Re: $10 O-Scope revisited

Post by rexnanet » Thu Mar 23, 2017 5:18 pm

Well done!

I've seen the video before the post :) It's running great. except near the end :) what happened?

mausi_mick
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Re: $10 O-Scope revisited

Post by mausi_mick » Fri Mar 24, 2017 11:03 am

I was coming in to "SINGLE"-mode (small touch screen with thick fingers :lol: ) and then it goes automatically to "HOLD" (red in the left upper corner). And nearly all is frozen. I have to change from single to auto and by pressing the switch on the encoder its starts again.

Now the shielding of the preamp is better:
DLO138-SPI_Display_shielded_preamp.JPG
DLO138-SPI_Display_shielded_preamp.JPG (57.71 KiB) Viewed 503 times

the green square wave is from an external generator over the reducer/preamp with MCP6S91 , the blue sinus is from the internal DDS
ADS9851, the noise on it is because I use an potentiometer without capacitive divider.

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rexnanet
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Re: $10 O-Scope revisited

Post by rexnanet » Fri Mar 24, 2017 11:14 am

Looks very good!

The noise levels seem ok. Are you using a breadboard or have you made a board for it?
The need for shielding might indicate some ground problems or too much attenuation+gain...

Now you could make some measures to see if the voltage levels match the real signal :)

IMO you could also make the videos a bit longer :) it's nice to see it in action

mausi_mick
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Re: $10 O-Scope revisited

Post by mausi_mick » Fri Mar 24, 2017 12:09 pm

I made small breadboard for it ( knife cut ! :lol: ).
DLO138-SPI_Display_Preamp.JPG
DLO138-SPI_Display_Preamp.JPG (46.18 KiB) Viewed 497 times
I have made a new video (with better Sinus over divider (10k/3.3k) and changing gain of MCP6S91 between 1 ... 8).


https://www.youtube.com/watch?v=GRtzcdL ... load_owner

dargas
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Re: $10 O-Scope revisited

Post by dargas » Fri Mar 24, 2017 2:25 pm

HELP :!: :!: :!: :!: I try to realize this oscilloscope. I use the STM32-O-Scope-byRex code. Fails to load code into the STM32.. I get the following error message, which I can not solve. :?: Perhaps you can provide links to the correct libraries, or upload into a single archive. ;)
Thanks

https://drive.google.com/open?id=0B6Eh8 ... JKUjVUb1Zr

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rexnanet
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Re: $10 O-Scope revisited

Post by rexnanet » Fri Mar 24, 2017 2:45 pm

dargas wrote:HELP :!: :!: :!: :!: I try to realize this oscilloscope. I use the STM32-O-Scope-byRex code. Fails to load code into the STM32.. I get the following error message, which I can not solve. :?: Perhaps you can provide links to the correct libraries, or upload into a single archive. ;)
Thanks

https://drive.google.com/open?id=0B6Eh8 ... JKUjVUb1Zr
That's normal, you have to have the libraries as in the links on the first post of this thread.
Get that one working and then try this one.
There's lots of info on the website and some links also in the original code.

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rexnanet
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Re: $10 O-Scope revisited

Post by rexnanet » Fri Mar 24, 2017 2:53 pm

mausi_mick wrote:I made small breadboard for it ( knife cut ! :lol: ).
DLO138-SPI_Display_Preamp.JPG
I have made a new video (with better Sinus over divider (10k/3.3k) and changing gain of MCP6S91 between 1 ... 8).
https://www.youtube.com/watch?v=GRtzcdL ... load_owner
It's the power supply on the right and the amplifiers on the left, right? :D

mausi_mick
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Re: $10 O-Scope revisited

Post by mausi_mick » Fri Mar 24, 2017 4:15 pm

yes, on the right is the stabilization with a LM7806 (and 2 Diodes to reduce to about 5V) and
the MAX660.
There are 3 connections to the preamp for -5V, 0V and +5V.

On the left is a input-stage similar DSO150 with an TLC072 and on the right a MCP6S91
and an amplifier / levelshifter from -5V ...+5V to 0V...+3.3V

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