Probing Many Pins

Thread Starter

ceres3

Joined Feb 6, 2019
5
I need to calibrate about 40 electronic boards which are going to be used in a physics experiment. In each of the boards I need to probe more than 50 pins with a picoscope. I have automated code for the calculations but the problem is that each time I need to physically move the probe to connect it to the specific pin that I'm calibrating, which is really boring and will take many hours. Do you have any suggestion to make this automated? I was thinking connecting 50 wires to the pins and then connecting all of them to the probe. But I need to find a way to read only a specific pin at the time. Is there any way to do it?

Thank you.
 

Thread Starter

ceres3

Joined Feb 6, 2019
5

djsfantasi

Joined Apr 11, 2010
8,652
Thanks for your suggestion. This would help. But my main problem is moving the probe to connect it to the pin that I'm measuring. Do you have any suggestion about hoe to make it automated?
What are you measuring with the probe? Voltage? Current? Are you looking for discrete or continuous values?
 

dendad

Joined Feb 20, 2016
4,251
Thanks for your suggestion. This would help. But my main problem is moving the probe to connect it to the pin that I'm measuring. Do you have any suggestion about hoe to make it automated?
As asked above, what are you measuring?
If they are all similar voltages, an analog multiplexer array could be used. If you have enough time and energy, a processor driven tester could be made. Or just use some rotary switches. It all depends on how you want to go. The pins could just come out to a row of terminal posts.
 

Thread Starter

ceres3

Joined Feb 6, 2019
5
I'm measuring voltage using a python script. Discrete values. I can read and save the data automatically, but the problem is than I need to move the probe each time to connect it to the pin that I'm probing. Taking data and calculation would take 3 minutes for each pin. It means I should spend 100 hours at least to calibrate 40 boards. If I can find a way to connect the probe, then I can just run the code and come back 3 hours later to switch to a new board.
 
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dendad

Joined Feb 20, 2016
4,251
If you go with it, and as there are 64 inputs with 4 of these chips, connect the unused ones to 0V and a known voltage so you can do self calibration at the start of each measurement cycle.
 

danadak

Joined Mar 10, 2018
4,057
This can all be done with one chip, using a small number of its resources -

upload_2019-2-7_7-2-8.png


PSOC 5LP. Not much code required, pipe results out to terminal session of UART or USB or....Note there is onboard Vref for A/D as well, A/D is 20 bit, but I would recommend considering limiting it to 16 bits when its configured.

This routed with 50 analog inputs. If you want you could LPF the results with the
onboard Digital Filter.


Regards, Dana.
 
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Thread Starter

ceres3

Joined Feb 6, 2019
5
This can all be done with one chip, using a small number of its resources -

View attachment 169666


PSOC 5LP. Not much code required, pipe results out to terminal session of UART or USB or....Note there is onboard Vref for A/D as well, A/D is 20 bit, but I would recommend considering limiting it to 16 bits when its configured.

This routed with 50 analog inputs. If you want you could LPF the results with the
onboard Digital Filter.


Regards, Dana.
Interesting! Thanks. What is this program in the screen shot? Can I program it so it send the output from pin N to somewhere on the chip and then measure that using the picoscope? Ideally I want to connect all pins to this chip and then tell it to send the signal from pin N to a channel that I'm probing, then wait for 3 minutes and then send the signal from the next pin. Can I directly read the signal with a picoscope and skip dealing with UART? Sorry for my lack of basic electronics knowledge and thanks!
 

djsfantasi

Joined Apr 11, 2010
8,652
What are you using as a microprocessor? What you are asking is very doable. But IMHO, to give you a more detailed answer requires that I know the total environment, including the microprocessor you are using.

Or maybe danadak’s solution can be implemented as a standalone device. Danadak is very familiar with that chip. I am not.
 

danadak

Joined Mar 10, 2018
4,057
Interesting! Thanks. What is this program in the screen shot? Can I program it so it send the output from pin N to somewhere on the chip and then measure that using the picoscope? Ideally I want to connect all pins to this chip and then tell it to send the signal from pin N to a channel that I'm probing, then wait for 3 minutes and then send the signal from the next pin. Can I directly read the signal with a picoscope and skip dealing with UART? Sorry for my lack of basic electronics knowledge and thanks!
Yes, you could just use it as a mux to a pin to picoscope. How do you want to select
channel ? With a knob, buttons, digital select signals....Keep in mind chip is capable
of doing all the measurements if you program it.....How do you want to know what
channel is being looked at, LED/LCD display ?

You have any experience with micros ? Also will you be laying out a PCB ?

The program is PSOC Creator, free. https://www.cypress.com/products/psoc-creator-integrated-design-environment-ide

You can do some basic logic and analog with this chip w/o writing any code,
but that would be only using 1% of its capability.....

Lastly yes you could time the selection to 3 minute intervals.


Regards, Dana.
 
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danadak

Joined Mar 10, 2018
4,057
I think this will work. A codeless design, a 3 min period clock (onchip)
drives a cntr which drives the mux address select inputs. The channel is
selected and stays selected for 3 min then automatically moves on to the
next channel.

This runs continuously, although a trigger/logic level could be implemented
to start/enable the mux if so desired.

This is a one chip design.

upload_2019-2-7_18-51-35.png


Regards, Dana.
 

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danadak

Joined Mar 10, 2018
4,057
Note could also add a trigger out pulse to indicate new channel is available.
To initiate/indicate a channel change has occurred.


Regards, Dana.
 
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