pg-Focus input signal from an one dimensional piezo (PI-E-753)

[soheil mojiri]

Dear Karl,

Hope this finds you great.

I am going to duplicate the pg-focus stabilization system for another microscope. However, 

I have a well-known (PI-E-753) piezo this time as the focus controller device. It has an Analog input to receive processed signal from the pg-Focus output.

However it's sensor communicates with computer using a ''RS-232'' cable (with digital signal). I am wondering how to connect make a communication between such sensor/computer and the pg-focus input? In other words, how to read and convert the piezo signal to the voltage signal that pg-Focus needs (±10V 14bit ADC)? 

Any suggestions would be of great help.

Best regards,

Soheil

[Karl Bellve]

Hi Soheil,

Sorry for the late reply. 

What I think you will be doing, correct me if I am wrong, will be changing the 3D position of your piezo using serial control. Before this happens, turn off pgFocus focus control, and when you get to the new focus position, turn back on focus control. pgFocus will reestablish focus control at the new Z position. The problem is that pgFocus will reset the focus control offset. 

I think turning off focus control, saving the current focus correction offset, and turning focus control back on, reusing the current focus correction offset is what you want to do. This might require a change in the firmware not to lose the current focus correction offset. Does that make sense?

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Karl Bellvé

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[soheil mojiri]

Dear Karl,

Thanks for your reply.

I am Sorry, as I think I could have described the issue more clearly.

I can send analog signal from pg-Focus to my piezo (Please see photo '1' attached where the 'output' of pg-Focus is connected to the 'analog In' of piezo). However, it seems my piezo sensor (piezo output) reads only digital signals (Please see the photo '2' attached taken from back side of my piezo where the RS-232 port connects to my computer interface). Now my question is that is there any easy way to send signals (analog signals) from piezo to pg-Focus?

(as you can see in the Photo '1', the input of my pg-Focus has already no connection).

regards,

Soheil

On Friday, October 4, 2019 at 9:29:38 PM UTC+2, Karl Bellve wrote:

Hi Soheil,

Sorry for the late reply. 

What I think you will be doing, correct me if I am wrong, will be changing the 3D position of your piezo using serial control. Before this happens, turn off pgFocus focus control, and when you get to the new focus position, turn back on focus control. pgFocus will reestablish focus control at the new Z position. The problem is that pgFocus will reset the focus control offset. 

I think turning off focus control, saving the current focus correction offset, and turning focus control back on, reusing the current focus correction offset is what you want to do. This might require a change in the firmware not to lose the current focus correction offset. Does that make sense?

On Tue, Oct 1, 2019 at 11:35 AM soheil mojiri <soheil...@gmail.com> wrote:

Dear Karl,

Hope this finds you great.

I am going to duplicate the pg-focus stabilization system for another microscope. However, 

I have a well-known (PI-E-753) piezo this time as the focus controller device. It has an Analog input to receive processed signal from the pg-Focus output.

However it's sensor communicates with computer using a ''RS-232'' cable (with digital signal). I am wondering how to connect make a communication between such sensor/computer and the pg-focus input? In other words, how to read and convert the piezo signal to the voltage signal that pg-Focus needs (±10V 14bit ADC)? 

Any suggestions would be of great help.

Best regards,

Soheil

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[Karl Bellve]

Hi Soheil,

I think this is the brochure for your E-753: https://www.pi-usa.us/fileadmin/user_upload/pi_us/files/product_datasheets/E753_Piezo_Controller_Electronics.pdf

I don't think you need to send an analog signal to pgFocus. pgFocus will just base its movements around 0V. That is great if you just want to maintain focus, but not change Z position, which is probably why you bought an E-753. We drive pgFocus with a Heka ITC18 DA. The latter sends a ±10V to set Z position. PgFocus is connected to our E-662.

I am trying to find a manual for tje E-753, but no such luck. I do have a manual for an E-750;

However, our E-750 needs to be switched to "analog in" mode from "digital mode". I think default is digital (via serial commands), and it will ignore an analog input. Only one mode can be active at any time, which is a shame because it would be cool if the analog mode could add a offset to the digital mode.

It is possible that you can change the E-753 piezo positions using pgFocus, assuming your in analog mode on the E-753. However, I never added Z-stage capability to pgFocus device adapter in micromanager. I think there is code there, I just never went to the testing stage. I am trying to recall the range, maybe ±5V? So not a full ±10V, but it may work for your needs.

The other way to do it is buy a something like a TriggerScope http://www.triggerscope.com/ to send an analog Z position to pgFocus, which then adjusts it for focus, which is then connected to your E-753.

If the E-753 is like our E-750, it can only be in one mode, digital or analog. It can't be in two modes at once. 

You could convert the information that pgFocus sends back to the host computer as it relates to focus position, and modify the digital signals being sent to your E-753. You wouldn't connect pgFocus to the E-753 at all. This would slow down the focus control hugely. The focus control from pgFocus would have to be on the host computer. This would require programming and probably take time to implement. 

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