To get 5V peak to peak voltage from STEMlab 125-14 board

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Arpit
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Joined: Wed Oct 16, 2019 12:11 am

To get 5V peak to peak voltage from STEMlab 125-14 board

Post by Arpit » Wed Oct 16, 2019 12:32 am

Hi guys,

For my application, I want to use my Red Pitaya 125-14 v1.0 board to control, in a feedback system, a Galvo mirror. This Galvo mirror is to be used to do a raster scan by controlling its X & Y rotational on-axis movement. The output of the Red Pitaya board is fed to the Galvo mirror. In order to operate the Galvo mirror, it needs to get about 5 Vpp (peak to peak) signal. Since the requirement is to carry out a raster scan, one of the channels, say X, is to be operated at about 100 Hz frequency and 5 Vpp; and the other channel, say Y, is to be operated at about 0.4 Hz frequency and 5 Vpp.

The issue is that the Red Pitaya board's maximum peak to peak output voltage is 2 Vpp. Does anyone have a good suggestion on what would be the best strategy to get 5 Vpp from Red Pitaya without distorting the signal?

Any direct or indirect help, or even a pointer, will be of great help. Thank you!

Best,
Arpit

redpitaya
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Re: To get 5V peak to peak voltage from STEMlab 125-14 board

Post by redpitaya » Wed Dec 04, 2019 8:58 am

Hi Arpit,
This is not easy task to implement. We will have it with 50 Ohm load for new models of boards due to popular demand for increased voltage range. For your application, maybe you can try to use an audio amplifier similar to this one: https://www.aliexpress.com/i/32948999863.html

Have you tried this already?

Arpit
Posts: 2
Joined: Wed Oct 16, 2019 12:11 am

Re: To get 5V peak to peak voltage from STEMlab 125-14 board

Post by Arpit » Thu Dec 05, 2019 11:23 pm

Thank you for your response.

I had contacted the Red Pitaya engineer and I was suggested to use this amplifier Protosupplies' LM358 operational amplifier module (not sure why am I not allowed to post the relevant url?). I tried working with that but the problem is that the load impedance of the amplifier module is quite high and the Galvo control system requires me to have <= 50 ohm impedance while the signal is being fed to it. I had to short the capacitors such that DC-like frequencies such as 0.4 Hz can be made to pass. Most of the commercially available amplifiers, that I looked into so far, have high load impedance. The impedance mismatch then creates a distorted signal resultantly. I am working on designing an amplifier circuit on my own, which is not a huge task, per se, but it is kind of taking away the attention from the main application development at hand.

While we are at it, I meant to ask about developing my application on LabVIEW. I have found that I need to modify/create the Red Pitaya library. I feel that Red Pitaya's LabVIEW library needs to be developed and evolved furthermore to be able to replace the NI's DAQmx and related libraries. Is that a correct assessment? Because, for example, by default any frequency less than 1 Hz is kind of not getting generated. Whereas, through a Python code, I can do it! Can you please be able to provide me with a good reference to look into specifically for the Red Pitaya project development on LabVIEW? This will be of huge help to me if this resource can help me work faster.

Thank you very much for anyone who is browsing through this post. Any kind of help will be greatly appreciated. These stepping stones will also allow me to be able to contribute to this forum in the future after having had a certain experience with Red Pitaya.

Kind regards,
Arpit

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