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I am trying to engineer a device to separate red blood cells from blood plasma in 100mm x 1mm capillary tubes using the Raspberry Pi GPIO pin PWM feature and a piezoelectric actuator.

The pulses generated by PWM will drive a piezoelectric actuator disk from Thor Labs using DC pulses.

The problem I face is that the Raspberry Pi GPIO pins only generate pulses around 3 V, but I may need a pulse that is 20 to 150 V at up to 1 A in order to drive the piezoelectric actuator. From my research, I believe I will need to link the GPIO output to a transistor that is capable of handling the load from a power source.

I need suggestions on designs for such a high-voltage circuit that wont blow up my Raspberry Pi or light my house on fire. The most useful circuit would be one that is hooked up to a variable resistor so I could modulate the voltage (would be dope if I could control that with the Raspberry Pi). Power supply recommendations would also be useful. Ideally I would be able to use the wall outlet as a power source.

The scope of this project is to replicate the results of these papers: Development of Micro Particles Separation Device with Piezo-Ceramic Vibrator by Katsutoshi Ooe, Toshio Fukuda

Transport and Concentration of Blood in Capillary Tube using Flexural Acoustic Wave by Eun-Sun Kim, In-Kag Hwang

Long –range Particle Manipulation in a Micro-Capillary tube using a flexural acoustic wave by Eun-Sun Kim, In-Kag Hwang

I intend to generate a single antinode in the center of the capillary tube to concentrate the RBCs and give me a clear view of the blood plasma that I can take a picture of using a Raspberry Pi camera with low focal length lens.

Any help is much appreciated!

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  • \$\begingroup\$ The functional block you need is an amplifier. A transistor amplifier is one way to achieve that, but for a one-off, a high-voltage op-amp may be better (but they're way more expensive). \$\endgroup\$
    – TimWescott
    Jan 19, 2019 at 22:11
  • \$\begingroup\$ If your pulse needs any wave shaping you may be better off finding a DAC that'll work with the Pi. A piezo device implies "higher than audio" to me, or I'd suggest searching on Raspberry Pi audio solutions. \$\endgroup\$
    – TimWescott
    Jan 19, 2019 at 22:14
  • \$\begingroup\$ Thanks Tim. I will be using a square wave configuration, do you have any specific product recommendations? \$\endgroup\$
    – Vincent D.
    Jan 19, 2019 at 22:20
  • \$\begingroup\$ Sorry, but we try to avoid recommending specific products on this site. Such recommendations don't often have lasting value, and are often just a matter of opinion. \$\endgroup\$ Jan 19, 2019 at 22:54

2 Answers 2

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You seem to have the answers you need. What you're asking for is essentially electronic design services, which this site is not set up to provide. Either engage an electronic designer, or just buy one of controllers recommended by Thor Labs. You can still control them from your Pi via the BNC or serial ports.

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Basically, you need a switch that can pass high voltages when activated by your low-voltage control signal.

This is a very common application for controlling actuators. Your simplest bet might be to buy a "Solid State Relay" (or SSR) that fits your parameters (can switch 150 V, 1 A with a 3 V control signal).

Shouldn't be very hard to find, I use a similar set-up to control the heating element in my espresso machine, PWM the control pin on an SSR to pulse 125 VAC from the wall to the machine's heating element.

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