How can I operate a thermal actuator at high frequencies and high currents?

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Discussion Overview

The discussion revolves around the operation of a thermal actuator at high frequencies, specifically up to 100 kHz, while passing a current of 1-2 A. Participants explore circuit designs and components that could facilitate this performance, addressing both theoretical and practical challenges.

Discussion Character

  • Technical explanation
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • One participant questions the feasibility of a thermal actuator changing states at 100 kHz, suggesting a misunderstanding of the request.
  • Another participant asserts that while the actuator's bandwidth is typically 3 kHz, modulation of the drive signal could extend its effective bandwidth to higher frequencies.
  • A participant emphasizes the need for a circuit that can deliver high current at the desired frequency, noting that standard DAQcards cannot provide the necessary current.
  • Concerns are raised about the thermal nature of the actuator and its ability to operate at such high frequencies, with suggestions for using a buffer or driver to achieve the required current.
  • Participants discuss the potential use of the OPA569 op-amp, which is noted for its capability to drive high currents at high frequencies, as a viable solution for the actuator's requirements.

Areas of Agreement / Disagreement

Participants express uncertainty regarding the capability of thermal actuators to operate at 100 kHz, with some questioning the practicality of the request. There is no consensus on the best approach, as multiple solutions and concerns are raised.

Contextual Notes

Participants highlight limitations related to the actuator's thermal response time and the challenges of achieving high current at high frequencies. The discussion includes references to specific components and circuit designs, but no definitive solutions are established.

Who May Find This Useful

Individuals interested in high-frequency actuator design, circuit engineering, and those working with thermal actuators in experimental or applied contexts may find this discussion relevant.

Excom
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Hi All

I hope that someone can help me. I have this thermal actuator with a resistance of ~1 Ohm that I want to operate at high frequencies, up to 100 kHz. In order to get the right amount of actuation I need to pass 1-2 A through the actuator.

Can anyone tell me what kind of circuit would be able to give this kind of performance?

Thanks
 
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Excom said:
Hi All

I hope that someone can help me. I have this thermal actuator with a resistance of ~1 Ohm that I want to operate at high frequencies, up to 100 kHz. In order to get the right amount of actuation I need to pass 1-2 A through the actuator.

Can anyone tell me what kind of circuit would be able to give this kind of performance?

Thanks

I think you may need to restate the problem. Maybe it's just me, but what I am hearing is that you have a device that acts based on temperature and you want it to change states up to 100,000 times per second. I don't see how that's possible, so I'm assuming I don't really get what it is that you are asking.
 
Well it is actually what I want to do. The actuators I am working with have a bandwidth of 3 kHz but at higher frequencies the amplitude starts to decrease as the time constant if the actuator is too long. However, by modulating the drive signal you can increase the bandwidth of the actuator. Put in another way. The flat region in a bode plot can be extended to higher frequencies.
 
V=I*R. You already know the resistance and current needed. Sounds like all you're going to do is plug in a 1-2 Volt source and you'll have your circuit. Of course if that doesn't solve your problem you'll need to explain more of what is going on in the circuit and whether you are controlling anything or not.. etc.
 
Thanks for your reply.

The problem/challenge is to get a high current at 100 kHz. Ideally I would like to drive my actuator using a DAQcard but a normal DAQcard is not capable of delivering a 2 A current.

So it is my plan control the signal to some extend.

At the moment my best option is a function generator or a DAQcard and non of them can deliver the needed current. Therefor I would like to build a circuit that can deliver the current and I can then control the circuit using either a function generator a DAQcard. An option is to use an op amp but I can't find an op amp with the needed bandwidth and current range.
 
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I think I am not the only one who is confused by your stated requirement. I can't think of any thermal device that can change at 100kHz rate - or is the 'thermal' word just incidental?
If you need 2A at 100kHz, I reckon you will need a buffer / driver between the OpAmp and your device. Not a problem, though.
 
Thanks for your reply.

By thermal I do mean thermal as in heating. An example of a thermal actuator operating at 10 kHz can be found in this paper, see figure 11: In depth characterization and control of AFM cantilevers with integrated sensing and actuation. I can't go into too much details about what we are doing as the work is not published yet but I can assure you that we are beyond the 10 kHz. And in the end we need a circuit that can go faster than the actuator.

I will have a look at the buffer/driver idea. Thanks.
 
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Are you simply asking for a device that can drive 2A at 100Khz? Here is 1 example when I searched for 2A opamp. http://www.ti.com/product/OPA569/technicaldocuments

It can drive 1.2Mhz with 0dB gain.

You may want a peripheral board containing a completed design. I didn't stumble onto one.
 
I've used the aforementioned OPA569 for something similar, I used built a small voltage to current converter, this was used as an amplifier (well, a transducer) for the output of a DAQ.
So this is probably the easiest solution.
 
  • #10
Thanks for the replies.

An OPA569 seems like a good option. I will go for it.

Again thanks.
 

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