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Amplifying Current from DAQ to Drive a Thermoelectric Cooler

Hello!

I need to essentially make a thermostat that outputs current to a thermoelectric cooler based off of readings from a thermocouple and I need to find a way to amplify the current coming out of the DAQ as its only capable of outputting a max of 5mA, and the cooler needs around 3A. My initial thought is a simple buffer op-amp but I checked and most op-amps have a max output in the 10's of mA range.

 

Any thoughts are helpful!

 

Also, the DAQ I'm using is a USB NI-6215 if that's helpful at all.

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Well this is more of an electrical engineering question than LabVIEW...

 

I have seen circuits that use an opamp to drive the base of a power transistor that are adjustable constant current sources that deliver higher amperage than an opamp itself..

 

You would have to modify them a bit, basically replace the manual current set potentiometer with the output of your DAQ. Also you will have to change your DAQ to output a voltage rather than current...

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=== Engineer Ambiguously ===
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It looks like Maxim integrated has the right chip for you,

 

santo_13_1-1656694010919.png

 

https://www.maximintegrated.com/en/products/power/power-management-ics/high-performance-pmics/MAX196...

 

If you don't want to create your own circuit, the evaluation kit is another option - https://www.mouser.com/ProductDetail/Maxim-Integrated/MAX1968EVKIT?qs=LbY2dft4ljBqQvMDBC7D%252Bg%3D%...

 

 

-Santhosh
Semiconductor Validation & Production Test
Soliton Technologies
NI CLD, CTD
LabVIEW + TestStand + TestStand Semiconductor Module (2013 - 2020)
NI STS for Mixed signal and RF

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Okay, I was curious if I might have to use a transistor. would a simple BJT emitter follower work?

 

Also is there a way to change the question group to EE instead of LabView?

 

Thanks!

 

 

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Thanks! I'll definitely look into this. I think my professor/supervisor would prefer to use some simple op-amp or transistor configuration to keep things simple, but I will definitely keep this in mind.

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@BigGuy3403 wrote:

Okay, I was curious if I might have to use a transistor. would a simple BJT emitter follower work?

 

Also is there a way to change the question group to EE instead of LabView?

 

Thanks!

 

 


You would have to post this question in EE-focussed forums such as eevblog, edaboard

-Santhosh
Semiconductor Validation & Production Test
Soliton Technologies
NI CLD, CTD
LabVIEW + TestStand + TestStand Semiconductor Module (2013 - 2020)
NI STS for Mixed signal and RF

New to the forum? Please read community guidelines and how to ask smart questions
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Would an emitter follower circuit be sufficient?

 

That depends a lot on your requirements! Such a circuit does in theory what you want, but not very accurate and with a maximum dissipation of energy around the 50% setting. So if it is only about somewhat varying the produced heat without any accuracy, and you design it so that the transistor can survive the maximum dissipation of energy, which will be about what the thermostat dissipates at 50% of the full power supply plus some safety margin, it can work. It’s also a nice exercise in calculating the correct components.

In industry the integrated solution might be often chosen because it is simpler to design, more accurate and wont dissipate as much energy in the control circuit, and the price may be cheaper than choosing a power transistor and adding a heat sink to it.

 

In times where energy efficiency is an important design choice, this should at least be considered and mentioned in any design document/report.

Rolf Kalbermatter
Averna BV
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