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I need to drive an inductive load from an Arduino Due analog output. The analog output delivers 0.55V-2.75V (yes, it doesn't deliver 0 volts).

I need to get something like 0-14V with up to 3A maximum and so that the output voltage is linearly dependent of the input voltage.

Now I am overwhelmed by all the possibilities to achieve this. I do not know if I have to use MOSFETS or Operational Amplifiers and so on. I have seen solutions like this but this doesn't get me currents up to 3A? I would like the simplest solution. If I can buy something small, even better.

I have also seen tools like the operation amplifier designer from TI but this gives step-down converter as results that convert a variable V_in to a constant V_out, which is not what I want. Or am I wrong?

JYelton
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kradant
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  • What kind of inductive load? Do you want to control the load voltage or current? Can you tolerate a bit of ripple, so you can use much more efficient PWM or class D? How much ripple is tolerable? Will the voltage/current be DC or AC, and if AC, what frequency? – bobflux May 22 '19 at 12:17
  • It is a coil. I want to control the voltage. I can tolerate ripples. It has not to be super precise. However I want to change the voltage from 0 V to 15 V in something like 0.5 milliseconds. The voltage will be DC. – kradant May 22 '19 at 12:25
  • OK, with max voltage how much current will the coil take? I presume its internal resistance will limit the current, that would be 5 ohms since you mention 15V 3A? Also do you want to be able to reverse polarity? – bobflux May 22 '19 at 12:28
  • Yes, excactly the resistance of the coil is about 5 Ohm. So at the max. voltage of 15V I get 3A max. current. This is the worst case. Yes, it would be definitely good to reverse the polarity! I didn't think about that. But yes, it would be a big plus. So that I can operate between - 14 and + 14 V. – kradant May 22 '19 at 12:36
  • OK, have you got the power supply, what is its voltage and current, or will you build/purchase it? – bobflux May 22 '19 at 12:43
  • Yes, at the moment I can use a PeakTech 6075 with 0 - 30 V/0 - 5 A DC, 5 V/3 A fixed. In the future I would like to use something more portable :) But this is ok at the moment – kradant May 22 '19 at 12:49
  • Check my previous posts on this forum and you will find LTspice simulations that will provide you with some Idea on using opamp for linear amplification of your arduimo signal. – Prashant Sep 23 '23 at 09:16

1 Answers1

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PWM

If you can tolerate a bit of ripple on the output and precision isn't critical, and since the load is an inductor, the simplest solution would be a PWM brushed motor controller like this one, or any other as long as it supports the required voltage and current.

The h-bridge principle is explained here. You'd control this with a PWM output from your microcontroller, and another pin for direction/polarity.

Advantages: simple, cheap, efficient, quick transient response, needs only one positive supply, no analog signal conditioning.

Drawbacks: the output is the PWM value multiplied by supply voltage, so its accuracy depends on the supply, and of course it will have ripple, so you'll have to calculate the current ripple in your inductor according to the PWM frequency to make sure that it will do what you want.

Analog

The link you give in the question will translate DAC output voltage to 0-3.3V but you still need to amplify it to 15V, with an amp that can deliver enough current, and if you want to be able to reverse the polarity while using a single power supply, then it will have to be a bridged amplifier.

Since your coil's DC resistance is 5 ohms, circuits designed for car audio (12V and 4 ohm loudspeakers) should be a nice fit, something like TDA7384, STPA008 etc.

Or you can use a current booster on an opamp, or even design a discrete amp, but if you want to keep it simple, if I were you I'd just use a very cheap class-D module with TPA3116. This will handle the current you need. You will have to short the input DC coupling cap to pass your DC signal though. Since these things cost under $10, it's worth a try.

bobflux
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