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From: Clive Arthur <clive@nowaytoday.co.uk>
Newsgroups: sci.electronics.design
Subject: Re: Interesting inductor
Date: Thu, 14 Mar 2024 10:42:57 +0000
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On 13/03/2024 22:43, john larkin wrote:
> On Wed, 13 Mar 2024 22:32:27 +0000, Clive Arthur
> <clive@nowaytoday.co.uk> wrote:
> 
>> On 13/03/2024 04:18, John Larkin wrote:
>>
>> <snip>
>>
>>> I'm hassling with inductors now too, but at the other end of the speed
>>> spectrum.
>>>
>>> We want a programmable inductor, from maybe 1 mH to 500 mH or so,
>>> maybe 100 mA. Sounds like an inductive DAC, a series string of
>>> inductors with shorting relays. If the step inductance ratio were,
>>> say, 1.8:1 we could have some hidden bits, more than the customer
>>> sees, so we could get pretty close to his requested value.
>>>
>>> We could test all 2^n steps, make a list, and select the closest to
>>> his request.
>>>
>>> We're simulating loads to an engine control computer, torque motors
>>> and solenoids and steppers.
>>>
>>
>> Gyrator?
> 
> We just yesterday had a brainstorm session about that. How can one
> make a programmable electronic fake inductor?
> 
> A real inductor stores energy, and can do things like high voltage
> flyback. So a fake inductor should store energy, or pretend to. It
> could be done with a current shunt, a fast ADC, some math in an FPGA,
> a fast DAC, and a big power amplifier with big power supplies. Too
> much work.

Yes, I got part way down the road of designing a gyrator to block 
telemetry signals on a power line comms device.  Soon realised it would 
need lots of power.

Just thinking out loud, and not really a serious suggestion, but would a 
variac with a fixed inductor on the secondary work as a variable 
inductor?  I guess 500:1 would be impossible.

-- 
Cheers
Clive