Re: Interesting inductor

On Fri, 15 Mar 2024 05:56:38 -0000 (UTC), Jasen Betts
<usenet@revmaps.no-ip.org> wrote:

On 2024-03-14, Clive Arthur <clive@nowaytoday.co.uk> wrote:

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.

>
it's probably easier to just use the output terminals as a variable inductor.

I need a surface-mount motarized variac!

General Radio used to make Variacs. I think they had the patent. The
brush was tricky.

GR was interesting. Long gone now.