[simpits-tech] Need a power supply...

[geneb]

On Mon, 7 Apr 2014, Matt Bailey wrote:

> On Sun, 6 Apr 2014 14:12:49 -0700 (PDT)
> geneb <geneb at deltasoft.com> wrote:
>
>> On Sat, 5 Apr 2014, Matt Bailey wrote:
>>
>>> On Fri, 4 Apr 2014 08:47:04 -0700 (PDT)
>>> geneb <geneb at deltasoft.com> wrote:
>>>
>> Yep, right Matt. :)
>>
>> Because the F-15 ADI & HSI are essentially irreplaceable, I'm going
>> to give them *precisely* what the specs say they need.
>
> Quite understandable. I feel the same way about the pair of Collins
> ADIs I have for the Sabreliner. I'm still itching to grab some synchros
> from something around here (perhaps my ADF heads...) and see how they
> react to house voltage. If I can test enough synchros long enough with
> house voltage and all is well, I might try it on complete instruments.
> It would *vastly* simplify power delivery.
>
I wouldn't do it.  You'll burn them up.  I talked to Mike Powell about 
this and his comments were:

"If the synchro is rated for 400Hz its impedance will be too low at 60Hz 
and too much current will result. Smoke, heartburn, stale beer, etc. etc.

When running a synchro at frequencies other than the nominal, scale the
voltage with the frequency.  So, at 60Hz, a 115VAC/400Hz synchro would be
better powered by (115) * (60/400) = 17.25 VAC."



>> I can drive a stepper motor using 16th steps using Pololu stepper
>> drivers
>> - many 3D printer use these in that configuration.  All I need is a
>> tiny "home" position indicator for each and I'm set. :)
>
> Keep us posted, I am curious as to how this goes. My biggest concern
> with steppers is, what if the instrument never gets around (or takes a
> long time) to the "home" sensor? Ergo, you might have a sensor at 0*,
> but if your HSI (for instance) runs for 2 hours on a long flight and
> never goes beyond the range of, say, 180* and 270*, will a stepper keep
> its position well enough to not "drift" the HSI? What sort of sensors
> (and how many) do 3D printers use?
>
A stepper will keep its position as long as it's powered and the force on 
the output shaft doesn't exceed the holding torque rating for the stepper.
In binding a stepper to a synchro transmitter, that will NEVER happen.

The 3D printers I have are all stepper based.  They go to a "home" 
position marked by end-stop switches and then work from there.

When setting this up for use with an instrument, I'd write the software so 
that the stepper goes to its home position on power up.  From there the 
software can track where the stepper is because it will know where it's 
been moved to.

Here's another question - can you safely use a standard meter to measure 
AC current @400Hz or will that higher frequency kill the meter?

g.



-- 
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