[187353] in North American Network Operators' Group
Re: small automatic transfer switches
daemon@ATHENA.MIT.EDU (Owen DeLong)
Wed Jan 27 20:03:20 2016
X-Original-To: nanog@nanog.org
From: Owen DeLong <owen@delong.com>
In-Reply-To: <CADHytMei=bH=Hv-5J-VMNakrXCO9rPnDzGGww+22MLoYHig_PQ@mail.gmail.com>
Date: Wed, 27 Jan 2016 17:02:04 -0800
To: Velocity Lists <volists@staff.velocityonline.net>
Cc: "nanog@nanog.org" <nanog@nanog.org>
Errors-To: nanog-bounces@nanog.org
If you=E2=80=99re willing to risk that solution, and want monitoring, a =
$10 Microcontroller
and ~$1.00 worth of ancillary resistors and diodes will get you =
monitoring. If you
want to get really fancy, you could mount it all to a custom designed =
PCB for
around $10 ($5/sq.in. for 3 copies of the PCB) from oshpark.com =
<http://oshpark.com/>.
If you want to get really fancy, you can change out the power cords for =
real
PCB mount IEC outlets and put the whole thing in sheet metal for ~$45 =
more,
yielding a total cost of <$100 + whatever you value your time at.
The software for the MC would be dirt simple and probably take less than =
an
hour to write and fully integrate into your monitoring system.
The time to design the PCB for the fully loaded version is probably a =
couple
of hours with Eagle (if you use an MC, relays, and outlets that have =
Eagle
Libraries for their parts). Takes 10 days+shipping from Oregon to get =
the
PCBs. For an extra $5, they=E2=80=99ll ship USPS Priority. One really =
nice thing about
Eagle and OSH Park is that you can do small stuff in the free version of =
Eagle
and you can submit the Eagle .BRD file directly to OSH without having to =
turn
it into gerber files. OSH gives you a very accurate preview of your =
boards
which is a nice final check before submitting the job for fabrication.
Note: I DO NOT RECOMMEND using this solution. It has a number f =
shortcomings.
1. It depends on some external force to make the decsion about =
starting
or stopping the generator.
2. It can lead to a really rough phase transition when switching.
If you=E2=80=99re just feeding a UPS and you can make sure that =
one side
is down well before you switch to the other side, this is =
probably OK.
If you=E2=80=99re feeding some sort of motor and there=E2=80=99s =
potential for a live
switch, this can be very hard on said motor and can lead to =
graphic
and spectacular failures of said motor as it attempts to change
it=E2=80=99s armature position instantaneously to match the =
phase of the
new power source.
3. It would almost certainly never pass UL, CSA, or any other =
certification.
4. It=E2=80=99s the kind of thing NEBS was developed to prevent.
5. The potential for combustion if the world ever violates your =
expectations
is not insignificant.
Now, with the same hardware, if you have the MC do some additional =
detecting and
control the switchover process, you=E2=80=99ll add a few failure modes =
into the system,
but you can make the whole thing a lot safer and actually more reliable. =
You can
at least build something that will not damage your equipment or catch =
fire.
The cost would be about the same (same hardware, after all), but you=E2=80=
=99d need to wire up
a few more pins (more traces on the PCB) to the MCU and you might need a =
couple more resistors
and diodes.
Owen
> On Jan 27, 2016, at 13:32 , Velocity Lists =
<volists@staff.velocityonline.net> wrote:
>=20
> If you are not looking for "monitoring" of it.
> A DPDT 120v 10amp Relay with three power cords cut and attached will =
make
> an ATS for under $30.
>=20
>=20
> Velocity Online
> 850-205-4638
>=20
> On Wed, Jan 27, 2016 at 4:16 PM, William Herrin <bill@herrin.us> =
wrote:
>=20
>> On Wed, Jan 27, 2016 at 3:29 PM, Chuck Anderson <cra@wpi.edu> wrote:
>>> Does anyone have any recommendations for a small, cheap, reliable =
ATS?
>>=20
>> The APC SU042 series sell for dirt on ebay.
>>=20
>> -Bill
>>=20
>>=20
>> --
>> William Herrin ................ herrin@dirtside.com bill@herrin.us
>> Owner, Dirtside Systems ......... Web: <http://www.dirtside.com/>
>>=20
