Re: power supply for servos?

David Heine

I have both 12 VDC and 5 VDC power buses on my layout, supplied from large switching power supplies I bought from Jameco. I use servos for most of my turnouts and all of the stub turnouts. (I had some new Tortise machines, so I used them on some point turnouts.)  I have some 3-way stubs that are controlled by the Tam Valley 3-way controller, which uses 12 VDC power, but most of my two way turnouts, of which most are servo-powered stub turnouts use 5 VDC controllers. The 12 VDC bus is powered by one large power supply. I broke the 5 VDC into three sections, each with it own power supply. If I had a smaller layout, I would just use one power supply.

Dave Heine
Easton, PA

On Thu, Mar 14, 2019 at 10:17 AM Ken Harstine <kharstin@...> wrote:
I use a separate 5V bus for my servos turnout controllers.  I currently
have about about ten installed.  I drive my bus with a switching power
supply.  Jameco probably has the best US prices.  I got mine via Alibaba
Express.  I wound up getting one with considerably higher Amperage
rating then you would think because of start up issues.  Normally the
servos use very little current to run but when first powered on they can
draw significantly more to get to the exact position currently
commanded.  At power up they all did this at the same time.  Sensitivity
to this issues is likely dependent on the servo driver.  I have been
using Pololu USB programmable drivers because of versatility.  However
they did not have an option to delay startup on individual servos.  I am
using a 5 Ampere supply currently.

The failure to start up properly was pretty catastrophic for me as it
led to bent wires at my servos.  Since getting a much bigger supply I
have had zero problems.  It would be interesting to know how the other
stuff out there behaves.  I am going to try the Swedish Möllehem
controllers going forward.  The pricing and delivery to the US was
excellent, they seem to be well made and they interface to Loconet which
are all priorities for me.  It will likely be a couple of months before
I actually install my first one.

Best Regards,

Ken Harstine
Holyoke, MA

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