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Hornby points question

Hello. Can anyone help please?

I know nothing about model railways but I'm asking for help on behalf of my father. Please excuse in advance my ignorance on this subject.

I understand that these points are designed to be activated by a pulsed

16v AC signal. Can any of you experienced modellers tell me the peak in-rush current for the solenoids employed and what the upper/lower pulse time limits should be? I've contacted Hornby but they do not seem to have a clue about the electrical specification of their own product! Also, Hornby refer to the points mechanism as a motor rather than a solenoid. Strange.

Furthermore, is it possible to drive the points from a regulated 12v DC source? I have a spare 3A regulated power unit leaving the 16v AC output on the controller free for other peripherals.

I know I could derive the above data for myself but lack of time dictates otherwise.

Thank you for any advice offered. Simon.

Reply to
simon
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Consider yourself excused!

The correct term would be "a pulse of 16 volts AC. - around 1/3rd of a second.

Placing a multimeter on each solenoid coil gives a reading of 4 to 5 ohms, not a reading that is consistant for every coil. If practice followed the theory then peak current would be 4 to 3.33 amps, (64 VA - 51 VA )but Hornby expect these mechanisims to work when driven by a transformer rated at 16 volts, 0.5 amps (8 VA) where the actual voltage is going to be down to something like 8-10 volts.

The on time needs to be over about 1/4 second - but the coil will withstand a few seconds of stuck finger before noticable heating occurs.

You haven't surprised us - those motors look very much like Peco products. Peco rate theirs at 5 ohms and 2 amps. (new Maths?)

Well, it is a double solenoid - that deserves a better name ;-)

The only problem might be that the wiring between transformer and point motor can absorb a lot of current - bigger wires! Since we didn't define a wire size in the first place you're left to your own devices ;-)

Reply to
Gregory Procter

In message , Gregory Procter writes

As I said, I could have calculated worst-case di/dt but you have saved me a great deal of time - I'm most grateful.

Simon.

Reply to
simon

Solenoids should work just as well on DC as AC, everything else being equal. I've done it with Atlas turnouts.

Reply to
MartinS

But its best to put snubber diodes across the coils to protect your control contacts from the arcing, with ac the arc is self extinguishing. Keith Make friends in the hobby. Visit Garratt photos for the big steam lovers.

Reply to
Keith Norgrove

[snip]
[snip]

At a guess, the double solenoids are "modelling" a piece of full-sized track equipment normally know as a "point motor", however powered or operated! After all, the bits of plastic driven by electric motors we are calling "locomotives" are modelling full-sized metal things driven by steam!

Speedy

Reply to
speedy2

In message , speedy2 writes

Ah... that explains the 'motor' bit, as I mentioned, I know absolutely nothing about railways/trains in general.

Point taken :-)

Cheers Speedy. Simon.

Reply to
simon

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