SEEP and Peco point motors paired

[RJS1977]

I have two points paired as a crossover, one with a Peco motor (PL10) and one with a SEEP.

 

The wires from the CDU to the coils (both the return and the feeds from the pencil studs) run on to the contacts on the Peco motor thence from there to the SEEP.

 

When I touch the probe on to the studs (for either direction), the SEEP fires, but the Peco does not. Given that the wires run first to the Peco, then to the SEEP, I don't think there's a fault in the wiring anywhere, and to have a fault on both coils of the PL10 seems unlikely.

 

Is it possible that the SEEP may be hogging the current and not leaving any for the PL10?

[Ray H]

Have you tried disconnecting the SEEP (at the SEEP, not at the PECO) and seeing what happens?

 

The reason I suggest disconnection at the SEEP is to ensure that there isn't a dry joint on the PECO which would show up if only the Peco is supposed to work.

[kevinlms]

10 hours ago, RJS1977 said:

 

 

Is it possible that the SEEP may be hogging the current and not leaving any for the PL10?

Measure the resistance of the coils (no other wiring attached) with your multimeter set to Ohms and probably all will be revealed.

 

You will almost certain;y find that the SEEP one has a lower resistance and so will take the lion's share of the voltage.

The only fix for a crossover, is to use identical point motors.

[ejstubbs]

7 hours ago, kevinlms said:

You will almost certain;y find that the SEEP one has a lower resistance and so will take the lion's share of the voltage.

The only fix for a crossover, is to use identical point motors.

 

Hang on.  If the coils are in parallel then they will both see the same voltage regardless of any difference in resistance.  If they're in series then the lower resistance coil will see a lower voltage, since the current will be the same through both coils (by Ohm's law).

[SHMD]

The coils have different inductances.

The coils work by the magnetic field the current in the each coil generates.

The current through a coil takes time to build up (exponentially) to where you can use Ohms law.

The Seep has a much lower inductance, (I measured one once), and will conduct the full load current from the CDU much quicker than the Peco Coil can.

This, however, drains the CDU of all charge before the Peco has got anywhere near allowing the current to rise to where it can actuate.

 

 

Kev.

[ejstubbs]

I was going to add "This is not taking inductance in to account" but decided not to muddy the waters as I was replying to kevinlms who specifically mentioned resistance and voltage, and did not mention inductance, and in that regard his assertion that a lower resistance would "take the lion's share of the voltage" was simply wrong.

 

But thank you for clarifying why a difference in inductance - which you have measured - can give rise to the results that the OP is seeing.

[Sol]

A lower resistance will take more current. I helped build a layout that had different brands of side mounted solenoids & had to add a high wattage but low value resistance into the low resistance coils to balance the load for both to work with a CDU.

Now if a CDU is not used but a normal AC or DC supply of around 3-4 Amp output and pushbutton or non-locking toggle, then current can be supplied for a longer period of time compared to a CDU and so both coils should activate as long as they don't burnout being activated for too long....

[SHMD]

Inductance is a fleeting but important part in understanding  "who takes the lion share" of the current - when the current is supplied from a CDU.

 

I will now look for the thread where I posted my Seep measurements.

 

 

Kev.

[SHMD]

I have a recent post, look about a quarter the way down ...

 

 

Where I measured 2.79mH and a resistance of 2.79Ohms for a SEEP point motor coil.

 

 

Kev.