Peco point motors 2: The Sequel

Dont be put off by Guys motor problem, suspect its unusual.

Was just wondering if motors are fixed to points via the tabs on motor case or if their held to baseboard some other way ? Does a complete motor move when it dont flip point- it wouldnt take much movement of motor to translate to no movement of point ?

cheers, Simon

Mounted through the baseboard and attached direct to the point, I have a 100% success ratio. When under the baseboard I am using the Peco mounting plates. I don't think that solenoid would be capable of flexing the motor frame if you put a million volts through it* but I could be wrong.

• In which case it would of course be an ex motor, it has ceased to be. Guy

I have my doubts that Peco point motor armatures are pure iron :-)

I tend to disagree - if the point motor won't throw when

16+volts from a 2200uf capacitor (12 volts times 1.4) then there is a definite mechanical or electrical problem.

Greg.P.

I did mean DC _or_ SDU. Sorry.

Greg.P.

Try reading what was written.

12V *DC* is 12V DC not 16V.

The 16V was AC, and was direct with no CDU.

If it will not throw with a 12V *DC* 2200uF CDU then try increasing the voltage or capacitance.

MBQ

It's rectified so it's probably 16V peak, which is what you'd get on a cap, even though it is 12V RMS. Sadly all those oscilloscopes on fleabay go for silly money. Guy

However, we are forgetting the first principles of fault finding - isolate the problem component. So take a working combination of point and motor (no switches) and a non-working one. Swap motors. Note results. Swap them back, note results.

CHeers, Simon

te:

So it wasn't 12V DC then!

MBQ

Let's not have that argument, eh? I have a B.Eng (hons) in electrical engineering so it could go on a while. Guy

Deadly, doesnt that mean you cant wire a switch without redesigning and adding circuitry for power smoothing, voice activation and a sound mudule for realistic noises :-)

Cheers, Simon

I'm well aware of what was written - unless you're using a regulated power supply such as one taken from a computer the 12 volts output will be a rectified sine wave. Smooth that with a capacitor and you will get a voltage across the capacitor of about 16 volts because the capacitor will charge to the peak voltage output from the power supply. That will be just over 16 volts, assuming you have a precision wound transformer - otherwise it will be a bit higher. (Transformer voltages are determined at an average current output, no-load average will be a volt or two higher.) You can test all this with a $10- multimeter and a capacitor if you don't believe me.

I assumed that. See my comments on actual voltages above.

If that is the case then most likely one of the following is the fault"

- Your linkage between motor and point bar is binding.

- your point blades are binding.

- your point motor has been screwed down too tightly and is damaged.

- your wires between power scource and motor are too small and are causing excessive resistance.

- you have two over center springs; point bar and motor mount.

- motor center point differs from tiebar center point.

- several of the above combined.

- something off the wall like having two solenoids in series.

- a dud point motor. (the very last possibility if they are new)

I've been using Peco motors for the last 40 years, many being second-hand and have had only one dud in that time - a second-hand one. They require some care in set-up but the force available is much more than is required.

Regards, Greg.P.

Stick an electrode in a potato, drop it in a bowl of coke, dangle another wire in the coke and drag the two loose ends across the terminals of a Peco motor and it will probably flop across :-) They will work almost as well with the circuit you're postulating!

Greg.P. (actually, you'd need about 3 potatos in series, but ...)

Very few power supplies labled 12V DC are actually 12V DC! Automotive (car) batteries are actually 13.8 volts when properly charged. Anything designed to run from a car battery will be optimised for 13.8 volts. Model railway transformers were intended as replacements for car batteries. (ok, that's arguable ;-) Way back, to get 12 V DC from a transformer one started with a 16 V AC transformer and a selenium bridge rectifier which would loose something close to 4 volts. Today we use silicon rectifiers which loose about 1.4 volts, so you'd need a 13.4 volt transformer to get 12 volts RMS.

12 volts RMS varies between 0 volts and 16.95 volts 100 times per second, averaging 12 volts. Electric motors don't care, they see the average.

Greg.P.

Did think of alternate power source but more towards solar than the truely esoteric :-)

Cheers, Simon

Mine is in electronic engineering plus a diploma and 30+ years practical experience.

Most reasonable people would assume "12V DC" to mean a regulated voltage at or near 12V, not some AC voltage that is full or half regulated, unsmoothed and peaks at 16V.

MBQ

Then you should know better. Guy

Certainly not when considering model railway supplies and controllers!!

Just because it says 12V DC on the back doesn't mean that it is a regulated & smoothed 12V dc coming out.

Jeff