Peco swithc machines

For DCC, I highly recommend the team digital SMD8. If you're not interested in controlling the switches remotely, circuitron makes a nice one. I've been using the low-current peco machine, and I don't think any CD out there is going to have the slightest trouble flipping them. That might not be true of the high current or long-pin ones though. *

"S> Can someone suggest (or point me toward) a capacitor discharge unit for "S> operating Peco twin coil switch machines?

Virtually ALL of the hits from the above search will work. Pick one that suits your situation (there is at least one commercial product listed, as well as a number of build-it-yourself circuits of varying complexity.

"S> "S> Jeff "S> "S> "S>

\/ Robert Heller ||InterNet: snipped-for-privacy@cs.umass.edu

|| snipped-for-privacy@deepsoft.com /\FidoNet: 1:321/153

Can you solder? Screw together wires in a screw block/chocolate block?

You need:

- an 1N4001 (or 4002/3/4/5/6/7) diode.

- an ordinary 12volt 50ma light bulb. (or similar - ma rating not in any way critical) (in a holder with leads if you can't solder)

- a 25 volt 2200uf electrolytic capacitor.

The circuit: Diode Bulb Transformer AC terminal o---+--[==>]--+--(X)---+-----------------+---- turnout motor switches. ..............................................................................|(+)......................|

...........................................................................===Capacitor........^

1N4001 diode. ..............................................................................|(-).......................|

Transformer AC terminal o-------------------------+----------------+----To turnout motor common.

The diode rectifies the current. The bulb limits the charging current to the capacitor and to the turnout solenoid coil if it remains in circuit. Recharging time is about half a second, long enough to recharge while your finger moves from turnout switch/button to turnout switch/button. Suitable capacitors normally come in 1000uf/2200uf/4700uf.

1000uf is just about enough to throw a sticky Peco point motor. 2200uf will throw any point motor unless the points are screwed/glued solid. 4700uf will throw 3 or 4 point motors at the same time if you want route selection.

You can connect this circuit to almost any MR transformer, even something like those tiny Bachmann train set controllers will do the job fine. You can add lots of these CDU circuits where you have multiple operators who might want to throw turnouts at the same time. You probably need separate CDUs where you have other brands of point motors which have different resistances to your normal type (Peco) because the coil with the lowest resistance will take the larger share of current. The total cost should be a couple of dollars.

Regards, Greg.P.

I've been throwing Peco point motors for the last 30 years with CDUs. The only problems I have ever encountered come from two sources:

- Peco motors on bases not correctly aligned with the tiebar, so that the physical resistance is excessive.

- When using the cheap Peco on motor switch to achieve 'end off switching' the action can be unreliable if there are other problems like ballast restricting point blade movement. I have motors which were second-hand and well worn when I bought them 30 years ago (plastic frame) along with current products and everything in between. The plastic framed ones could distort if you left them on for too long, otherwise they all just keep working until the turnout gives up!

Regards, Greg.P. NZ.

The power of the CD supply is in the size of the big cap. Smalleer caps should be used with the smaller switch machines. Caps can be very effectively paralleled so if you find that you don't have enough power then you can just get another cap of the same size and the power will be doubled. The voltage that they are run at also makes a difference with the higher voltages providing more snap. If you understand the circuit, the Current Blocking kind of CD supply is the best as the cap won't start charging until you release the pushbutton which means that you won't be heating up the swich machine if something gets stuck, you just won't be able to throw any more machines until you find the bad switch.

-- Why isn't there an Ozone Hole at the NORTH Pole?

Other than the godawful CLACK a small switch machine (like the atlas ones) makes when you use a powerful CD, there really isn't any downside - it doesn't seem to hurt them one bit.

Many CDs step up the voltage as well as storing the current. The circuitron one I used for a long time would deliver 25 volts from a 15volt accessory supply.

This is absolutely critical. Most switch machine motors will fry themselves very quickly if they get any amount of current for very long. Before I used the CD and switched on accessory power directly, it was quite common to have to replace a MELTED switch machine if a button got stuck. *

doesn't seem to hurt them one bit.< Years ago if you used a big enough cap PFM and similar type of machines would blow apart!

Anyone know if Ken Stapleton is still selling or making his twin-coil CD units?

Robert Heller wrote:

The only downside to overpowering the switch motos is the physical foce of the solenoid throwing back and forth hitting the end stops hard enough to break them. Often the switch motors will work for a year or more before snapping something in the switch machine. The voltage really doesn't get multiplied but rather the peak voltage of the power supply is the voltage that appears at the output of the CD machines. Put a voltmeter on the powesupply for the CD and you see the RMS voltage which is only .707 of the peak voltage of the output waveform.

-- Why isn't there an Ozone Hole at the NORTH Pole?

Use a vtvm instead of a vom and switch to AC? Get an osicloscope(sp) and see the wave itself?

Jim Stewart

There isn't a functioning stop on a peco point motor! The solenoid movement is halted by the point tie bar. or the Peco mounting base if you use one.

Correct.

Regards, Greg.P.

You just need to measure the peak voltage across the capacitor. This will never be more than the peak source voltage. If the source is a DC supply, its peak IS its voltage. If the CD unit is being fed from an AC supply it will be the peak, which is 1.414141414... times its RMS (rated) voltage. RMS = .70707070707 (1/.707070707 == 1.41414141414).

The only way you are going to damage a twin coil switch motor is putting too high a DC voltage across it. I'm guessing that the rated voltage assumes using the AC accessory output of a analog power pack (traditional model train power pack). Something like 16VAC. I'm guessing that a CD unit attached to this will yield 22.6V peak, which might be too much. 16VP > 11.31VRMS, so if you use an *AC* supply, limit for your CDs it to 12VRMS OR use a 12-16V *DC* supply. Eg a 12VAC wall wart. Or an old 12VDC computer power supply. If you use a CD unit, there is no need to jack up the voltage. The only reason to jack up the voltage is to re-charge faster and/or drive more switch machines at a time. The on-line article for the Switch Witch talks about this -- the *proper* solution is to use CD units on a *per switch machine* basis. The Switch Witch units are logic-level controlled.

"S> "S> Jim Stewart "S> "S> "S>

\/ Robert Heller ||InterNet: snipped-for-privacy@cs.umass.edu

|| snipped-for-privacy@deepsoft.com /\FidoNet: 1:321/153

I have to disagree with you on the voltage being the only thing that kills a twin coil switch machine. Rather it is the total energy that goes into the machine. For a reference, I used to work on a power supply (for a sonar system) that would put out a 1KV pulse. Put that across a coil and the coil wouldn't move at all or be destroyed. The total energy in the pulse wasn't that much and the pulse width was so narrow that the inductance in the coil would not really accept it so nothing happened. A high voltage in and of itself isn't the problem but rather how much energy that is actually used by the coil to drive the pistion of the twin coil machine to the other extent of the travel. There is a stop of some kind with all of the machines or the pistion would drive itself out of the machine. The typical CD system starts the piston going and doesn't stop it when it gets to the coil being activated as the energy is gone and done it's work by then so something has to stop the piston mechanically. The alternative is to use a lower voltage and a larger cap so that there is still some power in the coil to stop the piston magnetically. Even then, the piston tries to travel beyond the coil (inertia is what is happening here) and hits the mechanical stop even then. The secret to long life with the CD system is to provide only enough power to the coil to get the pistion moving without driving it too hard against the mechanical stop and you can sort of tell what is right by listening to the swichmachine as it throws. A softer sound than the normal full power of a regular not-CD power supply is about the right amount of power for the switch machine. As a little side note on those sonar drives, a carbon composition resistor would work for a few cycles but eventually the resistor would swell up and die from the peak current that the drive would put out. The big problem we had with testing them was finding a non-inductive resistance that we could use to load the drives.

-- Why isn't there an Ozone Hole at the NORTH Pole?