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I would like to power a PS2 motor directly from the track.  If I simply cut the motor leads, and tape them, and run new leads from the track to the motor, will I destroy the DCS system?  If not, will I still get chuff, whistle, and bell when actuated by the commander?

 

The system works great, but I have a different motor and gearbox, and the model runs too slow at my max voltage.

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Lot of variables here.

 

First, if you disconnect the Motor leads from the PS-2 board, nothing you do to the motors will hurt the PS-2 board since they are not connected.

 

BUT, sound effects produced are effected by what the tach reader sees, and possible feedback from the motor leads (not sure on this).

 

Second, the motors are DC motors.  If you are using AC track voltage, you still need to rectify the AC to DC before feeding the motors.  Since speed control is now track voltage changes, the PS-2 board will see varying voltage also.  Since you are operating conventional, you don't really need the PS-2 board.

 

Not sure what mods have created an engine that is too slow at max throttle, but the DC motors are rated at 12VDC, so how fast will it go at 12VDC with your gearing?  If you have to raise voltage higher, you risk burning out your motors.

 

Another alternative for you, may be to go to a PS-1 system.  You get conventional operation with sounds and you can install a PS-1 smoke unit in the unit too.

 

I have them available if you need a set up.   G

Bob

 

Lets slow down before any locomotives are harmed in the making of this film.  

 

Tell us more about your locomotive.  Is it a factory Proto 2 locomotive?  If so what is it?  Or, was it converted to Proto2?  Tell us more about the different motor and gear box.  Was the tach strip changed with the motor and gear box?

 

And tell us about your power supply.  What is it?  Is it AC or DC?  What is its maximum voltage?  What is its amperage capacity?

 

Proto 2 locomotives in "conventional" mode actually see the track voltage as a speed command.  The Proto 2 electronics convert a constant track voltage into a speed command and compare the commanded speed to the feedback from the tachometer.  The electronics then vary the pulse width sent to the motor until the commanded speed and the measured speed match.  The electronics also use the pulse width to change the steam exhaust sound or diesel prime mover sound the reflect how hard the motor is working (shorter or longer pulse) to achieve the commanded speed.  Of course the tach is also used to time the chuff sound on steam locomotives.  

 

Like other sound decoders, Protosound locomotives need to have some track voltage to run the electronics before they start to move.  Proto 2 and Proto 3 locomotives have very precise speed control in conventional mode.  Eight to twelve volts controls the 0-20 smph speed range.  Twelve to Sixteen volts controls the 20-120 smph range.  If you have an older power supply that only supplied the minimum 12 volts called for in NMRA Standard 9 and not the recommended 12-16 volts while delivering rated current you won't be able to get the full range of speed control out of PS 2 and 3 locomotives in conventional.

 

If you have an old power supply and want to run sound decoder equipped locomotives in conventional mode I strongly recommend upgrading your power supply to something with at least 5 amps capacity and a maximum output voltage under load of 16 volts for DC and 18-24 volts for an AC power supply.  RP-9 has been around since 1973 but most people with DC power supplies haven't worried about it until they get their first decoder equipped locomotive.

 

Don't hack into a perfectly good decoder equipped locomotive if a minimally compliant power supply is the problem.  It time for a power supply that meets recommend practice and is designed for running modern decoder equipped locomotives.  If your power supply is up to snuff we need to look at the gearing and tach strip.

Last edited by Ted Hikel

Thanks Ted.  This is my only sound- equipped locomotive -it is the J1e Hudson, with Pittman power, NWSL 24:1 gears, and modified tach tape to produce four chuffs.

 

I think part of my problem is indeed the power supply - it is Variac with condenser and rectifier,producing about 14 vdc.  I did try to change the ground to agree with 2-rail convention (easy, because I changed the drivers) but that did not work at all. 

 

I was just thinking of a quick fix, but did not want to kill the electronics.

Originally Posted by bob2:
... will I still get chuff, whistle, and bell when actuated by the commander?

 

 
By commander do you mean this is operating in command-mode with a "DCS Commander" DC-controller? 
 
 
Originally Posted by bob2:
I think part of my problem is indeed the power supply - it is Variac with condenser and rectifier,producing about 14 vdc. 

 

By rectifier, do you mean the 2-lead component?  If so, is it practical to replace it with a bridge-rectifier (4-lead component)?  This could increase your available DC voltage.  Or, if you have them, what are the values/part-numbers of your power supply components?

Bob

 

It sounds like a new power supply would make things much better.  A 16 volt power supply is needed for the full range of speed control for conventional PS 2 operation.  But, you can get more speed out of PS 2 at 12 volts in command mode.  You might consider picking up one if the little $40 DCS commanders.  A PS-2 decoder will never send more than 12 volts to the motor.  If the decoder gets 12 volts at the track in command mode it can then use pulse width modulation to send as much power to the motor as is needed to obey the digital speed command.

 

It is also worth taking a closer look at the PS 2 installation to see if you can improve that too.

 

You say that you have a J1e with a Pittman motor and a 24/1 gear box.  Is that a 2 rail brass model?  If so, who made it?  What is the driver diameter?

 

You also say that you produced a custom tack strip to get 4 chuffs per revolution.  Proto 2 chuff rate can be set from a DCS controller.  Do you know the set chuff rate?  What sound file are you using?  What size drivers does that locomotive have?

 

MTH "sound files" also contain all the speed and command control information as well.  While you may be getting 4 chuffs per driver revolution your smph may be way off depending on what sound file you are using and your custom Tach strip.  Proto 2 is really an integrated sound, smoke, speed and command control system.  Changing one variable like the tach strip may have fixed your chuff rate problem but thrown off other parameters like scale speed.  Your locomotive may be running faster or slower than PS 2 thinks it is depending what sound file you are using, the tach tape, gear ratio and driver diameter.

 

My brother Dave has put together a page at the link below on tach strip calculations for PS 2 conversions.  Using it will get you accurate speed control and proper chuff rates.

 

http://sites.google.com/site/h...hing-ps2-conversions

 

I hope that helps.

Last edited by Ted Hikel

The locomotive is an MTH Scale J1e with 80" cast iron drivers.  Absolutely  no changes have been made to the DCS except to adjust the tach tape.  I did that by computing the changed gear ratio and counting the stripes, then re-painting.  Worked fine to keep the chuffs in the proper places.

 

I will give the $39 Commander a try before I modify anything else.

 

I use bridge rectifiers exclusively. They are now so inexpensive that the old style selenium rectifiers get recycled.

 

Thanks for the help.

Hi Bob,

 

Do you know if this MTH J1e came from the factory with PS2, or is this a conversion from PS1?  Can you give us the MTH product number?

 

If this is a factory PS2 engine that has had its motor and gearbox changed than we shouldn't have much trouble calculating the correct tach strip to get the size to synchronize the speed and chuffing.  However, if the motor is not a 12 volt motor the PS2 electronics may not be able to supply enough current to ever move at an acceptable speed.  Before you spend any money on other potential fixes, please give us enough info to really understand your situation.

Originally Posted by bob2:
I will give the $39 Commander a try before I modify anything else.

Good idea.  Use the $39 Commander and see if the engine achieves an acceptable speed when pulling the desired load with 14VDC or whatever max voltage you can provide. I believe it will run faster than when you varied track voltage to control speed (i.e., when not in DCS command mode).

 

Yes, in principle you could bypass the DCS electronics and directly drive the DC motor from DC track voltage. You will gain top-end speed capability because this bypasses the engine’s internal bridge-rectifier which eats 1-2V.  If you ultimately go this route, note the engine might move with, say, 5V DC on the motor.  But the DCS electronics won’t operate at that low a voltage. So when you slow or stop the motor (engine), sounds and lights will turn off.  I’d find this a show-stopper but that’s just my opinion.  There would be other odd or head-scratching behaviors as well.

Thanks Dave.  It came as a PS-2 Hudson.  It chuffs at exactly four per driver revolution, so further recalculations of the tape would throw that off.

 

I will try the Commander, and if that doesn't work I will find a bigger transformer for my Variac output.  Then, in the end, I will install a DPDT switch at the motor for direct track voltage.

 

Thanks for the help- all of you.  Here it is:

 

Last edited by bob2

Hi Bob,

 

OK.  So we have a PS2 Hudson that is stock except for the NWSL 24:1 gear box.  That makes this pretty easy.  Using the calculator I developed for PS2 conversions we find that you need a custom tach strip with 32 stripes (black and white) measuring .108in. per stripe.

 

I know you said you made a custom tach strip to correct the chuffing.  Ignore the chuffing for the moment and install a tach strip with the specs I described above.  That should get the speed corrected.  Once we have the speed correct we can address the chuff rate.  The chuff rate is set in DCS.  Many early PS2 engines had a default chuff rate of 2 chuffs per revolution instead of 4.  This could be the case with your engine.  If you don't have a DCS set find someone who does.  Change the setting under DCS to 4 chuffs and it will be retained in conventional DC mode.  If your engine currently has a tach strip with 64 stripes it would chuff 4 times per rev (while set for 2 chuffs in DCS) but would run half speed.  For a PS2 engine running in conventional mode at 12 VDC that would equate to 10smph.

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