Adding smoke to b-unit

Dan,

FYI...

For the most part, Premier dummy A and B units in AB and ABA sets typically have smoke units. Dummy units in Rail King AA, AB and ABA sets typically do not.

Right just wondering if I can easier add smoke to the them. Im too heavily invested in the semi-scale now to switch to premier/full scale cars. Just wanted to add a touch more realism to the b units and non powered a units.

You could add PS-1 smoke, but not smoke that can be controlled by DCS without upgrading to a slave or full upgrade to PS-2.  G

https://ogrforum.com/t...ke-units-for-dummies

suggests running a tether to a 2nd PS2 smoke unit.

The tether is certainly the simple solution.

From the other post it looks like a tether is the way to go. With that in mind, after reading this post in the other thread:

 If my b unit has pickups for lights, how or what do i need to "electrically buffer the pulses" ? As gunrunnerjohn mentioned in the other thread the control boards are rated for 4amp, If i run it on medium output I cant see pulling too much juice. Plus arent these boards designed for two smoke units for the larger engines or are there single smoke unit boards only.

If these are 3V units, they'll handle two smoke units.  Earlier 5V boards would not handle two smoke units without modification.  Some of the later 5V boards were capable of handling two smoke units.

Yes, "same" main board drives 1 or 2 smoke units.  The slave board that GGG refers to has a 10-pin tether from the main A unit but this also has motor drive and light signals in addition to smoke.  What was proposed in the other thread, but was not confirmed by anyone who actually did it (as far as I can tell), is to run just the 4 smoke wires (2 heater, 2 fan) to a trailing A or B smoke unit.

The slave unit board which uses local track pickups buffers the heater signal from the main unit with a simple FET driver circuit (I'd guess a couple bucks of parts).  I don't know if anyone has published or tried to roll-your-own smoke buffer circuit.  In any event the buffer allows the "high" smoke currents to flow locally rather than over the tether.  One can debate the merits of the two approaches. 

My observation was that whether you go with the slave board with 10-pin tether or try to roll-your-own subset with or without buffer, that there ought to be some connectors, harnesses, or whatever from a dual-smoke main A unit that you might want to look into.

The slave board recommendation was for independent control.  As stated if you just want smoke linked to te A unit controls you bring over the smoke heater wires and fan wires (4).  The unit will respond to A unit controls.  G

G, what do you mean by "independent control"?  If we're talking about the same slave board, the power level to the slave smoke unit mimics whatever is going on with the main smoke unit.

Do you know if anyone has actually implemented a 2nd smoke unit across a 4-wire tether?  That is, where the "high" current pulsed electrical signals run a physically longer distance than between 2 smoke units within the same main A unit.

Stan your right.  Was thinking PS-2 not slave.  Yes the slave mimics the lead A.

I don't, but some of MTH large engines with 2 smoke units have long smoke harnesses.  You could just go up one wire gauge, but I don't think it will be an issue.  What is your concern?  G

The concern is why does the MTH slave board then have a buffer which adds cost.  Perhaps, to your point, a 10-wire tether would get rather thick and stiff if many of its wires needed to carry high current smoke and motor signals. That is, buffering allows smaller gauge wires in the tether.

Whats the cost of a slave board? I could see where both options could be useful. Especially in a situation where more than two smokes units would be useful like an ABA configuration. In most of the engines i would be doing this do they have diaphragms between the engines so the wire wouldnt be visible hardly at all.

Stan, What do you mean by buffering?  Are you taking about the 74HCT that control the FETs?  I thought they helped buffer the processor.  For the slave I was thinking the board is just measuring the output, and using it to control the slave boards own generated voltage.  Granted I have not studies the slave board to the same degree as the PS-2 boards.  Usually slaves come in for A motor FET repair only, so I figured out how to take measurements to determine which one is bad.

Internally to the A unit the wiring to the smoke unit is only 28 gauge.   So other than the extra distance the wire gauge is probably the same.  If a PS-1 harness was used the wire might be 22 or 24.

The smoke unit is about a .5 to .7 amp load on the Z-4000 meter when turned on in conventional.   G

I don't have one in front of me to photograph, but the slave unit I saw had a FET driver buffer on the board itself (in addition to the HCT logic gate buffer).  The slave's smoke unit is therefore pulsing (PWM) in sync with the main smoke unit pulses...except only low-current pulses are going over the tether.  The high-current supply is generated locally from the slave's own roller pick-ups/wheels; the slave board FET switches this supply voltage.

Although the current may only jump up 0.5 (or whatever) when you turn smoke on, as you know the low resistance smoke heaters are being pulsed using the Positive Supply voltage which can be, say, 18V.  So the pulsed current magnitude is V/R which is measured in Amps...understood about the average Amps which is relevant to wire-heating or gauge selection at these modest frequencies.

I found this posted photo of the slave board I'm thinking of in this thread:

https://ogrforum.com/t...or-mth-proto-diesels

There's the FET going to pin-3 of the 4-pin smoke unit so that's what tells me the smoke control pulses from the main unit tether are being buffered locally on the slave board.  I think it would be a serious undertaking to reverse-engineer the smoke-only portion of this board. It would take some thought but perhaps since we know 2 smoke units can be driven by one set of electronics, perhaps the 2 unpowered units in an ABA would only need one set of smoke electronics if that makes sense.

I converted that F3 to PS2, Still have the slave board around here somewhere if interested.

Stan,  The Lead PS-2 produces about 25VDC as Positive Voltage when the track voltage is 18VAC.  The Rectified AC is boosted via inductor and capacitor from what I have seen.

This voltage is sitting on the motor, heater element and lights.  It is also sent over the harness to the slave.  The motor leads also go over so the motor leads provide another source of PV for the slave.  The rest of the leads are the accessory returns and the PCB DC Ground.  I believe the slave produces it's own 5VDC for the fan and LEDs, another DC Source to run the microchips, and then it's own motor current.

Since the slave is only seeing the FETs return signal pulse to DC ground I am not sure any current flows?

Since we don't know the PWM for the heater we don't know the effective Voltage seen by the element.  We know lights are about 6V so the heater can be down that low also.  I have watched the bulb intensity on board tester and it is a 6V bulb so that may be a hint.  The program definitely varies the intensity of smoke heat depending on what the engine is doing. (Boost the heat at first motion then drops off.

So any way I think the current draw for the elements is probably under an amp, the fan takes less than .1A on the 1 amp 5VDC regulator.  So I still think the harness can take the current flow to run the remote smoke unit just like a larger Diesel or Gas Turbine that has 2 smoke units.  G

G, no disagreement on your analysis.  My point is the OP wants to run 3 simultaneous smoke units sync'd to the main A.  So while a direct tether may work for a 2 smoker AA configuration, the 3rd smoker in an ABA will need something akin to the buffered smoke circuitry on the slave board - in my opinion of course.

Got it, I missed that we went from 2 smoke unit up to 3.  I would still try the harness method but remove one heat element from each dummy smoke unit so they go from 8 ohm effective to 16 ohms each.  Now the 2 dummy smoke units would be the equivalent load of one normal unit on the PV.  Of course you pick up one more fan motor load on the 5VDC circuit.

Or you add the slave to the B, and then tether it to Dummy Trail A.  Now the PS-2 board carries one smoke unit and the Slave carries 2.  G

I think though at a price stand point by the time i buy a smoke unit and a slave control board to safely run a third unit I would be better off just buying a powered unit and running it as a lash-up. Yes I would have to independantly control the smoke but only when changing the levels. Plus I would have the dummy unit to sell to finance the powered unit. As far as my question abour running the slave unit in the above post I just wanted to make sure it was safe to just run a tether alone vs running a tether with a slave board. Thanks all for your help and I think i have a game plan. Have a tethered A-B unit with a "lash-up" to another indepentant powered A, this should give me what Im looking for.

One could always power a small digital relay via the heater wires and have the output complete a circuit to power the heaters. But it would need it's own power supply via the rail pickups which would have to be added and power routed thru a bridge rectifier into say a buck convertor...Only drawback is you'd lose the low, med & high smoke heat settings but the fan would still be powered via the PS2 main board.

Could possibly power 2 or 3 smoke units this way...would depend on the buck convertors capacity...Just a thought.

Dan, another route is the PS/2 upgrade kit to upgrade the dummy and then you'll have the powered unit and the capability to run two smoke units directly.  If you're a member of the MTH RR Club, the upgrade kit is $150.

Still though looking at the secondary market like the classifieds here or ebay, a lightly used or new railking engine only brings 150-200$. I would probably be better served just buying a completely seperate unit. The tether option on contrast is maybe less than 75$ in parts if you include the price of the smoke unit. Plus wouldnt I still need to buy the smoke unit when doing the ps2 upgrade? I could see maybe going the ps2 upgrade option on a premier engine where the engines are substantially more expensive.

Just offering another option.  You may not be able to find a powered B unit that has smoke for the Railking models.  Also, your specific road name may be scarce...

Maybe i misunderstood. The ps2 upgrade has powered trucks? I didnt realize this would make it a powered b-unit. Ill freely admit im not well versed on mth engines, just grealy prefer their rolling stock. Why lionel cant make it easier to distinguish between there semi-scale and scale rolling stock is beyond me.

Uh... no.  Totally overlooked that little problem.  That might get a bit expensive.

Would like some information, as I have tried to discern the above, and well

I have a 30-4144, mth, with a tether running back to the lighted second "A",

unit,   I would like to add a smoke unit to this 2nd " A".  Will the PS/2 board in the

primary "A", unit, function, and allow the 2nd smoke unit to work, and not blow up the main board.  It seems like I am seeing that style of info above, but would like to confirm

that information.

If it has the 3V PS/2 boards, there's no problem running two smoke units.  If it has the 5V PS/2 boards, the answer is maybe.  There is a mod to allow them to run two smoke units, I don't know when it was incorporated into production.  That set was 2005, which should make it a 3V board, but the sound file looks like a 5V sound file, so I'm not sure.

Thanks ,John. now I have the information, maybe an email to MTH

asking about the board will put me on the way!!

Terry

FWIW, I have a PS2 (5 volt board) ATSF 2500HP Transfer Diesel that has 2 separate smoke units.

Right Barry, I have the same engine.  There is a mod for some 5V boards to handle two smoke units, I'd have to dig out my binder to remember exactly how you recognize if the board is capable or not. 

Terry, you can just check the bottom of the engine, the square charging port is the 3V board, the round charging port is the 5V board.

You look at the Smoke FET Q-19.  It should be a LL2705 to support 2 smoke units.  G

Thanks John,  I 'll go and check out the charge port, 

GGG,  I know that you repair stuff, BUT , if that number is located

somewhere, and this may seal the deal,  can you get me a picture, of where

to Look.  I dont mind taking shell off  Front "A",  THANKS

EDIT:   It is Square, guess I can try it , if I can figure out what to mount it

          on !!!

The 5 volt PS2 board is designed to power only 1 smoke unit. To power 2 smoke
units from a single 5 volt PS2 board perform the following to the processor board.

• Replace Q311 with IRLL2705 and
• Replace Q307 with BSH101

To help with location that is on the bottom side of the board, usually faces up in a tender or diesel.  The 4 pin smoke connector would be directly under the location.   G

If indeed you have a PS2 5V board and can access it, here's a photo with the two FET devices GRJ identified circled.  This pic shows the one-smoker version (352A marking upside down in photo, small FET marked SS, large FET marked 3055L).  The BSH101 appears to be obsolete while the IRLL2705 is 93 cents at Digikey.  If you choose to attempt the mod and can't find a BSH101 and the MTH techs don't have a replacement, I'll find a Digikey alternative for you.

Photo revised per GGG correction below.

Thanks everybody,

Box Car Bill, sent a note about a
Conv, Lionel, Loco,   I do have 1 and I think since this is

numero uno, I might go that route, ( JUST, in case, I screw up)

&  after I have learned

with the Information, from you folks, (and it is appreciated)

I will try my hands, with the MTH,  1st thing, probably getting a

MTH, Unit !!

Stan, You circled the wrong component.  307 is below it.  The BSH101 is now a FDN 5630.  Not sure why 307 component is changed, I thought it was a BSH101.  It is the fan motor run FET.  The FDN5630 is what is used on the 3V board and is the replacement to fix failed FETs on the 5V for lights and couplers.  G