Control Smoke Output On PS1 Smoke Unit

you could lower the voltage feeding the smoke heating element resisters!

The PS/1 smoke unit has a primitive regulator circuit, so it tries to put out as much smoke as possible over a range of voltages.  That being said, you can reduce the voltage to 7-8 volts on the input and you will get less smoke.

@gunrunnerjohn posted:

The PS/1 smoke unit has a primitive regulator circuit, so it tries to put out as much smoke as possible over a range of voltages.  That being said, you can reduce the voltage to 7-8 volts on the input and you will get less smoke.

It seems no matter what voltage I use the smoke output doesn't change.  It's the best smoke unit I have ever seen and by far better than my Lionel smoke units.

@R Whitley posted:

It seems no matter what voltage I use the smoke output doesn't change. 

What kind of transformer are you using to provide the variable voltage?

There is a quirky behavior when you drive this type of smoke unit with a so-called chopped-sine controller.  It will put out more smoke than voltage measurements would suggest.  There have been previous OGR discussions about this and we can go down that rabbit hole again if need be.  

Or.  The PS1 smoke units I've seen discussed most often on OGR is as below schematic.  As GRJ says there is a rather curious heater regulator circuit.  Skipping over circuit design details, one way to cut heater power in half at low-voltages (like the 7-8V that GRJ suggests) is to short component D2.  This can be effected with a short piece of wire on the back of the board as shown.

I can see other ways to reduce heater power using additional/modified components but I asked myself, What would MacGyver do?   

@stan2004 posted:

What kind of transformer are you using to provide the variable voltage?

There is a quirky behavior when you drive this type of smoke unit with a so-called chopped-sine controller.  It will put out more smoke than voltage measurements would suggest.  There have been previous OGR discussions about this and we can go down that rabbit hole again if need be.

Or.  The PS1 smoke units I've seen discussed most often on OGR is as below schematic.  As GRJ says there is a rather curious heater regulator circuit.  Skipping over circuit design details, one way to cut heater power in half at low-voltages (like the 7-8V that GRJ suggests) is to short component D2.  This can be effected with a short piece of wire on the back of the board as shown.

I can see other ways to reduce heater power using additional/modified components but I asked myself, What would MacGyver do?  

Stan &  Gunrunnerjohn, I finally got back to his project today and I notice my PS1 smoke unit is different from the picture Stan posted. I still would like to slow the smoke output way down, so take a look at the pictures and see if a jumper would work on it. This unit will not go in an engine but will be used to generate smoke on a crash scene on the layout. I plan to control the smoke unit with a dedicated Lionel accessory transformer.

Robert

When you greatly reduce the voltage to the smoke unit, it will slow down the smoke production.  The only question remains, can you slow it down enough for your purposes before it simply shuts down.

@gunrunnerjohn posted:

When you greatly reduce the voltage to the smoke unit, it will slow down the smoke production.  The only question remains, can you slow it down enough for your purposes before it simply shuts down.

That's the problem, finding that sweet spot on the transformer.  The lowest setting makes the unit sound like it's sick.  I even tried attaching a piece of 1/4'' tubing with a shark bite cut off valve but that didn't work either because the smoke would seep out every crack of the smoke unit.

I suspect more "fine tuning" may involve changing components on the PCB.  My "first cut" might be changing the smoke resistors to a higher value, say 20 or 22 ohms.

@R Whitley posted:

..., I finally got back to his project today and I notice my PS1 smoke unit is different from the picture Stan posted. I still would like to slow the smoke output way down, so take a look at the pictures and see if a jumper would work on it.

...

Did you try jumpering the points indicated?  Yes, the 2 boards are look slightly different but  should be electrically alike.

When you say the unit sounds "sick" I assume you mean the tiny DC fan motor which blows the smoke is misbehaving?    As you adjust the transformer voltage, the DC fan motor should NOT change speed and it should just be a steady "whirring."

What component are you shorting or bypassing with the jumper wire? And with the added wire, what is it doing to the actual unit?

Been following this thread as I am probably going to do the same at my club in a scene on the layout.

@stan2004 posted:

Did you try jumpering the points indicated?  Yes, the 2 boards are look slightly different but  should be electrically alike.

When you say the unit sounds "sick" I assume you mean the tiny DC fan motor which blows the smoke is misbehaving?    As you adjust the transformer voltage, the DC fan motor should NOT change speed and it should just be a steady "whirring."

Stan, I didn't try the jumper because the board looked different. The "sick" sound was the DC fan misbehaving or it may be because I had the voltage so low.

The motor will slow with low enough voltage, I see that here.

@Ted Bertiger posted:

What component are you shorting or bypassing with the jumper wire? And with the added wire, what is it doing to the actual unit?

The jumper wire shorts a Zener diode.  Refer to schematic in my earlier post.  The circuit has a simple heater regulator that behaves as shown above in black.  Starting at low track voltage, as you increase track voltage heater power (and smoke volume) increases.  Then, at some threshold voltage (determined by the Zener diode), heater power is cut and the curve "restarts."

The jumper wire effectively moves the threshold voltage down to 0 which means the cut back is always in place.  Hence the heater power at low voltages will look like the orange segment.

So for lower track voltages, heater power will be lower.  For higher track voltages, the heater power will be what it was...following the black curve segment on the right.

These curves are representative and are purposely drawn without "scale" as it is affected by whether you are using a pure sine or a chopped-sine power supply and the discussion just becomes tedious.

I suggested this method because it is simple and "additive."  By additive I mean you don't need to cut, splice, remove, exchange components, etc.

Since it appears you have the ability to adjust the AC track voltage, this should be suitable to reduce smoke volume while still maintaining enough voltage to operate the DC fan motor.

Separately, if by fan mis-behaving you mean it is squealing or hiccuping in speed then that's a different issue than simply slowing down from lack of voltage.  A drop of oil strategically "dripped" down the motor shaft can often eliminate the squeal albeit you should be on the lookout for a replacement.

I added a 2 piece jumper so I could do a N/O and N/C test and I saw no difference in the output of smoke that was noticeable to my eye anyway.

I guess I forgot to put the Your Mileage May Vary disclaimer!

I just hooked up a PS1 unit I had and with a Z-4000 (pure sine output) watched the Volt and Amp meters as I adjusted the throttle handle.  The Z-4000 "starts" at about 7V and I could hear the fan motor start but clearly not to speed.  The fan reached a constant speed at around 10V (based on listening to the whirring sound).  Smoke started between 8-9V.  At about 12V, the smoke production was prodigious.  Since your interest is in lowering smoke volume, I didn't mess around at higher voltages and focused around voltages below that.

When I enabled the jumper, the Amp reading on the Z-4000 dropped so the power into the heaters is definitely being cut.  Then, with the jumper installed, I could alter smoke volume from 0 smoke at 7V to a little smoke around 9V to much smoke at 12V.  Yes, I realize "little" and "much" are not technical but the point I was able to smoothly adjust the smoke volume over a range.

Something curious happens when you enable the jumper.  You can hear the fan motor speed up!  In other words, at low track voltages when you cut the heater power, more voltage is made available to the DC motor regulator chip and the fan spins faster.  In other words, by cutting back on heater power, more voltage is made available to the fan.  This has to do with the AC-to-DC conversion as the heater resistor(s) and fan motor are driven by "pulsing" 60 Hz voltage.

Finally, to peel another layer of the onion.  This is somewhat counter-intuitive but the way the circuit cuts power to the heater resistor (when the jumper is enabled) is by inserting both heater resistors into the circuit...but in series.  This doubles the resistance so the actual power drops.  I bring this up because how you install the wicks in the chamber affects airflow since smoke is effectively "produced" where the wicks touch the heater resistors.

As previously mentioned, a chopped-sine voltage is processed differently by this circuit.  The objective here is to control your PS1 smoke unit ... not to devolve into technical mumbo jumbo. 

Bottom line.  In my sample-of-one experiment, the jumper indeed lowered heater power at low track voltages.  The smoke volume was adjustable by changing applied AC track voltage.

Stan, I will try another transformer probably a CW80 and see if I can fine tune the voltage output better. I ran my test by using a Lionel 1.8 Amp Accessory Transformer. Thank you and the others that chimed in on this topic. I still plan on using this smoke unit for the crash scene but only let it run for a minute or two.

Robert