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I'm starting a new topic to bring some information forward about the Aristo smoke units.
I am talking about the one referred to as the "prime mover" type, that is a rectangular box about 1 x 1 x 2 inches has a fan in the bottom. It's in all the newer locomotives, like the SD45, GP40, dash 9, etc.
The unit has 4 screws on the top, and removing the top cover reveals the back side of a circuit board. Pulling the board out reveals the housing has 2 chambers, one for smoke fluid and one that encloses the fan and electronics.
The smoke chamber has a capacity (advertised of 75 drops), and is dominated by a 5 ohm heating element, which has a thin wire spiral wound on it (probably nichrome), and a piece of fiberglas wicking that is clamped around the element and with the ends sitting down into the bottom of the fluid chamber.
There a a "Wall" that devides the 2 sections and there are 2 small notches in the top to admit pressurized air from the fan. The top of the circuit board over the element has a hole that the smoke is blown through. The full wave bridge rectifier is also on this "half" of the circuit board, 4 discrete diodes.
The circuit "half" of the board has the fan and motor and a number of components. There are no heat sinked devices, and the board obviously regulates the power to the heating element and the fan, though the fan runs at constant speed. It's a pretty good guess that the way it works is that the IC on the board is a small PIC processor functioning as a pulse width modulator to regulate voltage/current.
These units have various problems and many users are plagued with short run times, like 1-5 minutes.
This is the problem I'm investigating. There are also other problems, like the smoke fluid getting all over the circuit board and swelling the rubber plugs in the ends of the electrolytic caps and popping them off the board. Also, when the electronics fail, the unit often turns "turbo", the fan spins at a verh high speed, and it makes a lot of smoke for a very short time. Continued running usually kills the board.
A properly functioning Aristo unit (remember, only this model) will run in excess of 20 minutes on 75 drops. The ones I have that work run about 31 minutes before shutting off. There is still some fluid, and you can usually get 5-8 more minutes just cutting power and re-applying. (Thus the microprocessor guess)
Aristo's first response is "are you using our fluid?" The fluid makes no difference in failing or not, although continued use of some fluids tend to clog the wick.
One user has reported he put a 300 ohm 1/4 watt resistor in parallel with the 5 ohm element and that fixed it. This is highly unlikely, since 300 ohms in parallel with 5 ohms yields 4.92 ohms. Obviously that's very little difference in resistance, and the difference it would make in current drawn. It's also obvious that a 1/4 watt resistor could not be contributing to the heat output in a significant manner, since it would carry 60 times less current than the heating element, and 1/4 watt resistors aren't large enough to make any heat (for any length of time).
One interesting observation was my monitoring of the current of the unit while it was operating to see if I could determine what the system was doing to signal "time to shut down".
The current started (I tested at 14 volts dc) at .4 amps, and quickly settled down to .312 amps until the very end of the run, then it began to drop down to about .291 amps.
This all makes sense, the resistor would draw less current when not making smoke, i.e. running out of fluid. (The action of vaporizing the fluid MUST use more current than when the element is "dry").
What I will do next is try to closely monitor the voltage of the element, so as to calculate the current drawn, and see if I can deduce the "shutdown algorithm".
Possibly this may lead to an understanding of why some of these units never perform properly.
If anyone has the ability to measure the cold resistance of their element (a very good ohmmeter) that additional information would help.
I have a few friends sending me units that shut down prematurely to see if I can gain further understanding.
Why am I going to all of this effort? Because while the Aristo warranty is honored, most units back from repair have the same problem.
I'll try to post some pictures of the guts.
Please, I don't need comparisions of different smoke units, I'm trying to solve a problem, not hear "MTH is better" or "Mine is fine". I do want to hear from people who cannot get 20 minutes or more on their Aristo units.
Regards, Greg
I am talking about the one referred to as the "prime mover" type, that is a rectangular box about 1 x 1 x 2 inches has a fan in the bottom. It's in all the newer locomotives, like the SD45, GP40, dash 9, etc.
The unit has 4 screws on the top, and removing the top cover reveals the back side of a circuit board. Pulling the board out reveals the housing has 2 chambers, one for smoke fluid and one that encloses the fan and electronics.
The smoke chamber has a capacity (advertised of 75 drops), and is dominated by a 5 ohm heating element, which has a thin wire spiral wound on it (probably nichrome), and a piece of fiberglas wicking that is clamped around the element and with the ends sitting down into the bottom of the fluid chamber.
There a a "Wall" that devides the 2 sections and there are 2 small notches in the top to admit pressurized air from the fan. The top of the circuit board over the element has a hole that the smoke is blown through. The full wave bridge rectifier is also on this "half" of the circuit board, 4 discrete diodes.
The circuit "half" of the board has the fan and motor and a number of components. There are no heat sinked devices, and the board obviously regulates the power to the heating element and the fan, though the fan runs at constant speed. It's a pretty good guess that the way it works is that the IC on the board is a small PIC processor functioning as a pulse width modulator to regulate voltage/current.
These units have various problems and many users are plagued with short run times, like 1-5 minutes.
This is the problem I'm investigating. There are also other problems, like the smoke fluid getting all over the circuit board and swelling the rubber plugs in the ends of the electrolytic caps and popping them off the board. Also, when the electronics fail, the unit often turns "turbo", the fan spins at a verh high speed, and it makes a lot of smoke for a very short time. Continued running usually kills the board.
A properly functioning Aristo unit (remember, only this model) will run in excess of 20 minutes on 75 drops. The ones I have that work run about 31 minutes before shutting off. There is still some fluid, and you can usually get 5-8 more minutes just cutting power and re-applying. (Thus the microprocessor guess)
Aristo's first response is "are you using our fluid?" The fluid makes no difference in failing or not, although continued use of some fluids tend to clog the wick.
One user has reported he put a 300 ohm 1/4 watt resistor in parallel with the 5 ohm element and that fixed it. This is highly unlikely, since 300 ohms in parallel with 5 ohms yields 4.92 ohms. Obviously that's very little difference in resistance, and the difference it would make in current drawn. It's also obvious that a 1/4 watt resistor could not be contributing to the heat output in a significant manner, since it would carry 60 times less current than the heating element, and 1/4 watt resistors aren't large enough to make any heat (for any length of time).
One interesting observation was my monitoring of the current of the unit while it was operating to see if I could determine what the system was doing to signal "time to shut down".
The current started (I tested at 14 volts dc) at .4 amps, and quickly settled down to .312 amps until the very end of the run, then it began to drop down to about .291 amps.
This all makes sense, the resistor would draw less current when not making smoke, i.e. running out of fluid. (The action of vaporizing the fluid MUST use more current than when the element is "dry").
What I will do next is try to closely monitor the voltage of the element, so as to calculate the current drawn, and see if I can deduce the "shutdown algorithm".
Possibly this may lead to an understanding of why some of these units never perform properly.
If anyone has the ability to measure the cold resistance of their element (a very good ohmmeter) that additional information would help.
I have a few friends sending me units that shut down prematurely to see if I can gain further understanding.
Why am I going to all of this effort? Because while the Aristo warranty is honored, most units back from repair have the same problem.
I'll try to post some pictures of the guts.
Please, I don't need comparisions of different smoke units, I'm trying to solve a problem, not hear "MTH is better" or "Mine is fine". I do want to hear from people who cannot get 20 minutes or more on their Aristo units.
Regards, Greg