Heng Long Smoke Unit:

 

Heng Long smoke unit available from here .

Not surprisingly, very little information is available for this smoke unit, as it normally would be purchased as spare part for a Plug & Play connection to existing controller board in a Tank.

Optimum voltage for the heating element is 6 volts, the motor for the blower can be from as low as 3 volts up a maximum of 6 volts.

Both are frugal in terms of current, smoke unit element rated at 14 Ohms, has a maximum current of 0.76A when in use, the motor uses a paltry 0.17A.

Baby Oil, branded or supermarket own brand, using Fred & Flo from Tesco, just over £2.00 for 500ml.

Requires a DC supply regulated down to 6 volts, to run the heating element and the blower motor, an option would be a second regulated output, set at 3 volts for the blower motor.

Blower motor operated from a 1803BK manual speed controller, potentiometer with a built in On/Off switch, to vary the PWM to the motor.

On/Off switch for power to the voltage regulator module, whilst not clearly shown in the picture, is a 104 Capacitor soldered across the IN + and - on the module.

These modules can be somewhat difficult to set an exact voltage via the turn screw potentiometer on the module, as the voltage can fluctuate rapidly, the capacitor evens out the fluctuations and steady's the Input voltage, allowing for greater and finer control of the Output voltage.    

Manual control, for a static Animation scenario.

Short demo video of the Heng Long smoke unit operated by a manual speed controller.

Heng Long smoke unit in operation from a LGB 55021 DCC decoder, with proportional speed control from the Loco traction motor, control from a Navigator Handset, to operate the smoke unit motor and heating element.

The component PCB's were deliberately constructed 'oversize' to allow for clarity of the connections and how it all operates.

Top left, DCC in (White & Brown) and rectified to approx 22 V DC (21.10 V) by the Bridge Rectifier,  DC out (Red) and (Black) to the center COM connection on the bottom right, the DPDT Relay operated by the F1 Function Output, (Orange) and the (Red) Decoder Plus from the decoder.

Or via the little known F2 function output.

From the Relay when activated, COM connects to the NO contact (Normally Open) (Red) and (Black) to power the two voltage regulator modules, top of the two set to 6 volts to power the heating element pair of (Blue) wires.

Lower voltage regulator module set to 3 Volt (Red) and (Black) to the DC IN on the MOSFET module, above the voltage regulators in the picture above.

Connector next to it is the DC OUT to the smoke unit fan motor (Red) and (Black), can just be seen under this connector is a 1N4001 diode, to act as a 'fly back' to prevent spurious voltage spikes created by the DC motor from destroying the MOSFET module.  

On the front is a connector with (Green) and (Yellow) wires, which are direct from the traction  motor from the Loco for proportional PWM pulse control of the smoke unit motor.

For effective use the smoke unit motor needs to rotate forward to create the blowing effect of the smoke unit, the traction motor will operate in both Forwards and Reverse, to overcome this, the PWM pulse from the traction motor goes via another Bridge Rectifier, so irrespective of the direction of the traction motor the smoke unit motor will always operate forward to create the blowing effect. 

The PWM pulse is fed into the opto coupled MOSFET module which supplies the necessary pulse to drive the smoke unit motor, proportional to the traction motor PWM as controlled from the speed setting on the Navigator handset. 

 Video of the Heng Long smoke unit in operation, and yes it was windy!

Next stage cobbling together a test rig to test the activation of the Hall Sensor in conjunction with the opto coupled MOSFET Module.

Circuit at rest, not being activated by the Hall Sensor (Red and Blue LED's NOT ON!)

Connections similar to the details posted above, variance as follows. 

Hall Sensor three wire device, connected as below.

BLACK to NEG on the upper voltage regulator board. 

RED to POS  on the upper voltage regulator board AND to the PWM Input on the MOSFET Module.

GREY which is the Negative voltage output from the Hall Sensor to the GND Input on the MOSFET Module.

Other connections to the MOSFET module are DC voltage in, AND DON'T forget to include the diode on the Motor Output connections!

Circuit active Red and Blue LED's now on, Red indicates power out to the Smoke Unit motor, Blue indicates PWM pulse received from the Hall Sensor whenever a magnet passes across it, which is then passed as a pulse to the Smoke Unit motor.

Next ideas, as and when, would be to only use two magnets for activation instead of four, and design a better mounting for the Hall Sensor for fitting to standard LGB rolling stock.

Tasks for the winter months up here in Paradise, when it's to cold to working outside in the shed!

Purely coincidentally whist working on another totally unrelated project, had one of those 'ping' moments, the following could well be utilised  to operate the Heng Long smoke unit.

Refer to this Blog post for the info on the Hall Sensor.