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Turntable Commands |
This page details the commands used to program and operate the turntable on the D&B model railroad. A track number is entered using a 12 button telephone style keypad which causes the turntable bridge to rotate and align to the specified track. All track position data is user stored into the program using the keypad. Two modes of operation are provided, programming mode and operate mode.
Programming Mode
The keypad is used to manually position the turntable bridge and assign the position to a keypad number button. This information is stored in the BS2 NVRAM for reference during operate mode. It is necessary to enter this data only when the turntable related track configuration is changed; normally following the laying of the track. Each turntable position has a head-end and tail-end which corresponds to the bridge track end. No specific keypad button to track mappings are enforced. The same bridge track position and head/tail alignment may be programmed for multiple keypad buttons if desired.
The following table summarizes the keypad buttons and their corresponding functions in programming mode.
Button Function 0 Find home position and calculate circle size 1 Microstep turntable bridge counter-clockwise 2 Head-end of turntable bridge track aligned (default) 3 Microstep turntable bridge clockwise 4 Step turntable bridge counter-clockwise 5 Tail-end of turntable bridge track aligned 6 Step turntable bridge clockwise 7 Slew turntable bridge counter-clockwise 8 Remove current position data for track number/alignment 9 Slew turntable bridge clockwise ** Enter/exit program mode #x Associate current turntable bridge position and head/tail input with specified track number. Turntable motion keys 1, 3, 4, 6, 7, and 9 will auto-repeat when held down for more than 1/2 second. The following warning tones can occur in program mode.
1 tone - Circle size too large. Need less steps in circle.
2 tones - Unknown turntable bridge position or circle size.
3 tones - Invalid keypad input.
Gear Backlash
Drive gear backlash must be taken into account while programming the bridge track positions. When programming a position, the final rail alignment stepping should be done in a clockwise direction. The program incorporates a constant that is used to account for gear backlash. In operate mode, the value of this constant is used to overstep the specified track position when moving in a counter-clockwise direction. The turntable bridge is then immediately stepped the same amount in the clockwise direction resulting in the final rail aligned position. In this way, the effect of the gear backlash on the final position is eliminated. Depending on the drive gear reduction used, the constant may need to be adjusted slightly. The proper value for this constant will make the ending overstep and reposition movement imperceptible.
It is recommended that a locomotive or equivalent amount of weight be placed on the bridge track during programming. The weight has a slight effect on the final bridge track position due to gear drive backlash.
Programming Example
The following example illustrates the steps used to input the information for an approach track and two service track positions. The approach track is assigned to button 1 and the service tracks to buttons 2 and 3. Service track 2 is then removed. It is assumed that the controller circuit is connected to the turntable motor, power is applied, and the BS2 heartbeat indicator is flashing. For reference in this programming example, the head-end of the turntable is the end where the operators shack is mounted. The keypad buttons 1, 3, 4, 6, 7, and 9 are collectively referred to below as the move buttons.
1. Press the * key twice to enter programming mode. The heartbeat Led changes to solid on to show that programming mode is active. If three short tones are heard, an invalid key value was detected and is likely caused by a keypad wiring error.
2. Press the 0 key. This command finds the turntable bridge home position. If not found, the turntable bridge will rotate continuously in a counter-clockwise direction indicating a wiring or sensor problem. The turntable bridge is then rotated once in a clockwise direction to determine the circle size.
3. Use the move buttons to rotate the turntable bridge and accurately align the head-end bridge track with the approach track. The final alignment should be done in a clockwise direction to eliminate gear backlash. Press the following buttons in order: 2 # 1
4. Use the move buttons to rotate the turntable bridge and accurately align the tail-end bridge track with the approach track. The final alignment should be done in a clockwise direction to eliminate gear backlash. Press the following buttons in order: 5 # 1
5. Use the move buttons to rotate the turntable bridge and accurately align the head-end bridge track with storage track one. The final alignment should be done in a clockwise direction to eliminate gear backlash. Press the following buttons in order: 2 # 2
6. Use the move buttons to rotate the turntable bridge and accurately align the tail-end bridge track with service track one. The final alignment should be done in a clockwise direction to eliminate gear backlash. Press the following buttons in order: 5 # 2
7. Use the move buttons to rotate the turntable bridge and accurately align the head-end bridge track with storage track two. The final alignment should be done in a clockwise direction to eliminate gear backlash. Press the following buttons in order: 2 # 3
8. Use the move buttons to rotate the turntable bridge and accurately align the tail-end bridge track with service track two. The final alignment should be done in a clockwise direction to eliminate gear backlash. Press the following buttons in order: 5 # 3
9. To removethe head-end aligned entry for storage track two, press the following buttons in order: 8 2 # 3
10. To removethe tail-end aligned entry for service track two, press the following buttons in order: 8 5 # 3
11. Press the * key twice to exit programming mode. The heartbeat Led changes to flashing to show that operational mode is active.
Operate Mode
Two button presses are entered via the keypad to rotate the turntable bridge track. The first button pressed is the desired track number. The second button pressed is the turntable bridge end to align to the specified track. The turntable bridge track is rotated following the second button input. The keypad entry indicator will flash during the turntable bridge move operation.
A solid 'on' keypad entry indicator is used to show that a track number has been input and the program is waiting for a turntable bridge track end button to be pressed. If a turntable bridge track end button is not pressed within about 5 seconds, the entered track number button is ignored.
Upon power up, the program initiates a search for the home position sensor. This involves stepping the turntable bridge in a counter-clockwise direction until the home position sensor returns an active state. This search operation can be aborted by pressing any key during the search operation. The next bridge movement, in program or operate mode, will redo the home position search.
The following summarizes the keypad buttons and corresponding functions that are used in operate mode.
Button Function x# Position turntable bridge track head-end to track number x. x is a button 1 through 9. x* Position turntable bridge track tail-end to track number x. x is a button 1 through 9. 00 Re-index turntable bridge to home position sensor. 11 Toggle position of lead track turnout 1. 22 Toggle position of lead track turnout 2. The following warning tones can occur in operate mode.
1 tone - Unprogrammed track number specified.
2 tones - Unknown turntable circle size. Redo program mode key '0'.
3 tones - Invalid keypad input.
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Copyright © 2006 Don Buczynski
San Diego, California