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So how Does Legacy/ODYII Speed Control Work?

G GGGOGR Forum Member
Interesting reading the various post on Ground Plane, loss of Command Signal and the Speed Control issue I am having with a Legacy engine.

So when a Legacy engine loses the Command Signal it will stop, but if it loses the Speed Sensor signal it will go to full throttle?

Would seem from a saftey perspective a loss of Speed sensor should just make the train unresponsive except to a stop or direction change.

Any one understand the programing on how ODYII works? G
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gunrunnerjohngunrunnerjohnOGR Forum Member SUPPORTING MEMBERDIGITAL SUBSCRIBER
The difference is that the ODY speed control is counting pulses from the tach strip on the flywheel. If it starts missing some or all, it speeds up trying to match the speed setting. That's a hardware malfunction, so all bets are kinda' off. In a perfect world, the logic would be more intelligent and know that if you're not getting anything there's probably a problem.

Losing the TMCC signal, OTOH, is a different thing.
G GGGOGR Forum Member
Sure, but it would be easy enough (I beleive) to have Feed back from the VCO and R4LC that either a command for speed or a significant load has not changed warranting a full throttle response. Sort of a buffer.

I am still trying to understand how it responds properly until a certain threshold then takes off. Lionel Tech thought the speed sensor is the more likely area to check.

I am assuming a processor on that board may be the issue? Seems like the LED either works or it doesn't, yes? G
Dale ManquenDale ManquenOGR Forum Member MEMORIALIZED MEMBER
quote:
I am still trying to understand how it responds properly until a certain threshold then takes off


A common problem with tachometer servo systems is that the output from the tachometer falls off in amplitude as the frequency increases. When the motor reaches a speed at which this happens, it loses tach signal and speeds up, and that just makes the amplitude drop off even more - a runaway.

I suggest trying to improve the tach sensor placement or alignment to get the most signal possible.
RickORickOOGR Forum Member
quote:
Originally posted by gunrunnerjohn:
In a thread here several months ago, it was mentioned that some of the Legacy locomotives had a different sensor, magnetic? Someone had a problem with a loose one.



I believe TMCC locos have the magnetic flywheel/sensor. Legacy locos have the plastic tach "ring" with a reader,this is good part of why theres no more "oddssey lurch" with legacy.
S SantaFeFanOGR Forum Member
GGG

Depending on the electronics package, and software version, loss of sensor information could cause problems. The sensor is only used by the motor controller, not the Radio (IE: R4LC). In early Legacy, with the DCDS motor controller, 2 sensors are used. Only one is monitored for signal loss. If the signal loss is encountered on the one monitored, the motor stops.

In the latest electronics (RCMC), both sensors are monitored, and either signal loss will stop the motor.

If the Radio loses signal, the radio will send a stop command to the motor controller after a few seconds.
RickORickOOGR Forum Member
quote:
Originally posted by GGG:
Sure, but it would be easy enough (I beleive) to have Feed back from the VCO and R4LC that either a command for speed or a significant load has not changed warranting a full throttle response. Sort of a buffer.

I am still trying to understand how it responds properly until a certain threshold then takes off. Lionel Tech thought the speed sensor is the more likely area to check.

I am assuming a processor on that board may be the issue? Seems like the LED either works or it doesn't, yes? G



Have you checked to see whether the loco is losing the TMCC/Legacy signal and going into conventional?
Dale ManquenDale ManquenOGR Forum Member MEMORIALIZED MEMBER
I don't have any experience or access to a Legacy motor, but here is what happens for older versions.

The R2LC receives the Track signal and breaks it down into commands. Two of the outputs from the R2LC are control signals for two optocouplers on a "dumb" DCDR motor control board.

The DCDR board uses the optocouplers to turn on the two sides of an "H" bridge that has the motor connected as the crossbar of the H. For the DCDR, the optos' signals get no feedback and therefore don't know how fast the train is running.

When you replace the DCDR with a cruise assembly, you now add an extra "brain" to the system. This brain (a microcontroller or uC on the Cruise board) intercepts the opto commands from the R2LC, using these commands as data to determine how fast to run. The uC also receives tachometer information from the disk/ring on the motor. I don't know if the cruise board also uses the serial data line. (Can anyone chime in here?)

The uC generates a new set of drive signals for the optos, adjusting the drive signals to compensate for load.

The ERR Cruise works somewhat differently. It does not use a tachometer disk, but rather it reads the back EMF, a voltage generated by a DC motor as it spins.
The ERR Cruise board also uses the serial data output line from the R2LC. The back EMF scheme works well with can motors, but not with open-frame Pulmore motors.
N NortonOGR Forum Member
quote:
Originally posted by Dale Manquen:

The ERR Cruise works somewhat differently. It does not use a tachometer disk, but rather it reads the back EMF, a voltage generated by a DC motor as it spins.
The ERR Cruise board also uses the serial data output line from the R2LC. The back EMF scheme works well with can motors, but not with open-frame Pulmore motors.


The way it was described to me at the Lionel service school is the ERR cruise does use a tach signal but that signal is actually generated by the commutator. The arcing that is visible in Pulmore motors exists in can motors as well though, I expect, at a lower energy level. I've put a scope probe across a DC motor terminals and these noise spikes (collapsing armature current) are clearly visible.

Pete
gunrunnerjohngunrunnerjohnOGR Forum Member SUPPORTING MEMBERDIGITAL SUBSCRIBER
quote:
Originally posted by RickO:
quote:
Originally posted by gunrunnerjohn:
In a thread here several months ago, it was mentioned that some of the Legacy locomotives had a different sensor, magnetic? Someone had a problem with a loose one.



I believe TMCC locos have the magnetic flywheel/sensor. Legacy locos have the plastic tach "ring" with a reader,this is good part of why theres no more "oddssey lurch" with legacy.
I have a TMCC locomotive with factory cruise, the 6-28213 Amtrack DASH-8-32, and it has the optical tach ring on the flywheel.
G GGGOGR Forum Member
This is an early 2007 Legacy GP-30. It is programmed as #2. I can only see one speed sensor. Only one motor has the tach board. The sensor may be a U shaped with an element inside the tach wheel, but I am not sure. This is a DCDS J "?" board.

The Fly wheel is brass, and the ring is open frame like and impeller. I do think it is metal not plastic. The tach sensor has a diode marking on the back, which is why I believe it is an LED vice magnetic sensor.

If a loss of signal ultimately ends in a stop, I am not sure why the engine is taking off.

I don't think it is a Command Signal issue since all functions work, and the take off is at different parts of the layout.

Latest update is it is working better now. I used a brush and lint free cloth to clean between sensor and fly wheel. Looked like some dust/dirt may have been laying near the base of the sensor. Since the flywheel is like a ventilation impeller, I imagine it is possible to collect dust/fuzz.

It has very good low speed control, and did not take off until a much higher throttle setting ( I was using boost) and when I let go it actually slowed back down on it's own after a short delay. May have just been a dirty sensor.

Jon, information about ODY helps. If it still act up, I guess I will replace the Tach reader board first ($18), then the DCDS ($110 ouch!). Thank you for the input. G
S SantaFeFanOGR Forum Member
quote:
Originally posted by GGG:
This is an early 2007 Legacy GP-30. It is programmed as #2. I can only see one speed sensor. Only one motor has the tach board. The sensor may be a U shaped with an element inside the tach wheel, but I am not sure. This is a DCDS J "?" board.

The Fly wheel is brass, and the ring is open frame like and impeller. I do think it is metal not plastic. The tach sensor has a diode marking on the back, which is why I believe it is an LED vice magnetic sensor.

If a loss of signal ultimately ends in a stop, I am not sure why the engine is taking off.

I don't think it is a Command Signal issue since all functions work, and the take off is at different parts of the layout.

Latest update is it is working better now. I used a brush and lint free cloth to clean between sensor and fly wheel. Looked like some dust/dirt may have been laying near the base of the sensor. Since the flywheel is like a ventilation impeller, I imagine it is possible to collect dust/fuzz.

It has very good low speed control, and did not take off until a much higher throttle setting ( I was using boost) and when I let go it actually slowed back down on it's own after a short delay. May have just been a dirty sensor.

Jon, information about ODY helps. If it still act up, I guess I will replace the Tach reader board first ($18), then the DCDS ($110 ouch!). Thank you for the input. G

The "U" shaped sensor is actually a dual sensor. There are 4 leads to the encoder board on the motor, Power, Common, Sensor1, Sensor2. I believe you nailed it, that dust (or other foreign material) is interfering with the sensor at higher RPMs. You can remove the flywheel (very small slotted set screw, of which the OGR screwdriver set has the perfect tool) and use a flattened "Q-TIP", to clean the sensor. When placing the flywheel, make sure you don't set the slotted disk too deep in the "U" channel, it should be as close as possible to the bottom of the "U" without touching when rotated - gap to ~ 0.5mm.

I do not believe you have any bad components on the DCDS or Sensor board; but obviously I can't be 100% sure without actually testing the boards.
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