R2LC question (semi-hardcore)

Although I don't have a scope, my TMCC experiments have shown Mr Tuveson to be correct.

Pin 20 on the R2LC is the +DC voltage to the opto-isolators that control the triacs. Pins 16 and 18 control Fwd/Rev by grounding the appropriate opto-isolators.

So why only a 20% duty cycle?  I don't have any reason to think the R2LC is bad, it otherwise behaves  as expected.

 

I guess I could go forward and just see what the heck happens under TMCC.  But it should work with just a conventional transformer.

Dumb question, have you just connected a DCDR to see if the R2LC is functioning properly.  I confess to having never put a 'scope on the PWM outputs, but I've also never seen that part of the R2LC fail. 

 

Do the pulse widths vary with the command throttle input?  When you reverse, does the PWM output move to the reverse pin?

>have you just connected a DCDR...?  DON'T KNOW WHAT THAT IS

>Do the pulse widths vary with the command throttle input?  NO

>you reverse, does the PWM output move to the reverse pin? YES, WITH THE APPROPRIATE NEUTRAL STATE IN BETWEEN

 

I do have working engines I can mess with, although I hate to take them apart (quickest way to make non-working engines!).  My plan is to grab some headers here and just bench the R2LC by itself this weekend.

 

My belief is that the pulse widths should *not* vary under conventional control?  I always assumed that if the R2LC doesn't see the "halo", it assumes the speed will be controlled by the old-fashioned track voltage levels.  So it should open its own throttle wide and just let the motor see (rectified) track voltage.

 

That would be why we would have problems with engines taking off when they lost the TMCC signal -- the R2LC switched to conventional, but the track voltage was TMCC levels, and off to the races it was,

Darnit, I misread -- can we edit??

 

I haven't tried the "command" throttle, just run "conventional" with a post-war transformer.

 

I'm thinking about doing that, but I have to hook up the antenna and move everything from from the workshop to the train room.  Maybe the R2LC just needs a reset, it isn't fresh out of the box but was replaced in it's original engine due to a burnt out coupler drive.  Other than the coupler though the engine worked fine.

You may be right about conventional, I will freely confess to spending very little time on how TMCC stuff runs conventional.  It may well simply run "wide open" and depend on track voltage to control the speed.

 

The DCDR is the thing you're trying to build, it's the driver for the motor.  It connects directly to the PWM outputs of the R2LC

 

What does DCDR stand for?

Tuveson calls his driver board "MDB"-- presumably "Motor drivr board"

He may still sell them and one of them would make a good test fixture

for R2LC board.

 

Al W.

Well, I'm assuming the DC stands for Direct Current since there is also an ACDR for AC motors.  One would presume the last DR is for driver or something like that.  The DCDR has a very simple interface, just 5V, ground, and the two PWM inputs for forward and reverse.  The other larger four pin connector brings in track voltage and outputs the DC motor drive.

 

Like I said, it's functionality is exactly the same as what you're constructing.  The home-made model is a half-wave driver, so it won't develop the same top end for anything larger that the factory DCDR would. 

 

The stated goal of the home-made board is that it's smaller and will fit into smaller motorized units.  However, the ERR MiniCommander 2 is smaller than any DC driver board and R2LC combination, so I'm not sure I'd go to the trouble.

>However, the ERR MiniCommander 2...

I don't know what the MC2 costs but I remember the regular AC/DC Commander - which would easily fit in my tender- costs $69 *with* the $40 R4LC ... so this is totally not worth it!   I mean 39 bucks is not much more than what The Hobbit cost me to see with my daughter. 

I'm doing this just for the fun of it.  My background is in this stuff but I never get to do anything but software at work so it's great to wire some things together again.

 

Now, there are real benefits:  again, this is low-pressure fun.  Someday it will run and that will be cool.  I could work thru the same learning curve *after* one of my factory TMCC engines go up in smoke, but that would so not be fun. 

 

Also I do have two long-term things in mind that would tax even the tiniest implementations.   I have a powered Corgi PCC with interior detail which would require the boards to lay flat under the floor probably with point-to-point wiring.    Also I am intrigued by the Lionel $100 tank engine, I don't have one but it may present a similar challenge.

 

Anyway, as you can tell I've not gotten back to it but should be able to this weekend.

The MC2 is $60 I believe, and probably a bit cheaper from Boxcar Bill, he's an ERR dealer.  By the time I buy the R2LC and the parts for this project, I can have the MiniCommander 2.

 

However, as you say, it's for "fun", so have at it.  Post a picture when you get one working.

>>My belief is that the pulse widths should *not* vary under conventional control? 

Cap, the pulses are a very high frequency, and the opto-couplers on the driver board are triggering Triacs.  Once the Triac is triggered, it stays on until the zero cross - so all you need is a short pulse.

 

Why pulse?

The pulses are there as to not drag down the DC power in low voltage conditions during conventional operation.  The optos suck a lot of current from the 5vDC supply; and if there were no pulses, the processor would reset.

There you go, right from the horse's mouth!

>Once the Triac is triggered, it stays on until the zero cross - so all you need is a short pulse.

 

A ha!! Thanks jon. (thanks everybody!).. so I saw pulses and immediately thought "PWM" but that was wrong.  

 

Sigh.  It also means I have to re-think my DC board driver.  And on that note, although I am certainly going to do this someday, the engine I was messing with is a 1996 RailKing Challenger whose electronics slowly went up in smoke first sound, then smoke unit, then motor driver about 10 years ago.  Having it out of the box for the first time in years brought a real desire to see the big thing run again, so I'm going to hit the ERR webpage and buy what I need to get it going ASAP.