E-Unit Schematic and Theory of Operation

That's some really excellent work Paul.  As a former Navy Aircraft Q/A logs & records guy and working in IT within the aerospace engineering/manufacturing industry, I can definitely relate to getting accustomed to thorough documentation.

I'm going to keep a copy of your work for future reference, no question about it. 

Paul, Outstanding job, I reverse engineered quite a few boards but my notes are in pencil and a few word documents.  Your documentation is fantastic.

 

You will find for all the basic electronic reverse units a simple set up.

 

Power rectification, logic section, motor drive section.  They all are very similar.

 

Great job.  G

Paul, Now the operation lesson to go with this.  The reason the power transistors fail is a bad motor in the engine.  The motor going bad draws too much current and the transistor shorts.  Depending on how the operator ran the engine after the intitial failure determine if more components damaged.  Sometimes just one, but many time the pair fail.  G

GGG,

 

I agree. A motor malfunction makes sense as to why the transisitor blew.  When I got this locomotive, the motor was toast and the intermediate gear was missing.  I bet the prior owner had a motor lock-up, left it full power, the motor over heated, metled the gear, and finally blew the transistor on the E-Unit. 

 

After I got my E-Unit working I replaced all the power transistors because they were inexpensive and I had no idea on how much they were overstressed.

 

Paul

Adriatic,

 

Yes, the devil is in the details. There was a lot to chew on in the document.  I am awlays open to suggestions.  Thanks for the feedback.

 

Paul

 

In my first installation of the new ERR Cruise Commander Lite in a K-Line Interurban, I had it stall on a switch for just a few seconds.  That's all it took for the stalled motors to take out the driver FETs on the board.  They got hot enough to actually char the board, it was a total loss.  A stalled motor can zap things pretty quickly.

Paul, that is a VERY impressive piece of work.

 

Thanks for sharing it here.

 

And welcome to the OGR Forum!

I did want to say I too appreciate your work Paul and thanks for sharing it here.

I am saving it, thanks again.

Gunrunnerjohn,

I could design a thermal shutdown circut that would go in front of any direction controller board.  It would detect high temp an any one or more power transistors, then crowbar the supply until power is removed and the thermal condition cools.

That would be something like 4 thermistors, a few didoes, and a couple of FETs.

Paul

Probably not worth the effort for a $15 reverse board.  Also, depending on the power supply, you might cook something else in the process if you jump on the output voltage like that.

 

I have taken to using a PTC in the motor circuit of the ERR MC-Lite installations.  I use one that trips at 1.3 amps.  For the stuff that the MC-Lite would be running, that's plenty.  As you doubtless know, a PTC will handle a significant overload for a very short period before it trips, so starting currents aren't an issue so far.  I've actually had the locomotive stall and nothing bad happened to the board, so I'm slowly building faith in the process.  The MC-Lite is rated for 4 amp maximum drive current, so I think I'm giving it enough headroom.

 

My next plan is to install the MC-Lite into a A-A unit and see if it'll pull 20 or so cars, I'd like to see if we can trust this technique to save the MC-Lite board upon overload.

 

 

If I'm understanding this all, the 103 board is only rated for 1 amp? That seems woefully inadequate.

Romsk

 

Welcome to the forum.

Sounds about right.

 

Thanks for the great work and documentation Paul.

All,

Thanks for the positive feedback!

 

Gunrunnerjohn,

You may be right about a thermal overload protection circuit could actually blow out as well,  but I R AN EGANEER and that is what I do, colaborate with fellow engineers (like all of you) and solve problems.  So I will run some simulations and see what I can devise - at least for my own use at first - before I share it.  As far as PTCs (Postive Train Controls?) I do not have much experience with them, but now that I am geeting into the hobby I will bone up on them - Thanks!

 

Paul

Nvocc5,

 

You said "Carpet Layouts".  Are you in the carpet industry?  My uncles and cousins are in the carpet business.  The cloest thing I come to was laying down some Astroturf as grass on my train layout [smile]. Putting down carpets is truly an artform.  My uncle actually installed a carpet for Liz Taylor many years ago - there is a story ther but not for this forum [laugh].

 

Paul  

In case you noticed... it is after 1 AM Eastern Time... why am I posting?  I am in a hotel this weekend on business and they had a lot of children as guests - loud and unsupervised for the most part... kept me up to about 11:30.  They also had a weeding on the floor below me and the music did not end to 12:45.  So now all the kids and the wedding folks are off to bed and I am here now wide awake taking about trains... and missing my wife.

But I digressed, how about those Yankees!, I think they are gonna do it this year! (that is how I change the subject sometimes)... actually, I don't follow football.

 

 

Anyway.. back to topic.  When I get back to New Hamp-sha, I am looking forward to figuring out how a whistle/horn unit works.  If you have something for me figure out and document, let me know - I would be happy to to a look - this is the real fun for me in this hobby... all the cool do-dads and customization.

 

 

Good to know I'm not the only person burning the midnight oil...  I have the night shift this weekend, watching the Megawatts flow on the power grid.  The one side benefit is that I get to check the forum when there isn't anything else happening...  

Not quite the carpet layout he referred to, more like this.......

 

 

 

 

Small layouts on Moms carpet, or around the Christmas tree is how many of us began.

Its a great way to keep from rushing things. An outlet for running while building.

 

Dear Romsk

 

A "Carpet Layout" is a not permanent train layout. It is a term used in this hobby to describe a non permanent layout. Sorry I am not in the carpet business, I work for the US government and serve the US general public. I joined this fine forum a few years ago but just got active within the last year.  You will find people from all walks of life sharing there love for the hobby here. Since the hobby has changed over the last few years and we are spread out all over this country and the world it is a neat place to ask and give answer to various question that you might have. In regards to the electronics gurus we have a few (no name because there are so many of them) that are top, middle and bottom (me and much to learn) level. All very helpful and are able to answer most if not all your questions. Go to the topic led lights and crossing protection you will find most if not all the electrical gurus giving advise. Under there left column you will find their picture and name. click on the name and their profile will show up. On the right side of the profile you will find "follow". If you to follow what person is replying or new topic they have posted. This will send you an e-mail from the forum  which person is replying on what topic and what their reply was. The email will allow you to go to the topic via link neat little bonus of this forum.

Adriatic,

Carpet Layout, got it now.  I like that term.

 

nvocc5,

Thanks for the pointers, this is a great place to get answers.

 

WindupGuy,

Thanks for keeping the power flowing. We often take it for granted that we have electricity.  Every year in New Hampshire we have to go on home generator power for a day or two after a storm.  The very first thing I do is to report the outage [in a Grandpa Simpson voice] to the power company. I tell them I have a problem and I can't make toast.  Its one of those toasters that you need the power to get the toast out, so if they could skip the hospitals and police departments, I would appriciate it, because my toast is gettin kinda cold.  It always gets a good laugh [smile].  One time I thanked a crew as I passed.  I turned out to be a bit of a legend, "Oh, you are the guy who is making toast when ever the power goes out." [laugh].

 

Romsk

I'll be dare moday wit my tools poppin wheelies all ova da place.

 

My buddy is gets "ski-aired" when the powers out...don't hang up! 

 

Even a "crappy basement layout" takes more effort, and seldom seems to have straights run the length of the house.

And you haven't lived till you've delivered food from the kitchen to a bedroom on flats, and in a gondola.

Look at the actual size of what was there. That's nothing compared to some.

(One single guy(I assumed) in a big house had the whole upstairs level as his layout)  

The TIP31/32 are rated at 3amps.  But no heat sink and they connect back to back so the ambient temp is probably hotter as it approaches max current.

 

They are designed for starter set steam with 1 motor, or starter set diesel with 2.  Work fine, until a motor shorts or way too many cars pulled for too long.   G

Paul, the PTC that I mention is a Resettable Fuse, popularized by the PolyFuse folks.  They trip on an overcurrent just like a fuse, but they heal like a circuit breaker after they cool down.  They're good for places you don't want to fool around with fuses, and they're way more compact than typical circuit breakers.

 

That makes more sense. Those 4 components though, I believe, are the weak links. Are there suitable higher capacity units in the same or similar case that can be substituted in?

I was just looking up your e-mail so i can get your address off-list.  Then off to the train room for electronic projects. 

 

Lou N

Rob, if you simply add a decent heatsink to the drivers, you'd go a long ways to increasing the capacity of the board.

Gunrunnerjohn,

 

Ok, I have seen those before (PTCs), never actaully used one but they sound like a simple approach.  I will pick some up from Digi-key and add them to my train.

 

Thanks,

Paul

I'm installing them in all my ERR Mini-Commander Lite installations, and I'm going to undertake an experiment to see if the MC-Lite survives a full sized locomotive with a significant consist for extended running with these installed.  Should either be interesting, or time to replace the command board, I'm not sure which.

 

That will be my first "line of defense".

Some application like the starter set steam have no room for heat sinks.  There is a # of different TIP that might have some higher ratings.  But at $17 a board and the ability to repair, it may not be an issue.

 

I have one modified with a rectifier to run a PW Pulmore AC Alco and it runs fine pulling the 6 plastic MPC cars and a dummy alco.  G

Lou, do you have any insight on the RS 2.5 board design?  I have one with sounds, but won't activate the bell or horn.  Was trying to find what components did the offset detect.  No obviously damaged components.

 

Have one that keeps burning up the audio amp, so I was wondering what component on the board can be causing that.  Speaker and wiring is fine and works with other RS 2.5 board.   G

Do you have the field powered in series or shunted/parallel with the armature?

Series.  I did this a while ago with Dale M help.  Was a 2 position unit with double field, so there was two options.  Using each field via the rectifier, or just one and using the rectifier to hold field current in one direction.  Definitely series though. 

 

Runs well with good slow speed.  I think my seat of the pants experience was it lost some top end speed, but that is fine any way, and would be expected with the diode voltage drops.  G

Sorry G, I wish I could help.  I did not get into RS until 3.0.

 

Lou N

Lou thanks.  I had asked Jon Z a while ago and he looked into some records, but there really wasn't any thing of worth.  Would any of the detection circuits of RS 3.0 and up be relevant?  G

Wow, that is quite the impressive write up.  Much of it way over my head, but I understand enough.  Thanks for taking the time.  I'm using something similar in my project and having a schematic to compare to  is nice.  

 

“Kids should be allowed to break stuff more often. That's a consequence of exploration. Exploration is what you do when you don't know what you're doing. That's what scientist do every day.” - Neil deGrasse Tyson

All,

 

I am still in Canada on business, eh! When I get back I will start looking at those new projects.  I love Canada, flat, wide, and open - not like New England, which is nice too - err, ah, use yah blinka!

 

Lou N,

 

I have not been able to check my romsky.com email on the road.  I will answer any e-mail from that server when I get back home.

 

JohnGaltLine,

 

Thanks for the feedback.  At least you have a Parts List now that you can use to swap out parts.  Q1 thru Q4 are the ones that I can see blow out more often.  So even if your forte is not transistor circuits, you can still fix your boards for pennies on the dollar -if you want to do so.

 

Thanks

Paul

 

 

Canada's terrain varies quite a bit