# The Electronic E Unit



## T-Man (May 16, 2008)

Some people just don't want to spend 15 bucks and buy one. Building one is much more fun. But How?

I am talking about the electronic board using AC track power that will stop and reverse a DC motor engine.

SO HOW? We don't know. You cannot copy a Lionel unit. One IC is progammable. That is beyond me. A lot of us have seen the Squidoo page. Nice information but the diagram leaves the page totally useless.

So what to do? We investigate, examine, and come to our own conclusion and testing.

First I went to the page. 

You can tell a lot from the picture. The center is the two DPDT switches with the NPN transistors 2N3904. the motor is obvious, The 4017 is obvious. The bridge rectifier and the 7805, 5 volt regulator are obvious.
THe super duper MID400 it off to the right. What's missing is the size of the capacitors that won't be easy. The blur under the 4017 I am guessing is the LED indicator lights.
That is my preliminary investigation.
My next step is more technical. I pull the data sheets of the chips and compare that to his written descrption.


----------



## tjcruiser (Jan 10, 2010)

T-Man,

He offers a lot of info, but doesn't appear to have posted a higher-res image of his wiring schematic. I did a quick 'net search to see if I could find it somewhere else, but struck out.

Cheers,

TJ


----------



## T-Man (May 16, 2008)

The plan is to take it as far as it will go.
The MID 400 datasheet

The 4017 data sheet

The sheets tell the exact purpose of each pin. We just have to have a little savy and figure it out. In the end we will have a diagram to test.


----------



## gunrunnerjohn (Nov 10, 2010)

Truthfully, I think the parts for that would cost more than the pre-built model. He's talking about relays there, those will run up the price! I guess I'm just to practical to build something for $25 in parts that I can buy for $15 already assembled. 

I do have a fistful of PCB mount relays, so I could build a couple of these with junk-box parts.


----------



## T-Man (May 16, 2008)

Of course! A lot of projects can be done, but not cheaper. It' like a company. You have buy in bulk and mass produce to make it cost effective.

I will try it. The diagram is in the making.


----------



## gunrunnerjohn (Nov 10, 2010)

I'll be interested in seeing the result. 

Truthfully, I'd be interested in an electronic E-unit that's REALLY small, so I could put it into stuff like the cheap track inspection cars that just have a DC motor and rectifier. I modified a steam switcher with the Lionel unit, but it was a real task to get it to fit. I had to hack the frame (no big deal on a $10 engine!) to get it to fit. I have a couple of the cheap inspection cars that it would be cool to have directional control with, but the Lionel unit at 2.25" x 1.3/8" x 7/8" is simply too big to fit into any of them.


----------



## T-Man (May 16, 2008)

It was his first try. Keep in mind he used wires , with a little savy you can etch a board. The 5 volt relays aren't too big either. I wonder if the Radio Shack ones willl work.


This is part of the puzzle. This is the AC line sensor. The AC goes to 1 and 3. Supply voltage to 8. Ground is 5 and the signal from 6 goes to pin 14 of the 4017 chip. The rest came from the data sheet.


----------



## gunrunnerjohn (Nov 10, 2010)

The way to get the board size down is to use FET's for the switches and put the components on both sides of the board. However, that's somewhat expensive.


----------



## T-Man (May 16, 2008)

*4017*

Here is another part of the mystery

16 is 5 volt power
3,4 operate the transistor at the base for the relays
2,7 are wait s for neutral attach LED to signal the non action
10 to 15 to reset counter for next round
14 is the clock that connects to the pinn 6 and triggers a change.
13 is the ground for the clock pin 14
8 is the chip ground

That should cover those connections

Again the data sheet helped me on the reason for pin 13. The rest of the pins are extra counters.












You got me on the FET???

FUnctional electronic timer???


----------



## gunrunnerjohn (Nov 10, 2010)

Field Effect Transistor, they're used for applications like this. Low internal drop and you can get FET's that will handle 2000 or more amps, certainly enough for this job.


----------



## T-Man (May 16, 2008)

I have diagram, so I need parts. I am not sure if this works at all, so I do not plan on showing the schematic. I just think is is strange the author never replied to requests. I don't find it that complicated. Purchasing is next. Just the AC detecting chip is four bucks. The relays will be ten.


----------



## gunrunnerjohn (Nov 10, 2010)

Therein lies my problem with the roll-your-own approach. For $15 I get one already made and tested.


----------



## T-Man (May 16, 2008)

True ,but it only takes one to ask. "T-man, how can I build one?" 
I forget who, but the last one was a few weeks ago.

I don't mind, I learn something new. I am at a point where I can have a few failures.


----------



## tjcruiser (Jan 10, 2010)

gunrunnerjohn said:


> Therein lies my problem with the roll-your-own approach. For $15 I get one already made and tested.


Or ...

Sometimes it's the journey that enriches us more than the destination.



TJ


----------



## gunrunnerjohn (Nov 10, 2010)

Well, in this case, I'll skip the journey.  If I could roll one that was truly smaller than the existing ones, I might consider that. I may have to consider that. I'd like to put directional control into some of the small DC motor powers stuff like handcarts, little crew buses and trucks, etc.

If there's a viable design, I might try it. 

I'd be tempted to do a two speed unit, and just let it start in forward if it lost power for more than a few seconds. That would probably be more compact and do what I'd like to do anyway.


----------



## NKP Jen (Nov 18, 2012)

Greetings,,,I know its been a long time since there was a posting on this thread, but I just found it and am interested in trying to roll my own E unit replacement, even if I can buy something for 15 or 20 bucks...Did anyone ever end up re-creating a full schematic of this project, beyond the details on a few of the few chips? The original article on the other forum does indeed have poor graphics quality, and I was hoping for a complete schematic to work from that was readable. Cheers, 
NKP Jen


----------



## T-Man (May 16, 2008)

It's a pet project on the shelf. The one I have is only a guess and not tested. It is adapted from the poor original. Parts dealers do have them for under 20.


----------

