Reverse board

Here are the 4 positions of the e-unit:

There are other products out there that already do this:

Here is one described in O Gauge Railroading issue 105 April/May 2019 as a kit. This revised assembled version now uses surface-mount components.

Lionel 610-0103-100 or 610-0107-100 solid state e-units: 

Is the objective in rolling your own to save a few bucks, learn about train electronics, etc?  That is, on the $ front you can pick up a used basic reversing e-unit for $10 or so typically from someone who has upgraded an engine to command-control.  Or if it's about learning, there was a superbly done writeup on OGR that reverse-engineered a Lionel e-unit.

Done today, given the low-cost of so-called power FETs (transistors), I'd think the DPDT relay would be replaced with a so-called H-bridge which is 4 transistors wired up to perform the function of a DPDT relay.

But whether it be a DPDT relay or a transistor H-bridge, the general solution is some type of digital logic circuit that sequences through the 4 states of Neutral-before Forward, Forward, Neutral-before-Reverse, Reverse, repeat.  So every time power is interrupted on the track to change the state, the logic circuit advances to the next state.  The actual logic circuitry is not expensive at all - easily less than $1 in parts.  If there is a "trick" to it all, it's how to keep the logic circuitry active (powered) during the short interval when there is no power on the track.  This is pretty much universally done with a large capacitor.  If you use the relay method, this can mean a very large capacitor (perhaps the most expensive component on the board costing more than the relay) to hold the relay coil active without track power.  In part this is an advantage of the transistor H-bridge method which requires a fraction of the power of a relay to hold its state.

There are many H-Bridge chips that will supply a couple of amps for not much money if you want to design one.

Thanks Stan.  John.

I saw those H bridges.  I would go that route.  

I did see a reversing board for a few bucks .not sure if it would work. For a unit. You guys would know.

Bmo...i saw that a unit on eBay with other Lionel e units.

Any boards out there ready to assemble?.   I down loaded a pcb but not sure about the Copyright thing so removed it. I'll post it if ogr saids it's ok.

It's only one relay

riki posted:

Any boards out there ready to assemble?.

There was very little demand for the kit described in issue 105 because the assembled and tested version was just $10 more.  So I redesigned it for SMD and mostly robotic assembly.

If you want to support 4-state operation, it takes more than a DPDT relay.

Well, with no information on the board, it's pretty hard to say what you're looking at.

What he said!  

Riki, I've seen this phenomenon before - where you and only you can see the image, but the rest of us get Image Not Found.  If there is a copyright issue or whatever, just tell us how you got to it (what to google or whatever) and I'll take a look at the board you downloaded and comment.  It being 2020 I'm surprised anyone sells a DIY kit for a reversing e-unit. 

Stan . I might be able to find it again. But doesn't have info ..

This is the link I believe is being referenced:

https://www.robotroom.com/DPDT...al-Motor-Switch.html

And has this image: 

That's it.

Couldn't find it.

But found this 

These are ok to post?

Without any information, that's another fairly useless picture.   There are literally tons of H-Bridge boards around, the trick is to mate one to the requirements of the task at hand.

just to pick up on one of Stan's comments earlier - essentially why do this when there are commercially available boards for not much more money.  One aspect of those boards - the one I'm familiar with is from Dallee (with whom I have no connection other than as a customer) - is that they are set up so if the power is interrupted for more than a few seconds, the engine resumes running forward rather than having to go through the complete forward-neutral-backward-neutral-forward cycle.  They also have the benefit of having connections/outputs for things like directional lighting

The design of a decent electronic reverse board isn't rocket science, and it would be pretty cheap to build.  However, as others have said, what's the point?  There are so many commercial ones readily available, not to mention that probably half the people here have a parts box with a bunch of reverse units in them.  I probably have at least a dozen of assorted sizes and current capacity, from BEEP boards to high current Williams and Lionel boards.

What I don't like about dallee is that they regulate track voltage.

I'll end up using a dpdt switch.

What do you mean they "regulate track voltage"?  The reverse board just rectifies the voltage and passes it on to the motor.

Is this going in an engine? And you'd reach for the engine wherever it is on the layout to toggle the switch to reverse?

Your use of the term "e-unit" in the original post has me somewhat confused.  I don't know if there's an "official" definition of an e-unit but I always thought it includes some mechanism to reverse the direction electronically (e.g., from the train transformer, or wirelessly) rather than manually toggling a switch.

If you're just after a reverse board then a DPDT relay or an H-bridge does the reversing for a DC motor.  Then all you need is a bridge rectifier to convert AC-to-DC and some basic DC voltage regulation; that is the regulation might 12V DC for a 12V relay or even for that H-bridge you show which is limited to 14V DC max.

John

The dallee I have regulates track voltage. I remove dallee and I get full power to motor.

Stan.

I have a build a loco with a 60s type e unit.

I was seeing If there was something easy to make.

I really don't mind stopping engine and flipping a switch.

That e unit rides on the rear axle. No lock out lever.

If you don't mind flipping a switch to reverse, you just need a DPDT switch!  All you need to do is to reverse the brush connections.  This works for AC or DC motors as it turns out.  As Stan says, for a DC motor, a bridge rectifier goes between track power and the switch and motor.

That's will be the plan. John. I have mini micro switches 

This is a on. On. On. Switch if I put diodes can this be used for dpdt switch?....

Yep, for AC motors, no diodes needed, for DC motors, a bridge rectifier between track power and the switch is needed.

Thanks John.

Hook up same way. Crossing wires.. The X Pattern..

Yep, a simple X pattern on the outside contacts.  Run the motor from those, and feed the power in to the center two leads.

Thanks john