Need help wiring a tender backup light

In the following thread, member ROMSK reverse-engineered what appears to be your electronic E-unit:

https://ogrforum.com/t...-theory-of-operation

It's over a year old but it looks like you can still post to that topic so that might be another place to ask.

Do you want/need the reverse light to be "on" in neutral-before-reverse?  Or is it acceptable for it to turn "on" only when actually reversing (motor spinning)?

stan2004 posted:

In the following thread, member ROMSK reverse-engineered what appears to be your electronic E-unit:

https://ogrforum.com/t...-theory-of-operation

It's over a year old but it looks like you can still post to that topic so that might be another place to ask.

Do you want/need the reverse light to be "on" in neutral-before-reverse?  Or is it acceptable for it to turn "on" only when actually reversing (motor spinning)?

"Do you want/need the reverse light to be "on" in neutral-before-reverse?  Or is it acceptable for it to turn "on" only when actually reversing (motor spinning)?"

Original thought was only for reverse, stan2004, but what is prototypical for steamers?

I inquire because of your stated comfort-zone (or lack thereof) with electronic components and wiring.  I'd say the simplest method which guys have done in similar situations is to wire the reverse bulb/lamp on the DC motor output.  The E-unit puts out a positive voltage onto the motor when spinning in FWD, and a negative voltage onto the motor when spinning in REV.  So if you wire the bulb/lamp to light only on the negative voltage, you get a reversing indication.

But with this method the backup light goes out when the motor is stopped.  So if you back up a foot, stop, back up another foot, stop, etc., the light only goes on when physically reversing.  One way to think of it is your car's white backup light which comes on when you engage reverse - even if stationary.

To have the backup light stay "on" when stationary the modification and wiring would be more complicated and arguably not for a novice.  The parts cost would be modest (maybe $1 or less).

I think you're in a gray-area where to get the feature you want most guys would choose a higher-end E-unit which would include not just connectors to drive a reversing indicator...but also provide constant-brightness headlight and reverse light circuitry so the bulbs don't dim/brighten depending on speed (i.e., track voltage).

If you don't mind tapping into the E-Unit mentioned, I found these in that excellent document by Paul Romsky in the other thread referenced.  Here's the full document: Lionel E-Unit 00-0103-00 Theory of Operation

From the illustrations below, it appears the reverse signal will be present when you start moving in reverse, stay active in neutral after reverse, and be turned out for forward and the neutral following forward operation.  You'd have to connect a logic element that didn't consume much power to the REV output to drive your light.

Ahh, if we're getting down and dirty  the fly in the ointment with "simply" looking at the REV signal from the 4013 logic chip is, as GRJ points out, the reverse lamp would be on in Neutral AFTER Reverse rather than Neutral BEFORE Reverse.  Perhaps a trivial point but I believe you want the reverse light to turn on when in Neutral-BEFORE-Reverse (as well as when in actual Reverse).

So rather than looking only at the REV signal (the U1-A stage 2 Flip/Flop signal), you could look at both Flip/Flop signals and test when they differ (a simple logic test).  Again, it's not difficult to do from a circuit point of view...but I think a challenge for a novice to wire up the necessary components.

A logic gate would correct the signal, then you'd need a buffer for the light.   Looks like an XOR would do the trick.  The CD4030 could tap off the two signals, and do the trick.  Sip the power from the existing supply, run the LED on around 5-6ma.  If you want to go more robust, add a transistor or FET to handle the output load.

gunrunnerjohn posted:

A logic gate would correct the signal, then you'd need a buffer for the light.   Looks like an XOR would do the trick.  The CD4030 could tap off the two signals, and do the trick.  Sip the power from the existing supply, run the LED on around 5-6ma.  If you want to go more robust, add a transistor or FET to handle the output load.

Driving a 5mA LED from the available 100uF VCC capacitor will quickly starve the VCC voltage (logic circuit) too quickly when the Direction button is pressed.  The CD4030 could be powered from VCC...but I'd go with a FET which has essentially zero control current.  Again, this modification is not for the novice!

Can you get a back up light on a postwar tender only during reversing by putting a wire from the tender back up light to the postwar engines e-unit finger that is contacted during reversing operations?

Andy

stan2004 posted:

gunrunnerjohn posted:

A logic gate would correct the signal, then you'd need a buffer for the light.   Looks like an XOR would do the trick.  The CD4030 could tap off the two signals, and do the trick.  Sip the power from the existing supply, run the LED on around 5-6ma.  If you want to go more robust, add a transistor or FET to handle the output load.

Driving a 5mA LED from the available 100uF VCC capacitor will quickly starve the VCC voltage (logic circuit) too quickly when the Direction button is pressed.  The CD4030 could be powered from VCC...but I'd go with a FET which has essentially zero control current.  Again, this modification is not for the novice!

Yep, I was having second thoughts, that's why I mentioned the FET.  Perhaps a larger cap?

Train_Geek posted:

Can you get a back up light on a postwar tender only during reversing by putting a wire from the tender back up light to the postwar engines e-unit finger that is contacted during reversing operations?

Andy

I had worked out a way to do direction lighting with an AC motor and a standard E-Unit years ago, still looking for where that sheet is.