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Building an electronic e-unit for your Lionel DC Steam Engine
Here is a picture of what is known as the e-unit. Only Lionel locomotives that can run on AC current have them. They switch direction of the motor when AC current is disrupted momentarily. e-units of the past were purely electro-mechanical devices much like relays.
Building an electronic e-unit
In this Squidoo Lens, I am going to show you how to build your own electronic e-unit and retro-fit a DC (direct-current) Lionel Steam Engine that has a can motor so that you can run the steam engine on a Lionel AC power pack. This circuit uses common electronic components available from such sources like Mouser (http://www.mouser.com)
My electronic e-unit circuit schematic and circuit theory
My electronic e-unit uses a MID400 IC made by Fairchild to monitor the AC (alternating current) line voltage. When there is a sufficient drop in the AC line voltage on the track it pulls pin 14 on the 4017 Decade Counter IC low causing it to increment. Pins 3 and 4 of the 4017 Decade Counter control 2N3904 NPN transistors which drive relay coils that control the direction of the DC can motor. They also drive LEDs with 470 ohm current limiting resistors so you have a visual status of the e-unit. Pins 2 and 7 of the 4017 Decade Counter are the "neutral" settings where the motor does not turn in either direction. They also drive LEDs with 470 ohm current limiting resistors so you have a visual status of the e-unit. The diodes across the relay coils prevent voltage spikes from damaging the 2N3904 transistors. Pin 10 is connected to pin 15 so that the 4017 decade counter only counts up to 4 before resetting and starting the count over. A bridge rectifier converts the AC (alternating current) to DC (direct current) for the DC can motor. This DC voltage is then regulated by a LM7805 regulator to a constant 5 volts to drive the logic circuit. A high intensity LED is also driven by the 5 volt regulator for the front headlight of the steam engine.You will need a small Ceramic Capacitor, typically 0.1uF, soldered across the DC motor leads to suppress the electrical commutator noise. This is not pictured in the schematic. The circuit may act erratic without this capacitor in place. You may need to experiment with the capacitor's value as the electrical characteristics of each motor varies.
Caution: You need to have a basic knowledge of electronics to build this circuit. Build this circuit at your own risk! I take no responsibility for damage to you or your Lionel steam engine, tracks, or transformer.
Books on Electronics
This is the first book I ever read about electronics. Great reference book with test circuits in the back.
Great book covering block or direct current operation of a model railroad.
I salvage parts from old projects when possible
I am using reed relays to control the direction of the DC (direct current) can motor. I salvaged them from another project.
Always breadboard your circuits first before committing them to a solderable perfboard. This allows you to test the circuit and make changes to it on the fly. Here is a picture of me testing the logic part of my electronic e-unit. I put the relays, driver transistors, and high voltage protection diodes on a separate solderable perfboard.
Testing the e-unit
Here is a picture of me testing the electronic e-unit on my steam engine without the shell installed. I sat the breadboard containing the logic circuit and the relay perfboard on a Lionel flatbed car.
A closeup look at the breadboard
Here is a close up of my electronic e-unit breadboarded.
The relay perfboard
Here is a picture of me testing my relay board. As mentioned, the relay board also contains the 2N3904 driver transistors and high voltage protection diodes. I did not breadboard my relay board as it was a very simple circuit and committed it to solderable perfboard right away.
Committing the e-unit logic to perfboard
Here is my e-unit logic board committed to a solderable perfboard.
Mounting the logic and relay perfboards
Here is a picture of me mounting the logic and relay solderable perfboards in the tender care. The filter capacitor was too big to mount to the perfboard, I will use hot glue to mount it to the base of the tender car.
Wiring everything in place
Here is a picture of everything wired in place in the tender car.
Mounting the LED for the headlight
I mounted a high intensity LED in the front of the steam engine's shell to illuminate the headlight. It looks a lot better then an anemic incandescent bulb that came with the steam engine. Thanks to the 5 volt regulator the LED mounted in the headlight always glows the same intensity no matter if the steam engine is going slow or clipping along at full speed.
Securing the wires and high intensity LED in place
I used hot glue to secure the LED and the wires in place to the steam engine shell.
Adding wires to the motor and electrical pickups
I had to add wires to the motor and to the electrical pickups on the motor chassis. These wires are wired to the logic and relay perfboards in the tender car.
The wiring between the steam engine and tender
Finally all of the wiring is coming together, I covered the wiring between the steam locomotive and tender car in black heat shrink tubing so that it is less noticeable.
Soldering the wires from the steam engine to the perfboard
Time to solder the wires from the steam engine motor chassis to the logic and relay perfboards. I used a stay tie to secure the wiring from the steam engine to the tender car. Notice I also used hot glued to secure the power supply capacitor to the floor of the tender to keep it from flopping around.
Time for a little trial run before I put the top on the tender car.
The steam engine's headlight
Notice how nice the high intensity LED illuminates the steam engine’s headlight.
So with some common electronic components from Mouser, some solderable perboards and some basic electronic knowledge, you too can convert your DC (direct current) Lionel steam engine to run on a AC (alternating current) transformer.