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Discussion Starter · #1 ·
I got this today at an auction.





$20 (no shipping, free hotdogs :D)

I would like to wire up an electronic switch to operate the lights rather than use the original track connector.

Does anybody have a resource where I can find, or build something?

(Do I need a "flip flop"?)

Thanks
 

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Discussion Starter · #3 ·
That's a cool idea, but I want it to flash while nothing is running.
 

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Discussion Starter · #5 ·
Right now, I'm thinking of having it running all the time.
 

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Well, that wouldn't be all that realistic, but probably pretty easy. Here's a simple flasher circuit, to drive incandescent bulbs, you'd probably have to add a driver transistor for each bulb, I'd probably use some 2N2222A's from my junkbox.
 

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Discussion Starter · #7 ·
Well, that wouldn't be all that realistic, but probably pretty easy. Here's a simple flasher circuit, to drive incandescent bulbs, you'd probably have to add a driver transistor for each bulb, I'd probably use some 2N2222A's from my junkbox.
Is there supposed to be a diagram?

As far as realistic goes, the accessory is almost twice as tall as my loco:)

In my little city, we have a short line, and the gates are down and lights flashing all the time, without a train to be seen! It is so bad, arrest warrants have been issued for conductors!

My focus is lots of action, noise and entertainment for little ones.
 

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Discussion Starter · #9 ·
Thanks

Looks easy enough.

Where do the "driver transistor" thingys go?
 

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Discussion Starter · #11 ·
You would put them on the output to handle the current.
Well of course.

Whew! went right past me.

You got me on that one.

Here is what I found




Looks a little robust to my untrained eye, but what the heck.
 

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Well, it'll flash the crossing signal lights, or probably a dozen crossing signal lights! :D The 2N3055 is overkill for one lightbulb! :D

Truthfully, you could use that same circuit with the 2N2222 transistors for a single signal. It would make the whole package a lot smaller as well. I'm guessing you tune the 39K resistor value to change the flash rate of this circuit...
 

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You can turn off both lights by grounding the bases of both transistors. Do it through a resistor of about 100 ohms to limit the current. You can use transistors like a pair of 2N2222s to ground the bases of the 2N3055. Or you can use a DPST switch or relay. Or you could use an isolated outside rail to provide the ground to the power supply and then the lights would flash whenever anything was making a connection to the isolated rail.

My calculator tells me that the circuit is not going to work very well. The 2N3055s have a maximum current gain of 70 and a minimum current gain of 20. The 39k resistors with a power supply of 20 volts only provide about 0.5 ma of current into the base of the transistors. With a current gain of 70, the transistors will only supply 35 ma of current to the load. It ain't much. Obviously the circuit needs to be redesigned. A simple way to fix it is to add a 2N2222 configured as an emitter follower to increase the current into the base of the 2N3055. You would need a resistor of about 100 ohms between the emitter of the 2N2222 and the base of the 2N3055 to provide 200 ma into the base of the 2N3055 which (at a gain of 50) would provide 10 amps out of the 2N3055.

The collector of the 2N3055 transistors is connected to the metal can and so the metal can must be isolated from the heat sink. You need to heat sink the 2N3055 transistors as the can dissipate as much as 115 watts. Without the heat sink, their life will be short unless the collector currents are very small.

The 2N2222 has about the same current gain as the 2N3055, so the base current needs to be increased to drive more than 0.5 ma into the base. The 39k resistor is too big. The 2N2222 collector current can be more than 0.5 amps, so the base current needs to be about 10 ma. That means the 39k resistor is about 20 times too big. If you make the 39k resistor smaller, you have to make the 470u cap larger.

Personally, I think it would be easier to use a 555 timer and a pair of 2N2222s to drive the lamps.
Bruce Baker
 

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Discussion Starter · #14 ·
It works, but flashes too fast.

I don't understand your reply at all.

There is an error in the parts list. I'm sure you picked up on it.

The RS number is a 3.9k resistor! What a hoot!

All I have to do is slow it down and I'm happy.

 

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If you double the size of the 470u capacitor, you will slow it down by a factor of 2. If you want to slow it down by a factor of 4, you must increase the size of the 470u capacitor by a factor of 4. ETC. To get it slow enough to look realistic, this capacitor is going to get to be quite large which is why I said the circuit is not very well designed.

You can also slow it down by making the 3.9 k resistor larger, but if you go too large the collector current of the 2N3055 will become too small. You can experiment with the 3.9k resistors, making them larger to get the flash rate you want, and see if the 2N3055s will still drive the lamps.

Here is a data sheet for a 555 timer: http://www.fairchildsemi.com/ds/LM/LM555.pdf Look at the part of the data sheet that deals with astable operation. You can easily change the timing of the circuit by changing the two resistors and the two caps. The output of the 555 then can be used to drive the base (through a resistor of about 50 ohms) of one of the 2N3055s. The collector of this 2N3055 can then drive the base of the other 2N3055 through a resistor of about 200 ohms. Using these values the 2N3055s will drive about 5 amps. Leave the collector and 22 ohm resistor and light bulb as they are.
BB
 

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GO DAVE GO!!!!!!!

At this point I am going to watch.

No track detection makes it easier.

I found the Rollins site early on and though the graphics are nice, I have had better luck elsewhere. After you tweek it please post it!!!!!
 

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Discussion Starter · #17 ·
Well, the train show today was a bust.

I have more Lionel than they had for sale.

But I stopped by the ole Radio Shack and picked up a few more capacitors.




The two 470mfd capacitors were increased to 3470mfd.

Now all I need are some new painted #53 bulbs and I'll be in great shape.

Thanks to all for the tips and encouragement.
 

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Discussion Starter · #19 ·
If you drop into your hobby shop, you can buy clear acrylic paint and dip your bulbs, much cheaper than buying the colored ones. :)
I haven't tried dipping bulbs in acrylic paint.

Does it leave uniform color?

Painted bulbs are only $.20 each more, how much is the paint?
 
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