Have USA G Switcher hook up smoke generators

[ironacres]

I have my switcher running on battery 18.5 for a few months now, all working good.  Originally did not hook up smoke units being my first battery conversion and trying out.  Here is the problem it takes 7 to 8 volts to activate smoke at the board, LM puts out 5 volts.  I could run power from the battery output voltage on the LM would be 18.5 to a switch then to smoke board, but I would loose remote operation.  Or I thought of running a micro relay that I could energize the coil from the LM 5 volt output and feed power from the LM battery output to the smoke control board, that would be 18.5. I believe the smoke board will handle up to 24 volts G scale rated, the same if you were running track VDC. I tested using a veritable power supply to find start up voltage for smoke.  Has anyone else wired the same locomotive for smoke or am I missing something and over complicating things.     

[Joel W]

You are on the right track - a 5 volt relay to turn the smoke on and off, and control the relay with one of the outputs from the LM.  Remember to attach a heat sink to the (3 wire) transistor attached to the smoke board, and put it somewhere where it has good ventilation.  Note that smoke units use a lot of power and will significantly shorten your run time.

[Joel W]

Another possible solution is to explore the function of the transistor attached to the smoke unit and possibly trigger it directly from an output on the LN.  This will require more electronics knowledge than I have but it should be possible.  On mine it is a TIP122 which turns on when you ground the control voltage.

[ironacres]

I still have the weight that the transistor was attached to in the locomotive,  have to order a relay that will operate on 5 volts.  I can make it work with an on off switch on the loco but that defeats the purpose of wireless control, and takes the fun out of it.

[Alan]

Disclaimer: I have no experience with LM-3S-G. My experience is limited to HO LM-2 and LM-3.

I find it odd the LM outputs are only 5V when operating on a 18.5V supply. Are you certain of that measurement?

Smoke units will draw some serious juice because of the heating coils. Doubtful an LM can directly power. By your picture the original installation also required a driver circuit (the two transistors). Have you tried using the LM output to drive the base pin of the little transistor on the circuit board?

If you do go the relay route make sure to place a flyback diode across the relay coil otherwise you could damage the LM internal output transistor.

[JRad]

There are no transistors in the USA Trains smoke circuit. The square item on the board is a bridge rectifier and the three legged device is a voltage regulator.

The LM-3S-G outputs are all switched grounds.  Source voltage is EITHER the +5 terminal or the V+ terminal. V+ will output a volt or two under the battery voltage due to circuit losses.

I agree that you need a relay or a power transistor circuit for the smoke. Trying to pull that much current through the LM will either shut it down, or burn it up.  You could use either a 5 volt or 18 volt relay with one side of the coil attached to an output (ground) and the other side to either +5 or V+ depending on coil voltage.

Many of us that run battery power just eliminate smoke units because they use too much power reducing run time.

[Alan]

So, it is a LM7805 regulator in the picture? Interesting that it doesn't have a stabilization capacitor. Out of curiosity, what is the 5V supply used for on G locos? Bulbs and LEDs maybe?

What is the small transistor used for?

[Joel W]

Check your chip - the separate 3 wire device that is attached to the weight.  On both my NW2s it is a single TIP 122 Darlington transistor and only used for the smoke - the light bulbs are high voltage bulbs, On most of my other USA Trains engines there are two transistors - both voltage regulators - and the bulbs/LEDs are low voltage.

As others have mentioned, be sure to put a diode (like a 4001) across the relay coil leads to block the backwards voltage spike that will occur when the relay turns off.

[Alan]

Check your chip - the separate 3 wire device that is attached to the weight.  On both my NW2s it is a single TIP 122 Darlington transistor and only used for the smoke.

That makes a ton of sense. Exactly what is expected. Now we also know why the package isn't mounted to the board. I imagine the weight makes an excellent heat sink which will certainly be needed in this application.

Still curious why the little transistor...

[MichaelK]

Many of us that run battery power just eliminate smoke units because they use too much power reducing run time.

Yep! There's the best answer right there. USA Trains - I have four GP-9's, one F-3A/B combo, and one NW2. Drains the batteries like there's no tomorrow, so I took all of the smokers out of 'em.

[ironacres]

Yes I was considering the power draw and how much I want smoke.  Compared to the low volts that the Aristocraft units use.  I have a 5 volt relay, will try and see what the battery time is.  I am also installing a servo trigger board for my Kadee RC couple, no draw to speak of. Yes 5 volts relay output on LM to answer your question.   I looked and did see it is a voltage regulator, I should know better.  Thanks all for the continuing help. 

[ironacres]

Disclaimer: I have no experience with LM-3S-G. My experience is limited to HO LM-2 and LM-3.

I find it odd the LM outputs are only 5V when operating on a 18.5V supply. Are you certain of that measurement?

Smoke units will draw some serious juice because of the heating coils. Doubtful an LM can directly power. By your picture the original installation also required a driver circuit (the two transistors). Have you tried using the LM output to drive the base pin of the little transistor on the circuit board?

If you do go the relay route make sure to place a flyback diode across the relay coil otherwise you could damage the LM internal output transistor.

[trainman605]

I use the 12v LED's sold on eBay in both 3mm and 5mm with a resistor which drops to around 7-9 volts, I do the same for all my interior lighting powered by a 9v battery. I use both soft white and bright white LED's depending on location and how bright I want the light to be, usually HL and TL bright white and interior lights soft white. Do note here since RailPro light output is only 5v and using these 12v LED's surprising how bright these bulbs are at only 5v being supplied to them. I talked with Don Sweet at RCS of New England and he even suggested using the other power supply on the module which is what your battery power is (14.8v) and with the resistor on the LED you will probably get total brightness and not burn out the LED, but test before you install, you could add another resistor to adjust light output. All being said, LED's are very flexible going down in voltage, but up not so good, they tend to smoke and go puff. I know some who figure this out on paper using all there electronic knowledge, but I'm old world and commonsense works well for me.

trainman

[ironacres]

I use the same LEDs have no problems.

[ironacres]

Talking with Railpro some more on smoke generator hookup.  I could rout track or battery power to the modual relay output built into the LM, and get higher voltage to run smoke.  They do like the relay idea better it helps to isolate the LM from any problems. And the draw is much lower. Smoke generator draws more current than running relay.  I am also going to install a DPDT switch so I can run battery or track, depending on run time. See what happens, have all the parts and ready to install.