A fellow club member asked a bunch of us a question on increasing the starting voltage on locos. It goes like this. He has three DC only Kato locos, HO, that he runs as a consist,they pull a passenger train with 13 lighted cars. At present the locos start moving before the cars light up. He wishes to have the cars light up and then have the locos start to move. His question is: Can he put a resister in the loco to increase the starting voltage,( from the power pack) to the locos and accomplish his goal. He wants to avoid tearing onto each car to alter the lighting.I told him Iwould ask you guys whether is is feasable or not. At this point I have no information regarding the current starting voltage of the locos or what the voltage of the car lighting is.
-Dan
Builder of Bowser steam! Railimages Site
adding a resistor in series with the motor sounds like the last thing you would like to do. It would only partially reduce the starting voltage while limiting the maximum voltage. A 1 ohm 1W resistor in series with a motor that draws 1 Amp would drop the voltage across the motor by 1 Volt.
Wouldn't you also want the passenger cars lighted while sitting at a station? what about applying some AC voltage across the tracks, which would light the passenger cars but not cause the locomotives to move. (The motors would actually vibrate back and forth). Maybe the AC could be applied only when the DC is below some voltage and then shut off.
batteries in each passenger car may also be an option. They could power the lights at low votlages and charge at higher voltages.
greg - Philadelphia & Reading / Reading
A bridge rectifier wired in series with the motor leads will drop the starting voltage by 1.4 volts. Two in series will drop it by 2.8 volts which should be pretty close to the point of the LEDs being on.
Take the bridge rectifier and solder the plus and minus terminals together. The remaining AC terminals will be placed in series with one of the leads to the motor. I would recommend no less than a 1 amp rated bridge rectifier.
Mark.
¡ uʍop ǝpısdn sı ǝɹnʇɐuƃıs ʎɯ 'dlǝɥ
I have a circuit somewhere for building a high frequency AC generator from long ago. It applied a high frquency AC to the rails for keeping lights lit, but also required choke coils and other components in each engine to filter out the AC. Rather archaic by todays technology, but 50 years ago, it apparently was high-tech !
Havign all the old MRs, I've read those HF lighting articles. They go back to tube days, actually - then there were newer transistor ones. As far as I remember, only the power packs needed a choke coil, the motor leads acted as a coil on the loco side of things.
Diode bridges in the locos are the way to go, but this will also reduce the top speed. That's how many locos with constant lighting do it, low voltage bulb across a diode array that is in series with teh motor, so you cna crack the throttle, bulb lights but not enough voltage reaches the motor. Crank it up, drop across diodes (and thus voltage to bulb) remaisn constant, motor gets more and more voltage ans speeds up.
On board battery lighting, even better, just need to have some easy way to turn the lights on and off.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
You DON'T want AC on the rails.
There are a couple DCC systems that do that to run a DC loco with no decoder. Those systems put DC voltage that rides with the AC. The AC is a high frequency pulse type signal. The motor armatures continually oscillate, even when the loco is stopped. A well known issue. It has burned up a motor at times in others locos. There are no filters for this.
Below is a link about this issue that evryone should have.
http://members.shaw.ca/sask.rail/dcc/DCC-waveforms/DCC_waveforms.html
Rich
If you ever fall over in public, pick yourself up and say “sorry it’s been a while since I inhabited a body.” And just walk away.
You're right Randy - the article was from Practical Electronics Projects for Model Railroaders 1974. The choke coil was at the throttle, but each engine required a pair of 220uf - 25V capacitors, a diode and a 47 ohm resistor .... requiring much more room than a pair of bridge rectifiers !
Yeah, and that one was pretty weak - there was a followup to the artical in MR when it first appeared where some other engineers picked the circuit apart - some issues like the components of choice migth not even oscillate as expected. But WAY back, there was a tube-based one in MR.
It's AC< but it's not like hooking 60Hz AC to the track, or even the few KHz of DCC. This is 20-25KHz or better. The capacitors recommended in the loco and the coils on the trak power lines are effectively a bandpass filter and filter almost all of the HF component out and keep it away from the motor. Most standard permag motors will be fine, it might be an issue with coreless types. The PFM sound system actually used HF as part of the feedback for the chuff cams, and of course also sent audio frequency over the rails to the speakers.
Randy: I will pass along your suggestion as to the diode bridges. I asked him about reduced top speed and he told me it isn't a problem as he runs his locos at low speed, and should be ok at the speeds he runs even though the voltage output from the power pack would be higher than he normally runs. Thanks for the help. Now the math involved and the values needed will be next, but we are not to that point yet
Many years back I had an ABA FA set with Hobbytown drives ,the engines were loaded with extra weight. I added directional constant light devices constructed with 6 diodes and the old Protolight bulbs. They ran well but I did notice the FB unit was spinning its wheels at low to medium speeds .I realized that the FB had no headlights and no constant light units . The voltage drop across the constant light FA A units was enough to create a speed difference with the non equipped FB unit. I added a four diode unit with no lights to the FB unit this was enough to stop the spinning wheels. These engines were all equipped with the Hobbytown Flywheel drive and DC 70 motors. I had a little lower top speed but they ran just fine for me. A year or 2 back I converted them to LED lights and removed all 3 constant lights.So I think the diode bridge may help slow the start of the engines and may be enought to let the passenger cars light up closer to the starting speed of the engines.
Ron High
I recently added LED lighting to a Life Like Proto 1000 Budd car. These older Budd cars had a very dim headlight fed by a diode bridge constant light unit bypassing the old constant light unit gave my car a 10 to 15 % speed increase .I had been considering the NWSL gear kit to increase the speed but replacing the old constant light unit with LEDs gave me brighter directional control headlights and a speed increase.These units were notorious for their slow speed. The speed increase was enough to decide not to uae the NWSL gear kit. I also connected 2 short strings of surface mount LEDs mounted on the car ceiling to light the passenger seating area.