I was just reading through one of my model train mags, and it made an offhand reference to how 50's era DC model train regulated throttles were made with tubes, whereas of course now solid state analog and digital controls dominate. It had actually never occurred to me before that this would be the case, since trains run on low voltage DC.
I think such a throttle would be the cat's meow for the layout I am planning to build. Do any of you old hands have any schematics in your old files, or know of where to find them?
I think such a throttle would be the cat's meow for the layout I am planning to build. Do any of you old hands have any schematics in your old files, or know of where to find them?
When I was young I inherited my grandfathers huge train collection. I had several train controllers that varied in age from old (probably late 1930's) to new (late 1950's). They all were essentially low voltage variacs. The output was AC and went from zero to about 18 volts. Even at a young age I used a monster Lionel train transformer to "test" things.
The Tektronix model 504 scope had a switching power supply that used a 6DQ6 for the switch element. I haven't seen the schematic in years (like 20 years).
The Tektronix model 504 scope had a switching power supply that used a 6DQ6 for the switch element. I haven't seen the schematic in years (like 20 years).
tubelab.com said:
Yup, tubelab is correct about the variac controllers. I too inherited a Lionel train set as a kid (worth many, many $$$ today) and used the variable controller to experiment. Every year after taking the train set of out storage, I would carefully clean the tracks and sand the contacts clean so the locomotive would get enough juice to make it all the way around the track.
Don't ask me how, but more than once I put my tongue across the "hot" rails
!!! Thus, I became an engineer...
-- josé k.
korneluk said:
Don't ask me how, but more than once I put my tongue across the "hot" rails
Thus, I became an engineer...
-- josé k.
Hehehe, I once had the marvellous idea to put the wires of the 14VAC outlet of my train transformer in my mouth..
The worst electric shock I ever had, and I've had quite a few since..
In my ignorance, I would imagine that the important thing is the current feeding the locomotive. The tracks and wheels make intermittent, generally not very good contact, so I would think that voltage regulation is not very much use. A variable CCS supply might work best, maybe? Doesn't sound like a very good application for tubes, though.
I remember my transformer for the train set; somehow the wires "got together" and a lot of waxy stuff ran out... Still worked though - for years.
As for the valve CCS Ray suggests, I suppose you could float the whole thing at say 150V and sit it up on top of a nice pentode. That would discourage those busy tongues...
7N7
As for the valve CCS Ray suggests, I suppose you could float the whole thing at say 150V and sit it up on top of a nice pentode. That would discourage those busy tongues...
7N7
Hmm...
I once laid out a strip of track, put an engine on one end and somehow managed to connect one of those coffee pot cords to the track and plugged her in...
Smoke.. lots of sparks and the engine screaming across the room... Mother had a very perplexed look when she came into the room I was eight at the time...
ck
I once laid out a strip of track, put an engine on one end and somehow managed to connect one of those coffee pot cords to the track and plugged her in...
Smoke.. lots of sparks and the engine screaming across the room... Mother had a very perplexed look when she came into the room I was eight at the time... ck
Ciscokid said:Hmm...
I once laid out a strip of track, put an engine on one end and somehow managed to connect one of those coffee pot cords to the track and plugged her in...
ck
Superb!
I wasn't quite as ingenious; at around six I wired up a plug to a piece of cable, and proceeded to plug in to a wall socket (240v).
All well and good, except that I hadn't had a good look at the other end of the cable, where the wires were nicely "entwined".
The results were really very dramatic and the fuse-box didn't like it all, something it shared with my parents...
7N7
ray_moth said:
Well, yes and no. There are simple throttles that do not do any regulation, and in fact some are intentionally half wave rectifiers so that the voltage peaks make the motor overcome friction better for slow speed running. However, all the DIY analog throttles I have seen use an LM317 or LM338 as a voltage regulator.
ha ha, with me it was my sisters tounge and a scalextric. And the best part was I was young and managed to convince my mum i didnt know about electricity, I was only trying to run it over, honest!
Anyway, is there any reason you want to use valves for the controller, or just for the fun of it?
Anyway, is there any reason you want to use valves for the controller, or just for the fun of it?
Colt45 said:
Well, no, since this will be scratchbuilt, I can make the input transformer whatever I like. Using an LM317HV should accomodate a reasonably large variance in voltage drop with current draw. However, even 6CL3 isn't really beefy enough, a decent home throttle should be able to put out one amp of juice.
leadbelly said:
I wasn't intending to tease. As has been pointed out, there are two main problems with model cars and trains. Intermittent high resistance contacts and stiction. The solution in both cases is the same; short high voltage pulses. Of course, it's not going to be EMC compliant (not with those pulses connected to an aerial), but it will give good control. What you would need would be a line scan valve as your series pass element, driven by variable width pulses from a 555 or similar. A simple triode amplifier between the 555 and the PL519 would suffice. Poor smoothing before the controller would be useful.
The 317 approach is the exact opposite of what is needed.
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