RMweb Gold Phil Bullock Posted November 3, 2015 RMweb Gold Share Posted November 3, 2015 Hi JM, I would hope so, I wonder how many of them actually do. Cheers! Andy Abbotswood hasn't - but will do! Phil Link to post Share on other sites More sharing options...
Suzie Posted November 3, 2015 Share Posted November 3, 2015 ...I'm not sure 0.7 ohms is exactly a "high impedance"... There is more to impedance than the DC cold resistance when dealing with DCC that has frequency components well over 25KHz. Even thin wire like 7/02 has too much impedance when used in long lengths on DCC that are still well below half an Ohm at DC. It is all relative. Link to post Share on other sites More sharing options...
AndyID Posted November 3, 2015 Author Share Posted November 3, 2015 There is more to impedance than the DC cold resistance when dealing with DCC that has frequency components well over 25KHz. Even thin wire like 7/02 has too much impedance when used in long lengths on DCC that are still well below half an Ohm at DC. It is all relative. So what is the inductance of the filament? Link to post Share on other sites More sharing options...
Suzie Posted November 3, 2015 Share Posted November 3, 2015 So what is the inductance of the filament? I could not say, but it is a coil! Link to post Share on other sites More sharing options...
F-UnitMad Posted November 4, 2015 Share Posted November 4, 2015 Would you not still get a short as a wheel tread bridged the V-rails just beyond the insulated nose? Not if the wheels are coned, and they usually are.Sorry but that was exactly the problem I had with Peco points, & it was with modern US HO stuff - Kato, Atlas, Kadee etc, so not ancient Lima steamrollers but modern RP25 wheels. So I would expect it to happen on your version too, regardless of whether it should or not. If something can go wrong, then eventually it will. Switched frogs for me now in O scale, using Mono Frog Juicers. Simple to fit, & no problems at all. Link to post Share on other sites More sharing options...
AndyID Posted November 4, 2015 Author Share Posted November 4, 2015 Sorry but that was exactly the problem I had with Peco points, & it was with modern US HO stuff - Kato, Atlas, Kadee etc, so not ancient Lima steamrollers but modern RP25 wheels. So I would expect it to happen on your version too, regardless of whether it should or not. If something can go wrong, then eventually it will. Switched frogs for me now in O scale, using Mono Frog Juicers. Simple to fit, & no problems at all. Ah, that could be a problem then. Yes, RP-25 does not require coning. I suppose Peco didn't sell too many insulated frog turnouts in the US. Link to post Share on other sites More sharing options...
Junctionmad Posted November 4, 2015 Share Posted November 4, 2015 Makes "dead rail" schemes even more desirable. About 4 years and this topic will be an anachronism. For now just add 2 second super caps or keep alives to rail powered engines or other current drawing rolling stock and isolate the whole turnout. Avoid stopping on turnouts. of course you have a huge power supply to supply all that inrush current to those 30-40 super caps on startup , etc It will a long long time before we see dead rail layouts especially in smaller scales this still leaves all that wiring for block detection , etc anyway !!! Link to post Share on other sites More sharing options...
Junctionmad Posted November 4, 2015 Share Posted November 4, 2015 as a general comment, I dont see the fuss about frog polarity switching , its three wires and a micro switch or equivalent , not a big deal , Link to post Share on other sites More sharing options...
RMweb Premium Reorte Posted November 4, 2015 RMweb Premium Share Posted November 4, 2015 as a general comment, I dont see the fuss about frog polarity switching , its three wires and a micro switch or equivalent , not a big deal , The already-mentioned stalling I suppose. Anyone got DCC AWS? Come to think of it the microswitch could be also be used to switch in and out a section of track behind the turnout to stop a train reaching a frog polarised against it, as long as you're not in the middle of complex formations, but that would require a bit more switching and wiring. Link to post Share on other sites More sharing options...
RMweb Gold martin_wynne Posted November 4, 2015 RMweb Gold Share Posted November 4, 2015 three wires and a micro switch or equivalent , not a big deal Installing, adjusting and maintaining a micro-switch is a cruel punishment, in contravention of the Geneva Convention. Far, far, easier is to use a relay. Fit and forget, anywhere you like, with a quick dab from the glue gun. Same 3 wires, plus 2 more to slave it across the point motor, in series with a diode. Relays are not expensive, not much more than a micro-switch -- for example 10 of these are 92p each: http://www.rapidonline.com/electronic-components/song-chuan-842-1c-s12-pcb-mount-relay-12vdc-3a-spdt-51-0667 Martin. Link to post Share on other sites More sharing options...
AndyID Posted November 4, 2015 Author Share Posted November 4, 2015 Far, far, easier is to use a relay. Fit and forget, anywhere you like, with a quick dab from the glue gun. Same 3 wires, plus 2 more to slave it across the point motor, in series with a diode. Not if you are using those seismic solenoids Link to post Share on other sites More sharing options...
RMweb Gold martin_wynne Posted November 5, 2015 RMweb Gold Share Posted November 5, 2015 Not if you are using those seismic solenoids Hit a micro-switch with one of those and you will be under the baseboard replacing it within a few weeks. If you use a capacitive discharge unit to fire them, add an extra pole on the panel toggle switch and use that to switch the relay. Or use it to switch the frog polarity directly. Martin. Link to post Share on other sites More sharing options...
AndyID Posted November 5, 2015 Author Share Posted November 5, 2015 Hit a micro-switch with one of those and you will be under the baseboard replacing it within a few weeks. If you use a capacitive discharge unit to fire them, add an extra pole on the panel toggle switch and use that to switch the relay. Or use it to switch the frog polarity directly. Martin. Yes, but they are really good for exposing dry-joints! Link to post Share on other sites More sharing options...
rockershovel Posted November 5, 2015 Share Posted November 5, 2015 Mais bien sur! (Shrugs eloquently) Link to post Share on other sites More sharing options...
Nearholmer Posted November 5, 2015 Share Posted November 5, 2015 I've been holding-off asking this since joining RMWeb, for fear of appearing an idiot, but now that I've been here long enough to expose my idiocy by other means: what are "frog juicers"? I would love to know not only what their purpose is, but what they consist of. I'm pretty confident that my deliberately retro, centre-third-rail, railway is never going to need one, and I never felt the urge for one when I was operating two-rail(analogue), battery, steam, or clockwork, so this is pure curiosity! Kevin Link to post Share on other sites More sharing options...
gordon s Posted November 5, 2015 Share Posted November 5, 2015 They're an electronic circuit that will automatically change the frog polarity on a DCC controlled layout and eliminate the need for micro switches or relays on live frog pointwork. As has been highlighted before, there is a possibility of causing a short on incorrectly set pointwork on DCC layouts and shutting down the whole system. This piece of kit will automatically change the polarity as a loco crosses and avoid that possibility. It's very fast and will allow sound equipped loco's to cross over without any change to the sound output. http://www.tamvalleydepot.com/support/frogjuicers.html Link to post Share on other sites More sharing options...
Talltim Posted November 5, 2015 Share Posted November 5, 2015 What's green and turns red at the touch of a button? Link to post Share on other sites More sharing options...
RMweb Gold RFS Posted November 5, 2015 RMweb Gold Share Posted November 5, 2015 Talltim, on 05 Nov 2015 - 20:47, said:What's green and turns red at the touch of a button? A frog in a juicer ! Link to post Share on other sites More sharing options...
Nearholmer Posted November 5, 2015 Share Posted November 5, 2015 g s I now know what they do, thank you, Sir. Curious as I am, I don't think I'll be buying one so that I can try to understand exactly how it works. K Link to post Share on other sites More sharing options...
bike2steam Posted November 5, 2015 Share Posted November 5, 2015 A slight variation on the insulated frog. You mean you actually still use turnouts with an insulated frog/nose ?? Link to post Share on other sites More sharing options...
AndyID Posted November 5, 2015 Author Share Posted November 5, 2015 If you use a capacitive discharge unit to fire them, add an extra pole on the panel toggle switch and use that to switch the relay. Or use it to switch the frog polarity directly. Martin. Hi Martin, What kind of switches did you have in mind? If you use a toggle switch with a solenoid it better be a "passing contact" switch (unless of course you also have contacts to break the connection when the solenoid travels to the end stops, but they don't work terribly well either.) Cheers! Andy Link to post Share on other sites More sharing options...
RMweb Gold martin_wynne Posted November 5, 2015 RMweb Gold Share Posted November 5, 2015 What kind of switches did you have in mind? If you use a toggle switch with a solenoid it better be a "passing contact" switch Hi Andy, This design requires one capacitor per point-motor. The capacitor is charged through one motor coil and discharged through the other. It needs a beefy power supply able to deliver the charge current. A 15-volt 50VA transformer and 4 amp bridge rectifier is ideal. This design needs only a SPDT switch, so if a DPDT switch is used the other pole can be used for crossing (frog) polarity switching. A POINT-MOTOR CIRCUIT © Martin Wynne This circuit operates an impulse solenoid point-motor using an ordinary 2-way toggle or slide switch, or relay contacts. The advantage over sprung momentary-contact switches, electric pencils and other devices is that the switch setting indicates the points setting. The switch never breaks any current, so it can be a low-cost switch. (It must be "break-before-make" action, which rules out some types of rotary switch.) Another advantage of this design is that it allows impulse point-motors to be operated via relays, multipole switches, computer or hard-wired logic, etc. The only disadvantage is that it needs a separate capacitor for each point motor. Otherwise this circuit is simple, safe and reliable -- it is impossible to burn out the point motor and it will last forever. After first switching on the power, it is necessary to work the switch once each way to synchronize it with the points. Do not work the switch rapidly to and fro, as this is likely to lose the synchronization. If this happens work the switch slowly to restore sync. The capacitor can be at the panel end next to the switch, or on the baseboard next to the point-motor. It needs to be a few thousand uF or so, rated 25 volts or more -- a suitable common size is a 4700uF 25V capacitor, which costs typically around £1.25 each. Some trial and error of capacitor size with specific point-motors may be needed, and a smaller lower-cost capacitor may be adequate in many cases. The power supply must be DC (rectified AC), and the capacitor must be connected the right way round, as shown. If the supply voltage is more than the nominal 12 volts DC shown (typically from 15v AC rectified), increase the capacitor voltage rating accordingly. N.B. after switching off the power, the capacitor may remain in the charged condition. For safety if the layout is to be moved, stored, etc., work the switch once each way after switching off. More circuit ideas in this topic: http://www.rmweb.co.uk/community/index.php?/topic/44670-dpdt-to-work-seep-point-motor/ regards, Martin. Link to post Share on other sites More sharing options...
AndyID Posted November 5, 2015 Author Share Posted November 5, 2015 The switch never breaks any current, so it can be a low-cost switch. Thanks Martin. Because switch contacts have a certain amount of bounce, the current actually is interrupted. Despite that, most switches should survive for sufficient operations on a typical layout. There's a similar concern about the effect the high rate of change of current has on the life of the cap, but again, it's unlikely to show up as a problem on a layout. Cheers! Anndy Link to post Share on other sites More sharing options...
RMweb Gold martin_wynne Posted November 5, 2015 RMweb Gold Share Posted November 5, 2015 Because switch contacts have a certain amount of bounce, the current actually is interrupted. Despite that, most switches should survive for sufficient operations on a typical layout. There's a similar concern about the effect the high rate of change of current has on the life of the cap, but again, it's unlikely to show up as a problem on a layout. Well yes, but we are not designing life-support equipment, or even industrial grade. In practice the circuit has worked well on several layouts for years. It is worth getting a 35-volt rated capacitor for longer life, because typical 16vac rms transformers can go over 25 volts at the peak of the wave, although the rectifier will drop a volt or two. Martin. Link to post Share on other sites More sharing options...
Junctionmad Posted November 6, 2015 Share Posted November 6, 2015 How can that circuit work Martin. There isn't a circuit to recharge the cap once the switch is moved from 12 v. Link to post Share on other sites More sharing options...
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