adanapress Posted October 18, 2012 Share Posted October 18, 2012 I have read somewhere that small caps can help an analogue 12v. fed loco or power bogie to get across a bad pick up spot. Almost an electrical flywheel. Is this true? and if so what values please? Link to post Share on other sites More sharing options...
Adrian Wintle Posted October 18, 2012 Share Posted October 18, 2012 Start here http://www.rmweb.co.uk/community/index.php?/topic/54041-stay-alive-on-dc/ Adrian Link to post Share on other sites More sharing options...
adanapress Posted October 18, 2012 Author Share Posted October 18, 2012 Thank you Adrian, I'll now go away and think wether a tiny battery of any sort (?torch battery) might work instead of a capacitor as such, presumably with some sensing chippery. I'm certain that such a device - if it were possible and technically simple (and cheap) would have a strong market. After all, very old fashioned resistance controllers such as I use, only supply (relatively) clean approx 2v to 12v and a whiff of one and a half to three volts DC actually carried on board ought to get you over a spot of grot on the track, remember the loco arrives with a little inertia of its own, and almost gets over the spot, commonly in fact only giving a slight hesitation before proceeding anyway. I need some sparks feller to go away and think creatively. A most helpful read, much of which I did indeed understand. Clearly capacitors are out. DCC is entirely out of the question for me, as are locos at £100 each. The pension aint up to it. I have to make do with what I have from long long ago. Many thanks for that most helpful pointer. Link to post Share on other sites More sharing options...
noiseboy72 Posted October 18, 2012 Share Posted October 18, 2012 A battery will not help I am afraid, as the circuitry needed to charge it and then return the power when needed would be quite expensive. A better bet is to sort out the track until all the sticky points have been eradicated. On crossings, you often find that the cause of the pausing is shorting out as the wheels are wider than the rail and short out to the adjacent rail. Look for sparks when you go through at speed. Sorting out the back to back of the wheels or even a few coats of nail varnish applied over the rail will be a reliable fix. Decent track leveling - with a piece of flat steel as a guide also helps, as again, a lot of continuity issues are as wheels get lifted off the track. Just lift up the bad piece of track and pack some plasticard under it to get it flat Baseboard joints are the worst offender, as well as sags between bracing. Link to post Share on other sites More sharing options...
RMweb Gold Dagworth Posted October 18, 2012 RMweb Gold Share Posted October 18, 2012 A battery will not help I am afraid, as the circuitry needed to charge it and then return the power when needed would be quite expensive. A better bet is to sort out the track until all the sticky points have been eradicated. On crossings, you often find that the cause of the pausing is shorting out as the wheels are wider than the rail and short out to the adjacent rail. Look for sparks when you go through at speed. Sorting out the back to back of the wheels or even a few coats of nail varnish applied over the rail will be a reliable fix. Decent track leveling - with a piece of flat steel as a guide also helps, as again, a lot of continuity issues are as wheels get lifted off the track. Just lift up the bad piece of track and pack some plasticard under it to get it flat Baseboard joints are the worst offender, as well as sags between bracing. see http://www.rmweb.co.uk/community/index.php?/topic/41763-electronic-boosters/page__st__25&do=findComment&comment=450261 for a circuit which, while I haven't actually built it (I work in DCC), ought to work without major expense in components. Andi Link to post Share on other sites More sharing options...
RMweb Premium kevinlms Posted October 18, 2012 RMweb Premium Share Posted October 18, 2012 see http://www.rmweb.co...._25#entry450261 for a circuit which, while I haven't actually built it (I work in DCC), ought to work without major expense in components. Andi It is over 12 months since that circuit was posted. Has anyone had a go at it and does it work? Link to post Share on other sites More sharing options...
Suzie Posted October 18, 2012 Share Posted October 18, 2012 I don't think it will work. The relay will pull in for both directions - it needs a diode in series with the coil or your train will only go one way. Also it needs a capacitor across the coil to hold the relay in during loss of power or your train will instantly reverse on the loss of track power. The relay will need to be a low voltage type and will need some sort of voltage limiter to prevent it burning out. The capacitor required to hold the relay in will probably need to supply more power to the relay than the motor will take from the battery! A latching relay may get round some of these problems, but it will take some big welly on the controller to change direction. In conclusion I think that this circuit, with the required improvements to make it work, will be less effective and much more bulky than a simple bipolar capacitor arranged across the motor. Electronic switching, as used in a DCC decoder in DC mode, will be much more effective and could make good use of a low voltage battery suitably connected with a blocking diode to the Blue and Black/White wires of a decoder with suitable firmware to accurately measure the track voltage and control the motor accordingly. not really worth the effort though, DCC is much cheaper. Link to post Share on other sites More sharing options...
RMweb Gold Dagworth Posted October 18, 2012 RMweb Gold Share Posted October 18, 2012 Suzie, read the thread, the relay is a latching relay and only changes the position of the contacts when the track power polarity is reversed. Once power is lost the contacts stay at their last position without need for power to hold them. Andi Link to post Share on other sites More sharing options...
Suzie Posted October 19, 2012 Share Posted October 19, 2012 I read it twice and still missed the word 'Latching'. Whoops, sorry. Link to post Share on other sites More sharing options...
N15class Posted October 22, 2012 Share Posted October 22, 2012 I am with the sorting of the track and pick ups out brigade. I would also look to adding more pick ups as you might be getting no eletricity to the motor. You will not need all this electronics to make the loco go if the fundimentals are right. Link to post Share on other sites More sharing options...
jdp298 Posted October 29, 2012 Share Posted October 29, 2012 Lots of diversionary tactics, but this is definitely possible. The requirement is to pass a dead section/ dirty point/track. That's not far, say 2 or 3 mm tops. This is so much more possible with modern supercaps than even 5 years ago, or what I tried out as an electronic flywheel on DC. I can see this working provided you don't have a PWM (Pulse width modulation) controller. If you do I'm not totally sure what to suggest...track rubber/brass flywheel anyone? This needs to fit in the loco, as it has to work without external power. Musing off the top of my head. Assume half power, 6v, drawing 0.3A, total power 1.8W. Time needed to run, say 0.5 seconds (very generous), makes 0.9 Joules of energy storage required. A capacitor's energy is defined as 0.5 x C x V^2. Rearranging for C and we get a capacitance value of 0.05 Farads, or 50 milli-Farads. It's by no means impossible to hide a capacitor of that size in a 'OO' loco. I have 1F capacitors in my bike lights slightly thicker but the same diameter as a £1 coin. A lot of these will also only run at 5.5 or 6 volts, so you'd need 2 in series; to make sure they aren't polarised; and fit them in somewhere. 2 in series because that means they won't let out the magic smoke when you run at 12v. What I also discovered when I tried out the idea of the electronic capacitor flywheel was that the differences in curent draws by different engines massively affects the size of capacitor you need to achieve the same effect. By fitting it to each engine, though, you can measure the current draw for each engine and run the numbers accordingly. Yes, laying the track and cleaning things and listening to the live frog thought police is all well and good, but doesn't answer the question. It's an interesting idea and one I might experiment with in the future. Link to post Share on other sites More sharing options...
N15class Posted October 29, 2012 Share Posted October 29, 2012 Make the chassis work properly and you do not need eletronics to keep it going. Even a 0-4-0 with all four wheels on the rails will keep going over dead spots, less of coarse the dead spot is longer than the wheel base. Link to post Share on other sites More sharing options...
ozzyo Posted November 3, 2012 Share Posted November 3, 2012 I have seen a large German R-T-R tank loco (4-6-2 I think) in O gauge DCC fitted run along a sheet of A4 paper (so all wheels were off the track) with no loss of power. I'm not sure what it used to enable it to do this, but I would think that it would have some sort of capacitor fitted. So it can be done. OzzyO. Link to post Share on other sites More sharing options...
buffalo Posted November 3, 2012 Share Posted November 3, 2012 I have seen a large German R-T-R tank loco (4-6-2 I think) in O gauge DCC fitted run along a sheet of A4 paper... Probably the Lenz system, though there are others. No one is disputing that it can be done in DCC. However, the OP asked about "analogue 12v", i.e. DC, and that is a quite different problem. Nick Link to post Share on other sites More sharing options...
Suzie Posted November 3, 2012 Share Posted November 3, 2012 Perhaps someone should try a Lenz Gold with a PS1 on DC and see what it does. Should run for just as long on DC as it does on DCC, but might start to slow (according to the inertia configuration) because the DC track voltage cannot be detected as easily as the DCC signal to tell the decoder how fast it should be going when isolated from the track. Link to post Share on other sites More sharing options...
Horsetan Posted November 3, 2012 Share Posted November 3, 2012 I have seen a large German R-T-R tank loco (4-6-2 I think) in O gauge DCC fitted run along a sheet of A4 paper (so all wheels were off the track) with no loss of power. I'm not sure what it used to enable it to do this.... Flywheels. German modellers love flywheels. Link to post Share on other sites More sharing options...
ozzyo Posted November 3, 2012 Share Posted November 3, 2012 I have seen a large German R-T-R tank loco (4-6-2 I think) in O gauge DCC fitted run along a sheet of A4 paper (so all wheels were off the track) with no loss of power. I'm not sure what it used to enable it to do this, but I would think that it would have some sort of capacitor fitted. So it can be done. OzzyO. Flywheels. German modellers love flywheels. I don't think that this was done with just flywheels! Link to post Share on other sites More sharing options...
jdp298 Posted November 17, 2012 Share Posted November 17, 2012 If you really want to get fancy, then there are all sorts of circuits floating about that give you standlights on dynamo powered bicycle lights. The same effect would apply here, only that in OO there really isn't much space left over, especially in the RTR stuff. At its simplest, if I can find the right capacitors I'll post a link, but the 5.5V 0.22F caps from Maplin would serve the purpose once you factor in the charge/discharge inefficiencies, the exponential decay in rising and falling charges, and the need to run a pair, probably 3 or 4, in series. The real problem is with them being polarized caps. You can get round this by reversing the second cap, so connecting +ve to +ve or -ve to -ve when wiring them in serial. It's a bit of a trick but stops them blowing up. Your other option is to build a direction sensing circuit that automatically connects the big capacitors the right way round electronically based on the most recent direction of travel at the moment power was lost. By the time you've done that, the circuit board probably won't fit in anything less than an O guage pacific. And this is why we have chips for DCC rather than strip board and soldering irons. Link to post Share on other sites More sharing options...
RMweb Premium melmerby Posted November 17, 2012 RMweb Premium Share Posted November 17, 2012 Don't forget that 2 identical caps in series have half the capacity and twice the voltage rating of a single one. Keith Link to post Share on other sites More sharing options...
RMweb Gold Dagworth Posted November 20, 2012 RMweb Gold Share Posted November 20, 2012 How can it work with rectification? Either the motor (and loco) can only ever go one way, or the cap can only charge and never discharge if only that is on the rectified circuit. Please explain with diagram. Andi Link to post Share on other sites More sharing options...
N15class Posted November 20, 2012 Share Posted November 20, 2012 It does work, this is what i've found. Firstly the capacitor reduces internal motor friction and frees up the motor by soaking up the backfeed thus allowing the motor to turn for far longer for the same current, it also cleans up and makes stable the incoming DC current. The trick is to profit from this reduced motor friction by the use of a flywheel, a large flywheel, the final gearing should be no less than 80:1 otherwise the flywheel is rendered useless, 100:1 is best, any higher you get unwanted noise. Now i use this system which not only gives me excellent slow running, top flywheel effect, but most importantly for me gives the effect of mass (weight), which is what i'm most looking for, taking away the toy train and replacing it with something like the real thing albeit reduced in size. Ok now for the details, 12V rectifiction of the incoming current even if you think you don't need it then i have a polarised cap 25V 4700uf in parallel and onboard the loco i put a non-polarised 16V 1000uf cap in parallel measuring 10mm dia and 20mm long. To see the difference put a shunt on the two capacitors whilst running the motor, there is no comparison, what you are looking for is when the locomotive starts to move off it does so in an accelerating curve, in otherwards it starts to move off slowly and the acceleration itself gets faster as the speed picks up, no way should the acceleration be equal from start to end, it's this factor which gives you the effect of mass or weight. Remember, smooth out the current by rectifiction, then the two caps and the large flywheel, If you want realistic running this is it. I may be wrong but I thought DC was rectified other wise it was AC. The large flywheel will smooth out the motor without all the electronics. It is back to making a good chassis that works properly there is no need for any thing else. Link to post Share on other sites More sharing options...
RMweb Gold Dagworth Posted November 20, 2012 RMweb Gold Share Posted November 20, 2012 ..as i said before, rectification even if you think you don't need it. If the incoming current is AC or DC, rectify it, with the polarised cap it helps avoid unwanted explosions but it will also smooth out even more an already existing incoming DC current. And as I said and you have ignored, with on board rectification (and this whole topic is about on board capacitors) the loco can only go one way. Please explain??? Andi Link to post Share on other sites More sharing options...
N15class Posted November 20, 2012 Share Posted November 20, 2012 ..as i said before, rectification even if you think you don't need it. If the incoming current is AC or DC, rectify it, with the polarised cap it helps avoid unwanted explosions but it will also smooth out even more an already existing incoming DC current. So what happens when you rectify rectified current? I had hear of smoothing DC current, which some electronics like. Going back to the chassis without electronics a fly wheel will smoot it out. If the chassis is not working properly why try to hide it all with electronics. I am getting the feeling engineering is a dirty work and electronic is the saviour of the world. Link to post Share on other sites More sharing options...
RMweb Gold Dagworth Posted November 20, 2012 RMweb Gold Share Posted November 20, 2012 Firstly to me this is not electronics, this is really basic stuff. Taking for granted that the chassis has already been well constructed, this is to make the locomotive act like the real thing, it's to do with the illusion of mass, to make the locomotive seem heavy. No no no, replying to the postings that point out why your scheme won't work is basic stuff. Please answer the questions, noting also that I am the only one who has actually bothered to post a suggestion of a viable circuit in the thread linked to further up this topic. Andi Link to post Share on other sites More sharing options...
RMweb Gold Dagworth Posted November 20, 2012 RMweb Gold Share Posted November 20, 2012 So the rectification/4700uf cap is a red herring as it is in the controller power supply anyway then and thus completely away from what this topic is about which is keeping the loco moving when it loses contact with the rails. Andi Link to post Share on other sites More sharing options...
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