Thank You, but in about 7 days I will go to the next electronics store (30km) and I hope I will find them. I am waiting at the end of the month for the base structure (2.9 x 1.45m) for the layout, made by my local "carpenter" ; I can't build such big structures alone, planks are full length and there will be only one "big" plywood plate for the whole structure ; for my former layout I had my father helping. And in the present time I can't do anything else than experimenting on the kitchen's table (Fortunately there is no wife ... ). And then I am waiting for my rolling stock (about 4 weeks) and some tracks to build a testing oval, and test the PWM and distance for deceleration : this will define the place for track-insulators near the stations, a detector in the negative power line will trigger the decelerating and a second one on a section in the stations themselves the power off, so I can run my RDC's ; as You see the problem with diodes is not urgent !
Power supply for turnouts : the problem is that I don't know how many amperes I will need for my turnouts ... I wanna use the Kato system. There will be a maximum of 4 turnouts connected to the same switch ( = relay), and flipping together. Or should I use a double switch, 2 turnouts connected so the capacitor goes to Vcc, while the other 2 are "inverted" so that the capacitor goes to Gnd (I hope my explanations can be understood) : the current would be the same for both positions but divided by 2 ? I used a 0.2 Ohm shunt in series with one coil, but I got absolutely HORRIFIC values on my scope : +/- 1V peaks, and because the shunt is a pure resistive device, one can say that there are transients of 5A ... in both directions (I didn't yet replace the 1N4007 but I think this will not change anything) ! As I can remember from my time at school, it's called "damped oscillations". As I saw this I gave up the idea of controlling a turnout with 1/4 L293D, I think the driver would not survive to the transients. I planned to use a readymade 5A switching power supply but I think the transients will make trouble : activation of a breaker (if present) or damage(s) at the supply's electronics ! I think they are intended for use with "conventional" appliances, not inductive loads. Or are they protected against such issues ? It is not possible to get the information : "buy and don't grumble if You have problems ... " Or does anybody know which system Kato uses ? I saw a "KM-1" unit, 12v and 2A but I don't know if it's a conventional or switching power supply. All the way 12v (or even 15v on some descriptions) would be too much, but I only saw "regulated and filtered" ... I think it's "analog" technology. I thought of simply add a BIG filtering capacitor (with a limiting resistor to charge it, and I could decrease the "amperes" available at the supply), I know it should provide charge to several capacitors, so for 4x1500uF I am thinking about 10000 to 22000uF, because charge transfer quickly (exponentially) reduces the voltage available. But in this case recharging current will recharge (slowly) the capacitors at the turnouts, too ... and flow through the coils until the voltage reaches the nominal value. Not good ... Perhaps the simplest way would be a transformer, 6v and 1A per turnout switched at once, with a bridge rectifier or a simple P600 diode (6A) and no filtering at all ?
Last Edit: Apr 24, 2017 0:16:08 GMT -5 by alberich
Thank You for the answer, but I only wanna know what kind of power supply would reach to "fire" 4 turnouts simultaneously, without taking damage itself ... So I could use a 4PDT relay, one switch for the 4 turnouts (the contacts are for 250V 7A and the peak is very short, the freewheel diodes would help, too, to avoid sparks) and the 3 remaining for power to the tracks (with my detection system for stopping the MU Budds, each track in the station has 4 "poles", there is a supplementary insulator in each rail, so 3 "poles" must be switched ! ). I didn't want to protect anything ... only the power supply itself, so I thought that perhaps a basic (transformer + rectifier) 6V 4A supply could reach. KISS : Keep It Simple and Stupid !
Last Edit: Apr 24, 2017 14:01:38 GMT -5 by alberich
One though is how Rokuhan trips the turnouts. First their throttles can only supply 1A maximum. They consistently power two turnouts and generally will do 4. However their turnout switch discharges a 1000uFd capacitor through 1K resistor. So you really only need to supply 1mA to the turnout.
I'll check the switch one more time, but I've twice checked the PCB as I was surprised that the resistor is in the output. The input side is just two polarity steering diodes for the capacitors. And yeah, I should never do math without a calculator. I have a schematic of the C002 switch, but at the moment I'm not confident enough to publish it.
The Kato system (which is the simplest I have seen) works fine with 7.5v and a 1500uF capacitor for one turnout. My lab power supply is limited to 3 Amps. So I think that I will : 1) Build the Kato system as drawn by BAZman, without Led's but with four 1500uF capacitors, and increase the number of connected turnouts from 1 to 4 : I already bought 2 Rokuhan "Y cables" (for the 4 connectors), it's easier for the turnouts during test on the workbench ; so I can see if 3 Amps are enough ; and if not, I can use a simple proportionnality calculation ... Sometimes trial and error is the best method. On the final layout the turnouts will be "hard wired" ( = soldered). 2) Then I will buy a 6v transformer with enough VA and a margin, according to 1) ... And I will add a bridge "full" rectifier and no filtering. 3) But, as I have already seen, voltage peak goes up to 10~11v (minus 1.2v due to the loss in the diodes). So I will try again with only one turnout if I can't reduce the capacitor's value. 4) And finally I will build the new system with 4 capacitors and turnouts, and then hope it will work.
Last Edit: Apr 26, 2017 1:03:06 GMT -5 by alberich
The principle of the Kato system (look at it on page #1, post by Bazman) is to both discharge AND charge the capacitor through the coil, so there is no delay to allow the capacitor to recharge. I must admit that this system is VERY simple and ingenious ... and certainly more than the original Rokuhan system ; it could even be built with a bridge of two transistors ... but then there is no supplementary power switching to the tracks. Due to the topology of my layout I could even use power routing ; too long to explain in detail : simply said, there are 2 stations with the tracks in "parallel", two turnouts (among the 4) would switch one rail and the two others the second rail. But I wonder if power routing will STAY reliable ; on the other side most people who experienced issues used DCC with much higher currents than my "little" DC for the two Budd's. So, because I already bought 2 L293D's, which I don't need for other purpose, I will "sacrifice" one and try to adapt the Kato system with one driver per turnout ; if the system survives to about 25~40 back and forth switching, I think it could work ; otherwise I will "meet" the problem very quickly when the IC will go to "paradise for circuits" !
Last Edit: Apr 26, 2017 12:48:38 GMT -5 by alberich
As I wrote, sometimes the best method is "trial and error" ; I tried first with 6v (regulated-filtered), increasing the capacitor from 470uF (I bought a series of standardized values), the turnout didn't move, it needed at least 2200uF, but I was not satisfied so I tried again with 7.5v until I reached the minimum value for a "clean" operation, I found it was 1500uF ... and I will do it the same way with my final couple transformer-rectifier !
Last Edit: Apr 26, 2017 15:18:35 GMT -5 by alberich
Thank You for Your very useful tips, and for the time You spent to look at the datasheets, too ... For one moment I was looking at the L295, but I think I will finally use relays, they can switch the power to the tracks too, and so there is no trouble at all with power routing ... And for the locos : a transistor, controlled in PWM, and to reverse the power a relay (with my system I will have to use a 4PDT version) ; it's easier than the L295, too ... The next step is to buy now 3 additional turnouts, for the second testing phase (my layout will use 6 or 8, depending upon the number of freight tracks, but as I wrote they will flip pairwise or by one group of 4) ; I will post the power for the transformer I need, it could be interesting for somebody, and perhaps the new optimal value for capacitors, if different.
Last Edit: Apr 26, 2017 22:17:59 GMT -5 by alberich
This test is useless, because I will use the MINIMUM value for the capacitor which gives me a good function (so the energy through the coil is the minimum possible) and approximately the same voltage ; it MUST work, otherwise I should say that the turnout is defective. I made with my present configuration a test with about 10 times back and forth at 1 s intervals, and nothing happened, the turnout is still working ; so I think that with flips separated with at least 10 to 15 s on the final layout (and sometimes even 90 s), it won't work worse !
It should not be insulting, only I don't see any other SIMPLE way to solve the problem, see the different schematics I published before BAZman published the Kato switch. And all schematics use the discharge (and charge, in this case), so the problem is the same with every system, it's only a question of voltage and value of the capacitor, the total amount of energy through the coil remains the same for the different configurations. Neither I believe that an additional resistor in series with the coil could be used, it could only decrease the reliabilty ; I would rather decrease the voltage and/or capacity, but I made my tests with increasing voltage and capacity until it worked ... I remember that a not properly set turnout can cause a short circuit in the traction current, and so THIS problem rises again. So, if despite of the care I take not to destroy the turnout, it nevertheless overheats and "burns", then I might conclude that the turnout does not work properly and that the problem has no reliable solution ... with or without measuring the temperature ! Or do You think I should know it and then give up building my whole layout ? I hope THIS is not what You are trying to say. Fortunately this seems not to happen, as I wrote. And I hope it will stay so for a long time. If the turnout is re-activated in practical use only after a minimum 15 s and it survived my fast switching tests, I think I can rely on it in real use with a minimum of confidence. So long ...
Last Edit: Apr 27, 2017 16:02:56 GMT -5 by alberich
Rokuhan has already done all of this experimentation. I would STRONGLY suggest that you use their products to control their products. I'm tired of seeing, now 3 pages, of re-inventing the wheel!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
Tired ? Why ? This topic was created especially for this problem (see the first post) and is "closed" in itself ... Some people feel concerned, it's OK ; some others don't, it's OK too ! This subject does not spread over the other topics. And when my system will work (I hope time will come) I will publish the parameters I used, for the few interested people, I am aware of it. Unfortunately Rokuhan turnout controllers have no computer interface, it would raise the price, with only a few users ; or, even worse, they would use a proprietary or USB interface. Rokuhan products are sold as "plug and play", even for temporary "table top" or "carpet" layouts, with adapters for solderless use. The only solution would be to open them and modify, replacing the switch with a relay ... THAT's the problem ! Or use readymade DCC based solutions ? I want to build my layout myself, with plywood and "Roofmate", not a readymade base like Noch's ; this is MY choice, I don't criticize neither the users of readymade bases (it's their choice, too), nor Noch (especially since they import Rokuhan in Europe ! ). And so I wanna build my own electronics, which I can service later (See the topic about "DCC killing the hobby" to see that I am not alone with this problem). It's hard to say, but model railroading electronics ("pushed" by a few manufacturers) are becoming less and less a domain for individual creativity, and more a domain where readymade solutions are bought for a lot of bucks. This should not be insulting, but You should leave everyone having his own choice. To take a comparison : I used a Commodore 64 to control my former layout in the 80's, with a Basic program (further compiled) that I wrote myself, it had even some multitasking features. But nowadays I couldn't use a Windows based (or, worse, a Macintosh) computer to do the same things, without using a readymade sequencer program, or it would be very hard : try to program an infinite loop in a high level language for a control program, I experienced it without success, it leads to a program crash ; to say it immediately, I don't wanna start a topic about Linux. Former systems were much more "open" and let the user use his own creativity ; nowadays the only solution seems more and more to solve all problems with ... the credit card (or other ways of payment).
Last Edit: Apr 28, 2017 14:49:33 GMT -5 by alberich
Current for Rokuhan turnouts : My main problem was, how much current I would need with 7.5V and the Kato schematics (thank You again, BAZman), and a capacitor of 1500uF per turnout.
On my layout, 4 turnouts maximum will flip simultaneously (two stations, with one straight and one deviant track). So one solution would be to split them into 2 groups, 2 capacitors being connected to Vcc while the two others go to Gnd (with "reversed" turnouts) ; this would need a DPDT switch or 2 contacts on a relay. Unfortunately I will have only 1 contact available (the 3 remaining switch the tracks, yes, with my system I need 3 switches) ; and a 4PDT relay is the maximum available for 6V (6PDT exist, only for 12V and very expensive, and there will be no 12V available). I don't wanna use 2 relays, DPDT and 4PDT in "parallel" ; so my 4 turnouts will go simultaneously to Vcc ...
I built the Kato schematics 4 times and connected them to the same SPDT switch, and plugged the turnouts in, increasing the number. With two turnouts, my power supply (3A lab supply) had no problem and the turnouts flipped reliably. But with 3 turnouts, I saw briefly the "tilt" (short-circuit, overload ... ) when I switched to Vcc. So for 4 turnouts I will install a 7.5V 6A supply (this exists, made by MeanWell). And all the way the contacts on the relay are for 7A (250V).
Last Edit: Jul 8, 2017 17:38:56 GMT -5 by alberich
I don't really want to get back into this discussion, but consider that I can switch 4 turnouts with the Rokuhan controller (specified at <1A). Even if I am wrong, switching one turnout is still <1A. What you're seeing is the current inrush charging the capacitors. Try connecting 6000uF directly across your power supply and see what happens. You can cut you current requirements substantially by adding a current limiting resistor between the supply and the capacitor. It will mean that it will take a few seconds to recharge, but it will reduce your power needs.