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Everything posted by Junctionmad

  1. remember LEDs are designed to be supplied by a constant current , not a constant voltage , hence any power source thats not current limited runs the risk of destroying the leds . Hence with a voltage source like a traffo , resistors are always needed
  2. As mentioned , this “ may “ work , but often doesn’t
  3. The L298 is a very dated product . It does not have any instrinic current control . It has over temp protection but only on a short term basis , it provides a sense current oupu5 , but that in itself isn’t current control there are far better driver chips these days
  4. I don’t think he’s the only “ bitter “ person around , perhaps we could move on from this aspect.
  5. Depending on the design of the controller , it is possible to “ speed match “ both dc controllers , in theory , allowing a loco to cross from one circuit to another , this assumes that the polarity of both sections is the same , ie a consistent wiring strategy is followed. However it is always less then satisfactory and there is always a point where the loco is potential paralleling both controllers together and some controllers cant handle this this results in speed changes , jumps , and stops etc switching the track sections to the controller, known as DC cab control, is about the only practical way to handle multi controller implementations , the idea being that only one controller is activated for all the track route/sections need for the train to complete its journey . The situation can become complex , and can be further complicated should you want to incorporate interlocking to prevent users from assigning a track section to more then one controller at a time.
  6. As I mentioned elsewhere here’s my circuit , positioned close to the servo personally , and testing the configuration there are two benefits (a) the major benefit is the reduction of input resistance of the servo control line. This to me is the single biggest issue that is resolved (b) the introduction of a floating servo pwr , as far as the servo is concerned , ie no local GND , this means we get some additional noise immunity from induced noise shifting gnd or 5V or the signal line to the opto. the other area to take care off is the configuration of the drive signal , or a pull down resistor is useful for this ( for positive logic ) , this handles the issue of inadvertent transitions on the io line
  7. Pete Waterman’s extremely large O gauge layout is controlled exclusively by MERG CBUS
  8. Yes the nightmare that is SEEP point motors.
  9. By the way my latest panel is 3mm dibond in white this is then drilled for 3mm flat top leds that lie flush with the surface Using a copy mimic as a drilling template the mimic is printed on transparent acrylic vinyl and glued to the dibond hence no holes in the vinyl means easy cleaning , no rough edges and the precision of the holes doesn’t have to be exactly precise Dave
  10. heres my actual circuit R1 = 680R , R2 = 1K , R3 suits LED ( this is to support a signal lamp Led)
  11. The opto wired to active pull up with a resistor for pull down , is the best option as the default unpowered position will be low input place the opto within the standard servo cable distance noise on the 5V is balanced by the same noise on the OV , so my recommendation is to feed servo power And GND , from the servo control board, and hence in effect implement a balanced line. The alternative is bussing around gnd which isn’t as good. in my experience , the solution is excellent
  12. My merg boards do. ? In that I have a miniature SMD board with the opto close to the servo and a live driver board with the merg servo software my own view would be that the opto at the servo exposes a low ( lower ) input resistance and this resolves the noise immunity issue the common mode benefit is rather circumspect since many people will power the servos from the servo board so for the purposes of the servo , it’s a balanced line anyway.
  13. I did a big minic using 3mm dibond and simply had the plan printed locally on outdoor vinyl i then drilled 3mm as required about 200 holes in all the drill leaves the vinyl slightly ragged but not bad Worked well
  14. Given the merg modules are fine, I suspect the issue was the people involved may not have understood the issues around deploying servos
  15. Yes the opto is positioned right at the servo. the whole idea is to decrease the input resistance of the servo control line , that solves almost all issues I’ve tried experiments with power sequencing and I’m not convinced it adds anything to resolving the issue the main point seems to be to allow the control signal to be correctly established before the servo is powered up. But I’ve found appropriate pull up or down resistors achieve that and power sequencing adds nothing as a MERG member I can say their various servo boards are as good if not better then anything else on the market
  16. Actually each metal film resistor is laser trimmed to the required resistance and tolerance
  17. What I meant about set is being a component of a solution is that on their own they are not a complete solution to point control , unlike say a Colbalt point motor using servos requires electronic drive control , you then need to add frog switching either electronically , by relay or physical micro switches you also need to understand the issue around power sequencing and long live drivers to ensure that they don’t twitch etc. As I said , they are a “ component “ not a solution since 1000s are in use happily switching points and signals, including many merg members layouts , I suggest the issues you had may be a function of your setup rather then any fundamental issue with deploying servos
  18. Andy , I’ve used the opto method to drive the servo line , no twitches I’ve about 30 driving signals on a big O gauge so plenty of dcc current floating about servos are great , but they are a component of the solution not a complete solution , those that run into problems don’t seem to appreciate that
  19. The simplest is to buy a tortoise or cobalt point motor , which is ready to go , has the switches built in and is easy to install, no further electronics required
  20. Err , normally if you switch the frog , you would also bond the switch rails to their respective stock rails , then there is no issues switching the frog to any polarity at any time and no shorts occur
  21. To suggest a £10-£20 DMM is a luxury for an hobby powered by low voltage electricity is rather far fetched
  22. As a person that started with copper clad and now uses ply sleepers and plastic chairs , I’d say the 2nd method is far far better , you get correct rail height , wooden sleepers , and the ease of assembly of functional plastic chairs. Copper clad is now much more expensive then it used to be. I create my own ply sleepers from AA grade 4 sheets of ply and saw them up on a little proxxon table saw. don’t bother with pre made crossings and switch blades , make your own , it’s very easy once you’ve have made one or two. 00-SF , ie 1mm flangeways and 16.2 track gauge is a fabulous compromise for points. I flare back out to 16.5 and use conventional commercial track for straights. ive used peco bull head , c&L, Smp , and dcc Concepts. I won’t use stainless track ever again , thank you. the reality is that any of them used as straight track , ballasted , weathered etc , looks good. use commercial straight track , hand build the points , best compromise and remember while we are attempting to model a railway , it’s all an illusion , and a good illusion isn’t about precise numerical relationships.
  23. We built all our large O gauge layout baseboards , 20 baseboards , some as big as 5’ x 2’6” from 6mm high quality moisture resistant Scandinavian or Russian birch ply. We use 6mm 120mm deep sides and Centre longitudinals as well as diagonals , no screws or nails , hot glued initially , then PVA and fiberglass tape to all joins. Extremely rigid and light for their size end cheeks carrying pattern maker dowels are 12mm birch ply three years later and several exhibitions , it’s bomb proof , we tested each board by placing a 9 stone man sitting in the middle of the baseboard supported on its outer end , maximum deflection was 2mm All major dimensions were CNC saw cut. don’t use the cheap “ dark “ far eastern or Asian ply , it’s junk , birch ply is nearly white. and definitely don’t use MDF ( except in a enclosed stove) it takes track pins and screws very nicely ps. We investigated fully laser cut , but we wanted the ability to move the cross bracing based on the track diagram to ensure point motors could be fitted , so we have asymmetric box sections underneath busy track work boards
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