Exhibition Layout Details
Everything posted by Platy787
PWM and rising DC Controller from the N Gauge Forum https://www.ngaugeforum.co.uk/SMFN/index.php?topic=50101.0 The Roger Amos centre off is Project 8: Bi-directional Controller from his book Practical Electronics for Railway Modellers.
Straight forward build with seemingly too many transistors. I built on Vero board and haven't put it in a case or given it a reversing switch yet. No meter for the speedo, just a no frills build. Tested with a OO Dapol LT 57XX and adjusted to give smooth start and running. The PWM/DC switch gives a slight change, but I only tested it on 2meters of straight track. Similarly with my N gauge test, it can be adjusted for smooth start and running. I have an N gauge terminus with a roundy, roundy extension and shunting performance is most important to me. I already have a number of great controllers that work very well at low speed (including the Roger Amos centre off, Wireless World and Cooler Crawler) so I probably won't put this one in a case. If anyone wants an alternative PCM/DC combo controller, that also works well, there is a circuit available from the NGF.
If anyone has built this or is intending to (like me) you should be aware that there are differences in the circuits published in ETI February 1986 and Model Railway Electronics 2nd Edition (the book is later published than the magazine article). IC1 7818 / 7815 IC3 2N6050/TIP147 R11 390R/390K R14 and R13 names are swapped R13 1k/10k R14 10k/1k The regulator and darlington are probably due to component availability. R11 is probably wrong in the ETI article (390R) because the op amp gain in the article is given as 4.9. Was there ever an Errata published? I'm not sure about the R13, R14 change. I will build to the schematic in the book, but with a BD682 darlington.
I have a Gaugemaster Combi (which may operate differently to your D100) which has a red led as Track indicator. It increases in brightness from off to bright as the control is moved from 0 to 100. It comes on at about 10 on the dial when it is not connected to anything. When I short circuit the output of the controller the red led still comes on, but at 20 rather than 10. In a Combi the Track indicator is not directly across the output terminals, so it will still glow, at a higher dial setting than normal, even when there is a short circuit on the output, but the Track indicator is not an indicator of a short circuit. If you put a 12V 18W or 12V 10W automotive globe in series with one of the ac supply lines, or one of the track feeds, you will get a very obvious indication (and current limit) of any short circuit. Mark
I have a Combi and it is a simple full wave controller with no active feedback. For such a simple controller it works well, although for some mechanisms it may have a large "dead band". That is, you have to turn the knob up to 30 or 40 before anything moves. I have recently built 12 DIY DC controllers of various designs and "tested" them to see how my N gauge motors respond. These are a 5pole (Graham Farish GP tank) , a Dapol 45XX and a Kato tram with coreless motor. The Dapol and particularly the coreless motor were unhappy with any PWM controller, although most of these had feedback. Slow speed, smooth, jerk free performance was most important for me, so the "Cooler Crawler" design was my best because it worked nicely with all my 3 motor types Anyway, have a look at the 852B Varipulse. It is available built, kit or buy parts and make it all yourself (I did this on vero board). http://www3.sympatico.ca/kstapleton3/851.HTM I've think I've seen another recommendation for the 852B on this forum. Cheers, Mark
Hi Jim, All good. I was being a bit tongue in cheek. I'm sure we are all here to share and learn, and I think this is a really interesting topic and you have it well supported with the video. Like I said earlier, I've been a long time follower of your posts. Cheers, Mark
Hello Jim. Thank you for your rude post. I'm glad that we can all spell engineer. My aim is to share my experience with DIY DC controllers. I thought this was your aim as well. As I said in my PM to you, I model N gauge, so I could expect different outcomes from the different controllers from what you experienced. Please, stay safe, stay well.
Hi Jim, Brian had 2 circuits, so I made the NPN version of the 2mm Scale Association controller that Brian published in the 2mm Scale Association magazine. I've sent you a PM with the other 8 controller articles/circuits. For sheer simplicity and excellent operation the Roger Amos Project 7 "Sensitive Closed Loop controller" takes some beating. Although it has 3 transistors in the original circuit, I used a BD682 darlington, to make a 2 transistor controller. Mark
Hi Jim, I've built both these controllers, as well as 8 other different ones. I'm still deciding which are my favourites! I think that your UF is still firing the SCR at zero speed and I would suggest you reduce the value of the 22k. In the one I made I put another 22k in parallel with the existing 22k to give 11k. The original apparently had a 10k trimpot. I have N gauge models, mainly from the 1990s. Also, you mentioned the motors you use start and run at low current. That's ok, but these 2 controllers were designed for the motors of their time and may need tweaking to give best performance with low current motors, such as you are using. Thank you for the comparison video. I only recently joined RMweb, but have been a lurker for a while and have read your older controller posts. Thanks, Mark