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Posts posted by Platy787

  1. 13 hours ago, RobinofLoxley said:

     I introduced the feeds on the second board one by one and found a single straight piece of track, isolated from everything else by IRJ's, that caused the short to appear. I say short, the Guagemaster D100 power indicator remains red when the power dial is turned up, either direction, which I take to be a short.

    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.



  2. 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).



    I've think I've seen another recommendation for the 852B on this forum.




  3. 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.



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  4. 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.




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