FrankS Posted September 2, 2016 Share Posted September 2, 2016 As a low budget controller while I decide whether to go over to DCC, I've been using an Ebay bargain variable voltage regulator (see picture). Running off a 10v supply, and with the addition of a switch to reverse polarity, it works well enough for my current purposes (basically a test track where I try to sort out other Ebay bargains) - with one drawback: no short circuit/overload protection. Is there a simple way to add this? Link to post Share on other sites More sharing options...
RMweb Gold SHMD Posted September 2, 2016 RMweb Gold Share Posted September 2, 2016 A fuse. Kev. Link to post Share on other sites More sharing options...
RMweb Gold Dagworth Posted September 2, 2016 RMweb Gold Share Posted September 2, 2016 12v 21w light bulb in one of the output wires. The lamp will have no effect normally but a short will cause the lamp to light and limit the current. Andi Link to post Share on other sites More sharing options...
FrankS Posted September 2, 2016 Author Share Posted September 2, 2016 Thanks for these - The light bulb looks like the low budget kind of solution that I like! Link to post Share on other sites More sharing options...
brigo Posted September 2, 2016 Share Posted September 2, 2016 I expect the regulating chip is probably of the LM317 family which has built in overload, short circuit and thermal protection, so no additional device is required. For indication purposes a bulb as Dagworth suggests would do or add a LED (with a 1K0 resister in series) on the output of the module before the switch to indicate when it's on. Brian Link to post Share on other sites More sharing options...
RMweb Gold SHMD Posted September 2, 2016 RMweb Gold Share Posted September 2, 2016 The car light bulb is the traditional way before electronics made it cheaper* safer** and quicker***. *if built into the PSU **if built into the PSU. They cut the circuit instead of reducing the current. ***Electronics can be much quicker than waiting for a filament to warm up (including a Fuse!). You can get resettable fuses now (various ratings and properties) but even they don't "cut the circuit". You can also add a resister/LED in series across this resettable fuse to indicate a "problem" on the layout. Kev. Link to post Share on other sites More sharing options...
bertiedog Posted September 2, 2016 Share Posted September 2, 2016 I do not know what regulator chip this version uses, but all common voltage regulators are inherently short circuit proof. The circuit inside monitors the current drawn by the load, and shuts down as it goes outside limits. This assumes no further output stage has been added that is not protected. The load added by the bulb is a very good belt and braces solution. The Ebay Chinese regulator boards are very good, difficult to build one from scratch at the price. Stephen Link to post Share on other sites More sharing options...
bertiedog Posted September 2, 2016 Share Posted September 2, 2016 One thing the LM series are not good at is low voltage, they do not start upwards from zero volts to the max, and this can cause issues with sensitive coreless motors, so the extra resistance of the bulb helps, also you can add a diode in series, before the reversing switch, this drops further voltage. Both reduce the max voltage, but who uses max voltage all the time? Stephen Link to post Share on other sites More sharing options...
CourthsVeil Posted September 5, 2016 Share Posted September 5, 2016 Hi Frank, having a throttle that looks much the same as yours I suspect that it is not based on an LM317 IC. Instead it may be Thyristor driven *. If so, you should not use it for powering machines with portescap motors or small N-scale locos. Regards Armin *edit: in this case there would also be no overload protection built in. Link to post Share on other sites More sharing options...
DCB Posted September 6, 2016 Share Posted September 6, 2016 If it does regulate voltage then it is not ideal for a shunting plank but should be ideal for any layout with sharp curves and gradients. Morleys and OnTrack get over the low voltage issues with a control where 0 volts is half way from fast forward to fast reverse, with a centre "off" pot. With standard pot you can't really get a good low speed control. With 10 volts you can't get line speed from a lot of mechanisms, Bachmann Std 5 is one of the worst. Link to post Share on other sites More sharing options...
RMweb Premium BR60103 Posted September 6, 2016 RMweb Premium Share Posted September 6, 2016 The light bulb is a good visible indicator of a short as opposed to loss of contact or open circuit. Link to post Share on other sites More sharing options...
Lancs_fus Posted September 9, 2016 Share Posted September 9, 2016 For what it is worth I built a basic DC PWM controller with a 12 volt input supply because it had a fuse in it for protection and I posted a video of it here too. Link to post Share on other sites More sharing options...
bertiedog Posted September 11, 2016 Share Posted September 11, 2016 From Ebay, From China.....£3.74 inc postage , a PWM 12volt to 30volt input DC speed control board with a centre off reversing switch, and off board, plug in, speed control knob...I doubt you could assemble it for less, it appears to be MOSfets in the circuit, but the numbers are un-readable as usual. A section of the board is around an IC that appears to be the source of the PWM control circuit. No sure whether the output stage is short circuit proof. It works fine with conventional motors or large coreless motors, but is noisy with small coreless types. Shorts on 12 volts DC did not result in high currents, so protection must be in place. Note DC input, not AC input Stephen Link to post Share on other sites More sharing options...
Recommended Posts
Archived
This topic is now archived and is closed to further replies.