tag:blogger.com,1999:blog-20340207.post3117044978212884687..comments2024-03-28T22:24:18.546+00:00Comments on Phil's Workbench: BenUnknownnoreply@blogger.comBlogger2125tag:blogger.com,1999:blog-20340207.post-82870486019455581482020-06-28T05:48:15.563+00:002020-06-28T05:48:15.563+00:00If you connect a small silicon diode in a circuit ...If you connect a small silicon diode in a circuit it drops about 0.6v without generating much heat or taking up much space. Put 5 in a row and you drop 3v off a supply voltage, etc. If anyone remembers speed controllers on old model rc cars you may recall they had chunky power resistors on the speed controllers that were 2-3cm long each and almost 1cm in diameter. These got very hot in use if the car was made to go slow as the voltage drop they cause just gets turned into pure heat.<br /><br />I suspect you knew or found this out when the loco was built and so went for the small and runs-cool diode solution rather than big chunky wire wound resistors. Diodes are often a cheaper solution too.MikeBhttps://www.blogger.com/profile/06232138040515168541noreply@blogger.comtag:blogger.com,1999:blog-20340207.post-81558101799322004602020-06-26T19:08:29.448+00:002020-06-26T19:08:29.448+00:00I'm guessing that you don't have the circu...I'm guessing that you don't have the circuit for this stuff - not to worry.<br /><br />One useful thing about diodes is the way they can sometimes be set up to drop known potential differences ("voltages" to most of us).<br /><br /><br />(Throwaway thought alert.)<br /><br />You might remember one BRM project layout a few years back (Ruston Quays?), which featured a Diesel railcar going backwards and forwards, using a Gaugemaster shuttle unit. Well, if the layout had been much longer, I might have been tempted to suggest experimenting with extra track breaks near the ends - and some diodes, to more slowly increase and reduce the voltages (and thus speeds) - with all but the final track break at either end having a pair of diodes connected in inverse parallel.<br /><br />Saying that, this would have been experimental territory - quite possibly requiring either longer "run-offs", or only one bogie on the railcar to be fitted with pickups.<br /><br />If I ever get the time, I might have to do a "proof of concept" - using a piece of scrap track on a board, with a very short loco or model tram. Probably don't expect my results any time soon (if at all).Huw Griffithshttps://www.blogger.com/profile/11664683490163937931noreply@blogger.com