(01-07-2009, 10:12 PM)Peter Wrote: In 2005 your maths (with one exception, see later) and layout are spot on apart from the fact that you were trying to calculate the drop shunt using the rail voltage value for the pickup.
Thanks for noting these errors, otherwise I might of been scratching my head for hours! I have made an attempt at it - the 2005 TC question, and I didn't use any simultaneous equations ! Just basic ohms law. Have I been too simplistic?
Also I am struggling to understand how the current through the relay changes when there is no train present