blocking diodes

[jim currie]

Hi this post is aimed at ezy days you but any suggestions are welcome would D1 & D2 be a effective way to block the circuit or would i be better off putting blocking diode on the negitive side of the transistors. you will have to excuse the crappy drawing but can't get my circuit making program to work

 

[ezdays]

Jim,

You should be able to put a single diode either in the negative rail or in the positive rail. I'm not too sure why you need that one resistor coming off the positive rail though. Just size your other resistors for the full rail voltage and you should be OK. One diode should keep the circuit protected when you reverse the rail polarity. You are aware that your oscillator will only work with the polarity as you show it. If you want it to work with the polarity in either direction, I can tell you how to do that.

 

[jim currie]

thanks Don will try increasing the value of the resistor between the led and collector of transistor and put a diode in place of resistor on the positive rail. i only want this to work in this mode.want leds off when loco is backing up.