Going Partially Back To DCC

[faithie999]

On a more useful note... modules do employ CMOS technology so they are sensitive to static discharge. Don't handle a bare board without first properly grounding yourself. Standard CMOS rules apply to an unwrapped module. Touch grounded equipment or grounded plate immediately before touching any of the individual parts or the printed circuit board.

Alan--what is the purpose of the resistor?

thanks

ken

[Alan]

Safety. Prevents possible spark when metal plate is touched. Also provides protection should a voltage source accidentally touch the person or plate.

Imagine your elbow is touching a plate with no resistor when your hand touches an improperly grounded cabinet of electrified equipment. The water in your arm is of sufficiently low resistance that it allows full mains current to flow from the equipment case through your hand through your arm through your elbow through the plate to the grounded outlet. You get electrocuted.

Adding the high value resistor to the case/hand/arm/elbow/plate/outlet circuit limits the current to a fraction of a milliamp. You feel nothing.

It is important to dissipate static electricity by being grounded but at the same time you don't want the ground path to be able to carry lethal amounts of current.

[faithie999]

thanks for the explanation!

ken

[darryl.trains]

Hmmmm   Maybe this would help as I grab the metal door frame and open the door. I get a zap but strangely only during the winter? Wife gets the same thing or if we walk and touch each other. No carpet, just tile flooring. Weird eh? TOF