Electrical static shocks

[gsalmon4]

Hi there

Please excuse as I am a complete novice when it comes to electrics.

What causes static shocks? The reason I ask is that we have diagnostics tools that configure cars and sometimes when I power one up via a power adapter (not plugged into a car at this point), sometimes I get an electrical shock when I first touch it.

If I was to wear a heal static strap or a wrist earth strap grounded to the workbench would this shock not happen?

Can some one please explain grounding\earthing. Does evereythin electrical have to be grounded? Do we have to be grounded to stop shocks etc etc..?

Many thanks to all that respond

 

[dknguyen]

When two different materials move against each other (rubbing or simply separating) one material is more apt to hold onto electrons and the other is more apt to lose them. This causes each material to build up a charge of opposite polarity.

If one of these materials touches something else (either a different material or something of the same material), if it has a different amount of charge, the charge will try and equalize by producing a spark.

For no shock to happen when two things touch they need to have the same charge. "Grounding" tries to make everything the same voltage (things with a charge also tend to leak away this charge over time until they reach "ground" which is defined by the environment around it and is for the most part, the same). So you AND the thing have to be connected to each other (not necessarily the ground though it's a convenient sink/source for extra charge).

What part of the tool are you shocking? Circuits tend to be in cases so they can be shocked accidentally without destroying them.

 

[gsalmon4]

Thanks for that.

What do you mean by "apt"?

Its the actuall case that I get a shock off, inside are two circuit boards joined together by connections, ones a processor board and the other a pcmcia controller board. Should these circuit boards be totally isolated to the case? or should they be earthed to the case? There is an earht strip that touches the case on one of the externall connectors that we plug the cable into, the earth strip is just inside the case. Im sure this acts as a earth for the earthing circuitary of the two PCB boards.

What is earthing? Does it complete the circuit in a way that the current flowing needs to go somewhere\terminated otherwise no voltage current flows!!

 

[Space Varmint]

That's not static. What you are getting hit with is the potential from the different boards. You should connect the grounds together from both boards like they are inside the car. All ground goes to the body of the car.

 

[dknguyen]

Thanks for that.

What do you mean by "apt"?

More apt = more likely = more able

Earth is sometimes interchanged with grounding. "Earthing" means connecting to the GROUND you are standing on. While "grounding" is connecting to a common reference which may or may not be the earth.

Earth, ground, and neutral are three words that are thrown around carelessly in electrical engineering but they all mean very specific things. Earth is a type of ground, and ground is not always neutral.