Static electricity from vacuuming up spilled kitty litter

[SeanB]

With shopping trolleys Spar solved that by putting a small 4 link section of chain on the rear wheel, letting the one end drag on the ground, and the bolt for the fixed rear wheel holding the chain. Makro did that as well, seeing as the AC they use is actually effective enough to get the humidity in the building down below 30%, which is pretty impressive considering that it is currently 70%, and 30C, and Makro wants it to be 20C in the store. I used to look for the trolleys with the straps in winter, or just grab a regular one, grab the trolley wipe and clean the handle, and thus leave a film of detergent on it, and then while pushing the trolley bounce off every single steel upright I passed. Often with a loud crack as the spark discharged. New trolleys all have the chains, though they still are no wheel steer at times, or drive like a Taxi.

[Marco]

Clay is a cation exchange medium, so that might play a role as well.

Maybe clay being naturally negative charged is forming a complex with small particles of dust to hold the positive charge and the vacuum cleaning is separating them and expelling the positively charged dust to form a large net negative charge?

[NiHaoMike]

Some shopping centers have horrible static around them. I don't know if it's the floors or what but, whenever I'm in one of those I insist on being the one to push the cart. That way I can bump a metal shelf to discharge every couple of aisles.

On a very related note, a friend of mine, then a medical student, told a story about the time she was working in a research lab of a hospital. At one point, she had to take the elevator, where another worker was transporting a dead body on a cart. All of a sudden, there was the snap of static electricity discharging and she felt "someone" reach out and touch her, which was the dead body that came to life for a split second thanks to ESD. It was not only her scariest moment in life but also the most embarrassing since her scream brought over a crowd to see what all the commotion was about, where they saw that she literally just had the piss scared out of her.

[james_s]

That's hilarious, I remember discovering in elementary school that I could make the legs of a dead frog kick by using a small transformer and touching the wires repeatedly to a 6V battery.

On a related note, the other day I was using a belt polisher at my friend's machine shop while standing on a rubber mat and whenever I touched the body of the machine it would shock the crap out of me. I held the bar I was polishing with the tip about an inch from the machine there was a continuous crackle of sparks between them. It made quite an effective Van de Graff generator.

[jmelson]

That sounds like the triboelectric effect to me. Which combinations of materials charge effectively can be fairly unpredictable.

https://en.wikipedia.org/wiki/Triboelectric_effect

A great one is CO2 fire extinguishers!  They have a plastic "funnel" to direct the CO2, which forms snow as the liquid from the bottle expands.  It will generate sparks strong enough to cause people to fall down in some cases - like a taser!  They had to change the design of the extinguisher to make the nozzle conductive, so that charge didn't build up.  The concern was the spark could re-ignite a fire after you had put it out - and expended the extinguisher.

Jon

[GeoffreyF]

You can test this by discharging the static with a piece of metal such as a wedding ring, paper clip or whatever.

But in that case the energy would be spread over a much larger area, so one would expect it to hurt less.

Use as little a piece of metal as you like.  A pin if you like.  There is no shock from the static electric conditions we are discussing here.   

[Zero999]

You can test this by discharging the static with a piece of metal such as a wedding ring, paper clip or whatever.

But in that case the energy would be spread over a much larger area, so one would expect it to hurt less.

Use as little a piece of metal as you like.  A pin if you like.  There is no shock from the static electric conditions we are discussing here.

I'm not convinced. I know a get a shock from a piezo igniter if I directly touch the wire. I'll have to give it a go with static and a piece of insulated cable. The problem is at the moment the weather is mild and damp, so static charges don't hang around for long. Hopefully it'll get colder and dryer next month.

[james_s]

If I hold one hand on the belt polisher I don't get a shock. If I hold one hand on a Van de Graff generator and the other on a grounded object I don't get a shock. Generally static sources produce very little current, you only get a shock if a charge is able to build up.

[In Vacuo Veritas]

What do you feed your cat? Batteries?

[Terry01]

I have 2 cats.

A mostly black 1 with a couple of white patches and 4 white feet, and a mostly white 1 with some small black patches and a black tail.
I sometimes get small static shocks from the mostly black 1 when I pet him but only very occasionally get the same kinda shock from the mostly white 1. The white 1 is very soft to pet. This may be me gibbering but it seems to mostly happen when the 2 of us are standing up. If say  i'm sitting on the sofa and he jumps up on me to get petted I rarely if ever get the same shock.
A wee bit off topic I know, but maybe someone has the same experience or can tell me why it seems to only happen on the black 1 when we are standing up?

[james_s]

I have several cats and in the winter when it's dry I can pet them and see sparks crackling all over. If I stroke a small fluorescent tube across the cat it will flicker and flash.

[Terry01]

I have several cats and in the winter when it's dry I can pet them and see sparks crackling all over. If I stroke a small fluorescent tube across the cat it will flicker and flash.

Cool 

[GeoffreyF]

You can test this by discharging the static with a piece of metal such as a wedding ring, paper clip or whatever.

But in that case the energy would be spread over a much larger area, so one would expect it to hurt less.

Use as little a piece of metal as you like.  A pin if you like.  There is no shock from the static electric conditions we are discussing here.

I'm not convinced. I know a get a shock from a piezo igniter if I directly touch the wire. I'll have to give it a go with static and a piece of insulated cable. The problem is at the moment the weather is mild and damp, so static charges don't hang around for long. Hopefully it'll get colder and dryer next month.

Not my job to convince you especially when what I explained is black letter physics.  Read a book.

[joeqsmith]

Generally static sources produce very little current, you only get a shock if a charge is able to build up.

I am not sure what "very little" means but certainly several Amps is possible.   I measured around 5A peak with a gas grill ignitor.   The IEC standards call for even higher currents. 

https://www.silabs.com/documents/public/application-notes/AN895.pdf

[james_s]

I think a gas grill igniter is a rather extreme case. The shocks you get from ordinary static are as strong as they are because the charge builds up on your body and discharges suddenly when you touch something. If you hold onto that object and shuffle your feet or whatever was generating the static, no charge will build up and you won't get a shock.

[joeqsmith]

I think a gas grill igniter is a rather extreme case. The shocks you get from ordinary static are as strong as they are because the charge builds up on your body and discharges suddenly when you touch something. If you hold onto that object and shuffle your feet or whatever was generating the static, no charge will build up and you won't get a shock.

I agree that the grill ignitor I use is rather an extreme case in that it has a very weak spark.  The gun I designed to replace it is in the order of 15 Amps peak.   By ordinary static, I assume you mean not simulating it using electronics.   I can tell you that the my personal feeling of the ignitor is that the pain I get when discharging it into my finger is much lower than what I feel when I touch the door knob after walking on the carpet during the dry winter months.   

[IanB]

I think the discussion about static sources relates to peak current vs average current. For example, if you continuously discharged the grill igniter into a suitable RC filter and measured the average discharge current over time, what would it be? Microamps?

[joeqsmith]

We are talking about an event that is measured in 100ns or so.  The IEC standards show the waveforms and measure in peak.  They go into detail how the measurements are made as well.    If you wanted to consider the average current for the duration of the event, it would be easy enough to calculate.   

Just to be clear, obviously as we increase the period that we use for a single event, the average will approach zero.  It just doesn't make a lot of sense to me why one would consider what happens after the event.   The standards use peak currents/voltages and define the decay.  If you look at the current waveform, you can see it is not a nice shape.  Thinking in terms of average current alone would tell you nothing about that initial 800ps. 

Scope shot showing the output waveform from my gun during development (10A peak).  The overlaid waveforms are several events zoomed in. 

[Magicshark]

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[joeqsmith]

I had not seen the coins in a plastic bag before.  Seems the grill starter is the most common source those of us on a budget use.

https://www.edn.com/an-emc-troubleshooting-kit-part-2-esd-immunity/

I know it's and old thread about kitty litter......  A few other links that may be of interest:

https://electronics.stackexchange.com/questions/218024/diy-esd-generator-esd-gun
https://www.researchgate.net/post/Can_anyone_recommend_designs_for_a_high_voltage_switch_for_ESD_test