Print

Please login or register.
1 Hour 1 Day 1 Week 1 Month Forever
Login with username, password and session length

[Duane Sanders]

Our new building is about 6 years old and each winter we have had a loud static pop ignite when everyone stands for prayer. It sounds like a handgun being shot, so it is very scary.  It doesnt happen until a few people stand at the same time to create the static buildup.  This is only a winter time event because the air is very dry, which is great for static electricity. 
Our auditorium is built like a bowl with bleacher style seating, so we have this sound booth built in the center of the auditorium with standard wood and sheetrock platform.  There are several rows of pews in front of the sound booth.  The last row is right in front of the sound booth wall.  It actually touches it.  We have narrowed this static pop to this row of chairs so we have removed this row to stop the static pop.  I have not been involved the whole time so i will tell what i know.  Someone installed an extra ground rod under the sound booth and attached it to some copper wire that is ran along the carpet behind the chairs to possibly help remove any static charge coming from the chairs.  dont think that is working, but they tried.
All AV systems are grounded properly that i can tell.
Anyone have any ideas or questions to help understand (and eliminate) this issue? 

Thanks
Duane

[Stephen Swaffer]

I assume this is a carpeted area?  The problem is, the static charge is building up on the people or possibly the chairs as rubber shoe soles rub on the carpet.  Grounding the carpet can't help.

Two possibilites-everyiine in the row wears a static grounding wrist strap similar to what techs wear when workiing with static sensitive companents-of course each wrist strap has to be grounded.  This would be effective, but not practical.

More practical would be to treat the carpet with something along the lines of Static Guard-just quickly spray the carpet down before a service. 

[Robert Lofgren]

What mixer? Digital stagebox?

[Jonathan Johnson]

The idea of a ground plane for the chairs isn't a bad though, but it wasn't executed in the best manner possible.

First off, it would work better if, rather than a wire along the carpet, it was a grid (screen) or plate (copper foil) under the carpet in the affected area. Then, the carpet needs to be treated to improve its conductivity. Static guard spray (as mentioned by Mr. Swaffer) is basically fabric softener in a spray bottle. Fabric softener works by hydrating the fibers so they are more conductive, and lubricating the fibers so they are less likely to build a charge as they rub against each other. You may need to shampoo the carpet more frequently as the static guard can build up and trap dirt. (If you think about it, synthetic carpet fibers are basically plastic, and plastic is an insulator or dielectric. As you move across the carpet, your shoes strip electrons from the dielectric -- or maybe the electrons go the other way -- so you end up with an imbalance, or charge, between yourself and other objects.)

Secondly, this grounding needs to be bonded to the grounding system of the building. That helps to ensure that the voltage potential of that grounded area is the same as the voltage potential of the grounding of the sound system.

On the other hand, just using the static spray might be enough and no complicated grounding system would be necessary.

You might also recommend that your church have their HVAC contractor install equipment to help maintain the humidity in the building. Ideally, indoor humidity should be between 40% and 50% RH. Besides reducing static charging, proper humidity also prevents warping and cracking of wood furnishings and trim. If you have a pipe organ or piano, maintaining steady temperature and humidity is key to keeping those instruments in tune.

I am not an electrical engineer, but I play one on the Internet.

P.S. -- Thank you for reading the rules and using your full real name on your first post!

[John Rutirasiri]

Looking from the perspective of equipment rack/cabinet:

Is there more than one equipment rack (i.e. a rack for audio, a second rack for video/streaming equipment)?
Are the cables brought into the equipment rack(s) through metal conduits or cable tray?

Some installers do not put bonding wires between multiple racks, some do not bond a cable tray to the rack.  Even with EMT conduit, the far end of the conduit may just be hanging in the plenum space.
So it is possible that with the additional ground, you have different ground potential if not everything is bonded together.

This could be as simple as bonding multiple cabinets together or putting "sensitive" equipment on a UPS or isolation transformer, or more involved solutions requiring a balanced power system.

John R.

[g'bye, Dick Rees]

Static Guard is good.  I've tamed several church systems with "winter-pop" by simply putting drain wires from any rack rails and the mixer chassis to a proven ground.

[Duane Sanders]

I assume this is a carpeted area?  The problem is, the static charge is building up on the people or possibly the chairs as rubber shoe soles rub on the carpet.  Grounding the carpet can't help.

Two possibilites-everyiine in the row wears a static grounding wrist strap similar to what techs wear when workiing with static sensitive companents-of course each wrist strap has to be grounded.  This would be effective, but not practical.

More practical would be to treat the carpet with something along the lines of Static Guard-just quickly spray the carpet down before a service.

they have tried the a static guard mixture on the carpet...not much difference in the pop.

[Duane Sanders]

What mixer? Digital stagebox?

Behringer X32

[Duane Sanders]

The idea of a ground plane for the chairs isn't a bad though, but it wasn't executed in the best manner possible.

First off, it would work better if, rather than a wire along the carpet, it was a grid (screen) or plate (copper foil) under the carpet in the affected area. Then, the carpet needs to be treated to improve its conductivity. Static guard spray (as mentioned by Mr. Swaffer) is basically fabric softener in a spray bottle. Fabric softener works by hydrating the fibers so they are more conductive, and lubricating the fibers so they are less likely to build a charge as they rub against each other. You may need to shampoo the carpet more frequently as the static guard can build up and trap dirt. (If you think about it, synthetic carpet fibers are basically plastic, and plastic is an insulator or dielectric. As you move across the carpet, your shoes strip electrons from the dielectric -- or maybe the electrons go the other way -- so you end up with an imbalance, or charge, between yourself and other objects.)

Secondly, this grounding needs to be bonded to the grounding system of the building. That helps to ensure that the voltage potential of that grounded area is the same as the voltage potential of the grounding of the sound system.

On the other hand, just using the static spray might be enough and no complicated grounding system would be necessary.

You might also recommend that your church have their HVAC contractor install equipment to help maintain the humidity in the building. Ideally, indoor humidity should be between 40% and 50% RH. Besides reducing static charging, proper humidity also prevents warping and cracking of wood furnishings and trim. If you have a pipe organ or piano, maintaining steady temperature and humidity is key to keeping those instruments in tune.

I am not an electrical engineer, but I play one on the Internet.

P.S. -- Thank you for reading the rules and using your full real name on your first post!

Fabric Softener didnt work as well as they had hoped.
i have thought of the grounding and will have someone check it again to see if it is correct.
I am also planning to talk to the HVAC guy about indoor humidifier.

I want to thank everyone for their ideas and taking time to help me out here.

[Tim McCulloch]

Behringer X32

Are you using an S16/32, or DL16/32 digital snake box?  If so.... is your CAT5e cable shielded and terminated with Ethercon® connectors that bond to the RJ45 ground?

[ProSoundWeb Community]