Electric Gate vs Lightning

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Little Bill

Little Bill

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I have a customer that has an electric gate for his driveway. He says it has been hit by lightning several times and is very expensive to fix each time. He wants some sort of lightning protection for it and asked me about it. I don't know how to help this other than some type of extra grounding for the controller. So I'm asking for some advise on this.

I was busy doing another job for him when he asked so I didn't get to look at how the power was brought to the gate. I do know it's several hundred feet from his house to the gate. So I don't know if he has a voltage drop causing low power to the gate. I also don't know if low power would cause the problems for the controller or it's actually being hit by lightning.
He said the company that put in the gate controller and that has been replacing the parts said it was lightning. But I don't know if that is just there standard answer for problems with their equipment.

What should be done for the lightning if that is the case?

What else could be checked that would cause failure of the controls at the gate?
 
what is the power source? 120vac into a transformer down to regulated DC for the controller? lightning voltage will basically hop over/through anything, and if not the voltage/current itself the mag field can be strong enough to wipe out the IC's on controller. has anyone done any electrical forensics to see what part(s) of the controller has failed??

the parts of the gate should also be heavily grounded to earth, but not so sure how you do that on the rolling/swinging section of the gate. can the controller itself be moved to a remote location?

it might be solved by offering lightning an preferred path some short distance away from the auto-gate. maybe a 10-15ft ground leader 20-30ft away from the gate? when a step leader extends up to reach the charge in the sky it would most likely favor a taller ground leader (spike or wire). this however also provides higher probability of lightning striking, but at least its away from the gate.
 
FionaZuppa said:
what is the power source? 120vac into a transformer down to regulated DC for the controller? lightning voltage will basically hop over/through anything, and if not the voltage/current itself the mag field can be strong enough to wipe out the IC's on controller. has anyone done any electrical forensics to see what part(s) of the controller has failed??

the parts of the gate should also be heavily grounded to earth, but not so sure how you do that on the rolling/swinging section of the gate. can the controller itself be moved to a remote location?

it might be solved by offering lightning an preferred path some short distance away from the auto-gate. maybe a 10-15ft ground leader 20-30ft away from the gate? when a step leader extends up to reach the charge in the sky it would most likely favor a taller ground leader (spike or wire). this however also provides higher probability of lightning striking, but at least its away from the gate.
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As I stated, I was asked about this while "knee deep" in his other job so I didn't get to see any of the feeds or the controller. It was very late when I finished so I didn't get to look at anything.
That said, I imagine he has a 120V feed up to the gate control, which I assume is mounted on or near the gate, and then is converted to DC.
I don't know a lot about gate controls but from the ones I have seen, that's how they were.
 
I've seen similar issues with really long ATS control wiring. Ultimately, surge protection had to be added to the wiring to prevent voltage issues from lightning. It doesn't have to be a direct strike - it can be anywhere in the area. Those long lines will have high voltage crossing them somewhere, causing a spike in the wiring that can blow out the PCB. Whatever surge protection you use, it needs to have as low a clamping voltage as possible. The joules rating is probably not so important.
 
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if the PCB has good regulator (eg, LM78XX) then voltage spike on the transformer/rectifier should not really be seen on the aft side of the reg. however, its very possible to damage the transformer/rectifier/regulator.

i guess best advice i would give is, need forensics work done to determine the actual failure, then apply mitigating controls to keep it from happeneing again, etc.
 
FionaZuppa said:
if the PCB has good regulator (eg, LM78XX) then voltage spike on the transformer/rectifier should not really be seen on the aft side of the reg. however, its very possible to damage the transformer/rectifier/regulator.

i guess best advice i would give is, need forensics work done to determine the actual failure, then apply mitigating controls to keep it from happeneing again, etc.
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I called the customer and asked him to send me the info on how the controller is fed and the make/model of the unit so I can look up the specs on it.
 
FionaZuppa said:
if the PCB has good regulator (eg, LM78XX) then voltage spike on the transformer/rectifier should not really be seen on the aft side of the reg. however, its very possible to damage the transformer/rectifier/regulator.

i guess best advice i would give is, need forensics work done to determine the actual failure, then apply mitigating controls to keep it from happeneing again, etc.
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I agree forensics... get details on exactly WHAT is failing as first step.

Example... I have 3000 ft buried shielded cable from house to sensors at street (yes, long driveway). First year found welded reed relay output contacts EVERY single lightening storm. I tried movs around this n.o. contact, diodes, none stopped failures until I simply put .1mfd cap across the reed contacts. Then only failure is about once every 2years 7805 reg blows from close lightening strikes. So you must know exactly what he failure is.
 
Chances are you are getting transients on supply line or any controls including detector loops in the ground from nearby strikes more so then any direct hits to the fence. If you have no surge protection at/near the input to the gate it certainly couldn't hurt anything to start with adding that.
 
small transients might not be mitigated with std surge protectors, but these small transients could still damage the controller.

something else to think about, in addition to the line voltage surge protector, use a MOV or Zener on the aft side of the rectifier (it will need to be rated a few volts higher than peak voltage, etc). this will help but the transformer is still subject to windings arc-through if the voltage gets too high, but the input surge protector there might mitigate that.

problem is, surge protectors (like MOV's, which are commonly used in "surge protectors") degrade after their thresholds have been met and current flows through them, so in an environment that constantly gets hit this method might not last too long.
 
FionaZuppa said:
small transients might not be mitigated with std surge protectors, but these small transients could still damage the controller.

something else to think about, in addition to the line voltage surge protector, use a MOV or Zener on the aft side of the rectifier (it will need to be rated a few volts higher than peak voltage, etc). this will help but the transformer is still subject to windings arc-through if the voltage gets too high, but the input surge protector there might mitigate that.

problem is, surge protectors (like MOV's, which are commonly used in "surge protectors") degrade after their thresholds have been met and current flows through them, so in an environment that constantly gets hit this method might not last too long.
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What does last if it is constantly being hit?
 
Lightning strikes, sure they can happen; several of them, the odds start to decrease rapidly. Good surge protection can't hurt. Nothing wrong with using protection even if you don't think you need it.

Voltage drop? Over concern about voltage drop is the curse of the continuing education classes. It might be a problem, it's easy to check.

What else could be checked? I'm not gonna rule out what the gate guys have to say, but there is good chance they are just swapping parts and passing off a problem they can't figure out as an act of god.
Gotta get in there and look for the boring stuff- connections, dirt, too much grease, mice damage.... rule out every mundane possibility before you move onto making it a science project.
 
fried components come in a few flavors.

arc'd over and damaged part usually leaving physical evidence.
the silicon was damaged by magnetic field or over-voltage.

the 1st one is easy to spot, the 2nd one requires parts to be isolated and tested properly.

probing with a oscope (fluke handheld, other, etc) can also reveal where a problem might be.

using a sensitive low amp fuse inline with a zener from reg input to ground can help catch an overvoltage situation, the zener will shut and the fuse will blow. you can spec zener just below max input voltage allowed on the regulator, etc.

another method to help tame voltage spike (between rectifier and regulator) is inline inductor between rectifier and regulator, and a capacitor from reg input to ground.

however, all this requires kinda hacking the existing controller board, etc.
 
FionaZuppa said:
fried components come in a few flavors.

arc'd over and damaged part usually leaving physical evidence.
the silicon was damaged by magnetic field or over-voltage.

the 1st one is easy to spot, the 2nd one requires parts to be isolated and tested properly.

probing with a oscope (fluke handheld, other, etc) can also reveal where a problem might be.

using a sensitive low amp fuse inline with a zener from reg input to ground can help catch an overvoltage situation, the zener will shut and the fuse will blow. you can spec zener just below max input voltage allowed on the regulator, etc.

another method to help tame voltage spike (between rectifier and regulator) is inline inductor between rectifier and regulator, and a capacitor from reg input to ground.

however, all this requires kinda hacking the existing controller board, etc.
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I'm sure they will happily warranty a field modified board if it fails;)
 
kwired said:
I'm sure they will happily warranty a field modified board if it fails;)
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pros and cons. pick your poison, etc.

maybe ask maker to modify the board with some suggestions that were posted here.......
 
one of these right across terminals #19 to #20
http://www.digikey.com/product-search/en?vendor=0&keywords=V47ZA3P
24vac has peak V of 33.94v. the 35v MOV is too close, so 42v is next one up.

this will absorb voltage spike. it would be better to insert a small inline fuse on one of the terminal lines (19 or 20) so when MOV trips the fuse sees the short and blows. fuse goes before MOV, etc.

a $2 fix and can be done by anyone and will not void board warranty.
i would use good volt meter to see what that 24vac really is, then choose MOV accordingly. if it measures below 35vac then the MOV i listed should suffice.
 
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Little Bill said:
He says it's been the board everytime except one
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Can you get the old bad boards? If not, be extremely cautious in claims you can help him.... Until YOU see the actual damage area, you cannot do much more than throw various MOV, fusing, etc things at it that may or may not help.

If it was my customer, I would throw this stuff recommended here at it, and then tell customer these are only 'best practice' ideas, to really do better, I would need broken pcbs so I could see which area of the circuit is the weak link. After getting 2, 3 of these, I could then tell if there is a trend or weak link and address it.....
 
FionaZuppa said:
one of these right across terminals #19 to #20
http://www.digikey.com/product-search/en?vendor=0&keywords=V47ZA3P
24vac has peak V of 33.94v. the 35v MOV is too close, so 42v is next one up.

this will absorb voltage spike. it would be better to insert a small inline fuse on one of the terminal lines (19 or 20) so when MOV trips the fuse sees the short and blows. fuse goes before MOV, etc.

a $2 fix and can be done by anyone and will not void board warranty.
i would use good volt meter to see what that 24vac really is, then choose MOV accordingly. if it measures below 35vac then the MOV i listed should suffice.
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The Mfg offers a surge suppressor for both high & low voltage. Would their LV suppressor be any different than the MOV you linked to?

Also, would you not also want one on the incoming 120V line? How would it connect to the incoming lines, in-line with both hot & neutral? I don't think I have ever used a surge suppressor for 120V other than some type of plug-in unit.
I tried to find an image of the Mfg's version of both the high & low voltage suppressors but couldn't find any.

mike_kilroy said:
Can you get the old bad boards? If not, be extremely cautious in claims you can help him.... Until YOU see the actual damage area, you cannot do much more than throw various MOV, fusing, etc things at it that may or may not help.

If it was my customer, I would throw this stuff recommended here at it, and then tell customer these are only 'best practice' ideas, to really do better, I would need broken pcbs so I could see which area of the circuit is the weak link. After getting 2, 3 of these, I could then tell if there is a trend or weak link and address it.....
Click to expand...

I believe the board that is in it now is bad but I doubt the customer has any of the previous defective boards as they were replaced by the gate installer.

I never told the guy that I could help him. He actually asked me about installing a lightning protection system. I have another customer that had similar issues with his gate and he had someone install some type of grounding system. I just told the guy I would check with my other customer to see who did his. I did tell him I would do a little investigating for other possible causes. I think the person with the similar problems has had to replace his boards even after the additional grounding. So I got to thinking that something else besides lightning could be causing this. That is why I came here for suggestions.
 
I was able to find a picture of the high/low voltage suppressors (along with the high voltage prices - $78.50:eek:hmy:)

High voltage

1876-010-2.jpg


Low voltage

1878-010-2.jpg
 
owner should buy both. why were they not installed before is the big Q. they are multi MOV with what looks like inline chokes. it looks like 4 MOV's with one self-resetting fuse.
 
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