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Author Topic: Fluorescent Lights and Interference  (Read 3735 times)

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Fluorescent Lights and Interference
« on: November 22, 2012, 06:32:35 AM »
Just wondering if fluorescent lights could cause interference with limit switches and home switches.

Earlier tonight I was trying to solve some odd behaviour with the Z axis home switch (photo interrupter type) on my router.  The slit in the switch faces up so one possibility was the collector was seeing the light from the flouro, either directly or reflected off the blanking blade.  To test the theory I turned the lights off  ::)  To my surprise the home switch behaved itself.  When I turned the lights back on, my stepper motors seem to re-energise - they certainly rattle with the flouro as it blinks on.

My router is in a small garden shed.  The headroom is so low the double flouro battens are just above head height.  Realistically, I couldn't get then closer to the router if I tried.

Anyone got an opinion?

A new shed is on the cards when funds allow.  LED lighting?
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Ian B

Offline RICH

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Re: Fluorescent Lights and Interference
« Reply #1 on: November 22, 2012, 06:55:20 AM »
Never had a problem running the Sherlines / opto's located on a bench with flourecent lighting located within 42" above the machines.
If I  get a chance I'll check the RF intensity but believe it would be very small and not enough to couple and create problematic noise.
Not the case for a very sensitive reciever though.
RICH

Offline BR549

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Re: Fluorescent Lights and Interference
« Reply #2 on: November 22, 2012, 11:48:54 AM »
I was looking at some of your pictures of your machine and reading some opf your voltage to frame comments and you have serious grounding problems .

Just a thought(;-) TP
Re: Fluorescent Lights and Interference
« Reply #3 on: November 22, 2012, 04:30:50 PM »
BR549,

If you can see any flaws in my wiring then please let me know.  Any constructive comments would be greatfully appreciated.

Just telling me that I have "serious grounding issues" is like throwing a rock on the chook house roof.
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Ian B

Offline BR549

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Re: Fluorescent Lights and Interference
« Reply #4 on: November 22, 2012, 06:51:18 PM »
One of your pictures show what looks like limit wires having the shields going to the frame. Bad idea. Another picture show s the back of the controller and shields going to the supply earth AND you ALSO looped pairs together at the controll box  THERE was serious grnd loops.

The idae of star point grounding is that ALL sheilds lead to ONE terminal point at the EARTH GROUND.

In one post you talk of the motor frames and sheilds being CHARGED with voltage. That means you have crossed the DC common and grnds somewhere. and you have a current loop leaking voltage back to earth ground.

You really need to start over.   Earth Ground is NOT DC common and not AC neutral.  TH earth ground is a last chance safety to help keep you from frying yourself when something shorts and you are touching the machine .

Earth ground is also a place to drain any noise that accumalates in the wiring sheilds.  You never want to piggy back grounds to easch other or to DC comm or AC neutral.


I would start from the begining.  Surely you have the wiring schematic for the controller. Wire it as the drawing  THEN check for stray voltages. THERE should NOT be any anywhere. IF there are find out WHERE it is coming from. You could have a miss wired control box that is bleeding voltage out to chassis grnd inside the controller.  A GOOD RMS voltmeter is your friend.

The problem could also be the SUPPLY side of the machine someone COULD have mis wired a neutral to a grnd somewhere in that curcuit and YOU are getting the backfeed at the plug.

BUT rest assure you have a problem somwhere and it could get deadly at some point.

Trying to trouble shoot your electrical problem from thousands of miles away is like fishing with rocks.

I would start at the wall plug and start adding on componets  and work your way out untill the problem showed up,  then fix it.  Look for stray voltage from the chassis/case/frame back to earth ground. Seeing as you have already let some magic smoke OUT it could be from anywhere or from a damaged component inside the boxes.

(;-) TP
« Last Edit: November 22, 2012, 07:00:35 PM by BR549 »

Offline BR549

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Re: Fluorescent Lights and Interference
« Reply #5 on: November 22, 2012, 07:13:02 PM »
IF you do not understand what it is you are looking for PLEASE get qualified help to find the problem BEFORE something bad happens.

Just a thought, (;-) TP
Re: Fluorescent Lights and Interference
« Reply #6 on: November 26, 2012, 08:04:08 AM »
BR,

Thanks for the detailed reply.  It is appreciated and I'd meant to respond before now.

I have arranged to borrow a power outlet tester, so in the very near future I will be able to verify my 240V 50Hz supply is good.

No doubt I have lots to learn about grounding, and as you have suggested I have started again.

You say I must have crossed "the DC common and grnds somewhere" since I can measure voltages between stepper bodies and supply ground.  But I expect you will always be able to measure a small parasitic DC voltage between stepper body and ground when the motors are energised and not grounded.  When energised, steppers are always drawing current so in the presence of permanent magnets a voltage will be produced.

I am going to ground mys stepper motors and also isolate them from the machine (aluminium extrusion) body.

My controller is designed and made in Australia.  It was a deliberate purchase to support a local business.  God knows we don't make much in our country any more - only dig holes in the dirt.  The IC3A controller is plug and play for many, many customers.  But obviously my use is one of a kind.  The provider has been very ill, and helpful to a limited extent, between hospital stays.

I will introduce components one at a time until a problem presents - thanks for the tip.  

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Offline BR549

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Re: Fluorescent Lights and Interference
« Reply #7 on: November 26, 2012, 01:25:35 PM »
Your assumption would be generally wrong on the motors.  Unforturnately That is part of the problem.

(;-) TP
Re: Fluorescent Lights and Interference
« Reply #8 on: November 26, 2012, 04:16:41 PM »
BR,

From my controller, the supply to the steppers is floating.  And the steppers themselves are not grounded internally.

So what do you think is my assumption and why do you think it is wrong?
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Ian B

Offline BR549

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Re: Fluorescent Lights and Interference
« Reply #9 on: November 26, 2012, 04:41:33 PM »
You were assuming that the magnetism in the case causes electrical current outside the case. The only reason to have stray current at the motor case would be to have considerable internal wire insulation leakage OR you have a ground current loop that is backfeeding the case with current. Either way is NOT good.

From your description SOMETHING is leaking current BACK into the chassis and IF you test it to GROUND you get voltage and current flow.  That also means YOU could get into the loop going to ground and get shocked at some point.

(;-)TP