Re: MACH1GTO VIBRATING


Joe Zeglinski
 

Hi Biker,
    Glad to see that you concur.
 
    Sometimes I feel I am shouting in the dark. Unfortunately, there is nothing we can do about improper designs in many if not almost all controllers out there,. But I was hoping the later generation controller, CP4 would have finally got it right – but it didn’t. Hopefully,  the CP5 got the chassis grounding right this time.
 
    Sometimes this problem is so easy to fix just by choosing the correct component to bolt onto the control panel.
For example, there is a choice for something as simple as the DB9 serial port connector. Manufacturers can choose one that has its logic ground pin, isolated and used strictly for power supply ground return. Or,  for some reason, they choose to buy one that already has the logic ground pin welded to the DB connector body. As soon as that kind of serial connector is screwed onto the panel, the logic ground on the circuit board,  now shares “chassis ground” with everything on the system, including the panel screws. How simple would that practice be to correct?
 
     I noticed, while ring out the resistance on other connectors on my CP4, this sharing of logic ground with chassis ground doesn’t seem to be done for USB, Ethernet, and other connectors, so it may only be caused by a poor choice of serial port connectors during design, rather than someone purposely attaching a wire between a chassis screw and the logic board circuit ground during assembly.
 
    However, I can see how some sloppy designers just assume ANY ground is just a plain ground, so to protect the user and satisfy their own lawyers, they divert ALL types of ground points to the chassis body lest a 5 volt signal might kill a customer,  and the above serial connector is an easy way to do that.
 
    Anyway, not much we can do to protect our controllers from this hazard. This kind of bad practice has been out there probably for decades, and most of our equipment is already irreversibly affected.  I’m just shocked – excuse the pun – that this practice still continues.
Just have to be wary to watch out for distant thunder storms.
 
Joe
 

From: biker123@... [ap-gto]
Sent: Friday, October 11, 2019 5:25 PM
To: ap-gto@...
Subject: Re: [ap-gto] MACH1GTO VIBRATING
 


Joe,
Wow....did you cover a lot of sins manufacturers and weekend warriors commit that can compromise their gear or kill it.To cover all this would take a lot of typing ;-)
 
But you are dead right. The sad part is that electricians often don't get it right and pass on bad information to others. One of my duties was to meet with contractors to discuss electrical safety....low voltage as well as high voltage when working around primary distribution lines (12 KV and higher). I and my partner met several of these guys who argued with us....until we did some demos to show we were right ;-)
 
For a start I recommend others to get that test block I mentioned above to determine if their house wiring is good and wired correctly. And make sure everything is connected correctly. I am not going to recommend that people take their equipment apart to check chassis ground, etc. as they could likely get into trouble if they don't know what they are doing. But if they ever get a tingle when touching metal cases....that is a sign something isn't right.
 

Join main@ap-gto.groups.io to automatically receive all group messages.