Machsupport Forum

Mach Discussion => General Mach Discussion => Topic started by: joeaverage on March 21, 2019, 02:02:40 AM

Title: Have you ever blown up a PC?
Post by: joeaverage on March 21, 2019, 02:02:40 AM

Hi All,
trying to get a feeling for the number of people who may have damaged a PC because they chose not use
opto-isolated inputs.

Thanks for taking the time to respond.

Craig

Title: Re: Have you ever blown up a PC?
Post by: Tweakie.CNC on March 21, 2019, 02:32:30 AM

On my parallel port operated machines I do not use opto-isolation and have never had any PC problems. However, I only use 5 Volt TTL level for inputs and switches and my stepper drivers have their own opto-isolated inputs.

Title: Re: Have you ever blown up a PC?
Post by: joeaverage on March 21, 2019, 02:36:25 AM

Hi Tweakie,
when I used parallel ports I had the same arrangement as you and never had any problems either.
I now use an ESS, and I suppose it is just as possible for a 'bad' input to damage the ESS, and yet it
hasn't happen either.

Craig

Title: Re: Have you ever blown up a PC?
Post by: Tweakie.CNC on March 21, 2019, 03:01:09 AM

Hi Craig,

One thing perhaps worth consideration...

We both have an understanding of electronics but there are probably a great many out there who just connect wires and see what happens.  :'(

Title: Re: Have you ever blown up a PC?
Post by: reuelt on March 21, 2019, 04:51:31 AM

Most industrial machines run their limit switches on 24V to improve reliability. A noise must change nearly 12 volts before giving a false trigger.
In those situations, opto-isolation of the parallel port in very important.

If we run our limit switches on 5V only, it is unlikely to blow up the parallel port even if the BOB only use ttl buffers and NOT opto-isolation for the inputs. Limit switches at 5 volts can be more easily triggered by noise. A change of 2.4 volts can already cause a false trigger.

While I have NOT blown up any PC myself, I have customers returning PC with USB ports burnt or the Parallel port burn. When the parallel port is on the motherboard, the circuit nearby like the Ethernet and USB got burnt too. I had a cheaper PCIe parallel card destroyed too.
Customers do make mistakes. e.g. some would set the motion controller from USA to 110v and then plug into Australian 240v instead of the step down transformer supplied. The company that I sold PCs to, repairs a lot of blown external motion controllers by sending them back to USA for repairs.
Now I only sell PCs with AXXON 5V PCIe parallel Port cards from Canada which can withstand 15,000V without breaking down. They cost even more than ESS or UC300..but they are very robust for industrial use.

Title: Re: Have you ever blown up a PC?
Post by: ger21 on March 21, 2019, 10:45:01 AM

Off the top of my head, I haven't really heard of any in the 15+ years I've been reading DIY CNC forums. But I'm sure there have been a few.

My machine is not isolated, and has been fine for over 10 years. But the parallel port powers everything, so it's pretty hard to damage anything.

You really have to wire a power supply wrong and fry the breakout board to damage the PC.