• Scam Alert. Members are reminded to NOT send money to buy anything. Don't buy things remote and have it shipped - go get it yourself, pay in person, and take your equipment with you. Scammers have burned people on this forum. Urgency, secrecy, excuses, selling for friend, newish members, FUD, are RED FLAGS. A video conference call is not adequate assurance. Face to face interactions are required. Please report suspicions to the forum admins. Stay Safe - anyone can get scammed.

Magic Smoke

whydontu

whydontu

I Tried, It Broke
Premium Member
discovered new stuff today while trying to check motor voltage on my engraver. Wanted to know how dirty the signal was, and the PWM frequency.

Scope in hand, 10X probe connected since the motor supply is 24 VDC.

Chinese CNC manufacturers are colour-blind, or don’t know colour-code conventions.

The +24VDC line to the spindle motor on a Chinese-made 3018 CNC engraving machine is black, ground is red.

When you feed +24VDC to the shell of a USB port on a Lenovo Tiny desktop PC, the Lenovo motherboard emits magic smoke.

Once the magic smoke is dissipated, a Lenovo Tiny PC becomes a quite useless paperweight.

Lenovo 20VDC power supply connectors are impossible to test, unless you cut off the connector to get at the bare wires.

The $150 CNC machine survives power spikes better than the $800 Lenovo Tiny PC.

I probably should have checked polarity on the motor before I hooked up the scope.

Sigh.
 
That really sucks.......

Why were you connecting it to the Lenovo usb port?
 
whydontu said:
discovered new stuff today while trying to check motor voltage on my engraver. Wanted to know how dirty the signal was, and the PWM frequency.

Scope in hand, 10X probe connected since the motor supply is 24 VDC.

Chinese CNC manufacturers are colour-blind, or don’t know colour-code conventions.

The +24VDC line to the spindle motor on a Chinese-made 3018 CNC engraving machine is black, ground is red.

When you feed +24VDC to the shell of a USB port on a Lenovo Tiny desktop PC, the Lenovo motherboard emits magic smoke.

Once the magic smoke is dissipated, a Lenovo Tiny PC becomes a quite useless paperweight.

Lenovo 20VDC power supply connectors are impossible to test, unless you cut off the connector to get at the bare wires.

The $150 CNC machine survives power spikes better than the $800 Lenovo Tiny PC.

I probably should have checked polarity on the motor before I hooked up the scope.

Sigh.
Click to expand...
That sure sucks...... I've let more than my share of magic smoke out of a wide assortment of things in my time. You would think I would be a better magician by now......:rolleyes:
 
Susquatch said:
That really sucks.......

Why were you connecting it to the Lenovo usb port?
Click to expand...
CNC is floating ground 24 VDC power supply, connected to Lenovo USB port

Scope ground is connected to outlet ground.

I think I ended up with a nice ground loop when I connected scope ground to 24VDC motor wire, then started the motor.
 
whydontu said:
CNC is floating ground 24 VDC power supply, connected to Lenovo USB port

Scope ground is connected to outlet ground.

I think I ended up with a nice ground loop when I connected scope ground to 24VDC motor wire, then started the motor.
Click to expand...

Ah yes. So it was a power supply ground loop that got you. An isolated scope probe would not have saved you then.

That really sucks. Is the whole laptop smoked or just the USB system.
 
Whole thing is toast. No lights, no fan, nada. I hope the SSD and RAM survived, but I don't have another machine that uses the same RAM so I can't test it. Tomorrow is lug out another PC from storage and see if I can recover the files from the Lenovo SSD. Ah well, gives me something to do instead of spending all day scrolling through FB.
 
whydontu said:
Whole thing is toast. No lights, no fan, nada. I hope the SSD and RAM survived, but I don't have another machine that uses the same RAM so I can't test it. Tomorrow is lug out another PC from storage and see if I can recover the files from the Lenovo SSD. Ah well, gives me something to do instead of spending all day scrolling through FB.
Click to expand...

Nothing working at all might actually be a good thing.

Power supply might be toast and just need fixing. If you are really lucky, might be a board trace or a diode. Or even a fuse......
 
Welcome to the club.

I smoked an expensive Dell PC with a USB device I purchased off Amazon. I really should have known better to trust the dangerous crap they sell. The device applied full mains voltage to the USB port!

Amazon zero recourse.

I just don't understand how if I want to develop a Mains powered product to sell in Canada I'm legislated to go through considerable expense for safety approvals, yet these absolutely hazardous products with zero regards to CSA standards or even the most basic safety standards that have zero chance of getting CSA approval are being sold by the thousands to Canadians every day. Something is not quite right.

My advice after this episode is if it plugs into mains make sure it has a CSA logo, and don't be fooled with the other non safety logos like FCC that give the illusion that it's a safe product. Keep in mind in my career we had some electronics manufactured overseas and we were often asked what safety logos do you want us to print on the product with zero regard to us providing any paperwork for such appovals.
 
Last edited:
I don't know if this product for Lucas will work, it was a vital necessity years ago for any English vehicle, but worth trying.
 

Attachments

  • magic smoke.jpg
    magic smoke.jpg
    34.9 KB · Views: 9
I have this vision of Mr Lucas and Mr Smith attempting to cross the Sahara in a Morris Minor. Can't see where they're going and no idea how far they've driven.
Lucas was the inventor of darkness....someone had to do it.
 
when I was an apprentice auto mechanic, the boss had taken a TR6 that had been "freshly renovated" from a customer who owed a decent invoice...
I was tasked with going through it... Mr. Lucas should really be sunk to the ankles in manure...upside down...
Besides the fact most of the wiring was the same gauge and colour, it hadn't been touched during the reno.
Then factor in just how shite grounds are with those cars...
He ended up ordering an aftermarket harness and Pertronix kit for the ignition system...
And not much further ahead on the debt of the invoice...
 
Ironman said:
I have this vision of Mr Lucas and Mr Smith attempting to cross the Sahara in a Morris Minor. Can't see where they're going and no idea how far they've driven.
Lucas was the inventor of darkness....someone had to do it.
Click to expand...
This just triggered a memory from when I was about 15, my older friend just got his license and we were "cruising for chicks" in the Morris Minor, we're chatting up a couple of young ladies at the local DQ, we were supposed to follow them somewhere, except the car won't start, the battery is dead. My buddy tells me no problem they have a hand crank starter in the trunk, I'm thinking what is he talking about the chicks are getting away. Pulls out this 3' long hand crank that fits through a hole in the front bumper and mates with the front of the crankshaft. A few cranks later the engine sputters to life, but it's too late, they are gone.
 
slow-poke said:
A few cranks later the engine sputters to life, but it's too late, they are gone.
Click to expand...

That was your wife's great great grandparents looking after you. But don't take my word for it. Just go ask your wife. Wives can talk to the dead. Mine talks to me all the time and I can tell whether I'm living or dead by the tone of her voice.
 
slow-poke said:
This just triggered a memory from when I was about 15, my older friend just got his license and we were "cruising for chicks" in the Morris Minor, we're chatting up a couple of young ladies at the local DQ, we were supposed to follow them somewhere, except the car won't start, the battery is dead. My buddy tells me no problem they have a hand crank starter in the trunk, I'm thinking what is he talking about the chicks are getting away. Pulls out this 3' long hand crank that fits through a hole in the front bumper and mates with the front of the crankshaft. A few cranks later the engine sputters to life, but it's too late, they are gone.
Click to expand...
There's a cranking it by hand joke in there somewhere, I swear.
 
You must log in or register to reply here.
Back
Top