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Page 1 of 2 out of 16 messages.

What the f*** is the problem with "cheap" power supplies... :(

Posted 2yr ago
by njbuch | King | 26,158 exp
Posted 2yr ago
by njbuch | King | 26,158 exp
I am doing it on a regular basis, trying to use a computer AC adapter, or any other adapter with a barrel plug that fits the USB-DP or elsewhere.

Quite a few times I have nuked my system, or if lucky, if have only had lots of weird interrupt triggers, or strange events in the system.

Can anyone explain why that happens, and what the real problem is with these supplies??
7 likes
Reply #1 — Posted 2yr ago
by ianlee74 | Superhuman | 127,688 exp
Reply #1 — Posted 2yr ago
by ianlee74 | Superhuman | 127,688 exp
The real question should be... "Since I have proven to myself multiple times that cheap power supplies are crap and not worth the risk, why the f*** am I still using them??" Banging Head
Reply #2 — Posted 2yr ago
by njbuch | King | 26,158 exp
Reply #2 — Posted 2yr ago
by njbuch | King | 26,158 exp
@ianlee74 - Good point. : Smiley
Reply #3 — Posted 2yr ago (modified)
by Mr. John Smith | Legend | 42,263 exp
Reply #3 — Posted 2yr ago (modified)
by Mr. John Smith | Legend | 42,263 exp
Do you plug them into a line conditioner? Does your facility have stable mains voltage etc? Do these power supplies have active power factor controller?
Reply #4 — Posted 2yr ago
by michaelb | Senior | 1,398 exp
Reply #4 — Posted 2yr ago
by michaelb | Senior | 1,398 exp
Are they regulated, or unregulated power supplies? Unregulated ones require a minimum amount of current to keep the voltage in an acceptable range, and could easily be exceeding what is acceptable on the input.
Reply #5 — Posted 2yr ago
by njbuch | King | 26,158 exp
Reply #5 — Posted 2yr ago
by njbuch | King | 26,158 exp
@Mr. John Smith - Nope, no line conditioner. The voltage in DK is pretty stable. How do you see if a given supply has active power factor controller?
Reply #6 — Posted 2yr ago
by Mr. John Smith | Legend | 42,263 exp
Reply #6 — Posted 2yr ago
by Mr. John Smith | Legend | 42,263 exp
@njbuch - its written on the box. Other than that I dunno.
1 like
Reply #7 — Posted 2yr ago
by Brett | Superhuman | 125,590 exp
Reply #7 — Posted 2yr ago
by Brett | Superhuman | 125,590 exp
michaelb says:
Are they regulated, or unregulated power supplies? Unregulated ones require a minimum amount of current to keep the voltage in an acceptable range, and could easily be exceeding what is acceptable on the input.

I fully agree that a regulated supply is the only way to be sure that 12v (or 9v) means 9v, and I've gone away from buying non-regulated supplies - and in most cases it's not significantly more expensive to buy a regulated one anyway.

But that may not really be your problem

@Neils can you elaborate on what you have actually had happen? A DP module for example should isolate the mainboard and attached peripherals from voltage fluctuations, assuming you don't exceed the 30V the DP module supports. If you use an unregulated 12v supply, that was producing say 19v, that should still work via the DP. Perhaps you actually have a grounding issue more than anything, using an earth reference ground on one and not on another that caused issues. Since the other active thread today has been about your motor driving experience, it's possibly more to do with trying to use multiple power sources that's caused the issue.
Reply #8 — Posted 2yr ago
by njbuch | King | 26,158 exp
Reply #8 — Posted 2yr ago
by njbuch | King | 26,158 exp
@Brett - Hmm, now we are talking. In most setups I am using one or more modules that needs seperate power, where I normally just use an AC adapter. So in my setup with the motor driver, I am using the usb plug to power the board while debugging, and the motor driver is both attached via a Gadgeteer cable and the power from the AC.

I guess thats a terrible thing to do and the two GNDs should be connected or what...?

The biggest problem is that I have fried several drivers without knowing what the problem was, but on top of that the systems I am working on are unreliable with weird interrupts and other strange things happening....

This has to be a common challenge... Thinking
Reply #9 — Posted 2yr ago
by michaelb | Senior | 1,398 exp
Reply #9 — Posted 2yr ago
by michaelb | Senior | 1,398 exp
With respect to multiple power supplies in the system, the Grounds should all be tied together inherently, as the load modules Gnd pin is connected back to the main board.

Now, that said, I have seen a case in the past, where we were using control transformers to provide 12v ac to chain two motors together, so if one started the second started. I don't remember the exact setup, but I did see where voltage would come out of a wire on one transformer, and complete the circuit by being connected to a wire from the second transformer 30' away in a completely different enclosure / power source. A better way to picture this,, is cut all but one pin off of two power supplies, plug them into the wall,, and have them work by connecting both to the same circuit. Converting to DC normally avoids this issue,, but depending on the quality of the power supply, just a thought.

This would be similar to having two car batteries, connecting only the positive terminal of one of them, to the negative terminal of the second one, and having them melt down because they were short circuiting.

The other scenario that I've had,,, for example when debugging,, watching buttons being pressed that are NOT being pressed,,, is reboot the computer. I've just gotten to the point where when I'm deploying on site software,,, I reboot as I arrive on site. I've seen this happen about 5 times over the last couple of years,, where I spend a couple hours trying to figure out what I was doing wrong,, to have the solution be a restart.

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