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Question for an electrical engineer - USB Power inside machine

jttest1423

Plastic
Joined
Apr 23, 2019
So I am installing a Ethernet-to-wifi adapter on a few of the machines here. This way we can connect them wireless and transfer files back and forth. I am using this adapter IOGEAR - GWU637 - Universal Wi-Fi N Transmitter- Ethernet to Wi-Fi N 300Mbps which takes the standard 5V DC from being USB powered and 500mA. I only seem to have 24Vdc sources in the cabinet. I would like to do a permanent install meaning I want everything to remain tidy in the cabinet so I looked into this:

https://www.amazon.com/DZS-Elec-Con...AKQM8VJKEJFZ&refRID=FRQWME5KAKQM8VJKEJFZ&th=1

Which would be perfect except that it outputs 3A. Will I still be okay with using this device or is there a better solution here?

Also side question but why does it seem like all the Okuma's I have worked with have -24Vdc power rails. Is there any way to get a +24Vdc terminal on the Okuma Machines, One being a very old MC-6VA and a very new 2SP-V920EX. To get around that I am currently planning on just buying a Din Rail Power Supply.
 
Not an electrical engineer, but that will work, because it isn't forcing 3 amps, that is only it's rated output. It will put out less if your device draws less.
 
Also side question but why does it seem like all the Okuma's I have worked with have -24Vdc power rails. Is there any way to get a +24Vdc terminal on the Okuma Machines, One being a very old MC-6VA and a very new 2SP-V920EX. To get around that I am currently planning on just buying a Din Rail Power Supply.

To convert from -24VDC to +24VDC just reverse your ground and power connections.
 
I would think there is a good chance you have 5V DC somewhere in the control cabinet. That's a standard voltage for optical encoders. If you can find the control power supply unit, I bet you will find a +5V DC terminal. I would think it would have 500mA to spare.
 
On a CNC, this would just about be guaranteed to kill the I/O boards in the control. Don't do it!
I think he meant only to reverse the connections to the stepdown supply.

As long as he didn't let any "grounded" part of the stepdown board, or the Wifi adapter, touch the machine ground, it should work okay.


I'm not sure how well the antenna would work, with it's "ground plane" being at +24V...
 
I think he meant only to reverse the connections to the stepdown supply.

.......

I'm not sure what he meant. In any case it is not a detailed enough reply to be sure that someone that did not understand what was meant would not try swapping the output of the 24V power supply in the control.
 
I'm not sure what he meant. In any case it is not a detailed enough reply to be sure that someone that did not understand what was meant would not try swapping the output of the 24V power supply in the control.


Vanc
I believe the OP has stated that he's planning to install the device as shown in his link.
Said device is a 5-36V INPUT to a 5V - USB OUTPUT converter, basically a DC to DC converter with a USB plug on it's rear end.

The device needs a DC input between 5 to 36V, but the op has only a -24V power source inside the cabinet.

To that, drcoelho replied that he can still use the -24V supply, except that the device's + input pin must be connected to Ground, while the - input pin must be connected to -24V.
So, as long as this device won't be attaching itself to common ground in the machine, it's USB output will provide the necessary +5V to power the Wifi adapter.
 
STOP!

Unless you know it is isolated fully you risk smoke...

Past life we worked on -48 vdc cell site equipment that had what looked like USB connections but some were serial others USB.

The power supply controller has a USB connector labeled as such but plugging in a laptop that also plugged into a.c. main let's lots of smoke out of lots of things!

Easy option is to look for a maintenance plug, a 120 vac outlet that may be installed in cabinet.

Replace it with one that has built in sub charger port.

Sent from my SAMSUNG-SM-G930A using Tapatalk
 
STOP!

Unless you know it is isolated fully you risk smoke...

Past life we worked on -48 vdc cell site equipment that had what looked like USB connections but some were serial others USB.


Ok, well first you do know USB stands for Universal Serial Buss right? Secondly any manufacturer that uses a commonly specific connector like USB outside of the USB protocol deserves a kick in the nuts and never to get there equipment bought by anyone.
 
Ok, well first you do know USB stands for Universal Serial Buss right? Secondly any manufacturer that uses a commonly specific connector like USB outside of the USB protocol deserves a kick in the nuts and never to get there equipment bought by anyone.
Read it again. I don't believe he said he was working with exclusive USB. I believe the quote was "equipment that had what looked like USB connections but some were serial others USB." End quote.

The other mention was "past life". I take that to mean some time ago. Maybe Universal Serial Bus, wasn't that Universal, back in the day. All standards need a time to settle between invention and adopted as standardized.

But feel free to admonish at will. Like you will be the next modern day Whitworth? Hows that Mach3 bridgeport working out for you?
 
I'm not familiar with Okuma equipment, but having a DIN Rail with -24VDC, and wanting to get +24VDC is trivial as I mentioned, simply take whatever device you are trying to connect and reverse your +/- connects and you'll get the desired +24VDC out of it. This is presuming there is a ground somewhere on the DIN Rail as well, which I would be very surprised there is not. The only risk then is if your device pulls more amperage than the DIN Rail power supply can provide, in which case you'll blow a fuse.

Now given all that, I myself wouldn't mess with the Okuma DIN Rail and would just use a separate DC power supply, maybe $10 worth and zero risk of messing up the Okuma.

And yes, I am an electrical engineer.
 
Hold my beer and watch this while I connect -24V to ground.
CarlBoyd

Please read more carefully, I DID NOT suggest connecting -24V to ground, i said "reverse" your connections, e.g. on your device you are trying to power which has +/- connects, connect the + to ground, and the - to -24VDC and you'll now have a +24VDC power to the device.

On the other hand, the beer sounds good ;)
 
I'm not sure what he meant. In any case it is not a detailed enough reply to be sure that someone that did not understand what was meant would not try swapping the output of the 24V power supply in the control.

I was referring STRICTLY to the idea of reversing the out-board device power connections the OP was trying to connect, and most definately was not suggesting messing with anything within the Okuma itself. Swapping power polarity inside the Okuma would be really bad news and highly inadvised. As long as the device does not exceed the power supply capacity of the DIN Rail, I don't see how any harm could come.

DC powered devices are very simple, all you need is +/- connects...DC devices derive power from the delta between the +/- and utilize the - as their ground.
 
Read it again. I don't believe he said he was working with exclusive USB. I believe the quote was "equipment that had what looked like USB connections but some were serial others USB." End quote.

The other mention was "past life". I take that to mean some time ago. Maybe Universal Serial Bus, wasn't that Universal, back in the day. All standards need a time to settle between invention and adopted as standardized.

But feel free to admonish at will. Like you will be the next modern day Whitworth? Hows that Mach3 bridgeport working out for you?


I am Not Witworth, thats not my surname. The USB standard is well defined, i did not write it, i have followed i tthough. if you knew anything about it you would fully understand why a USB plug and socket combo should never be used for anything else. Equally you would understand why its by default safe to plug any USB device into any other USB device if the manufacturers have followed the USB std. The std predates USB connector manufacture (untill the std was written USB did not exist) so its really not a real world issue. This is why it should be safe for the OP to use that adaptor and simply connect his machine to the positive side and the minus 24V to the ground side of that board. He will almost certainly though have to keep the board away from the machine and not have any contact between the shielded USB plug and the machine. The wifi adapter though will almost certainly need to be pulled outside the control cabinet to get signal. The Positive ground plane of the machine may affect transmission, all depends on the Ariel on the wifi router. Several style it will have no impact, others it may.

The Ethernet cable to the control should be fine so long as its not running POE. Which i doubt it would be. Std Ethernet is a floating system and does not share a common system ground at each end, so the voltage difference should not matter, so long as he once again does not connect up a shielded cable with a shield connection at both ends. Again the details in the fine print on all this, but if the parts are correct and they have followed the stds and he takes minimal care there should be no issues here, i would personally add a fast blow fuse on the 24V feed to that USB board though.

As to the Bridgeport, thought i made it clear, i only ran Mach for a fortnight several years ago, its shit and back then i went back to turbocnc a realy dead simple dos based step generator that worked with the kinda reliablity you only find on the simplest of looo roll dispensers! That said on Linux, like it has been for over a decade, yeah its plodding on nicely, Clearing a couple of jobs in the last fortnight that were making me north of £50 a hour (92 aus$), how many people get to own - run equipment that works and in under 2 days earn more than they paid for it :-) Its called making money, maybe something you could try and the money means you don't have to be so poor and fucking miserable in real life!
 
Don't mess - use a encoder supply line, sure they may be 5V, but few would supply anything like a half amp, typical encoder needs at most 100ms, lots are in the sub 30ma range and the whole reason most drives have there own encoder supply is down to electrical noise reduction, you really don't want it connected to anything else unless you want a seriously strangely acting machine.
 
I was referring STRICTLY to the idea of reversing the out-board device power connections the OP was trying to connect, and most definately was not suggesting messing with anything within the Okuma itself. Swapping power polarity inside the Okuma would be really bad news and highly inadvised. As long as the device does not exceed the power supply capacity of the DIN Rail, I don't see how any harm could come.

DC powered devices are very simple, all you need is +/- connects...DC devices derive power from the delta between the +/- and utilize the - as their ground.

That was not clear in your first reply and the reason I immediately posted a warning. Keep in mind that many that will read through these forums today and in future are not experienced in electrical and electronics. An ambiguous post about swapping polarity could lead an inexperienced person to make a grave error.
 








 
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