Is there a safe way to power a netduino plus with a 5v regulated supply that will not cause problems when a usb cable is connected?
Safe Way to power netduino with 5v Regulated Supply
#1
Posted 07 February 2013 - 01:34 AM
#2
Posted 07 February 2013 - 04:15 AM
Do you mean powering the board from the +5V pin of the header and from the USB at same time?
#3
Posted 07 February 2013 - 06:12 AM
#4
Posted 07 February 2013 - 07:05 AM
first: it doesent matter if its 5 or 9 volt, when you would actually connect that to usb your usb port would be damaged.
than: iam very very sure the netduino does have a protection for that, so that you can power it with a 7.5 to 9v power supply and still have it connected to usb
#5
Posted 07 February 2013 - 09:41 AM
So...
Barrel plug / Vin.
They are exactly the same rail: you can apply as low as +6..7V up to +10..12V. Higher voltages may be applied, but there's an issue related to the protection circuit, so consider +12V as the upper bound. Below the lower threshold, the protection circuit will consider the USB power as primary.
Let's say that between +5 and the lower threshold, the power is supplied in a mixture of ways. Since there's no a clear ripartition of the currents in the supply stage, I would discourage to apply voltages falling in this interval.
This rail has a protection diode which prevents damage when the power is applied inverted by mistake.
USB power.
Any USB host supplies +5V (0.5 A max) to the connected device. As long the above (barrel/Vin) rail is missing, the entire circuit leverages on the USB power.
+5V header.
The "old" Netduinoes expose the +5V rail straight to the header, thus you could power your board by avoiding both the Vin and the USB. However, this voltage must be exactly +5V, well stabilized. That's because the on-board +5V regulator provided by the Netduino is actually bypassed.
The new Netduinoes "2" have a mosfet for switching the +5V header on/off. I may explain the details behind my consideration, but I would discourage to power the Netduino (Plus) 2 uniquely from the +5V header. It works, but it stresses a lot the mosfet.
+3.3 header.
In brief: never provide your own +3.3V external supply to the +3.3V header pin.
NOTE: the above description is just a *SIMPLE* list of what you may and what you shoud not do. However, there are many (complex) implications involved. I believe they should dig only for advanced users.
Hope it helps.
Cheers
#6
Posted 10 February 2013 - 06:22 PM
Hello, let me re-phrase this question. My Netduino Plus 2 can be powered by:
1) a PC via USB cable or
2) a stand-alone 7.5-9VDC power supply.
Can both cables (USB and 7.5-9VDC) stay connected to my Netuduino Plus 2 card at the same time?
Regards,
Zbyszek
#8
Posted 10 February 2013 - 08:52 PM
Yes, you can connect a USB cable at the same time as supplying power into the Vin/barrel input.
There is a transistor that disconnects the USB's 5V line when Vin is available.
Paul
Thank you.
Zbyszek
#9
Posted 14 February 2013 - 03:29 PM
hello,i have a problem with external power.
My project include: netduino plus2, 2 "probe 1-wire" DS18B20, 2 relay with pilot (transistor bc337-25 and coil 5V).
the software to manage the probes and relays is OK of course.
i have connect netduino only with usb power.
The problem is:
when i use the pin +5V and gnd on netduino board to feeding the circuit (probes and relays) is all ok,
but if i connect the same circuit to external power (and so on netduino i have only 3 digital pin to use) i have not results (the temperature of probes is 0 and the relays don't click)
the external power is a pwer pack 5V 0,5A
#11
Posted 14 February 2013 - 09:21 PM
Hi Robbypet,
Welcome to the forums!.
Can you post a circuit diagram of what you have wired up. The problem will probably be obvious then.
Paul
#12
Posted 16 February 2013 - 02:03 PM
#13
Posted 17 February 2013 - 09:04 AM
Try joining the ground of the Netduino to the extetnal power supply's ground.
In simple terms, without it the signals don't have a reference for what is a high or a low signal.
Paul
#14
Posted 17 February 2013 - 04:19 PM
ok, it is that.
Thanks paul
My next step is a web interface.
see you soon
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