Powering the Z-Uno with USB AND external supply

Discussion about Z-Uno product. Visit http://z-uno.z-wave.me for more details.
Post Reply
A.Harrenberg
Posts: 201
Joined: 05 Sep 2016 22:27

Powering the Z-Uno with USB AND external supply

Post by A.Harrenberg »

Hi,

I am using a breadboard with a power supply (can be set to 3.3 or 5 Volt) and plan to power the Z-Uno from this source by connect e.g. to pin 3 GND and pin 4 3.3 Volt.

Will it be safe if I plug in the USB at the same time? Are there diodes in the circuit to prevent damage to the power supply of the USB-Port of my computer as well for the Z-Uno itself and the external power supply of the breadboard?

I noticed that If I have the connections made and only plug in the USB that the LED of the power supply from the breadboard is on. So I assume that it will no be a good idea to use both at the same time...

Could someone please confirm if it is possible or not to use both at the same time?

Best regards,
Andreas.
fhem.de - ZWave development support

User avatar
PoltoS
Posts: 5626
Joined: 26 Jan 2011 19:36

Re: Powering the Z-Uno with USB AND external supply

Post by PoltoS »

It is definitelly not a good idea to power from two sources!

I strognly suggest to unpower 3.3V when you plug your USB cable. This is because Z-Uno DC-DC will take 5V to power 3.3V.

A.Harrenberg
Posts: 201
Joined: 05 Sep 2016 22:27

Re: Powering the Z-Uno with USB AND external supply

Post by A.Harrenberg »

Hi PoltoS,

thank you for the clarification. I expected that, but it would be much easier if that would be possible. I need to remember ALWAYS to unplug the power before inserting the USB, I will for sure forget it somewhere in the future...

How will it work if the Z-Uno is installed or even soldered into a PCB and gets its power from there? How will it be possible to upload a new sketch if the power is the connected the complete circuit. The board need to be switched off, but by connecting the USB the board will be powered by the USB... It might be possible that the consumption of the PCB is higher than what can be delivered by the USB-Port. (or what can be delivered @ 3.3V by the MCP17000 on the Z-Uno)

So I guess a jumper in the power supply between the Z-Uno and whatever source is used would be a good Idea if a reprogramming of the Z-Uno is needed...

Is there a schematic of the internal power supply of the Z-Uno available? For 5V -> 3.3V you wrote that you were using MCP1700, what is used for the 7-15V supply?

Thank you,
Andreas.
fhem.de - ZWave development support

michap
Posts: 368
Joined: 26 Mar 2013 10:35
Contact:

Re: Powering the Z-Uno with USB AND external supply

Post by michap »

A.Harrenberg wrote:For 5V -> 3.3V you wrote that you were using MCP1700, what is used for the 7-15V supply?
http://z-uno.z-wave.me/technical/


7–18 V → 5 V: NCP1117ST50T3G, max current sourcing from 5V pin 900 mA
5 V → 3 V: MCP1700, max current sourcing from 3V pin 200 mA

Michael

A.Harrenberg
Posts: 201
Joined: 05 Sep 2016 22:27

Re: Powering the Z-Uno with USB AND external supply

Post by A.Harrenberg »

Thanks for the info, there is so much info spreaded over the website I overlooked that.

900mA for the 5V supply is pretty much ,-)
fhem.de - ZWave development support

Post Reply