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Netduino GO Power Question

Started by Pete Brown, Aug 10 2012 03:41 PM

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15 replies to this topic

#1 Pete Brown

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Posted 10 August 2012 - 03:41 PM

Quick question on powering the GO: Does power have to come in through the USB port (even with a battery->USB adapter) or is it possible to have a power module with a GO socket. Basically want to know if the +5v and +3v3 pins are one-way or if you can power the whole board and its modules through one of them. Has anyone tried using one of the Gadgeteer power modules? Seems it would work as long as the above is covered.. Pete

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#2 Mario Vernari

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Posted 10 August 2012 - 04:26 PM

Hello Pete, and congrats for the VS-Live. That's a very smart question!...Despite I never tried it, by reading the schematic it *SHOULD* be possible supplying the +5V from any of the sockets. Well, it should be working just for a lucky (or unlucky) condition: the protection diode embedded in any MOSFET being used for switching the power of the socket on. Basically, even you don't feed the +5V from the USB port, you (theoretically) would not able to supply the power from the GO! sockets, because the MOSFETs shut them. Since they are controlled by the MCU, until it won't be powered, then there is no way to activate them. So, at first glance, you should *NOT* able to power the board from a socket. However, each MOSFET embeds a diode, reversely polarized respect to the nominal current flow. That is, if you supply the +5V to it, the current will flow toward the MCU, that should start (almost) regularly. As soon the bootstrap will activate (normally) the MOSFET, the circuit SHOULD keep alive by itself. I'm not sure at 100% that it actually works, but it probably will do. Much like a trick than a recommended way to power the board, however. Hope it helps. Cheers

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#3 Nevyn

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Posted 10 August 2012 - 05:08 PM

Does power have to come in through the USB port (even with a battery->USB adapter) or is it possible to have a power module with a GO socket. Basically want to know if the +5v and +3v3 pins are one-way or if you can power the whole board and its modules through one of them.

Has anyone tried using one of the Gadgeteer power modules? Seems it would work as long as the above is covered..

I've not tried any of the Gadgeteer modules but I did notice an interesting effect a few days ago.

I've been playing with the STM8S chips for a blog series I'm writing and had a breadboard circuit set up. Normally I've been powering this from the GO! which has a USB connection. For some reason I had disconnected the USB but had a power module connected to the breadboard and I powered this up with 3.3V output.

Interesting effect, the module sprang to life as did the GO!. I also had the Komodex Labs 7-segment display connected - that also started working even though I believe the display requires 5V. It's dimmer than when the GO! is powered through the USB but it's working as I would expect.

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Mark

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#4 Stefan

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Posted 10 August 2012 - 05:44 PM

I can say I have tried it with my Netduino Go! Hacker, and it can power up the main board. But with an important footnote:
It's not designed that way. So I don't know for sure if it'll keep on working.

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#5 Arron Chapman

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Posted 10 August 2012 - 06:29 PM

I can say I have tried it with my Netduino Go! Hacker, and it can power up the main board. But with an important footnote:
It's not designed that way. So I don't know for sure if it'll keep on working.

I'll add to this.

You must supply 5V to the mainboard if you power it via a module. Supplying it with 3.3V leaves the 5V rails at ~3.1V

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#6 ErikN

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Posted 11 August 2012 - 12:47 AM

I remember talking to Arron about this a little while ago. Looking at the circuit it certainly seemed possible by coincidence but it looked like it was not designed that way. When powered "correctly" there seems to be a lot of effort put toward clean power and keeping selfish components from affecting the stability of the power. When supplying power from a module - this is all bypassed. You'd need to be very careful not to supply dirty, reversed or spiky power. Chris popped in to catch the tail end of it and ended the conversation with an abrupt: "Don't do that.*" I suppose if you have a large supply of Go boards and don't mind some waste - go ahead! But if you only have one precious, treat it kindly and power it as designed. *I think this was the direct quote. It's been awhile though.

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#7 Pete Brown

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Posted 11 August 2012 - 03:11 AM

Thanks, guys. Lots of great info here. So, it sounds like any power module would need to have a USB connector. Admittedly, that adds complexity and cost to something as simple as a battery pack. It's also not something I can screw down on, say, a robot. USB connectors are pretty tight, but they tend to have even less tight of a fit than a good barrel jack. Chris, if you're reading this, I'd suggest that any Netduino GO v.next include solder pads or something for us to work with (I'd suggest screw terminals, but I suspect that would be offensive to the Netduino design aesthetic <g>) Or you could just add a barrel jack

Pete

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#8 Stefan

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Posted 11 August 2012 - 07:03 AM

So, it sounds like any power module would need to have a USB connector. Admittedly, that adds complexity and cost to something as simple as a battery pack.

True, but have you seen this one?
http://nwazet.com/power

A power module occupies a socket. If it uses a USB cable (and I have one of 10cm), then you still have 8 sockets left. It's a matter of choice of course.

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#9 Chris Walker

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Posted 11 August 2012 - 09:19 AM

One of the design goals of GoBus is to ensure safety and simplicity with the power supply flowing to modules. To sum it up, all power flows downstream. We've made room in the spec for smart in-line power boosters for module chains and a few other power options...but the power always needs to be provided to modules rather than from them. With Arduino shields and .NET Gadgeteer modules, you can end up in situations where you burn up components. With the clear GoBus power system we can calculate power allocations and, optionally, programmatically ensure that enough power is available for all modules. USB has become the defacto power standard for small electronics, so in most scenarios the MicroUSB port works out really well for power. For other scenarios, a 3" MicroUSB cable and a "phone charger" power supply or battery pack should work well. For instance, [nwazet has built a power supply module that works with Netduino Go. We can also evaluate adding a power barrel jack to a future Netduino Go board. Or someone may make a Netduino Go clone which adds a power barrel jack and a 5.0V LDO power regulator. Chris P.S. Yes, if you plug a Gadgeteer power module into one of Netduino Go's GoBus sockets it will power the mainboard. You'll also lose a bit of voltage through the FETs. This is not an officially supported scenario and if combined with USB power can be dangerous...but it is possible.

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#10 Lunddahl

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Posted 11 August 2012 - 11:31 AM

USB has become the defacto power standard for small electronics...

European Union also have some regulations stating that all electronic devices sold, should be able to use the same Power Supplies, i'm not updated on the technical side, but i know Micro USB is the connector.

Why, well i think some politician forgot his cellphone charger, and then had to much spare time...:-)

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#11 Chris Walker

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Posted 11 August 2012 - 11:36 AM

European Union also have some regulations stating that all electronic devices sold, should be able to use the same Power Supplies, i'm not updated on the technical side, but i know Micro USB is the connector.

Yup! The number of proprietary cell phone chargers thrown away every year is huge.

The new MicroUSB standard is really exciting, and the EU regulations are the primary reason we picked MicroUSB as the connector for Netduino two years ago. At the time, several resellers expressed concerns that users might not have the cables...so we have been giving away free MicroUSB cables with every Netduino, just in case.

With all the USB power sources (rechargeable batteries, computers, AC adapters, etc.) users have a lot of options. And since polarity, voltage, power regulation, and current requirements are all built into the USB spec...those sources should "just work."

As a bonus, we can deploy and debug over the same port

Chris

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#12 Pete Brown

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Posted 11 August 2012 - 08:48 PM

Thanks I was mostly concerned about robotics. Typical USB cable doesn't have a tight bend radius, and even if it did, puts a lot of stress on the socket. The socket itself is a friction fit (much like a barrel jack), not screwed in or something like a terminal. There's good potential for it to be pulled out, loosened, or otherwise not do its job. Just thinking through possible uses in the future and the potential issues there. Sounds like the USB jack will be the only recommended way of getting power to the GO, so that's what I'll work with.

Pete

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#13 Pete Brown

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Posted 11 August 2012 - 08:55 PM

True, but have you seen this one?
http://nwazet.com/power

A power module occupies a socket. If it uses a USB cable (and I have one of 10cm), then you still have 8 sockets left. It's a matter of choice of course.

Yes, and it's a very cool module. If thinking about robots, though, now there are *three* friction fit connectors (barrel, USB A and USB micro

and a fair bit of cable (smalles USB cable I've seen has been around 3'). Although I just looked it up and see you can get them as short as 9". Not ideal, but better than 3' for sure.

Again, not shooting the idea down -- I'll probably pick up one of those adapters as I really could have used it during a demo on Thursday, but just thinking about points of failure for stuff that shakes and moves.

Pete

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#14 neslekkim

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Posted 12 August 2012 - 08:22 AM

I would like to have something like this: https://www.adafruit.com/products/259 and hook up an microusb on the load so the netduino could get power. I don't like that they still use miniusb, so I'm not buying it yet..

--
Asbj�rn

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#15 Fabien Royer

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Posted 17 August 2012 - 07:32 PM

Hi Pete,

Does power have to come in through the USB port (even with a battery->USB adapter) or is it possible to have a power module with a GO socket. Basically want to know if the +5v and +3v3 pins are one-way or if you can power the whole board and its modules through one of them.

I know that it's a 'frowned upon' practice by Chris but I do it all the time during module development: it prevents issues with the SWD / SWIM debug interface caused by the Netduino Go! recycling the power to the module every time it starts. If you use a well regulated supply at the same power levels as expected by the Go! main board, it works without damaging the board.

Just my 2 cents

-Fabien.

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#16 nakchak

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Posted 17 August 2012 - 10:19 PM

Thanks

I was mostly concerned about robotics. Typical USB cable doesn't have a tight bend radius, and even if it did, puts a lot of stress on the socket. The socket itself is a friction fit (much like a barrel jack), not screwed in or something like a terminal. There's good potential for it to be pulled out, loosened, or otherwise not do its job.

Just thinking through possible uses in the future and the potential issues there. Sounds like the USB jack will be the only recommended way of getting power to the GO, so that's what I'll work with.

Pete

you could always get a 90 degree usb plug which would help with cable routing...

Also you can get locking micro usb plugs which require you press tab down on the plug body to disengage the lugs on the plug and release it from the socket

Nak.

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