maybe so but i believe you are bypassing all the conditioning/filtering circuits and essentially back feeding the device

Jase2985:

 

maybe so but i believe you are bypassing all the conditioning/filtering circuits and essentially back feeding the device

 

The switching mosfet for the vin to USB switching will prevent any backfeed to the USB input, and the USB to serial chip seems fine with it.

Switching is lacking on a few of the clones, which can lead to the same crashed USB ports as a dodgey hub that backfeeds will do.

There is still capacitors across it. They dont have LDO's on them so you need at least 6.5ish V on the vin to get 5v where you need it. Obviously a 3.3v arduino would be able to run off 5v thru there.

im not meaning to the USB, im meaning its like powering your house by connecting a generator to one of your wall sockets

im just saying Arduino dont advise it

"+5V. This pin outputs a regulated 5V from the regulator on the board. The board can be supplied with power either from the DC power jack (7 - 12V), the USB connector (5V), or the VIN pin of the board (7-12V). Supplying voltage via the 5V or 3.3V pins bypasses the regulator, and can damage your board. We don't advise it."

Neither am I meaning the USB, I am meaning putting 5v into the pin on the board labeled 5v, which is done all the time and recommended.

Its nothing like putting power into your wall outlet since that is going back thru circuit protection the wrong way, the 5v on the arduino is just the 5v bus that is used by everything else on the board.

then why does Arduino clearly state "We don't advise it"

you can say youve done it often all you like, and you may have been lucky but when the manufacture recommends not to do it, they are probably saying it for a reason

Jase2985:

 

then why does Arduino clearly state "We don't advise it"

 

you can say youve done it often all you like, and you may have been lucky but when the manufacture recommends not to do it, they are probably saying it for a reason

 

Because they do not want to have to explain to people why they have toasted their board when they put more than 5v into it. Check boards from other manufacturers and they dont have that silly non-recommendation on it.

richms:

 

Jase2985:

 

then why does Arduino clearly state "We don't advise it"

 

you can say youve done it often all you like, and you may have been lucky but when the manufacture recommends not to do it, they are probably saying it for a reason

 

 

Because they do not want to have to explain to people why they have toasted their board when they put more than 5v into it. Check boards from other manufacturers and they dont have that silly non-recommendation on it.

 

This is effectively what I've just been reading on numerous forums over the past hour.  

It's unregulated and is therefore "advised against" but doesn't mean it can't be done.  I think a few people mention just to put a diode before the 5V pin to ensure you don't nuke the USB port if you plug that in too and only to use it if you're confident the 5V power source is regulated (which, being that the HRV sends 5V to power its control panel, I'd suspect it is)  I've just tried the Arduino with an 1N4001 diode and it still runs ok.  

End of the day, it works, the diode should help protect it and even if I do nuke it, well an Arduino Uno ain't that expensive.  If anyone can advise differently, I think I'll just run with this for now.

Wouldn't a safer way to do it be, Connect the HRV's 5v power to a USB cable and use the USB cable to power the Arduino.

Similar situation with Raspberry Pi, it can be backpowered through GPIO and USB ports but doesn't have the same safety as the USB port

Yabanize:

Wouldn't a safer way to do it be, Connect the HRV's 5v power to a USB cable and use the USB cable to power the Arduino.

Similar situation with Raspberry Pi, it can be backpowered through GPIO and USB ports but doesn't have the same safety as the USB port

Here's a link to the code if anyone wants to try it out

http://www.geekzone.co.nz/forums.asp?forumid=141&topicid=195424

If you do, then feel free to recommend any extra's you find or post code if you can be bothered controlling the control panel from OpenHAB.  

Its fairly hacked together, but it works.  Includes checksum code to ensure TTL serial is good before sending to MQTT broker.

Cheers

chimera:

 

...  I've just tried the Arduino with an 1N4001 diode and it still runs ok.  

 

End of the day, it works, the diode should help protect it and even if I do nuke it, well an Arduino Uno ain't that expensive.  If anyone can advise differently, I think I'll just run with this for now.

 

 

Try using a Schottky diode instead of the IN4001 - it has a lower voltage drop.

When forward current flows through a solid-state diode, there is a small voltage drop across its terminals. A silicon diode has a typical voltage drop of 600–700 mV, while a Schottky diode has a voltage drop of 150 – 450 mV.