I am working on a home automation project in which I have a Mega (2560) and a Yun. I am powering the Mega USB input from a Kara Mobile regulated switching 5v supply with a hacked USB cable (+/- 5v only - no data). I saw no discussion about the USB shield so I also connected the hacked USB cable connector shield/shell to the minus 5v line of the supply. All seems OK to this point. I powered the Yun “Vin” from the Mega’s 5 volt buss. This also seems to work OK but my problem is the large amount of current the Yun will be pulling and hence total power coming into the Mega.
It seems that I could create 2 hacked USB cables in parallel on the regulated supply output to separately feed the two controllers. Question: if doing this, should the the USB connector shield/shell be connected to the supply minus 5 volt line in both hacked cables? Should there also be an additional ground between the Yun and Mega, since I hope to have them communicating in the future?
Alternately, it seems I could directly wire the regulated 5v to the Mega’s 5v buss and also to the “Vin” on the Yun with the Grounds connected together. However, this would bypass any internal fuse/protection that the USB input would provide. Any recommendations would be most appreciated.
Thanks.
saylur:
I am working on a home automation project in which I have a Mega (2560) and a Yun. I am powering the Mega USB input from a Kara Mobile regulated switching 5v supply with a hacked USB cable (+/- 5v only - no data). I saw no discussion about the USB shield so I also connected the hacked USB cable connector shield/shell to the minus 5v line of the supply. All seems OK to this point. I powered the Yun “Vin” from the Mega’s 5 volt buss. This also seems to work OK but my problem is the large amount of current the Yun will be pulling and hence total power coming into the Mega.
It seems that I could create 2 hacked USB cables in parallel on the regulated supply output to separately feed the two controllers. Question: if doing this, should the the USB connector shield/shell be connected to the supply minus 5 volt line in both hacked cables? Should there also be an additional ground between the Yun and Mega, since I hope to have them communicating in the future?
Alternately, it seems I could directly wire the regulated 5v to the Mega’s 5v buss and also to the “Vin” on the Yun with the Grounds connected together. However, this would bypass any internal fuse/protection that the USB input would provide. Any recommendations would be most appreciated.
Thanks.
You also have to remember that a USB 2 port can only output 500mA. Running the two from one port may overload the port. I understand that USB 3 ports (the blue ones) can output 1A.
Henry_Best, thank you for your reply and comment.
I should expand and clarify my intentions with the hacked USB cable approach, which is in fact, the way I will proceed pending no adverse concerns are voiced. To clarify, I would not be connecting to any computer with the hacked USB cables but solely use those cables to supply power from the separate regulated 5v supply which is external to my enclosure with the Arduinos. Also, these hacked cables will be short pigtails which terminate in USB female sockets. This will allow me to externally connect to unaltered USB cables which enter an enclosure and remain permanently connected to the Arduinos. When a code update is required, I can unplug the unaltered USB cable from the supply pigtail and connect to a computer long enough to do the code upload.
For operation...
Regulated supply with hacked USB cable, which terminates in a female socket... plugs into permanently mounted unaltered USB cable which plugs into the Arduino
For code updates…
The permanent mounted unaltered USB cable is unplugged from the hacked supply cable female socket and plugged into a computer. (computer… unaltered USB cable… Arduino)
More complicated than my original post but hopefully more concise.
Thanks again for your comment.
When a code update is required, I can unplug the unaltered USB cable from the supply pigtail and connect to a computer long enough to do the code upload.
If and only if the PC can provide enough power!
Mark