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Having stability issues with a BBB running from 24VAC that could be power related (1500mA transformer using 6 ft of cable). The same system is very stable when a 5V 1000mA DC supply is connected to the BBB directly. The system is a BBB with an EDIMax Nano USB wireless adapter and microSD card. No valves, rain sensor, etc. are connected.
Things at improve stability on 24V AC: limiting CPU speed to 600MHz (not a big difference), using wired Ethernet rather than wireless USB adapter (much improved stability)
Activities that reliably cause the system to lock up on 24V AC: any wireless traffic (e.g. ping once per second), compiling the kernel at 1GHzShould the BBB be allowed to run freely, or be limited to low CPU speed and no USB wireless? I see the power supply is meant to provide 750mA, which sounds sufficient but does not allow a lot of margin.
Suggestions to improve stability?
Make sure you are measuring AC voltage, not DC. 33-34V AC sounds too high for a transformer rated 24V AC. Perhaps cheap multimeters have issues measuring AC accurately (as the AC measurement is supposed to the root mean squared value). In any case, if OSBo runs off it fine, it should be ok.
When you say ‘having difficulty getting my OSBo controller to run stably from AC power’, do you mean the WiFi is unstable (i.e. lose connection) or that OSBo is not powering up? If it’s WiFi, I am not completely surprised: I also occasionally have trouble getting WiFi to stay on. It works better when the controller is placed close to the WiFi router. I think BeagleBone Black is not as forgiving as Raspberry Pi in terms of powering WiFi dongle through its USB port. Adafruit’s BeagleBone tutorial (http://learn.adafruit.com/beaglebone/wifi) mentions repeatedly that it requires a beefy power supply. I suggest that you try to use a wired Ethernet cable first, and see if that makes the system more stable.
Yes, was measuring AC voltage. It’s probably a badly calibrated multimeter as all the AC voltage readings seem high.
I started with a wired Ethernet cable and 5V DC supply, and things worked well. Switching to wireless took a lot of time, but now I’ve got the wireless drivers working with good reliability.
The issue is that the system seems prone to brown-outs often when running from 24V AC with the USB wireless adapter. System works perfectly (wireless connects and passes traffic without lockups, regardless of CPU load) with a 5V 1000mA DC supply connected directly to the BBB in the same physical location. I’ve replicated this on the bench (short cables) and in the field.
I think I can have 120V AC available where this unit will eventually be installed, so I may just end up with two power supplies– a 24V AC brick for the valves and a 5V power supply connected to the BBB. Is there any problem powering the system with both a 5V brick (connected to BBB) and 24V AC simultaneously? I assume the 5V rail will draw from whatever supply has the higher voltage, but want to confirm that supplying 5V to the BBB will not harm the on-board AC-DC supply.
Project shelved for now. I could not get the BBB to run reliably from the onboard 24V AC-DC supply with a USB wireless adapter. Did work OK with wired Ethernet.
Sorry to hear that, and thanks for your feedback. Which WiFi dongle are you using?
There are some related discussions about WiFi adapter drivers in another thread:
viewtopic.php?f=34&t=423
You may want to check it out to see if it helps.Another workaround is to use a powered WiFi adapter, such as this one:
http://www.amazon.com/TP-LINK-TL-WR702N-Wireless-Repeater-150Mpbs/dp/B007PTCFFW/
Basically you can plug it into Bone’s Ethernet jack and it provides a WiFi interface to the Bone. This should work pretty reliably.Regarding your earlier question on having two +5V sources powering the same board, in general you shouldn’t do this. If you want to power Bone from an external power supply only, you can clip off the +5V header pins on OSBo so that it won’t compete with the external power supply. The +5V header pins are number 5 and 6 on P9 (the third column from the right end).
I will have to think about improving the power supply design to make WiFi more reliably for Bone. The 24VAC -> 5VDC regulator circuit is the same on OSPi and OSBo, and it has worked well on OSPi. The Bone probably has higher current or EMI requirements and I will have to investigate further.
I am the author on the wireless thread– Edimax Nano wireless adapter is the device in question. Also tried some old dual band Broadcom b43 wifi adapter I had in the parts bin, but it needed even more power and reliably crashed the bone. My BBB is the A6 revision, which is the currently shipping model.
I tested VIN-GND voltage when Bone is powered up with a dongle, and it’s within spec. So I am not sure if the problem is due to the power supply not being able to deliver enough current. I wonder if this has to do with EMI from the switching regulator and inductor. If so, using a USB extension cable to place the WiFi dongle away from the board may help. When I get time, I will try some experiments to figure out the exact cause
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