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i like to power 2 Rsp3b+ via a Power USB hub, i have a usb power hub that is 12v @ 2A and im worrying it will blow or burn the ic's of the pi's due to over voltage, would this be true?

I like to add that both of these Pi's will have their own Camera module connected.

I plan to build a AR headset using this mentioned products.

enter image description here My question is what is the best way to power both of these Pi's?

Arlet Paz
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USB is a standard and must have 5V. The 12V you mention are the output ratings for the HUB's power supply. To be compatible with USB there must be an additional DCDC converter inside the HUB. Whether this HUB is capable of driving 2 RPis or not depends on the current it can provide, not its output voltage. A voltage of ~5.5V must not be exceeded!

Note that by standard a USB port does not provide enough current to drive at least one RPi, but those HUBs might be off standard. The only way to find out is trying. When doing so, monitor the voltage. If it drops significantly with the PIs connected you should choose a different PSU. Actually I recommend using an ordinary 5V-PSU or a USB charger.

Sim Son
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  • i might have to add more details to my question as i see you must off misunderstood what im asking or using, why would you suggest to plug the RPI's to the hub if you just stated that i cannot exceed ~5.5V ? i already said that my power hub is 12V. – Arlet Paz May 29 '19 at 16:42
  • What I mean is: the HUBs output voltage is 5V (otherwise it wasn't compatible with USB) and its **input** voltage is 12V. You should verify this with a multimeter before plugging the Pis in! – Sim Son May 29 '19 at 16:46
  • no the hub is not 5V where are you getting this from i took a picture so everyone can see and it clearly says 12V 2A – Arlet Paz May 29 '19 at 16:51
  • Thank you for the pictures They are useful. ALL USB hubs output (or provide) +5 volts, to do otherwise would not be normal. Your hub is powered by a 12 volt power supply, that is fine. But ALL USB hubs output 5 volts. The Hub converts the 12 volts to 5 volts. All of this being stated, what Sim Son stated is correct, if the hub is a "normal" USB hub it will probably not be able to power even one RPi, or at least not reliably... – Wendall May 29 '19 at 17:04
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    If you have a multimeter simply verify what I said by measuring the voltage. I now saw that the HUB also has two fast charging ports. From my experience "fast charging" usually happens with currents at ~2A, which would be absolutely sufficient to power your PIs. If you don't trust: buy a proper PSU... – Sim Son May 29 '19 at 17:23
  • okay okay thanks now we're talking. So i do own a MM and i ran a test and see that what Wandall mentioned is true and confirms Sim Son post as well, this is converting or stepping down the Voltage across its ports so i did see 5V respectfully on all ports and i did a current test which kinda got me worry as it displays 2.8A on all ports so i guess my new question is "would this blow my Pi's" since RPI take 2.5A – Arlet Paz May 29 '19 at 17:37
  • Now that you know it has 5V everything is fine. The PIs will not blow up as they won't sink 2.8A (take a look at Ohm's law). How exactly did you measure the current?! If you short the ports **they** are the ones that might blow up :/ – Sim Son May 29 '19 at 17:45
  • i actually used a spliced usb plug and a short one at that to so that the resistance from a longer wire dont mess with my math and i plugged the MM to those exposed usb wires and plugged that into the power hub, the MM has a DC10A function for testing AMPS and it also has one to test DCmA. I like to point out that that i plugged in the Pi and a 7inch lcd via HDMI and im getting the lighting bolt for under power hmmm?! – Arlet Paz May 29 '19 at 17:50
  • Sounds like you shorted the ports through the MM. If you still get 5V you're lucky, but don't do it again. You didn't mention that you also have a display in use. Is this display powered by the same 5V or is it a completely external display. The lighting bolt is not a reliable indicator in my experience. I for myself have one of those proprietary RPi touch displays and I'm getting the lighting bolt as well, even though I have tried with a very strong PSU for up to 20A while my display needs up to 6A if I remember correctly. – Sim Son May 29 '19 at 18:00
  • the display screen is only to se if i was going to see that bolt, thats all and yes i had everything plugged in the hub with no bolt but when i plugged the lcd to the pi the bolt did popped up, i did forgot to mention that i have a small fan that fits snug in the pi but was drawing 0.20mA even with no lcd https://www.amazon.com/gp/product/B01F3801A2/ref=ppx_yo_dt_b_asin_title_o02_s00?ie=UTF8&psc=1 – Arlet Paz May 29 '19 at 18:08
  • When there was no bolt has the lcd's backlight been on? And how did you know there was no bolt when the display hasn't actually been connected to the Pi? I don't know if I got you right this time, but I guess the bolt appears due to the display being on (bright). If you don't need the display anyway I would check for the bolt with a TV (which has its own PSU). – Sim Son May 29 '19 at 18:20
  • Let's not make it so complicated :D to me it looks like you have a suitable power supply and there is absolutely no magic about it. So, final steps: 1. measure the voltage (check) 2. plug the PIs in (check) 3. measure the voltage again. If it's still 5V there is nothing you have to worry about and you can go ahead with your project (and finally close this question) :D – Sim Son May 29 '19 at 18:26
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You can not power a Pi reliably from a hub!

The USB3 fast change ONLY works with phones which support and can negotiate the protocol - the Pi CAN’T because it doesn’t even have data lines on the power port.

Milliways
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Question

Power 2 Rsp3b+ via a Power USB hub [powered by 12VDC 2A, 24W wall wart]

Will blow or burn Pi's due to over voltage?

Answer

Well it is 90% likely (but no guarantee!) that everything should go well, if you use the "[2.4A] Intelligent charging" and "[2.4A] Quick charging" ports, one for each Rpi.

six port usb hub

References

Amazon 24W 6-Port USB Hub, USB3.0 x 4, Quick Charging [2.4A] x 1, Smart Charging [2.4A] x 1

Quick Charge - Wikipedia

Quick Charge is a technology found in Qualcomm SoCs, used in devices such as mobile phones, for managing power delivered over USB. It offers more power and thus charges batteries in devices faster than standard USB rates allow.

Quick Charge is a proprietary technology which allows for the charging of battery powered devices, primarily mobile phones, at levels above and beyond the typical 5 volts and 2 amps for which most USB standards allow. Numerous other companies have their own competing technologies; these include Mediatek's Pump Express, OPPO's VOOC (licensed to OnePlus as Dash Charge).

To take advantage of Qualcomm Quick Charge, both the host providing power and the device must support it. In 2012 the USB Implementers Forum (USB IF) announced that their USB Power Delivery (USB PD) standard had been finalized which allows for devices to transfer up to 100 watts of power over capable USB ports. This new technology was first seen in Xiaomi's Mi Mix 4 that went from 1% to 100% in a mere 17 minutes.

Beginning with version 3, the driving technology behind Quick Charge was named INOV (Intelligent Negotiation for Optimal Voltage), with ensuing versions successively improving upon allowed charging voltage levels.

Quick Charge version 4 was announced in December 2016 alongside the Snapdragon 835. Version 4 implements additional safety measures to protect against overcharging and overheating, and is compliant with both USB⁠-⁠C and USB Power Delivery (USB-PD) specifications.

Smart battery charger - Wikipedia

A smart battery charger is mainly a switch mode power supply (also known as high frequency charger) that has the ability to communicate with a smart battery pack's battery management system (BMS) in order to control and monitor the charging process. This communication may be by a standard bus such as CAN bus in automobiles or System Management Bus (SMBus) in computers. The charge process is controlled by the BMS and not by the charger, thus increasing security in the system. Not all chargers have this type of communication which is commonly used for lithium batteries.

Besides the usual plus (positive) and minus (negative) terminals, a smart battery charger also has multiple terminals to connect to the smart battery pack's BMS. The Smart Battery System standard is commonly used to define this connection, which includes the data bus and the communications protocol between the charger and battery. There are other ad-hoc specifications also used.

How does fast charging work? - digitalTrends 2019may22

tlfong01
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