The B+ has 4 USB ports. Great. Now there are more opportunities to draw too much power from the Pi's processor and cause it to go wonky. Is there any way to tell whether you have connected too many power hungry USB accessories? The CPU reports it's temperature. Can it report it's avg power or power fluctuations?
When the Pi is acting strangely 90% of the time it's a power issue. But how can you tell if it's due to the USB accessories drawing too much power?
Thanks,
B+ Power Requirements
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Talk about Adafruit Raspberry Pi® accessories! Please do not ask for Linux support, this is for Adafruit products only! For Raspberry Pi help please visit: http://www.raspberrypi.org/phpBB3/
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- michaelmeissner
- Posts: 1830
- Joined: Wed Aug 29, 2012 12:40 am
Re: B+ Power Requirements
Well Adafruit sells the Charger Doctor (https://www.adafruit.com/products/1852) that you can use to keep an eye on the power draw (if it is repeatable).
- adafruit_support_mike
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Re: B+ Power Requirements
One of the big things in the B+ design is a complete overhaul of the power supply:
https://learn.adafruit.com/introducing- ... wer-supply
It's capable of 2A, and includes full switching buck converters for the 3.3v and 1.8v rails. It also has a hot-swap protection circuit for the USB ports.
https://learn.adafruit.com/introducing- ... wer-supply
It's capable of 2A, and includes full switching buck converters for the 3.3v and 1.8v rails. It also has a hot-swap protection circuit for the USB ports.
- pieman99
- Posts: 8
- Joined: Mon Apr 28, 2014 7:37 pm
Re: B+ Power Requirements
Thanks for the replies. The Charge Doctor gadget looks potentially useful, but it would be nice to know the power that is left for the CPU. Maybe on the next design there could be a voltage/current level that could be read out with a single command like the CPU/GPU temperature can be read out now. The Charge Doctor might solve my problem (trying to tell if a big USB mic is drawing too much power or USB mic + WiFi, etc + display, etc).
- michaelmeissner
- Posts: 1830
- Joined: Wed Aug 29, 2012 12:40 am
Re: B+ Power Requirements
Well you can get multiple Charger Doctors, one for the power going into the pi, and one for each of the accessories. There are now units that can measure the capacity of the total power delivered, and appear to be able to save the amount of power in an internal counter to tell you the total amount of power delivered before a battery died. I have one on order from an Asian ebay seller, but it hasn't arrived yet.
- adafruit_support_mike
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Re: B+ Power Requirements
The CPU hasn't changed, so the current consumption there will be the same as on a regular RasPi: about 350mA when idle, rising to about 700mA for CPU-intensive operations.
The B+ uses buck converters rather than LDOs for the 3.3v and 1.8v rails, so those rails put less load on the 5v supply than in a standard RasPi. Buck converters turn excess voltage into extra current, so even taking converter losses into account, 100mA from the 5v rail turns into 140mA on the 3.3v rail and 260mA on the 1.8v rail.
The power input system allows up to 2A onto the PCB, so it's easy to make sure a B+ has more than enough power.
The B+ uses buck converters rather than LDOs for the 3.3v and 1.8v rails, so those rails put less load on the 5v supply than in a standard RasPi. Buck converters turn excess voltage into extra current, so even taking converter losses into account, 100mA from the 5v rail turns into 140mA on the 3.3v rail and 260mA on the 1.8v rail.
The power input system allows up to 2A onto the PCB, so it's easy to make sure a B+ has more than enough power.
Forum rules
Talk about Adafruit Raspberry Pi® accessories! Please do not ask for Linux support, this is for Adafruit products only! For Raspberry Pi help please visit: http://www.raspberrypi.org/phpBB3/
Talk about Adafruit Raspberry Pi® accessories! Please do not ask for Linux support, this is for Adafruit products only! For Raspberry Pi help please visit: http://www.raspberrypi.org/phpBB3/