Power Supply & USB Power Cable

[Admin]

Hi All

I thought I shoud start a thread to talk about this.

The power supply and USB cable are extremely important.
The RPi will draw approc 1.1A, so you need an AUX regulator which is going to supply 2.1A

The USB cable must be a high quality cable to ensure no voltage drop down the cable.
You should look for a cable which says
20AWG for the Charge, the Data does not matter

AWG = American Wire Gauge, the smaller the number, the thicker the wire == BETTER

Thx
Lee

[Mig29fuk]

Lee Hi!
As I fly a non-electrical vintage Aircraft power needs careful thought.
I'm using a 12000mAh Power Bank with 1 X 1A USB and 1 X 2.1A USB.
The charge life is excellent and means I can leave aircraft Aux battery (No charging) for Radio only.
A newer better value version is here:
http://www.amazon.co.uk/gp/product/B00F5Q4F0U?keywords=ec%20technology%20power%20bank&qid=1439328119&ref_=sr_1_1&sr=8-1
I power the PilotAware set on 2.1A output using 50cm USB Cable..
Regards
Gerry

[Admin]

Hi Gerry
I also use one of these, i have got the 50,000mah version. I managed to run Pilotaware for about 5 hours on one of these.

Power cable is still paramount.
Short and heavy duty is best

Thx
Lee

[Richard]

How about a Charge 4 USB Power?

 http://www.charge4.co.uk/

They are Software run. I currently use on on the IPad. But not yet tested with Pilotaware.

Richard.

[Admin]

How about a Charge 4 USB Power?

 http://www.charge4.co.uk/

They are Software run. I currently use on on the IPad. But not yet tested with Pilotaware.

Richard.

Hi Richard,
I have not tried these, they do look expensive 
I own a couple of these

http://www.ebay.co.uk/itm/External-50000mAh-Power-Bank-Portable-DUAL-USB-Battery-Charger-For-Mobile-Phone-/271955860042?hash=item3f51d51a4a

When fully charged, they will run PilotAware for about 4-5 hours
charging does take a long time
Thx
Lee

[BobD]

Hi Guys,

I have just joined the Forum, and am in the process of ordering the bits I need to have a go at building a Unit. Regarding the Power Supply, would this unit be suitable (and possible better as it re-charges itself via solar power as well as DC4.8-5.4V) ?

http://www.ebay.co.uk/itm/50000mAh-Solar-Battery-Charger-Power-Bank-For-iPhone-iPad-Tablets-Smart-Phones-/321814230008?hash=item4aed9f73f8

Forgive my ignorance, I have a little knowledge (dangerous  ) of things electrical, but I am a dab hand at following instructions, so feel free to use me for idiot testing purposes 

BobD

[Admin]

Hi all

I think in all these examples of powrr banks, I hear mixed stories.
So its difficult to know which ones wil live up to their claims

Last night I was running my PilotAware from a powerbank, and it worked fine.
I picked up Russ Hicks from about 12 miles, and he could see me.
But like stocks, past performance is no guarentee of future gains, so
Its difficut to comment on all the batteries on the market.
If they live up to their claims, then all is good.

I think if the voltage drops to about 4.6v at the input to the Pi, then
It will become unreliable.

I am in the process of trying to make accurate measurements of
All components, and will post some results tomorrow

Thx
Lee

[Richard]

Lee,
  Yes the Charge4 Is about £100 but you get what you pay for.
       I tryed diffrent 12v power supply and all gave bad transceiver interference. the Charge4 has been worked to reduce Transceiver interference, and it does what it says on the tin. I have one fitted permanently in my Aircraft panel.
     I will report back on the ability to power both the PilotAware and IPad at the same time.

Richard

[Admin]

Lee,
  Yes the Charge4 Is about £100 but you get what you pay for.
       I tryed diffrent 12v power supply and all gave bad transceiver interference. the Charge4 has been worked to reduce Transceiver interference, and it does what it says on the tin. I have one fitted permanently in my Aircraft panel.
     I will report back on the ability to power both the PilotAware and IPad at the same time.

Richard

Hi Richard 2.4a per port is easily enough, especially as they report no voltage drop at full load

Thx
Lee

[Admin]

Hi All

I bought myself one of these which measures instantaneous and peak voltage(low)/current(high).
http://www.maplin.co.uk/p/maplin-usb-power-meter-n55ce
My previous version, was not capable of capturing the peak values, and only gave instantaneous,
This does not capturethe worst case scenario.

I wanted to see different configurations of USB cable on PilotAware, it has confirmed
what I had believed regarding power supply/usage.

The scenarios are as follows
1. USB Auxilliary socket noted as 3.1Amp rating, I bought this
http://www.ebay.co.uk/itm/3-1-Amp-USAMS-Twin-Dual-2-Port-USB-12V-Universal-Car-Socket-Charger-UK-New-/321686700107?hash=item4ae605804b


2. Tested against the following 3 cables
2.1 http://www.ebay.co.uk/itm/BLACK-50cm-20AWG-Premium-Fast-Micro-USB-Charger-Cable-for-Android-Phones-Tablets-/271936509656?hash=item3f50add6d8

2.2 http://www.ebay.co.uk/itm/USB-to-Micro-USB-with-ON-OFF-Switch-Cable-Charger-Power-for-Raspberry-Pi-Android-/351330415704

2.3 http://www.aliexpress.com/item/10pcs-1M-Micro-USB-2-0-Male-A-Sync-Data-Charge-Cable-For-HTC-Android-For/1750791723.html

Here are the results for Peak Voltage (low) and Peak Current (high)

Measured at WiFi Dongle
2.1 PV=4.83V PC=0.24A
2.2 PV=4.67V PC=0.24A
2.3 PV=4.20V PC=0.24A

Measured at DVB-T Dongle
2.1 PV=4.83V PC=0.18A
2.2 PV=4.67V PC=0.18A
2.3 PV=4.20V PC=0.19A

Measured at Power Source
2.1 PV=5.13V PC=1.16A
2.2 PV=5.13V PC=1.17A
2.3 PV=5.13V PC=1.21A

When the Voltage level drops to around 4.67V, the RPi is approaching a brownout.
so cable 2.3 is really bad, 2.2 is OK and 2.1 has some good margin.

The interesting thing is the range the voltage drop from best(2.1) to worse(2.3) is 0.63v
in this case that is massive 15% difference.

One other thing worth mentioning, the total current draw at the USB is (0.24 + 0.18) 0.42A
There is a (default) cutoff limit of 0.6A on the RPi, this is quite close.
This cutoff point can be doubled in Software to 1.2A, and sounds like a good idea,
especially if future enhancements will be to make use of external GPS etc

Thx
Lee

[JCurtis]

Hi,

I am the designer and maker of the Charge2 USB chargers mentioned in this post.  If anyone has any questions over them, please feel free to drop me an e-mail to the address on the website.

Have to say this looks like an interesting project.  I dug out the previous generation Pi I have here and powered it up via a Charge2, it all seemed to be working fine.

if you need any help getting accurate power readings etc. I have various tools and test gear which can help with that.

[Admin]

Hi,

I am the designer and maker of the Charge2 USB chargers mentioned in this post.  If anyone has any questions over them, please feel free to drop me an e-mail to the address on the website.

Have to say this looks like an interesting project.  I dug out the previous generation Pi I have here and powered it up via a Charge2, it all seemed to be working fine.

if you need any help getting accurate power readings etc. I have various tools and test gear which can help with that.

Hi Jeremy

Many thanks for the heads up on your findings.
I would just point out that by default, the Pi draws quite a small amount of current, probably about 600mA.
Could you clarify the figures I quoted would be OK, whereby I expect the Pi in this setup to be drawing a peak current, possibly upto 1.5A

In this configuration, the radio module pulses for about 1-5ms ever 1-2 seconds, which would result in a spike of current draw of 330mA, so in other words the effective quiescent current is probably about 750mA, with the cyclic pulse of an additional 330mA taking the total to approx 1.1A.

I think your unit could cope with that no problem, but wanted to give you the opportunity to comment.

Thx
Lee

[JCurtis]

Hi,

I am the designer and maker of the Charge2 USB chargers mentioned in this post.  If anyone has any questions over them, please feel free to drop me an e-mail to the address on the website.

Have to say this looks like an interesting project.  I dug out the previous generation Pi I have here and powered it up via a Charge2, it all seemed to be working fine.

if you need any help getting accurate power readings etc. I have various tools and test gear which can help with that.

Hi Jeremy

Many thanks for the heads up on your findings.
I would just point out that by default, the Pi draws quite a small amount of current, probably about 600mA.
Could you clarify the figures I quoted would be OK, whereby I expect the Pi in this setup to be drawing a peak current, possibly upto 1.5A

In this configuration, the radio module pulses for about 1-5ms ever 1-2 seconds, which would result in a spike of current draw of 330mA, so in other words the effective quiescent current is probably about 750mA, with the cyclic pulse of an additional 330mA taking the total to approx 1.1A.

I think your unit could cope with that no problem, but wanted to give you the opportunity to comment.

Thx
Lee

The chargers have a very fast transient load response combined with reasonable capacitance on each output port.  I can look at simulating that kind of load by pulsing GPIO pins with loads on etc. but I don't think it would be a problem in terms of voltage or current.

As an aside, looking at the 3.3v regulator (based on the pic of it anyway) it seems it employs a AMS1117 LDO regulator, which the data sheet for recommends 22uF output capacitance but the silk screen says 10uF.  It would be interesting to scope the output of them with the radio is running to ensure it's stable.

[Admin]

As an aside, looking at the 3.3v regulator (based on the pic of it anyway) it seems it employs a AMS1117 LDO regulator, which the data sheet for recommends 22uF output capacitance but the silk screen says 10uF.  It would be interesting to scope the output of them with the radio is running to ensure it's stable.

Hi
Are you referring to the 3.3v regulator on the pi itself ?
If so, this is not used to power anything, it does not have nearly enough power.
The ARF radio has a dedicated regulator, capable of supplying 800ma
Thx
Lee

[JCurtis]

Are you referring to the 3.3v regulator on the pi itself ?

No not the one on the Pi but the additional ARF 3.3v regulator shield.  This is only going by the silkscreen but it looks like they have 1uF on the input and 10uF on the output.  The data sheet recommends 10uF and 22uF respectively. Might not be an issue but it would be interesting to see the output as the load jumps up and down.