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by Paul Hutch
Thu Oct 12, 2017 10:35 am
Forum: General discussion
Topic: How to measure current draw of the RPi
Replies: 31
Views: 11595

Re: How to measure current draw of the RPi

Be careful when using those inline USB power meters. They can only show the voltage into the cable but for any significant length (10 cm+) there will be a significant voltage drop. Here's a Google Sheet that calculates the voltage losses for varying cable lengths and gauge. https://docs.google.com/s...
by Paul Hutch
Wed Oct 11, 2017 10:05 pm
Forum: General discussion
Topic: How to measure current draw of the RPi
Replies: 31
Views: 11595

Re: How to measure current draw of the RPi

Heater wrote:
Mon Oct 09, 2017 7:37 pm
3) If you see less than 5.2 volts then throw that supply in the bin. Smart or other wise.
The low voltage limit for Raspberry Pi's is 4.75V. The maximum limit is 5.25V. There are very few 5V USB spec power supplies that supply more than 4.9V while supplying 2A.
by Paul Hutch
Fri Oct 06, 2017 8:55 pm
Forum: Python
Topic: Led Matrix
Replies: 9
Views: 1402

Re: Led Matrix

Since you are using 4 GPIO pins and four LEDs I recommend one LED per GPIO instead of a matrix.
by Paul Hutch
Thu Oct 05, 2017 12:30 am
Forum: General discussion
Topic: FCC Part 15 C Testing
Replies: 8
Views: 1523

Re: FCC Part 15 C Testing

Many thanks for the follow up info Sytrus. Did a tiny bit of looking since my last post and I see that only the transmitter portion of a pre-certified transceiver is not re-tested. This means using a pre-certified radio transceiver probably only saves 33% of testing costs vs., what I hoped, a 66% sa...
by Paul Hutch
Sat Sep 30, 2017 6:49 pm
Forum: General discussion
Topic: is what i want to do possible (menu with apps).
Replies: 14
Views: 1937

Re: is what i want to do possible (menu with apps).

My experience is that any USB keyboard or keypad works fine plugged in to the USB port of a RasPi. So if you can find a keypad that has the symbols you need, it should work.

I've never seen a keypad with letters, all I've seen are regular keyboards and numeric keypads.
by Paul Hutch
Sat Sep 30, 2017 6:22 pm
Forum: General discussion
Topic: FCC Part 15 C Testing
Replies: 8
Views: 1523

Re: FCC Part 15 C Testing

Thanks for the link to the integrator program fruitoftheloom, I'll definitely check in to that if I end up using a Pi in a commercial product. If you don't mind Sytrus, please post back with any further information you get on this testing situation. Having to duplicate the spurious emissions test of...
by Paul Hutch
Sat Sep 30, 2017 6:09 pm
Forum: General discussion
Topic: Powered USB hub advice
Replies: 10
Views: 16363

Re: Powered USB hub advice

3) Rather than "hacking the cable" why not build something like I did to test & block back-powering: http://www.cpmspectrepi.uk/raspberry_pi/MoinMoinExport/HubPort2PortResChk.html ? Trev. Very nice list of results, thanks for doing all that work. I'm surprised how many of them are not properly isol...
by Paul Hutch
Fri Sep 29, 2017 12:29 am
Forum: General discussion
Topic: is what i want to do possible (menu with apps).
Replies: 14
Views: 1937

Re: is what i want to do possible (menu with apps).

The last item in the list of countries is "Rest of the World", I almost missed it too. They give two choices both of which are good distributors I'm familiar with so pick the one with the best shipping terms to Israel.
by Paul Hutch
Fri Sep 29, 2017 12:20 am
Forum: General discussion
Topic: FCC Part 15 C Testing
Replies: 8
Views: 1523

Re: FCC Part 15 C Testing

It been a few years since I've done this part 15 intentional radiator stuff, but that sounds like full on, get your own FCC ID, intentional radiator testing. I thought that as long as you don't modify the radio circuitry you only need to test a RasPi based product as an unintentional radiator and yo...
by Paul Hutch
Thu Sep 28, 2017 10:27 am
Forum: General discussion
Topic: Best way to run a python script at startup?
Replies: 35
Views: 322842

Re: Best way to run a python script at startup?

Whatever user is used when launching from .config/lxsession/LXDE-pi/autostart needs to be a member of the dialout group.
by Paul Hutch
Wed Sep 27, 2017 11:01 pm
Forum: General discussion
Topic: Pi in hot attic a fire risk?
Replies: 27
Views: 5239

Re: Pi in hot attic a fire risk?

The Pi's on the ISS have no fans and are enclosed in a thick aluminum housing. That arrangement makes any fire concerns almost completely vanish.
by Paul Hutch
Wed Sep 27, 2017 10:20 pm
Forum: General discussion
Topic: Raspberry pi frequency tester?
Replies: 2
Views: 433

Re: Raspberry pi frequency tester?

The type of device you want is a spectrum analyzer for audio frequencies. It will show you a spike in the display at the feedback frequency. I did a quick search via Google and there are a number of RasPi projects however the couple I looked at used LEDs for the display only giving a low resolution ...
by Paul Hutch
Tue Sep 26, 2017 8:53 pm
Forum: General discussion
Topic: Powered USB hub advice
Replies: 10
Views: 16363

Re: Powered USB hub advice

For setting up Pi Zero and Zero W's I use a Tripp-Lite charger/OTG hub all the time. I connect the Zero's power port to one of the 2A charging ports and the Zero's USB port to the OTG port. https://www.tripplite.com/4-port-usb-charging-station-otg-hub-5v-6a-30w-usb-charger-output~U280004OTG/ I'd bee...
by Paul Hutch
Wed Sep 20, 2017 1:35 pm
Forum: General discussion
Topic: Pi in hot attic a fire risk?
Replies: 27
Views: 5239

Re: Pi in hot attic a fire risk?

Don't use a fan, it will literally fan the flames spreading the fire if something goes wrong.
by Paul Hutch
Fri Sep 08, 2017 5:19 pm
Forum: General discussion
Topic: 20% discount on RPi3B
Replies: 7
Views: 1602

Re: 20% discount on RPi3B

Just got an email from Arrow saying that in addition to the RPi3 the 20% discount is now offered on some RPi power supplies, cases and accessories.
by Paul Hutch
Wed Sep 06, 2017 4:03 pm
Forum: General discussion
Topic: 20% discount on RPi3B
Replies: 7
Views: 1602

Re: 20% discount on RPi3B

The discount is applied part way through the checkout process when it asks for the coupon code. Ordered one yesterday and it was only $27.99 and includes free overnight shipping (should be here in few hours). A very good deal.
by Paul Hutch
Fri Aug 25, 2017 3:28 pm
Forum: Camera board
Topic: Is this RPi 'mini camera' official?
Replies: 6
Views: 1609

Re: Is this RPi 'mini camera' official?

That does not appear to be the official camera. When I visited that page down below were links for the two official cameras (regular & NOIR).

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