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by j_hof
Sun Oct 29, 2017 2:23 pm
Forum: Wanted
Topic: Need 20-30 raspberry pi 1 model b (with ethernet and RCA)
Replies: 4
Views: 2377

Re: Need 20-30 raspberry pi 1 model b (with ethernet and RCA)

I have four of these, three unused. Interested?
by j_hof
Sat Aug 13, 2016 1:59 pm
Forum: Beginners
Topic: Power a pi with a li-ion battery
Replies: 13
Views: 2283

Re: Power a pi with a li-ion battery

Did you get an answer to your question? My apologies for muddying the waters in my earlier posts by trying to point out that a battery powered solution won't keep your Pi powered for very long. Either of the boost converters you ask about will probably do the task.
by j_hof
Mon Aug 08, 2016 5:04 pm
Forum: Beginners
Topic: Power a pi with a li-ion battery
Replies: 13
Views: 2283

Re: Power a pi with a li-ion battery

Well, shucks, you're right that I made a foolish math error, wonky or otherwise.
by j_hof
Mon Aug 08, 2016 3:38 pm
Forum: Beginners
Topic: Power a 5v relais with GPIO
Replies: 8
Views: 1301

Re: Power a 5v relais with GPIO

I stand corrected. The diagrams are correct.
by j_hof
Mon Aug 08, 2016 3:35 pm
Forum: Beginners
Topic: Power a pi with a li-ion battery
Replies: 13
Views: 2283

Re: Power a pi with a li-ion battery

Well, to clarify my earlier post, with a 1000mA-Hr battery at an average terminal voltage of 3.6V, an 80 percent efficient boost converter that outputs 5 volts at 0.5A, it will stay alive for just over 30 minutes. Perhaps I was not clear that the 0.5A was the current drawn from the 5V output by the ...
by j_hof
Mon Aug 08, 2016 1:21 pm
Forum: Beginners
Topic: Power a pi with a li-ion battery
Replies: 13
Views: 2283

Re: Power a pi with a li-ion battery

Let's suppose that the current is within the capability of the boost converter. Then the issue becomes how long will it power your Pi. The battery itself has a milliamp-hour rating. The voltage of a lithium ion battery is typically about 4.2 volts at full charge and droops to about 3 volts when it's...
by j_hof
Mon Aug 08, 2016 12:33 pm
Forum: C/C++
Topic: SPI from RPi to atMega328p
Replies: 2
Views: 1623

Re: SPI from RPi to atMega328p

In general, the SPI protocol, if there is such a thing, uses one device as the master and one device at a time as the slave. The master is responsible for clock generation and for generation of slave select, usually an active low signal. Then there is the issue to have the clock polarity and the pha...
by j_hof
Mon Aug 08, 2016 12:06 pm
Forum: Beginners
Topic: Power a pi with a li-ion battery
Replies: 13
Views: 2283

Re: Power a pi with a li-ion battery

In concept, this works, but the boost device you point out is capable of only 0.5A at most. Not good enough if your Pi needs 1A.
by j_hof
Mon Aug 08, 2016 12:01 pm
Forum: Beginners
Topic: Power a 5v relais with GPIO
Replies: 8
Views: 1301

Re: Power a 5v relais with GPIO

With all due respect, you have the polarity of the diode backwards. You want the anode to 5V, the cathode to the junction of the relay coil and transistor collector. This diode is there to clamp the voltage spike when the coil of the relay turns off.
by j_hof
Sun Jul 31, 2016 1:35 pm
Forum: C/C++
Topic: header files for GPIO
Replies: 1
Views: 544

header files for GPIO

Are there some standard functions for accessing the available GPIO resources using C or C++? I presume there are and I see reference to BCM2835.h header file to access them. But I'll be darned if I can find where it is available and modest documentation for how to use it.
by j_hof
Sun Jul 31, 2016 1:14 pm
Forum: Beginners
Topic: Error resizing existing FAT partition
Replies: 4
Views: 1434

Re: Error resizing existing FAT partition

For anyone who cares, I managed to resolve the issue getting the above error. I first plugged in the SD card into the windows based PC. I then used the storage management tool to reformat the card as a FAT32 type. Then I used SDFormatter to quick format the card, resize on. Finally, copy the unzippe...
by j_hof
Mon Jul 25, 2016 12:09 am
Forum: Beginners
Topic: Error resizing existing FAT partition
Replies: 4
Views: 1434

Re: Error resizing existing FAT partition

I'm getting the same error message when I use a 16Gb microSD card. It's a class 10 card. I have used SDformatter, version 4, to format it with full format, resize on, as the instructions say. I am then copying all of the contents of NOOBS version 1.9.2 to the card. The properties of the card shows F...

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