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by gregeric
Fri Mar 24, 2017 12:56 pm
Forum: General discussion
Topic: I have problems with my electronic circuit
Replies: 34
Views: 4182

Re: I have problems with my electronic circuit

OK, here's how I'd do it: mosfet.png R2 ensures the MOSFET is off if ever left floating. It also overcomes the default ~50k pullups on GPIOs 0-8 to ensure it's off during booting. If you connect instead to one of GPIOs 9-27 (with default pulls down at boot), you could omit R2 & even R1. There are ot...
by gregeric
Fri Mar 24, 2017 11:14 am
Forum: General discussion
Topic: I have problems with my electronic circuit
Replies: 34
Views: 4182

Re: I have problems with my electronic circuit

There'll be a variation, part to part, of the Hfe. The next transistor you pick may not work so well, it's on the limit.
by gregeric
Fri Mar 24, 2017 10:52 am
Forum: General discussion
Topic: I have problems with my electronic circuit
Replies: 34
Views: 4182

Re: I have problems with my electronic circuit

That circuit won't work properly - with a 1k resistor the base current will be limited to (3.3V-0.7V)/1K = 2.6mA. From the 2N2222's datasheet, the gain (Hfe) will be around 60, so the collector current will be around 150mA, less than the 250mA a 2.8W 12V load demands. You could use a lower value res...
by gregeric
Fri Mar 24, 2017 9:41 am
Forum: Troubleshooting
Topic: Pi Zero W identifying as "B Rev 2"
Replies: 20
Views: 6482

Re: Pi Zero W identifying as "B Rev 2"

Sounds like the revision hasn't been written to OTP at the factory. See viewtopic.php?f=43&t=160611
by gregeric
Thu Mar 23, 2017 8:52 pm
Forum: General discussion
Topic: Install DS3231 Real Time Clock - Latest Info
Replies: 69
Views: 57663

Re: Install DS3231 Real Time Clock - Latest Info

That's somewhat more robust than my efforts alphanumeric, though a little bigger: https://twitter.com/gregeric/status/841005509171908610
by gregeric
Thu Mar 23, 2017 7:18 pm
Forum: General discussion
Topic: Install DS3231 Real Time Clock - Latest Info
Replies: 69
Views: 57663

Re: Install DS3231 Real Time Clock - Latest Info

If the unit in your hands has what appears to be a supercap, but only the two i2c pullup resistors and decoupling capacitor in addition to the DS3231, then either 1. It's not a supercap. or 2. It's not a genuine DS3231, as the genuine part is UL certified *not* to trickle charge, hence rendering it ...
by gregeric
Thu Mar 23, 2017 6:51 pm
Forum: General discussion
Topic: Install DS3231 Real Time Clock - Latest Info
Replies: 69
Views: 57663

Re: Install DS3231 Real Time Clock - Latest Info

Using the figures you have researched, the BOM is around $5. Rule of thumb, multiply that by 3 to 4 for the retail price your distributors sell at. Hence the realistic price of the Adafruit module, $14. I have around six of these, plus three Chronodots, plus a plain chip bought from RS. Of the ridic...
by gregeric
Thu Mar 23, 2017 6:02 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: Add an I2S mic using device tree & simple-audio-card
Replies: 37
Views: 27341

Re: Add an I2S mic using device tree & simple-audio-card

That's good to hear, and thanks for coming back to post your enhancement.
by gregeric
Wed Mar 22, 2017 12:34 am
Forum: General discussion
Topic: Install DS3231 Real Time Clock - Latest Info
Replies: 69
Views: 57663

Re: Install DS3231 Real Time Clock - Latest Info

If they can fake a Maxim chip it's not too much of a stretch to stamp a lithium primary cell with marks to suggest it's otherwise for some marketing claims :lol:. How's the charging circuit looking? And the timekeeping? Compare the picture of the PiHut module with the Adfruit module available from t...
by gregeric
Tue Mar 21, 2017 1:43 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: Add an I2S mic using device tree & simple-audio-card
Replies: 37
Views: 27341

Re: Add an I2S mic using device tree & simple-audio-card

The mics sample to 24 bits, supporting S24_LE & S32_LE formats natively. The former is still 32 bits wide, padded with 00's - perfect for our 32-bit processor. If you want 16-bit, you'll have to do it in software. That's probably do-able by editing that .asoundrc chain with another plugin to do the ...
by gregeric
Tue Mar 21, 2017 10:54 am
Forum: General discussion
Topic: Eric Anholt offically announces support of VC4 without acces
Replies: 27
Views: 3522

Re: Eric Anholt offically announces support of VC4 without a

You are about 4 years late to the party. I know it can be tiresome to repeat things, but the ongoing success of the Pi means it will attract new users like 321a over and over. I remember the time I first read about the fascinating internals of the Broadcom chip, the same intrigue I imagine 321a is ...
by gregeric
Tue Mar 21, 2017 6:56 am
Forum: Automation, sensing and robotics
Topic: Sensing 12v input using GPIO
Replies: 12
Views: 3007

Re: Sensing 12v input using GPIO

The use of open/closed & my misunderstanding/its ambiguity seems to stem from whichever crude model you relate to: the plumbing model with a valve controlling the flow of water (open=on), or the electrical model of a mechanical switch (open=off).
by gregeric
Mon Mar 20, 2017 12:30 pm
Forum: Automation, sensing and robotics
Topic: Sensing 12v input using GPIO
Replies: 12
Views: 3007

Re: Sensing 12v input using GPIO

I've always used open/closed for a transistor in the switch sense ie on=conducting=closed and off=non-conducting=open. But there again I'm a self-taught hobbyist of 40 years, not the electronics pro I suspect you are... also that's why i suggested "conducting" may be less ambiguous.
by gregeric
Mon Mar 20, 2017 10:30 am
Forum: Automation, sensing and robotics
Topic: Sensing 12v input using GPIO
Replies: 12
Views: 3007

Re: Sensing 12v input using GPIO

I think you also meant to say "while the transistor of the optocouplers-isolator is closed", or even better conducting, not open.
by gregeric
Fri Mar 17, 2017 8:41 pm
Forum: General discussion
Topic: Graph & timeline of Pi Sales
Replies: 88
Views: 28076

Re: Graph & timeline of Pi Sales

Now that 12.5 million sales have been registered, there has appeared an official Pi chart (gerrit) of sales by model, published at https://www.raspberrypi.org/magpi/raspberry-pi-sales/

Figures for Zero interesting - knocking on for 500k Zeros, plus in excess of 100k ZeroW already.
by gregeric
Fri Mar 17, 2017 12:04 pm
Forum: Troubleshooting
Topic: Powering by MOSFET, why undervoltage lightning bolt?[SOLVED]
Replies: 34
Views: 4298

Re: Powering by MOSFET, why undervoltage lightning bolt?

Sorry, I didn't read beyond the strapline of your MOSFET's datasheet • 32A, 60V, RDS(on) = 0.035Ω @VGS = 10 V and assumed it wasn't driveable directly by logic levels. It appears it should be OK however - problem must lie elsewhere, or it's the sum total of all those little resistances there & elsew...
by gregeric
Fri Mar 17, 2017 11:08 am
Forum: Troubleshooting
Topic: Powering by MOSFET, why undervoltage lightning bolt?[SOLVED]
Replies: 34
Views: 4298

Re: Powering by MOSFET, why undervoltage lightning bolt?

Use a different MOSFET: one with low RDS_ON *and* capable of being driven fully on by 3V3 or 5V logic as you prefer. The resistance should be as low as possible - 10's of milli ohms. I use FDN304P for a high side switch on the 5V rail. You could take a leaf out of the RPi engineers book & use the sa...
by gregeric
Fri Mar 17, 2017 10:57 am
Forum: Graphics, sound and multimedia
Topic: Raspberry PI Zero (W) - Why no audio???
Replies: 12
Views: 8436

Re: Raspberry PI Zero (W) - Why no audio???

Don't overlook the fact that on the ZeroW we enjoy Bluetooth audio out too for a neat wireless solution.
by gregeric
Thu Mar 16, 2017 10:41 pm
Forum: General discussion
Topic: Design software
Replies: 2
Views: 489

Re: Design software

Thanks for posting that >>+1, I enjoyed the videos in your links.
by gregeric
Thu Mar 16, 2017 6:28 pm
Forum: Beginners
Topic: mems microphone
Replies: 7
Views: 2798

Re: mems microphone

I'm 99% certain that the Knowles SPH0645 used on that Adafruit breakout will work with the driver & steps for the Invensys ICS43432 I described here: viewtopic.php?f=44&t=173640
by gregeric
Thu Mar 16, 2017 11:17 am
Forum: General discussion
Topic: LED flashes on Power off on the PiZero W [solved]
Replies: 15
Views: 4472

Re: Power off on the PiZero W

That dtparam solely affects how the linux kernel handles the LED re active lo or hi. It doesn't invert the VPU's notion of the LED's wiring: the power-down flashes are the same on the Zero irrespective of that setting. I've no idea if the W's lack of the power-down flash sequence is by design, or un...
by gregeric
Wed Mar 15, 2017 9:42 pm
Forum: General discussion
Topic: GPIO Power Safety Margin?
Replies: 7
Views: 1047

Re: GPIO Power Safety Margin?

Better to split the clean logic supply from the dirty motor supply rails, not try to use one rail for both.
by gregeric
Wed Mar 15, 2017 9:27 pm
Forum: Troubleshooting
Topic: USB insertion causing reboots
Replies: 11
Views: 1594

Re: USB insertion causing reboots

Ensure the Pis have an adequate supply via the micro-USB port & that's your job done.

If you are so concerned, put a blanking plate over any/all of the four USB ports which are not required.
by gregeric
Wed Mar 15, 2017 9:06 pm
Forum: Troubleshooting
Topic: USB insertion causing reboots
Replies: 11
Views: 1594

Re: USB insertion causing reboots

It should also be mentioned that on Pi models B+/2B/3B there's a USB current limiting switch which will suspend the USB Vbus supply if USB peripherals draw too much current. Given an adequate power supply, ie one which can meet the Pi's USB 1200mA-across-4-ports plus SoC & peripherals requirements, ...
by gregeric
Tue Mar 14, 2017 2:51 pm
Forum: General discussion
Topic: Pi Zero official case
Replies: 14
Views: 2734

Re: Pi Zero official case

Time for another video Graham!

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