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by Burngate
Wed May 08, 2019 6:07 pm
Forum: Beginners
Topic: Raspberry pi GPIO.low
Replies: 7
Views: 208

Re: Raspberry pi GPIO.low

GPIO14 is also the UART TXD.
Quite possibly Linux isn't aware that you've grabbed it, and is still driving it; hence the odd voltage you're measuring.
Somewhere else on the forum, someone else was told to disable the UART, but for the life of me I can't find it!
by Burngate
Wed May 08, 2019 5:54 pm
Forum: General discussion
Topic: Fried my pi . Please help me to understand the root cause.
Replies: 34
Views: 998

Re: Fried my pi . Please help me to understand the root cause.

IP55 enclosures will make no difference if a lightning strike is the cause. Nor will pretty much anything else. One place I worked had two sites separated by a road. The network connections between them were in a metal tube buried underground. Lightning struck the middle of the road, with the result...
by Burngate
Wed May 08, 2019 10:03 am
Forum: The MagPi
Topic: Etcher instruction wrong Issue 81
Replies: 29
Views: 958

Re: Etcher instruction wrong Issue 81

fruitoftheloom wrote:
Wed May 08, 2019 9:43 am
Whenever I have used Etcher it has erased any previous partitions !
Not as a separate operation.

What was on the card before is irrelevant. Each memory bit is set/cleared to what is required, without needing to know what it used to be.
by Burngate
Mon May 06, 2019 5:36 pm
Forum: General discussion
Topic: Fried my pi . Please help me to understand the root cause.
Replies: 34
Views: 998

Re: Fried my pi . Please help me to understand the root cause.

My guess - and it's only a guess - is that pins 1 & 2 of the GPIO header have pierced the plastic sheet and made contact with some metal underneath.

Pin 1 is 3v3, and doesn't like 5v, and the power management chip has died.

To avoid a repeat, put the Pi in a case.
by Burngate
Mon May 06, 2019 10:36 am
Forum: Off topic discussion
Topic: Using a PC fan
Replies: 3
Views: 205

Re: Using a PC fan

A 12v fan will probably work off 5v, but there're no guarantees Personally, I'm against unplugging anything if you don't have to - two reasons. 1) There'll come a time when you forget. 2) There's a chance you might replug it wrongly, each time you plug it back in. Another thing - the 5v pins on the ...
by Burngate
Sun May 05, 2019 10:23 am
Forum: Beginners
Topic: Pi Zero booting a PC? Hal9000 Project.
Replies: 10
Views: 315

Re: Pi Zero booting a PC? Hal9000 Project.

The shut-down bit is easy.

On receiving the BRB signal, the wav file "I don't think you should do that, Dave" is played, and nothing else happens.
by Burngate
Sun May 05, 2019 10:18 am
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: power the Pi from 5V GPIO Pin possible?
Replies: 14
Views: 40202

Re: power the Pi from 5V GPIO Pin possible?

I don't know. When an ordinary fuse blows, the heat causes the metal to melt, and an air-gap forms. No residual current flows, and it cools down, but still no current flows even with any reasonable high voltage applied. (Actually, in some circumstances, the metal vaporises instead of melting, and ca...
by Burngate
Sun May 05, 2019 9:59 am
Forum: Beginners
Topic: Powering RPi with PSU by Pin 2 - what about Pin 4?
Replies: 2
Views: 129

Re: Powering RPi with PSU by Pin 2 - what about Pin 4?

- should I connect this to both Pin 2 and Pin 4 to give the RPi a beefier connection to the power - or just Pin 2? Simple answer - just one is necessary. One of my longer answers: Both Pin 2 and Pin 4 connect to the same bit of copper track, about 2.54mm apart. The impedance between them is minimal...
by Burngate
Sat May 04, 2019 5:38 pm
Forum: Beginners
Topic: Why does the requests.post keep firing?
Replies: 6
Views: 168

Re: Why does the requests.post keep firing?

Yes, you're right - every time it gets to if buttonState == False: it fires off the appropriate post, whatever it did last time round. What you want it to do is only fire once, until it finds a change, and that means remembering what it found last time. So, maybe, put buttonStateOld = GPIO.input(but...
by Burngate
Sat May 04, 2019 11:01 am
Forum: Python
Topic: setting an alarm to wake up the rasp using RTC DS3231
Replies: 2
Views: 116

Re: setting an alarm to wake up the rasp using RTC DS3231

Not a Python guru but, ... The data sheet for the chip has this to say, regarding the alarm and control registers: ADDRESS BIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0 FUNCTION RANGE 0Bh A2M2 10 Minutes Minutes Alarm 2 Minutes 00–59 0Ch A2M3 12/24 AM/PM 10 Hour Hour Alarm 2 Hours 1–12 + AM/PM 20 ...
by Burngate
Sat May 04, 2019 9:21 am
Forum: General discussion
Topic: Is this an official power supply?
Replies: 20
Views: 826

Re: Is this an official power supply?

It's not the international "official" power supply, but it is good enough to run a RPi3B+. Microcenter label it as an "official" supply. https://www.microcenter.com/product/602881/raspberry-pi-official-power-supply---white It's made in China for a company in Reading, Berkshire, UK that specialises ...
by Burngate
Sat May 04, 2019 8:58 am
Forum: General discussion
Topic: Raspberry Pi so small that it fits on a post stamp ;-)
Replies: 3
Views: 276

Re: Raspberry Pi so small that it fits on a post stamp ;-)

hippy wrote:
Fri May 03, 2019 10:51 pm
Do I win a ... Free Postage Stamp ?
Send us a stamped, self-addressed envelope and I'll give you by return of post one of the other stamps
by Burngate
Fri May 03, 2019 11:14 am
Forum: Beginners
Topic: MCP23017 Specs mA per IO and overall mA across all IOs
Replies: 3
Views: 124

Re: MCP23017 Specs mA per IO and overall mA across all IOs

It's not the most easily understood datasheet, but here's the way I would interpret it. The 20mA figure you quote, I'm guessing, is from the two lines for "Input clamp current and Output clamp current". Those are for when things are going seriously wrong, and something is trying to drag a GPIO above...
by Burngate
Wed May 01, 2019 5:52 pm
Forum: Beginners
Topic: Fan ramps up very quickly on 3B+
Replies: 18
Views: 706

Re: Fan ramps up very quickly on 3B+

Just a quick question - have you tried swapping things round, and if so, does the noise go with the Pi, the case, or the fan?
And do all the fans go the same way round?
by Burngate
Tue Apr 30, 2019 8:45 am
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: power the Pi from 5V GPIO Pin possible?
Replies: 14
Views: 40202

Re: power the Pi from 5V GPIO Pin possible?

Trip current and hold current appear right, but the maximum voltage is only 6v, whereas the one used on the 3B+ is 16v In normal use, that shouldn't make any difference - there shouldn't be more than 5¼v - but then, normal use isn't what the fuse is there for! And we hear tales of people putting 24v...
by Burngate
Mon Apr 29, 2019 5:53 pm
Forum: Beginners
Topic: Controlling temperature chamber using Peltier and PWM signal with external power source
Replies: 26
Views: 683

Re: Controlling temperature chamber using Peltier and PWM signal with external power source

Just tried them, get the bad same response. Interestingly, while it appears to be Portuguese, it seems to be on a server in Canada. When I tried https://ca.grandado.com/ I was sent to an American server, https://no.grandado.com/ and the response was "Blocked by Content Security Policy An error occur...
by Burngate
Mon Apr 29, 2019 10:17 am
Forum: Troubleshooting
Topic: No power on pins and disconnected GNDs
Replies: 10
Views: 255

Re: No power on pins and disconnected GNDs

FreakyFriends wrote:
Sun Apr 28, 2019 4:18 pm
... (and the red LED was on then and now too)
If the red LED is on, there must be 5v present.
by Burngate
Mon Apr 29, 2019 10:08 am
Forum: Compute Module
Topic: Power Supply Sequence
Replies: 8
Views: 368

Re: Power Supply Sequence

I´ve seen a couple of baseboards (WaveShare Compute Module IO is one of them) that simply takes 5V and connects directly to the following LDOs: 1117-3.3V 1117-2.5V 1117-1.8V (This one is connected to the 1117-3.3V output) The earliest Pis had almost exactly that - the 2.5v regulator was also connec...
by Burngate
Mon Apr 29, 2019 9:51 am
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: I damaged the TX/RX pins. Is there a way to remap the serial port to another free GPIO port?
Replies: 6
Views: 268

Re: I damaged the TX/RX pins. Is there a way to remap the serial port to another free GPIO port?

funnel wrote:
Sun Apr 28, 2019 1:11 pm
Somehow a current spike damaged the 14 and 15 pin on my Rpi Zero 1.3.
Note that over time any damage can propagate throughout the SoC, causing it to fail, so any "fix" is likely to be only temporary.
by Burngate
Sun Apr 28, 2019 10:09 am
Forum: General discussion
Topic: Two Batteries, One Transistor...
Replies: 7
Views: 253

Re: Two Batteries, One Transistor...

There are of course other differences between valves and (bipolar) transistors. Left to its own devices - that is, with nothing connected to its grid - a triode valve would allow the full current to flow from anode to cathode, so the grid was driven negative* to reduce the current. A transistor is m...
by Burngate
Sun Apr 28, 2019 9:20 am
Forum: Beginners
Topic: no readings from sensors
Replies: 4
Views: 139

Re: no readings from sensors

i can't get any readings from the sensors What sensors? , i'm wondering if the problem is why my wiring or if i accidentally ruined my sensors. It's a bit difficult to tell, but ... One sensor (the blue block) appears to be fed from 5v, with output to GPIO18 (pin 12) and a 10k pull-up to 5v. That's...
by Burngate
Sat Apr 27, 2019 9:03 am
Forum: Troubleshooting
Topic: I let the smoke out with 24volt into 3B+
Replies: 12
Views: 447

Re: I let the smoke out with 24volt into 3B+

Unfortunately, even if it were still available, that refill kit wouldn't fix the polyfuse. It only works on silicon devices, but the polyfuse is made of organic polymer. Maybe someone's out there in the Amazon looking for a related species of moss more suitable for these devices - but don't hold you...
by Burngate
Fri Apr 26, 2019 5:25 pm
Forum: Advanced users
Topic: LM386 Audio Amp Module Producing buzzing/cracking noise
Replies: 6
Views: 243

Re: LM386 Audio Amp Module Producing buzzing/cracking noise

I've tried to use an additional power supply for the audio amplifier and it doesn't produce as much noise as the previous method I think I am facing the ground loop issue but I am not sure about it, or how to solve it You may very well be right about the ground-loop. One way to check is to disconne...
by Burngate
Fri Apr 26, 2019 9:43 am
Forum: Automation, sensing and robotics
Topic: Raspberry Pi Robot failure protection
Replies: 3
Views: 202

Re: Raspberry Pi Robot failure protection

... suddenly the raspberry pi crashed and shut down, but while motors where running. The motors have pushbuttons which are pressed when the legs reach the maximum amplitude, and they stop the motors. Unfortunately, at the time of the crash three motors where still running, and the pi didn't shut th...
by Burngate
Thu Apr 25, 2019 6:04 pm
Forum: Beginners
Topic: How to calculate resistors...
Replies: 68
Views: 1549

Re: How to calculate resistors...

... Is the 50mA maximum only related to the GPIOs, or the whole 3.3v bus (inlcuding the GPIOs and the 3.3V pins - like pins 1 and 17), or does that also include the 5V pins (2 and 4)? That 50mA is only for the GPIOs themselves. The 3.3v on the header - pins 1 & 17 - comes directly from the regulato...

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