Go to advanced search

by davidcoton
Tue Aug 14, 2018 1:32 pm
Forum: General discussion
Topic: LCD display returning 5V
Replies: 32
Views: 617

Re: LCD display returning 5V

Sorry, misunderstood your earlier post. Phantom powering is from Pi to LCD, not from a peripheral to the Pi. Setting all GPIOs low will obviously stop it, but why does it matter? 5V will presumably normally be connected and if the system is shut down, 5V will be removed from ther Pi. The resistors (...
by davidcoton
Tue Aug 14, 2018 9:29 am
Forum: General discussion
Topic: LCD display returning 5V
Replies: 32
Views: 617

Re: LCD display returning 5V

TThe problem is probably "phantom power " from the HDMI cable, or a USB port. Does the LED go out when you disconnect all the separately powered peripherals?
by davidcoton
Fri Aug 10, 2018 3:27 pm
Forum: General discussion
Topic: LCD display returning 5V
Replies: 32
Views: 617

Re: LCD display returning 5V

The resistors will not be the problem. Either the display just won't work with the Pi 3V3 signals, or there is some other issue with it. I don't have a similar display, so I can't really guess any further.
by davidcoton
Fri Aug 10, 2018 8:59 am
Forum: General discussion
Topic: LCD display returning 5V
Replies: 32
Views: 617

Re: LCD display returning 5V

I have connected the 10K resistor as described above. The voltage immediately falls to 0.8V. Is it OK to work with RPi? Won't it damage it? Your experiment shows that the potential current from the 5V source is very low (~100 microamps) and so the possibility of damage to the Pi is also low. With a...
by davidcoton
Thu Aug 09, 2018 10:01 pm
Forum: Advanced users
Topic: What value are those parts?
Replies: 36
Views: 891

Re: What value are those parts?

"Logic clearly dictates that the needs of the many outweigh the needs of the few". I imagine Spock would not be considered much of a businessman. Surely the need to have Pi at all is greater than the need to have circuit diagrams of it? Most of the interesting circuitry is published (ie, the interf...
by davidcoton
Thu Aug 09, 2018 8:26 pm
Forum: General discussion
Topic: LCD display returning 5V
Replies: 32
Views: 617

Re: LCD display returning 5V

OK. So how to select the right resistor? This could be as simple as adding a resistor from the input to ground to pull the voltage down to 3V3 when the Pi is disconnected (value found by experiment -- not less than about 3K3), or some form of level shifting buffer. Will be a 5K OK? Start with 10K. ...
by davidcoton
Thu Aug 09, 2018 5:40 pm
Forum: General discussion
Topic: Pi MAC-address uniqueness
Replies: 7
Views: 1269

Re: Pi MAC-address uniqueness

DougieLawson wrote:
Thu Aug 09, 2018 5:24 pm
Is it really related the birthday paradox as that has a much more limited number of possible values from a set of 365 with one edge case?
I think so. The maths is identical, even if the range of inputs (and therefore outputs) is much greater.
by davidcoton
Thu Aug 09, 2018 5:38 pm
Forum: General discussion
Topic: LCD display returning 5V
Replies: 32
Views: 617

Re: LCD display returning 5V

What about 3V3 zener diode on each of pins? Can it work? Or just a diode which blocks the voltage from the LCD? The zener will do much the same as a carefully selected resistor, with less experimentation but also less knowledge of the current flow it causes. In my book a resistor is simpler and the...
by davidcoton
Thu Aug 09, 2018 5:14 pm
Forum: General discussion
Topic: LCD display returning 5V
Replies: 32
Views: 617

Re: LCD display returning 5V

So the voltage is higger than 3V3 while not connected to RPi? And after connecting it falls to less than 3V3? Yes, that is entirely possible. The display pulls its inputs to 5V, the Pi asserts either 3V3 or 0V. The Pi will be sinking current (originating from the display) -- this is entirely normal...
by davidcoton
Tue Aug 07, 2018 9:20 pm
Forum: Off topic discussion
Topic: Definition of ironic
Replies: 32
Views: 849

Re: Definition of ironic

You didn't hear the irony in my post? (Sorry it should have had a :lol: or a :rofl:)
by davidcoton
Tue Aug 07, 2018 9:15 pm
Forum: Troubleshooting
Topic: Raspberry Pi3 Smoke 19V power supply
Replies: 10
Views: 321

Re: Raspberry Pi3 Smoke 19V power supply

Most likely a gallant self-sacrifice by the SMBJ5.0A (D5 on a Pi3B, D7 on a Pi3B+), exactly as it is supposed to do. (If you're lucky the diode survives until the polyfuse opens. Normally the diode fails short circuit first. If you are really unlucky the diode fails open circuit first, and the whole...
by davidcoton
Tue Aug 07, 2018 8:54 pm
Forum: Off topic discussion
Topic: Definition of ironic
Replies: 32
Views: 849

Re: Definition of ironic

Time to trade, Pixel for Pie?

Or sue Google til the raspberry pips squeak.
by davidcoton
Tue Aug 07, 2018 8:44 pm
Forum: Beginners
Topic: Live Voice Translation Device - Where to begin?
Replies: 4
Views: 89

Re: Live Voice Translation Device - Where to begin?

As far as I know even state of the art voice recognition and machine translation won't give you anything like a usable result. Have a look at what Google translate does to text, and then imagine that on anything but the most precise, limited vocabulary speech. Test by entering English text, translat...
by davidcoton
Tue Aug 07, 2018 5:10 pm
Forum: Beginners
Topic: Power supply
Replies: 9
Views: 287

Re: Power supply

the led strip requires 18 wat/meter (as such 90 wat for 5 meter) and runs on DC5V, as such it requires 18A (90/5) power supply? The pi requires DC5V and 2,5A. Will both devices work on a 5V 18A power charger? Or will this break the pi? It probably won't break the Pi, but it may not work. The SDCard...
by davidcoton
Tue Aug 07, 2018 4:58 pm
Forum: Advanced users
Topic: STICKY: HOWTO: Create Custom HDMI modes
Replies: 187
Views: 224817

Re: STICKY: HOWTO: Create Custom HDMI modes

jamesh wrote:
Tue Aug 07, 2018 4:52 pm
What are your current config settings?
Congrats Jamsh on reaching 20K posts. Keep up the good work (sorry if this is too off-topic)!
by davidcoton
Mon Aug 06, 2018 10:12 pm
Forum: Other projects
Topic: Power the Pi using NiMH rechargable batteries
Replies: 13
Views: 423

Re: Power the Pi using NiMH rechargable batteries

Do not connect the batteries direct to the Pi. Your batteries will last about 30 minutes powering a Pi3B+, using a suitable converter (sorry I don't have a link). You can calculate this by converting the battery capacity to Wh (Ah x V), and working out the Pi's consumption in W. Rermember that NiMH ...
by davidcoton
Sat Aug 04, 2018 3:35 pm
Forum: Troubleshooting
Topic: MOSFET switch is leaking current when off
Replies: 15
Views: 352

Re: MOSFET switch is leaking current when off

To avoid this connect the disconnected transistors gate to a GPIO ground pin Perhaps I'm misunderstanding what was said above, but isn't that what the pull-down resistor doing? AKA - connecting the gate to ground when not actively being set to high? Yes. But Burngate has edited his post since Peter...
by davidcoton
Sat Aug 04, 2018 3:28 pm
Forum: Troubleshooting
Topic: Where are the detect pins?
Replies: 1
Views: 98

Re: Where are the detect pins?

Schematics are available: CM and Pi.

If that doesn't tell you, then the information is probably not available. IIRC the SDCard detect is not used, not sure about HDMI.
by davidcoton
Sat Aug 04, 2018 10:16 am
Forum: Beginners
Topic: Power Options for RPi 3 Model B
Replies: 11
Views: 294

Re: Power Options for RPi 3 Model B

... That is my understanding, also ... though not the mention of "shock or electrocution" - putting a human body across a current source is going to result in damage long before a fuse has a chance to blow. A properly designed mechanical breaker such as a RCB can break a circuit within a small frac...
by davidcoton
Fri Aug 03, 2018 10:08 pm
Forum: Beginners
Topic: Power Options for RPi 3 Model B
Replies: 11
Views: 294

Re: Power Options for RPi 3 Model B

For example it would be no good putting a fuse at the PSU end if the power cables could burst into flames when there was a fault at the Pi end. You would need the fuse at the Pi end to protect the cable. That doesn't sound right. The cable will only "burst into flames" if too much current is flowin...
by davidcoton
Fri Aug 03, 2018 6:29 pm
Forum: Beginners
Topic: " apt " vs " apt-get "
Replies: 9
Views: 320

Re: " apt " vs " apt-get "

The main difference appaears to be the default parameters -- apt is optimised for interactive use, apt-get remains for use in scripts.
There is at least one other syntax change (more of a clarification I think):
apt-get dist-upgrade
becomes
apt full-upgrade
by davidcoton
Fri Aug 03, 2018 6:25 pm
Forum: Beginners
Topic: Power Options for RPi 3 Model B
Replies: 11
Views: 294

Re: Power Options for RPi 3 Model B

BoCoKeith wrote:
Fri Aug 03, 2018 2:30 am
davidcoton wrote:
Wed Aug 01, 2018 10:24 pm
Use the GPIO pins, but add your own polyfuse of the same rating as the on-board one.
How would I go about doing that mechanically?
Piece of stripboard (eg veroboard)? Haven't needed this approach myself, so I don't have a tested answer.
by davidcoton
Thu Aug 02, 2018 9:18 pm
Forum: Advanced users
Topic: rPi3, Audio out + Neopixel control. Onboard vs HDMI
Replies: 1
Views: 61

Re: rPi3, Audio out + Neopixel control. Onboard vs HDMI

My question is this: If I use that HDMI/TFT display, can I just pull audio from the display output, or will the broadcom blacklist still kill the audio output even on HDMI Welcome to the Forum. AIUI, 1) Yes and 2) No. The HDMI output is digital and does not use the on-board PWM, so using it for Neo...
by davidcoton
Thu Aug 02, 2018 5:43 pm
Forum: General discussion
Topic: Safety question for a project
Replies: 14
Views: 328

Re: Safety question for a project

davidcoton, 12V is safe electrically. 12v is not about to electrocute anyone but that does not mean it is unconditionally safe. It's energy that is dangerous not voltage. With enough amps behind it starting a fire with 12v is easy. @heater, I'm happy for you to quote from my posts, but please do so...
by davidcoton
Thu Aug 02, 2018 5:35 pm
Forum: General discussion
Topic: Unpleasant new board smell ?
Replies: 67
Views: 7165

Re: Unpleasant new board smell ?

ShiftPlusOne wrote:
Thu Aug 02, 2018 9:02 am
Sounds like a whole new segment.
[pedant]
  1. You can hear the smell?
  2. A segment of Pi is known as a slice.
[/pedant] :lol:

Go to advanced search