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by drgeoff
Sun Oct 21, 2018 8:55 am
Forum: General discussion
Topic: Power supply for Rpi 3
Replies: 12
Views: 322

Re: Power supply for Rpi 3

the £2 poundland 5v transformer usb plugs sustain a 2.4a draw according to big clives utubes iirc, i have 3 x headless pi-0-w s running off them .. How big are the transformers? And how long is the cord? My Raspberry is about 1.2m away from a socket. Thanks, Y More or less the same footprint as a s...
by drgeoff
Sat Oct 20, 2018 9:45 am
Forum: Networking and servers
Topic: Combining two or more raspberry pi's into one unit
Replies: 14
Views: 8358

Re: Combining two or more raspberry pi's into one unit

Ok, this is interesting, everyone keeps just saying no... Innovation starts with people telling people no. Now it's time for the innovators to shove the No's back in their faces. Innovate! The concept of combining multiple 'computers' to act as a single more powerful one has been around and impleme...
by drgeoff
Fri Oct 19, 2018 11:47 pm
Forum: Graphics, sound and multimedia
Topic: Pi3 as a digital pot/audio matrix
Replies: 5
Views: 132

Re: Pi3 as a digital pot/audio matrix

The following does not have any circuit schematics or code, just a basic principle. Put a resistor between an analogue audio output stage and an analogue audio input stage. Put a bipolar transistor or FET as a switch between that input and ground. When the switch is open the audio passes through. Wh...
by drgeoff
Fri Oct 19, 2018 8:40 pm
Forum: Beginners
Topic: Powering Screen through 5V GPIO
Replies: 11
Views: 172

Re: Powering Screen through 5V GPIO

Having looked at your photo again and having taken an old B out of storage to check with a continuity tester I think you have the video wires reversed. The point where you have soldered the yellow wire is ground and where you have the black wire is video. Oh okay, so in that case I shall have to tr...
by drgeoff
Fri Oct 19, 2018 8:33 pm
Forum: Beginners
Topic: Powering Screen through 5V GPIO
Replies: 11
Views: 172

Re: Powering Screen through 5V GPIO

Having looked at your photo again and having taken an old B out of storage to check with a continuity tester I think you have the video wires reversed. The point where you have soldered the yellow wire is ground and where you have the black wire is video.
by drgeoff
Fri Oct 19, 2018 7:49 pm
Forum: Troubleshooting
Topic: USB electrical heat/zap
Replies: 5
Views: 160

Re: USB electrical heat/zap

Wow, you've got A/C driving into the ground plane of your exposed and sensitive electronics and you're asking if something could get fried? Let me be perfectly blunt: Until you get that grounding sorted all out, unplug EVERYTHING. If you can feel the A/C by touching the USB jacks, then just imagine...
by drgeoff
Fri Oct 19, 2018 7:36 pm
Forum: Beginners
Topic: Powering Screen through 5V GPIO
Replies: 11
Views: 172

Re: Powering Screen through 5V GPIO

Ok I tried attaching the red wire to either side of the polyfuse still with the same results, however I have only tested this via touching the connectors since I don't have my soldering equipment with me right now. Will that have made a difference? Pressing the end of the wire (with solder on it) f...
by drgeoff
Fri Oct 19, 2018 6:50 pm
Forum: Beginners
Topic: Powering Screen through 5V GPIO
Replies: 11
Views: 172

Re: Powering Screen through 5V GPIO

... and a 3" car backup monitor I modified to run off 5V. How have you modified it? I assume you tested it and know it's working, but do you have any figures for the current it takes, or the voltage range it requires? I assumed that when the OP wrote "I know the screen is working because I got it t...
by drgeoff
Fri Oct 19, 2018 6:14 pm
Forum: Beginners
Topic: Powering Screen through 5V GPIO
Replies: 11
Views: 172

Re: Powering Screen through 5V GPIO

Try moving the red wire to one end of the polyfuse - the green rectangle in the top right corner of your photo. One end of that is electrically connected to the same point as your red wire is now. The other end is connected directly to the 5 volt pin of the micro-USB power input socket. You want the...
by drgeoff
Fri Oct 19, 2018 6:05 pm
Forum: Beginners
Topic: Pi Zero USB via GPIO?
Replies: 6
Views: 122

Re: Pi Zero USB via GPIO?

A Zero possibly has enough speed that one could emulate the USB 1 protocol but you would need additional hardware to do voltage level translation. USB 1 uses 5 volts signal levels whereas RPi GPIOs are 3.3 volt. I doubt a Zero would be fast enough to emulate USB 2. Even if yes, again you would need ...
by drgeoff
Fri Oct 19, 2018 1:06 pm
Forum: Off topic discussion
Topic: Add Analog to Digital pins to the pi
Replies: 9
Views: 876

Re: Add Analog to Digital pins to the pi

Isn't that a crib of what Lincoln is reputed to have said? https://historynewsnetwork.org/article/161924
by drgeoff
Fri Oct 19, 2018 12:31 pm
Forum: Beginners
Topic: will Raspberry Pi 3 fry if i use a 5V/850mA power supply?
Replies: 8
Views: 188

Re: will Raspberry Pi 3 fry if i use a 5V/850mA power supply?

If the ebay listing said 2000 mA and the one you received says 850 mA, contact the seller. If that doesn't get you a refund or a proper replacement, open a case with ebay.
by drgeoff
Fri Oct 19, 2018 9:16 am
Forum: Advanced users
Topic: Using my Pi with an AC mains connected preamp.
Replies: 11
Views: 327

Re: Using my Pi with an AC mains connected preamp.

Any ripple and noise on the -28 volt rail needs to be at a very low level compared to the input signal as they are added to it.
by drgeoff
Fri Oct 19, 2018 9:04 am
Forum: Troubleshooting
Topic: [SOLVED] Cannot Connect Via Ethernet - Router Problem?
Replies: 8
Views: 211

Re: Cannot Connect Via Ethertnet - Router Problem?

Usually if the Ethernet plug on the router doesn't show link activity, then you have a wiring issue. Simply try another cat5/6 cable after rebooting the router, and then rebooting the pi. There can be several reasons for reach-ability issues: * wrong type of cable other network cards can auto corre...
by drgeoff
Thu Oct 18, 2018 11:32 am
Forum: Other projects
Topic: RF Transmitter
Replies: 2
Views: 121

Re: RF Transmitter

Except for a few specific frequency bands, operating an RF transmitter without a licence is illegal in most countries.

RPis are not suitable as the basis for the RF part of any RF transmitter.
by drgeoff
Thu Oct 18, 2018 11:20 am
Forum: Français
Topic: ssh not working in Raspbian Desktop (june 2018)
Replies: 16
Views: 304

Re: ssh not working in Raspbian Desktop (june 2018)

Vladam57 wrote:
Thu Oct 18, 2018 11:13 am
Aie ... But if I install the version RASPBIAN STRETCH LITE, I can use my cpu 64 bits ?
All versions of Raspbian are 32 bit OS irrespective of the capabilities of the ARM CPU(s) in the host RPi.
by drgeoff
Thu Oct 18, 2018 11:10 am
Forum: Français
Topic: ssh not working in Raspbian Desktop (june 2018)
Replies: 16
Views: 304

Re: ssh not working in Raspbian Desktop (june 2018)

Vladam57 wrote:
Thu Oct 18, 2018 9:01 am
I have installed the version "DEBIAN STRETCH WITH RASPBERRY PI DESKTOP" of June 2018 in my Raspberry pi 3 B+ .
No you have not.

Raspbian Stretch with desktop runs on RPis.

Debian Stretch with Raspberry Pi desktop runs on computers with x86 processors.
by drgeoff
Thu Oct 18, 2018 11:00 am
Forum: Advanced users
Topic: [SOLVED]Overscan issue
Replies: 2
Views: 74

Re: Overscan issue

The number in the overscan_left type statements has units of pixels. Setting that to 1 will produce such a small shift that you are unlikely to notice it. Try using larger numbers eg 100 to get a feel for the effect.
by drgeoff
Thu Oct 18, 2018 10:51 am
Forum: Advanced users
Topic: Using my Pi with an AC mains connected preamp.
Replies: 11
Views: 327

Re: Using my Pi with an AC mains connected preamp.

Imperf3kt wrote:
Wed Oct 17, 2018 10:49 pm

Recently I built a 6J1 Tube preamp which I intend to use to filter the audio output from my Pi. It runs off 12v AC.
12v AC is not what I would expect a tube/valve anything to run from.
by drgeoff
Wed Oct 17, 2018 10:19 pm
Forum: Troubleshooting
Topic: Under Voltage Detected despite usb power injection from PC PSU
Replies: 3
Views: 105

Re: Under Voltage Detected despite usb power injection from PC PSU

Some possibilities:

1. The wires from the PSU to RPi are too thin and/or too long.

2. The PSU is outputting a low voltage. Are you using the 5 volt SB output? That is often quite far from 5.00 volts.
by drgeoff
Wed Oct 17, 2018 7:39 pm
Forum: General discussion
Topic: solid state relays
Replies: 2
Views: 80

Re: solid state relays

The "high level trigger" or "low level trigger" usually refers to the logic polarity, not the absolute voltage, which determines if the relay is operated or not. If your current 16 channel relay is 12 volt low level trigger you can use your current interface board but will need to add a logical inve...
by drgeoff
Wed Oct 17, 2018 6:24 pm
Forum: Troubleshooting
Topic: Raspberry pi heating up but won’t start
Replies: 6
Views: 144

Re: Raspberry pi heating up but won’t start

ironman4575 wrote:
Wed Oct 17, 2018 3:53 pm
Do I need to send it in for repairs
RPis are "consumables". Repair is not commercially economic.
by drgeoff
Wed Oct 17, 2018 6:08 pm
Forum: Beginners
Topic: Image processing and classifying
Replies: 2
Views: 52

Re: Image processing and classifying

The real question is not can a RPi do it. Percentage of false positives, percentage of false negatives and time available to test each image are key criteria. The image capture hardware and the software dominate the first two of those, the software and the processing hardware figure in the third.
by drgeoff
Wed Oct 17, 2018 9:38 am
Forum: Beginners
Topic: Cable tester for trailers
Replies: 9
Views: 216

Re: Cable tester for trailers

Put a 10k series resistor on each of the 7 output GPIOs and enable the 50k internal pulldown on the 7 inputs. Set 1 output at a time high and check that only the corresponding input goes high.

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