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by drgeoff
Sun Jan 19, 2020 5:00 pm
Forum: General discussion
Topic: Measure 12v supply with pi
Replies: 16
Views: 409

Re: Measure 12v supply with pi

Yes, use a voltage comparator, with it open collector output used with a pullup to 3V3. for example a LM339. https://i.stack.imgur.com/sogPg.png I would modify that. Use the nominally 12 volt from the battery instead of 24 volts that mahjongg shows. Connect one comparator input to the junction of a...
by drgeoff
Sat Jan 18, 2020 5:32 pm
Forum: General discussion
Topic: How to control one Pi from another over Ethernet?
Replies: 33
Views: 715

Re: How to control one Pi from another over Ethernet?

rin67630 wrote:
Sat Jan 18, 2020 5:23 pm
VNC works across NATs and firewalls. You must not even know the IP to connect worldwide.
True for implementations such as RealVNC's Connect which use a cloud server in the middle but false for pure point to point situations.
by drgeoff
Sat Jan 18, 2020 5:20 pm
Forum: Troubleshooting
Topic: DIY Power Bank issues
Replies: 6
Views: 169

Re: DIY Power Bank issues

"Schub Modul 2A Ausgang 1A eingang" I dont would buy such stuff. If it use 1A at input(3.6x1=3.6W) and can output [email protected]=10W something is wrong there. Yes, the thing that is wrong is your understanding of the specification. The 1 amp input is when the board is charging the cell from power supplied i...
by drgeoff
Sat Jan 18, 2020 9:07 am
Forum: Automation, sensing and robotics
Topic: virgin post: need help with external pull up resistor
Replies: 13
Views: 349

Re: virgin post: need help with external pull up resistor

It appears as though you're using the 741 op amp as a comparator. Instead, I'd opt for an LM393. It probably has a higher input impedance, and is designed to work with single or dual supplies. Also, adding hysteresis, if needed/desired, would be easier. +1 A 741 has bipolar input ransistors which n...
by drgeoff
Sat Jan 18, 2020 1:21 am
Forum: Troubleshooting
Topic: Accidental 12V Overvoltage and smoke
Replies: 15
Views: 301

Re: Accidental 12V Overvoltage and smoke

semicolon4life wrote:
Sat Jan 18, 2020 12:20 am
So for now, I can remove the TVs and just short the two leads that connect to the tvs?
NO!

Just remove the TVS. Do not replace with a short. The diode is between +5volts and ground.
by drgeoff
Fri Jan 17, 2020 11:08 pm
Forum: HATs and other add-ons
Topic: HAT for storage (e.MMC?)
Replies: 4
Views: 138

Re: HAT for storage (e.MMC?)

Is there any evidence that eMMC is more reliable or has better long term endurance than SD or USB flash drive?
by drgeoff
Fri Jan 17, 2020 11:01 pm
Forum: Troubleshooting
Topic: Accidental 12V Overvoltage and smoke
Replies: 15
Views: 301

Re: Accidental 12V Overvoltage and smoke

odroid wrote:
Fri Jan 17, 2020 10:28 pm
You may try power it through the GPIO pins. I suppose this path bypasses diode AND poly-fuse.
No, powering via pins on the GPIO header does not bypass the diode.
by drgeoff
Fri Jan 17, 2020 6:27 pm
Forum: Troubleshooting
Topic: Cant get pins to output 0
Replies: 4
Views: 139

Re: Cant get pins to output 0

pcmanbob wrote:
Fri Jan 17, 2020 5:08 pm
4. I am not even sure you can drive an LED from the output of a logic gate directly.
74HC08 is specced for +/-25 mA output maximum. The spec sheet gives minimum output voltage when sourcing 5 mA and maximum voltage when sinking 5 mA. Ample for a modern LED.
by drgeoff
Fri Jan 17, 2020 6:13 pm
Forum: Beginners
Topic: Unable to connect from Mac to Raspberry Pi4 using SSH
Replies: 7
Views: 184

Re: Unable to connect from Mac to Raspberry Pi4 using SSH

Is this another case of not being aware that Linux does not echo the password characters? Not even asterisks. Just press the keys on the keyboard and finish with the Enter/Retun key.
by drgeoff
Fri Jan 17, 2020 2:21 pm
Forum: General discussion
Topic: Raspberry and FPGA
Replies: 16
Views: 523

Re: Raspberry and FPGA

There are two aspects - hardware and software. There is a very good possibility that a RPI can provide the required programming waveforms but some additional interfacing circuitry such as buffers/level-shifters may be needed. FPGAs are usually programmed using software provided by the FPGA maker. Ty...
by drgeoff
Thu Jan 16, 2020 11:34 am
Forum: Beginners
Topic: [Solved] Why is rpi-eeprom also needed on an RPi0W?
Replies: 3
Views: 101

Re: Why is rpi-eeprom also needed on an RPi0W?

Because Raspbian does not contain only the files needed to run on the specific model of RPi. An up to date card should run on any RPi. You can update Buster on a Zero and then put the card in a 4B and it will work.
by drgeoff
Thu Jan 16, 2020 11:25 am
Forum: General discussion
Topic: Navit on raspberry pi 4, vehicle cursor problem
Replies: 2
Views: 110

Re: Navit on raspberry pi 4, vehicle cursor problem

I'm not a Navit user but it sounds like the cursor you are seeing is the cursor intended for use when selecting menu items etc, not the vehicle position and direction indicator.

Possibly your issue is not specific to RPi and you might do better to ask on a Navit forum rather than here.
by drgeoff
Thu Jan 16, 2020 11:11 am
Forum: Beginners
Topic: Newbie, nothing on screen (with no OS on card)
Replies: 5
Views: 165

Re: Newbie

I have a Pi 3B (not sure if it's a plus) and a 3500ms j supply. I am not sure there's an OS on the card but shouldn't I at least get a splash screen? I've tried both HDMI to HDMI and HDMI to VGA adapter to a known good monitor. Any suggestion? TIA, No OS, no display, not even a splash screen. (And ...
by drgeoff
Thu Jan 16, 2020 10:19 am
Forum: General discussion
Topic: Help on GPIO use
Replies: 3
Views: 95

Re: Help on GPIO use

by drgeoff
Thu Jan 16, 2020 8:32 am
Forum: Troubleshooting
Topic: Boot failure
Replies: 1
Views: 71

Re: Boot failure

nana199685 wrote:
Thu Jan 16, 2020 7:56 am
I connect the GPIO of rpi to my computer with putty but the information of rpi can't be read.
How are you connecting GPIO to your computer?
by drgeoff
Thu Jan 16, 2020 12:34 am
Forum: Troubleshooting
Topic: Fails to boot/No display
Replies: 4
Views: 107

Re: Fails to boot/No display

What have you written to the micro-SD card? Have you read the "not booting" sticky? I have read that post, yes. I have just burned the file to the sd card with dd and modified those sections that I mentioned in the post to what they are now. I will say that it is a pi 4 and I haven't tried it with ...
by drgeoff
Thu Jan 16, 2020 12:20 am
Forum: Beginners
Topic: power rpi-4 via the 40 pin header
Replies: 17
Views: 2810

Re: power rpi-4 via the 40 pin header

Thought I'd post this here since it took me several hours to figure out, and a lot of folks saying it wasn't possible with Pi 4B to direct power through the 40 Pin GPIO. I don't know where you've seen that. It's common knowledge that the Pi 4B can be powered via the "GPIO" header if you supply a st...
by drgeoff
Thu Jan 16, 2020 12:05 am
Forum: Troubleshooting
Topic: Fails to boot/No display
Replies: 4
Views: 107

Re: Fails to boot/No display

What have you written to the micro-SD card?

Have you read the "not booting" sticky?
by drgeoff
Wed Jan 15, 2020 10:10 pm
Forum: General discussion
Topic: what have i got?
Replies: 32
Views: 903

Re: what have i got?

When I click on "save image location" I get https://lh3.googleusercontent.com/iPQClDK09xDROuDsBywQI3ND1JnQktjq3EwT74emRAPIKExvZMEl3R_Di2KWVXFpxixnY3QjZUOD2atRDkmvCpaOCvmY5saeNcZ89i753L6IkQi6EPS3riBMuWh7JgI2gDayKHqA74pQ6N9ZSRZ_6Cx8zQijrN2QxGbkzoQKBwUehXGZxDL0NmDPZpfa9qPw2JYP3GzJLb0qt8YZ04z3ZaGuPIvaI...
by drgeoff
Wed Jan 15, 2020 7:26 pm
Forum: General discussion
Topic: Pi 4 power?
Replies: 11
Views: 422

Re: Pi 4 power?

MuntyScruntfundle wrote:
Wed Jan 15, 2020 7:08 pm
Do I have to tell it I'm providing power to the header? Any card restrictions? I had assumed they'd run with the same stuff plugged in.
No, no and yes.

Read the "not booting" sticky, especially the parts that are RPI4B specific.
by drgeoff
Wed Jan 15, 2020 6:32 pm
Forum: General discussion
Topic: what have i got?
Replies: 32
Views: 903

Re: what have i got?

psychosaffa wrote:
Wed Jan 15, 2020 6:26 pm
Botspot wrote:
Wed Jan 15, 2020 3:21 pm
BTW the pictures aren't displaying for me.
might just be you B?
No, not just B. I'm seeing only "No Entry" signs, but grey and write instead of red and white.
by drgeoff
Wed Jan 15, 2020 6:08 pm
Forum: Networking and servers
Topic: Turning my RPi3 into an IP camera that's ONVIF compliant
Replies: 6
Views: 18660

Re: Turning my RPi3 into an IP camera that's ONVIF compliant

tung256 wrote:
Wed Jan 15, 2020 4:16 pm
hmchen wrote:
Mon Jul 03, 2017 6:50 am
If you also have a Pi camera module v1 or v2, my test firmware can turn your Pi into an ONVIF compliant camera.
where's the firmware? i really need to turn my rpi3 and the cam module into an onvif camera
https://www.raspberrypi.org/forums/view ... 1#p1182171
by drgeoff
Wed Jan 15, 2020 5:44 pm
Forum: Troubleshooting
Topic: pi 4 model B fail to boot with irregular green led flashes and 1 red led blink, official raspberry pi 5.1v power supply
Replies: 5
Views: 205

Re: pi 4 model B fail to boot with irregular green led flashes and 1 red led blink, official raspberry pi 5.1v power sup

Thaaaanks for the reply. The 128GB is genuine and it costs a small fortune, indeed I am trying to install NOOBS and followed the official instruction to load the card (sd formatter + guiformat). In fact I tried with another Lexar 633x 32GB card but still no luck. Is there any good card recommended ...
by drgeoff
Wed Jan 15, 2020 5:32 pm
Forum: Beginners
Topic: Which power supply for the Raspberry pi Zero
Replies: 6
Views: 142

Re: Which power supply for the Raspberry pi Zero

That should be more than adequate unless you intend to attach a USB hub that does not have its own PSU and some USB peripherals that need lots of current.
by drgeoff
Wed Jan 15, 2020 5:00 pm
Forum: Troubleshooting
Topic: PI 4B will not boot
Replies: 12
Views: 215

Re: PI 4B will not boot

I have emailed the manufacturer, so hopefully I get myself a working replacement. If you really have emailed the manufacturer (all 4Bs to date have been manufactured by Sony UK), then don't get your hopes up. They are made under contract for RS and Farnell who sell them to distributors, retailers a...

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