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by Burngate
Thu Sep 12, 2019 10:06 am
Forum: General discussion
Topic: Back Voltage from USB Hub
Replies: 8
Views: 283

Re: Back Voltage from USB Hub

The B+ had a AP2553 acting as a reverse-current blocking device. Apparently the 4B does not. One of the dangers is that two power supplies, as you have here, with slightly different voltages can fight each other, with unknown consequences. Would it be possible to open the hub and cut the 5v trace to...
by Burngate
Wed Sep 11, 2019 5:00 pm
Forum: General discussion
Topic: RPI 4 USB-C supply
Replies: 37
Views: 1242

Re: RPI 4 USB-C supply

Don't, whatever you do, argue with Jamesh.
He's an engineer, he's a moderator, but more to the point, he's all-powerful

If you argue, he makes life difficult for the rest of us
by Burngate
Wed Sep 11, 2019 4:51 pm
Forum: Beginners
Topic: Relay - can it be used in reverse (signal microcontroller) ?
Replies: 14
Views: 548

Re: Relay - can it be used in reverse (signal microcontroller) ?

ElEscalador wrote:
Wed Sep 11, 2019 12:25 pm
You could certainly use a relay with a 100vac coil like this one https://amzn.to/2NVr0RV
Unless you're in Britain, or Europe, or other places with 230V AC
by Burngate
Mon Sep 09, 2019 6:10 pm
Forum: Off topic discussion
Topic: Ouch
Replies: 9
Views: 479

Re: Ouch

I'm British. I understand British humour. It appears I don't understand US humour.
by Burngate
Mon Sep 09, 2019 6:03 pm
Forum: Beginners
Topic: Connecting whilte LED strip to Pi
Replies: 14
Views: 317

Re: Connecting whilte LED strip to Pi

It's got to get its power from somewhere, and the Pi can't provide all that, so it needs another source.
It seems that "amplifier" wants 12v, but I would guess at rather more than 2A.

But give it a go - buy it, try it, see what happens!
by Burngate
Mon Sep 09, 2019 5:56 pm
Forum: Automation, sensing and robotics
Topic: Mechanical clock hands, position set by pi or controller?
Replies: 5
Views: 178

Re: Mechanical clock hands, position set by pi or controller?

I've got several of those MSF clocks around the house, and discovered they all have their own fixed error. The cause is my cack-handed positioning of the hands relative to the motor unit and the clock face. And, of course, the low level of the Anthorn signal this far from the civilized reaches of Cu...
by Burngate
Mon Sep 09, 2019 5:30 pm
Forum: Beginners
Topic: Connecting whilte LED strip to Pi
Replies: 14
Views: 317

Re: Connecting whilte LED strip to Pi

That amplifier seems expensive to me, at $14, compared to the FETs at $2.3 each. Still, it's your wallet. You first mentioned RFP30N06, then 2N7000 was mentioned, now IRLZ34N. What they all have in common is their gate threshold voltage of 1v - 2v, comfortably below the 3v3 that the Pi can provide o...
by Burngate
Mon Sep 09, 2019 10:38 am
Forum: Other projects
Topic: About adding a LED...
Replies: 5
Views: 144

Re: About adding a LED...

That current is provided by the Pi, and it's value - 5mA - was decided by rpdom. To make sure that was the current, he calculated the correct resistance to put in series. If he'd wanted more current - say 10mA - he'd have put 0.01 into his equation instead of 0.005, and out would have popped 110 ohm...
by Burngate
Mon Sep 09, 2019 10:26 am
Forum: Beginners
Topic: Connecting whilte LED strip to Pi
Replies: 14
Views: 317

Re: Connecting whilte LED strip to Pi

The third pin (SOURCE) in each MOSFET in his diagram connects to Ground, the second (DRAIN) goes to the GPIO, and the first (GATE) goes to the external power source. Not quite! He has (red, green, & blue) wires connecting the GPIOs to the gates. His black wires connect the GND of the Pi, the source...
by Burngate
Sun Sep 08, 2019 9:06 am
Forum: Beginners
Topic: How to connect four TCRT5000 to my Rasperry Pi 3
Replies: 1
Views: 60

Re: How to connect four TCRT5000 to my Rasperry Pi 3

I had to Google for TCRT5000; this is what I found: https://components101.com/sites/default/files/component_datasheet/TCRT5000%20Datasheet.pdf It seems it can be used with 3v3 - it doesn't need 5v Your Pi has only two 3v3 pins (1 & 17)), but you can use each to drive more than one thing. So long as ...
by Burngate
Sat Sep 07, 2019 9:38 am
Forum: Automation, sensing and robotics
Topic: Longer cable for GPIO-sensor?
Replies: 10
Views: 485

Re: Longer cable for GPIO-sensor?

Back to the original question: I read on the internet that the optimal cable length for GPIO-communication with standard jumper-wires are 20cm-30cm. Where did you read that? There're a couple of reasons for limiting the lengths of wires. One is the voltage drop over a longer wire if if it's carrying...
by Burngate
Sat Sep 07, 2019 9:16 am
Forum: Troubleshooting
Topic: Help with 4-20mA and Raspberry Pi 3B+
Replies: 6
Views: 244

Re: Help with 4-20mA and Raspberry Pi 3B+

Just a couple of thoughts. Top diagram: the only connection between the current-to-voltage convertor and the ADS1115 appears to be a single wire - no ground connection. Bottom diagram: the current-to-voltage convertor has a pretty red wire between its GND and its power supply negative, but it's only...
by Burngate
Thu Sep 05, 2019 10:25 am
Forum: Beginners
Topic: GPIO pin turns off immediately when switch is connected, turns back on when disconnected
Replies: 3
Views: 127

Re: GPIO pin turns off immediately when switch is connected, turns back on when disconnected

I'm not sure I understand your description. I have no problem turning on and off pins on my rpi4 ... so you've set the GPIOs to ouput , and you can set them to 0 (gnd) or 1 (3v3) at will. How are you checking they do what you want? A meter? a LED and resistor? however when I connect a wire (which is...
by Burngate
Thu Sep 05, 2019 9:06 am
Forum: Beginners
Topic: Connecting existing Doorbell (AC door bell with bell switch ) to raspberry pi 3 GPIO
Replies: 16
Views: 327

Re: Connecting existing Doorbell (AC door bell with bell switch ) to raspberry pi 3 GPIO

I don't suppose you could post some details of this doorbell - make, model, etc. - and maybe pictures of what's inside it?
We can all guess what it should be like, but reality often surprises us.
by Burngate
Wed Sep 04, 2019 6:18 pm
Forum: Beginners
Topic: Raspberry Pi ** Sold over 25million units **
Replies: 19
Views: 687

Re: Raspberry Pi ** Sold over 25million units **

epoch1970 wrote:
Wed Sep 04, 2019 1:41 pm
Indeed... Pi 4/4 in a solid gold case. A bit bling, but very good for cooling.
Diamond would be better
by Burngate
Tue Sep 03, 2019 9:31 am
Forum: Beginners
Topic: GPIO pull up resistors.
Replies: 4
Views: 141

Re: GPIO pull up resistors.

Internal 50k resistors can be applied as pull-ups or pull-downs, and before anything else happens, most GPIOs have pull-downs by default. If you leave them as-is, the internal 50k pull-downs together with your external 10k pull-ups give a potential divider, ending up with a pull to about 2.75v throu...
by Burngate
Mon Sep 02, 2019 5:43 pm
Forum: Off topic discussion
Topic: designing a rubic cube box
Replies: 11
Views: 843

Re: designing a rubic cube box

That explains (I think - I, too, am a slow learner!) the black splodges on your drawing - his kneck and arm holes! You've got a couple of months, yet, before it needs to be finished, plenty of time - just so long as he doesn't grow out of his box! My understanding is that 20mA is the maximum current...
by Burngate
Mon Sep 02, 2019 11:30 am
Forum: Off topic discussion
Topic: designing a rubic cube box
Replies: 11
Views: 843

Re: designing a rubic cube box

I've been a Rubik's Cube nut for the last ... is it really 45 years? I really should get out, more. I find your post most frustrating, and I doubt I'm the only one. For a start, my cubes don't look quite like your picture - they're quite symmetrical, with 6 3x3 faces (except one with 6 4x4 faces) so...
by Burngate
Mon Sep 02, 2019 10:32 am
Forum: Automation, sensing and robotics
Topic: Dust collection automation 20A circuit
Replies: 17
Views: 514

Re: Dust collection automation 20A circuit

I think I've been told one time too many that I'm out of my depth so I will end this conversation here and work on this on my own I would suggest you don't work on this on your own, but rather find someone close by who is familiar with equipment such as this to help you. After all, letting loose a ...
by Burngate
Sun Sep 01, 2019 9:36 am
Forum: Troubleshooting
Topic: Rasbperry Pi 3 B+ overheat problem
Replies: 5
Views: 137

Re: Rasbperry Pi 3 B+ overheat problem

I have used the GPIO ports to switch on transistors with a few milliAmps (~5 mA). What type of transistor, and how did you conect them? For example, if they were bipolar NPN, and you connected the emitter to gnd and the base to the GPIO without a series resistor, a large current could flow, enough ...
by Burngate
Sat Aug 31, 2019 10:13 am
Forum: Troubleshooting
Topic: Red light and it is not starting
Replies: 1
Views: 77

Re: Red light and it is not starting

Red LED blinking = power problem.

If it happens with multiple power supplies, then either none of them is good enough, or your Pi is faulty.

https://www.raspberrypi.org/forums/view ... 28&t=58151
by Burngate
Sat Aug 31, 2019 8:59 am
Forum: Other projects
Topic: Pushbutton multiple inputs
Replies: 12
Views: 405

Re: Pushbutton multiple inputs

by External Ground I mean the Ground for my Power supply for the Pi . Almost certainly, your power supply is what is known as "floating". That means there is no connection between its input and its output - if you were to use a multimeter to measure the resistance between either of the output wires...
by Burngate
Fri Aug 30, 2019 5:52 pm
Forum: Other projects
Topic: Pushbutton multiple inputs
Replies: 12
Views: 405

Re: Pushbutton multiple inputs

What, precisely, do you mean by "External Ground"? If you mean the pin labeled Earth on your mains supply (or some soil outside your house, which ought to be similar) then it may be at a very different voltage from the pin labeled GND on your Pi. The idea behind the pull-down resistor is to make sur...
by Burngate
Fri Aug 30, 2019 10:53 am
Forum: Troubleshooting
Topic: PI 4 PWR Led Flashing no boot, STICKY: Is your Pi not booting? Read throughugh
Replies: 9
Views: 263

Re: PI 4 PWR Led Flashing no boot, STICKY: Is your Pi not booting? Read throughugh

With nothing but the power supply connected, and no SD card, the green LED should blink four times then repeat.
The red LED SHOULD NOT BLINK

If it does, then you have a faulty power supply or faulty Pi.
by Burngate
Fri Aug 30, 2019 9:32 am
Forum: Troubleshooting
Topic: Pi 3 Model B USB not working
Replies: 1
Views: 84

Re: Pi 3 Model B USB not working

Several things come to mind, though how helpful you'll find them I don't know - probably not at all! Finding short-circuits can be difficult, in part because the resistances involved are similar to the resistances between your meter probes and the copper traces. You measured 0.6Ω across C97, and tha...

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