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by Burngate
Fri Aug 23, 2019 5:37 pm
Forum: HATs and other add-ons
Topic: Can I use a vending machine coin acceptor for the Pi Zero?
Replies: 5
Views: 595

Re: Can I use a vending machine coin acceptor for the Pi Zero?

If it's anything like ones I've seen, it may be just a bunch of switches, with no power supply or electronics.
If so, it's just a bunch of switches - use them as you wish.
by Burngate
Fri Aug 23, 2019 5:33 pm
Forum: Troubleshooting
Topic: GPIO Input Pin Voltages
Replies: 3
Views: 117

Re: GPIO Input Pin Voltages

I am not turning any of the internal pullup resistors on and I assume they are not on by default when a GPIO is configured as an input. Actually, they are - the first nine (0 - 8) are pulled up by default; the rest are pulled down. Ohm's law - GPIO 13 has 50k pull-down, you've provided 4k7 pull-up ...
by Burngate
Fri Aug 23, 2019 10:19 am
Forum: Off topic discussion
Topic: Best Raspberry Pi Alternatives 2019
Replies: 62
Views: 6221

Re: Best Raspberry Pi Alternatives 2019

When all is said and done, Dr. Upton is a nice guy. He's also a clever guy. Not many have both. The guy who came to fix my guttering is a nice guy, but he's not clever. If he had been, and if a neighbour hadn't called in the Authorities, he'd maybe have got several grand out of me, mug that I am. I...
by Burngate
Fri Aug 23, 2019 9:16 am
Forum: Off topic discussion
Topic: Solder Question
Replies: 13
Views: 1745

Re: Solder Question

Traditional electronic solder has several cores of rosin (or similar) flux to aid wetting and removing oxides. Although the company is called "Multicore", this solder is solid - no cores. Not knowing where you work, I have no idea what your company (or someone in it) was thinking about doing, but .....
by Burngate
Thu Aug 22, 2019 6:22 pm
Forum: General discussion
Topic: Newbie question! Noobs or etcher?
Replies: 8
Views: 388

Re: Newbie question! Noobs or etcher?

It's a question of History. In the beginning, it was thought rather difficult for a beginner to use Windows tools to load an SD card, so Noobs was invented as an easy and economical method to have more than one OS. Think quil pen v. hammer and chisel. But the cards rapidly grew to a size that meant ...
by Burngate
Thu Aug 22, 2019 5:18 pm
Forum: Troubleshooting
Topic: RPi 2 B+ reboots on USB drive connect
Replies: 14
Views: 324

Re: RPi 1 reboots on USB drive connect

That does explain the problem with disconnection, though, unlike everyone else's explanation.
After all, where can the current that's already flowing go when you disconnect the drive?
by Burngate
Wed Aug 21, 2019 10:39 am
Forum: General discussion
Topic: 12 v for driving electromagnets PCA9685
Replies: 31
Views: 1241

Re: 12 v for driving electromagnets PCA9685

I'm not sure about how to calculate the maximim current and the inductance on the coil. Sorry ... Calculating the inductance of electromagnets you've wound yourself ... could be difficult! But having wound them, you may be able to measure it. The same goes for the maximum current. But the maximum c...
by Burngate
Sat Aug 17, 2019 6:31 pm
Forum: General discussion
Topic: Are Speaker Magnets A Problem For Pi?
Replies: 18
Views: 1745

Re: Are Speaker Magnets A Problem For Pi?

Just as an addendum, it's perhaps worth noting that the magnetic devices on board the Pi were designed to be as efficient as possible, which means they don't spray magnetic fields around if at all possible. The corollary is that stray magnetic fields around them have little effect. Speakers should b...
by Burngate
Sat Aug 17, 2019 6:09 pm
Forum: General discussion
Topic: Temperature conversion
Replies: 9
Views: 898

Re: Temperature conversion

Since 0C = 0Ré and 100C = 80Ré, multiply by 5/4
by Burngate
Fri Aug 16, 2019 5:53 pm
Forum: General discussion
Topic: Positives of the Official Raspberry 4B Youtube video.
Replies: 14
Views: 1067

Re: Positives of the Official Raspberry 4B Youtube video.

Sorry for the rant.
There's plenty of bad sound out there - mostly on youtube, but a fair amount on channels like the Beeb, ITV, Ch4, etc.
Missing high frequencies (people speak to each other rather than the audience), mumbling then shrieking and expecting the electronics to compensate, ...
by Burngate
Fri Aug 16, 2019 5:36 pm
Forum: General discussion
Topic: Positives of the Official Raspberry 4B Youtube video.
Replies: 14
Views: 1067

Re: Positives of the Official Raspberry 4B Youtube video.

I was trying to watch this video with my wife sleeping next to me and i found it next to impossible. The audio was horrific, it went from low tone mumbling to over deviated laughing. I "worked" in the Outside Broadcast TV world, for many years. Back then, we had several departments: We were the eng...
by Burngate
Fri Aug 16, 2019 9:32 am
Forum: Beginners
Topic: Leak sensor
Replies: 15
Views: 1690

Re: Leak sensor

For the water sensor the water itself does act as a resistor but it sounds like it may be too much to trigger an active low. Very true. Think of the water as a very poor-quality switch - when it's off, it's off, but when it's on, it's really not very on - more of an off-ish on than an on-ish off! Y...
by Burngate
Fri Aug 16, 2019 9:14 am
Forum: Beginners
Topic: Leak sensor
Replies: 15
Views: 1690

Re: Leak sensor

We used a 10Kohm pull down and connected the other side of a switch to 3.3V with a 1K current limiting resistor. A diagram would be easier to understand than a description in text. But ... Do I understand correctly that you mean this? 3v3_________ | | / switch | | GPIO--[1k]--| | | [10k] | GND_____...
by Burngate
Thu Aug 15, 2019 9:40 am
Forum: Beginners
Topic: Leak sensor
Replies: 15
Views: 1690

Re: Leak sensor

The internal pull-ups are about 50k, so 150k between the GPIO and ground is unlikely to pull it low enough to register.

Far from adding resistance, I would look at reducing that 150k, by perhaps reducing the separation, or increasing the size of the probes.
by Burngate
Thu Aug 15, 2019 9:36 am
Forum: Troubleshooting
Topic: Only green light on
Replies: 5
Views: 228

Re: Only green light on

Also, the cable between your "10000 mAh battery supplying 5v @ 2.4A through a USB-A" and the Pi is important.

Other than very early Pis, the red LED turns off when the supply voltage drops too far.
The symptoms you describe indicate that too much voltage is being dropped through that cable.
by Burngate
Thu Aug 15, 2019 8:56 am
Forum: Troubleshooting
Topic: Rpi 4 not booting doesn’t have 3.3v
Replies: 2
Views: 161

Re: Rpi 4 not booting doesn’t have 3.3v

According to the schematic, the green LED is powered from the 3v3 rail.
Since green LEDs usually have a forward voltage of a couple of volts, I don't think it would light with only 1v3 on that rail.

So either your measurement is incorrect, or your green LED isn't lighting even dimly.
by Burngate
Mon Aug 12, 2019 4:38 pm
Forum: Other projects
Topic: Creating an heart attack detector
Replies: 14
Views: 1639

Re: Creating an heart attack detector

Just as a matter of interest, while being tested for other things, I was asked to wear a 24-hour monitoring device. It appeared to record ... something ... during that 24 hours, from a couple of electrodes taped to my chest. Quite what they thought about my heart stopping for a couple of hours I don...
by Burngate
Sun Aug 11, 2019 9:27 am
Forum: General discussion
Topic: Protect over voltage on Voltage Divider ciruit
Replies: 12
Views: 390

Re: Protect over voltage on Voltage Divider ciruit

I'm not convinced about using higher value resistors. With 1k & 330Ω across 14v, it's only dissipating ~150mW, well within what a standard ¼W through-hole resistor can handle, though a bit much for a standard 0603 Thick Film SMD Resistor ±1% 0.1W. The OP states I am trying to monitor a remote 12v ba...
by Burngate
Sat Aug 10, 2019 5:16 pm
Forum: General discussion
Topic: Run fan off USB port
Replies: 11
Views: 551

Re: Run fan off USB port

the underside of the board. The electrons cannot tell the difference. That is true, it is because they are leptons and have no quarks. Only the hadrons (proton, neutron etc.) have up, down, top and bottom quarks. :o :D :mrgreen: I'll get my coat >>>>>> I find that strangely charming Though neutrino...
by Burngate
Thu Aug 08, 2019 9:35 am
Forum: Beginners
Topic: power rpi-4 via the 40 pin header
Replies: 9
Views: 697

Re: power rpi-4 via the 40 pin header

There's a SMBJ - effectively a zener, etc. - on board, so you won't gain by providing your own. Davidcotton is suggesting you provide a fuse that can blow when you trigger the SMBJ by doing something wrong. Polyfuses can handle 6v and upwards. You need to choose one that can handle the full current ...
by Burngate
Thu Aug 08, 2019 9:31 am
Forum: General discussion
Topic: To the Raspberry Zero Production line...
Replies: 41
Views: 2221

Re: To the Raspberry Zero Production line...

The very first Pis didn't have holes!
by Burngate
Thu Aug 08, 2019 9:28 am
Forum: Beginners
Topic: Help me verify my idea?
Replies: 6
Views: 279

Re: Help me verify my idea?

The device creates a 6v pulse, which goes on to something else. You want to log and act on those pulses. Why cut the wire - which stops the pulse going further - then recreate the pulse? Why not just feed an optoisolator input in parallel, without disturbing anything. Then count, etc. the pulses fro...
by Burngate
Thu Aug 08, 2019 9:22 am
Forum: Media centres
Topic: sdtv_disable_colourburst
Replies: 2
Views: 1278

Re: sdtv_disable_colourburst

I know that the option sdtv_disable_colourburst=1 in file /boot/config.txt "disables colourburst on composite video output. The picture will be displayed in monochrome, but it may appear sharper." This statement unfortunately is wrong, ... It's not wrong. That option, as you say, only removes the c...
by Burngate
Thu Aug 08, 2019 8:51 am
Forum: General discussion
Topic: A question about the Raspberry Pi 4 PCB layout
Replies: 21
Views: 1400

Re: A question about the Raspberry Pi 4 PCB layout

Imperf3kt wrote:
Wed Aug 07, 2019 10:08 pm
... heat rises.
Only in a fluid, and then only in a gravitational field.

The Pi is solid. Heat spreads by conduction, without the help of gravity.
It's only after it reaches the air that convection starts to be important.

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