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by Burngate
Fri Apr 26, 2019 9:43 am
Forum: Automation, sensing and robotics
Topic: Raspberry Pi Robot failure protection
Replies: 3
Views: 203

Re: Raspberry Pi Robot failure protection

... suddenly the raspberry pi crashed and shut down, but while motors where running. The motors have pushbuttons which are pressed when the legs reach the maximum amplitude, and they stop the motors. Unfortunately, at the time of the crash three motors where still running, and the pi didn't shut th...
by Burngate
Thu Apr 25, 2019 6:04 pm
Forum: Beginners
Topic: How to calculate resistors...
Replies: 68
Views: 1549

Re: How to calculate resistors...

... Is the 50mA maximum only related to the GPIOs, or the whole 3.3v bus (inlcuding the GPIOs and the 3.3V pins - like pins 1 and 17), or does that also include the 5V pins (2 and 4)? That 50mA is only for the GPIOs themselves. The 3.3v on the header - pins 1 & 17 - comes directly from the regulato...
by Burngate
Wed Apr 24, 2019 5:17 pm
Forum: Beginners
Topic: is dead 3V3 a widespread issue?
Replies: 15
Views: 514

Re: is dead 3V3 a widespread issue?

In all our investigations, we have not come across any failures that were proveably spontaneous. i.e. all the boards we got back had been 'abused' in some way. But let's assume your 200, and multiple by 10 to increase the failure capture rate. We've sold about 3M devices with PMIC in, so that's 200...
by Burngate
Wed Apr 24, 2019 10:10 am
Forum: Beginners
Topic: 3B+ as webserver 24/7 on iPad charger
Replies: 16
Views: 420

Re: 3B+ as webserver 24/7 on iPad charger

... 3B+ on an iPad charger ... And will the charger get as hot as when you're charging phones for a long period? If it gets hot charging a phone for a long period, it's not very good even for that. After a short period actually charging the phone's battery, it shouldn't have to do much so it should...
by Burngate
Tue Apr 23, 2019 9:48 am
Forum: Troubleshooting
Topic: Could I Change MXL7704 Chip with Soldering Machine
Replies: 14
Views: 490

Re: Could I Change MXL7704 Chip with Soldering Machine

It depends on the "regular soldering machine" you have access to. I would suggest you try and see! Sourcing the PMIC may also be problematic. But my reason for replying is more my curiosity about how you've damaged so many Pis - what have you been doing to destroy them? The main chip is fairly robus...
by Burngate
Tue Apr 23, 2019 8:13 am
Forum: General discussion
Topic: Can a 128GB SD card work as memory?
Replies: 15
Views: 732

Re: Can a 128GB SD card work as memory?

Great reply below: https://www.raspberrypi.org/forums/viewtopic.php?f=91&t=36729&p=861719#p861719 But that was a reply to a different question! That thread started with a query "I'm thinking in to buy the SanDisk Extreme 128 GB SDXC Class 10 UHS-1 Flash Memory Card 45MB/s SDSDX-128G-X46 sd card, bu...
by Burngate
Fri Apr 19, 2019 5:49 pm
Forum: Bare metal, Assembly language
Topic: Low level RPI programming
Replies: 6
Views: 542

Re: Low level RPI programming

I don't know much about raspberry pi, but I have an interest in low level assembly programming. I realise a raspberry pi is not the best thing for this ... Wrong! It's perfect for this! For a start, it's a lot less difficult to get out of the mess you'll inevitably create on a Pi than on your expen...
by Burngate
Fri Apr 19, 2019 5:30 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: Relay Showing Voltage on Input Pin
Replies: 4
Views: 243

Re: Relay Showing Voltage on Input Pin

1. Yes. 2. No, but ... 3. No. A GPIO configured as an output will attempt to maintain either 3v3 or 0v, by sourcing current for the former, or sinking current for the latter. If it's set low to switch the relay on, the resistor on the relay board should limit the current to something reasonable - wh...
by Burngate
Fri Apr 19, 2019 10:57 am
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: Relay Showing Voltage on Input Pin
Replies: 4
Views: 243

Re: Relay Showing Voltage on Input Pin

2-relay-module.jpg With 5v or 3v3 on Vcc (and also on JD-Vcc) and your meter connected between IN1 and GND, a very small amount of current flows through R1, the LED in the optoisolator, LED1, and your meter. Not much voltage drop in R1 (because it's a very small current) but both LEDs will have a f...
by Burngate
Tue Apr 16, 2019 8:59 am
Forum: General discussion
Topic: Powering RPI 3B+ With 24VAC
Replies: 17
Views: 619

Re: Powering RPI 3B+ With 24VAC

Yes it does look bulky, cf Imperf3ct's suggestion. I only have two excuses: firstly, I was looking for something that would easily accept the wires on the SMAKN PSU, whose size I didn't know; and secondly, I didn't search very far. I also like RS - they've been good to me ever since they were Radio ...
by Burngate
Mon Apr 15, 2019 5:58 pm
Forum: Beginners
Topic: Resistor Question
Replies: 3
Views: 164

Re: Resistor Question

The schematic isn't quite as useful as it might be: wr.jpg But the resistors are there on the input side to protect the LED in the optoisolator; it depends on the voltage you're going to use on the driving side. The resistors on the output side are pull-ups, though quite where the output connection ...
by Burngate
Mon Apr 15, 2019 10:22 am
Forum: Advanced users
Topic: Relay Breakout Module with Opto-Isolation is uln2003a needed?
Replies: 2
Views: 121

Re: Relay Breakout Module with Opto-Isolation is uln2003a needed?

Google tells me you meant PCF8574, which can sink 10mA (when low) but only source 100μA (when high) ULN2003, ULN2803, etc. are Darlington arrays. They're effectively high-gain NPN bipolar transistors. They don't take any current when their input is low, but to turn them on they need upwards of 1mA t...
by Burngate
Sun Apr 14, 2019 9:44 am
Forum: General discussion
Topic: Powering RPI 3B+ With 24VAC
Replies: 17
Views: 619

Re: Powering RPI 3B+ With 24VAC

What if I soldered to a mini usb cable and used the standard port? Actually micro usb. Typically not recommended as a standard microUSB connector usually introduces a lot of resistance and therefore, voltage drop. ... make sure the wires are thick enough (18 AWG). Most USB cables have much thinner ...
by Burngate
Sat Apr 13, 2019 5:53 pm
Forum: General discussion
Topic: Cluster Pi via gpio pins
Replies: 34
Views: 1028

Re: Cluster Pi via gpio pins

The OP's use of the word "Cluster" in the title was possibly a mistake. An easy error for a Noob to make, but with unfortunate consequences. He/she seems to want to "play games and stuff", with a 3B+ driving the official 7" screen and a ZeroW possibly connected to a 3.5" screen, communicating other ...
by Burngate
Sat Apr 13, 2019 8:52 am
Forum: Troubleshooting
Topic: New Raspberry PI 3b+ setup HDMI video is not working, never has.
Replies: 11
Views: 473

Re: New Raspberry PI 3b+ setup HDMI video is not working, never has.

May be semantics, or maybe not. A lot is happening behind the scenes to enable the monitor/TV to display what the source is sending. They both have to know what the other is capable of, in terms of resolution, frame rate, and so on. I would interpret "turned off" or "not enabled" to mean that commun...
by Burngate
Fri Apr 12, 2019 6:09 pm
Forum: General discussion
Topic: what is use of GCIO_GCLK
Replies: 5
Views: 215

Re: what is use of GCIO_GCLK

GPIO4, pin 7, is called that on the 3B+ schematic.
GPIO4-GPIO_GCLK.png
GPIO4-GPIO_GCLK.png (18.14 KiB) Viewed 129 times
by Burngate
Fri Apr 12, 2019 6:00 pm
Forum: General discussion
Topic: What's the best way to more securely fix wires to a breadboard?
Replies: 11
Views: 377

Re: What's the best way to more securely fix wires to a breadboard?

One possible solution - or at least work-round: strip twice as much, fold the end over and twist it.
That way you get twice the diameter, and more friction
by Burngate
Thu Apr 11, 2019 10:49 am
Forum: Beginners
Topic: Powering a Raspberry Pi zero plus two IO Zero expander boards.
Replies: 1
Views: 78

Re: Powering a Raspberry Pi zero plus two IO Zero expander boards.

Since, on the Zero, the 5v & Gnd of the USB sockets are connected directly to the two 5v pins and the many Gnd pins, it should make no difference which you use.
by Burngate
Wed Apr 10, 2019 5:48 pm
Forum: Automation, sensing and robotics
Topic: 26 GPIO to drive 26 Optocoplers
Replies: 16
Views: 781

Re: 26 GPIO to drive 26 Optocoplers

2uk wrote:
Wed Apr 10, 2019 3:08 pm
the LED is optional the resistor I am not shore
The resistor is necessary, to control the current through the opto's LED
by Burngate
Wed Apr 10, 2019 5:46 pm
Forum: General discussion
Topic: LED without resister
Replies: 10
Views: 306

Re: LED without resister

A Pi's GPIO tries its best to be at either 0v or 3v3, and will give 16mA if it needs to, more if pushed, until it breaks. A LED will take as much current as necessary to keep the voltage across it at ~ 2v (for a red one), until it breaks. So the two will fight - one wanting only 2v, the other 3v3. I...
by Burngate
Tue Apr 09, 2019 5:14 pm
Forum: Advanced users
Topic: Pi 3 b+ power supply issue
Replies: 13
Views: 795

Re: Pi 3 b+ power supply issue

So Is It not an amperage issue? If I buy a power supply ( real 5V/3A) than the project will work perfectly? :| No, and yes. I can carry a 140 lb sack, and run at 10 mph,* but not both at the same time. Lots of "chargers" will give 5v unloaded, and up to 3A if necessary, but not both at the same tim...
by Burngate
Tue Apr 09, 2019 10:30 am
Forum: Automation, sensing and robotics
Topic: Connecting and relaying +100 button connection
Replies: 6
Views: 1297

Re: Connecting and relaying +100 button connection

You seem to have two parts to the problem: physically mounting switches on the Keymanager board, and connecting those switches to the Pi. Andyroo's suggestion of the ModMyPi's expansion Hat would seem the best way to go, with 16 outputs driving rows and 16 inputs looking at columns for 256 switches ...
by Burngate
Tue Apr 09, 2019 9:17 am
Forum: Automation, sensing and robotics
Topic: 26 GPIO to drive 26 Optocoplers
Replies: 16
Views: 781

Re: 26 GPIO to drive 26 Optocoplers

Short answer: yes. Slightly longer answer: at power-on, GPIOs 0 - 8 are pulled up, with the rest pulled down, and all set as inputs. Pretty soon, many of them change to their ALT functions - I2C, UART, etc. But you can change them to what you want when you want. Since you say you want to drive optoc...
by Burngate
Tue Apr 09, 2019 8:52 am
Forum: Off topic discussion
Topic: Why Avoid BASIC on RPi?
Replies: 2312
Views: 86935

Re: Why Avoid BASIC on RPi?

... an annotated list addressing the question why avoid Basic for all versions which run on the Raspberry Pi. Does that mean only under Raspbian, or can you include RISC OS Basic? After all, this thread was started by DavidS who is known to be a fan of RISC OS He said right at the beginning I poste...

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