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by NGC6543
Tue Apr 09, 2019 1:47 pm
Forum: Beginners
Topic: Is 2.4A 5V not enough for pi 3 b+?
Replies: 17
Views: 2289

Re: Is 2.4A 5V not enough for pi 3 b+?

It amazes me how many times this question comes up here since I joined a few weeks ago. But then, the first thing I tried to use was a proper, branded 2.5A phone charger. Low voltage warning instantly, :lol: Phone chargers are not power supplies - at best they have poorly regulated, approximate volt...
by NGC6543
Tue Apr 09, 2019 1:38 pm
Forum: Automation, sensing and robotics
Topic: 26 GPIO to drive 26 Optocoplers
Replies: 17
Views: 2066

Re: 26 GPIO to drive 26 Optocoplers

I agree with using port expanders on the SPI or I2C bus for that many outputs. That gets away from the current limit on the GPIO pins as well.
by NGC6543
Mon Apr 08, 2019 9:24 am
Forum: Beginners
Topic: Power supply
Replies: 8
Views: 870

Re: Power supply

When our cat was a kitten and teething (I guess), she chewed almost every mains wire in the house. I'm amazed she survived; some of the wires (like the one she found while hiding behind the washing machine) were chewed almost to shreds. I could see the copper shining though the holes! On topic... I ...
by NGC6543
Sun Apr 07, 2019 11:37 pm
Forum: Troubleshooting
Topic: WLAN MAC address changes at every reboot?
Replies: 24
Views: 9998

Re: WLAN MAC address changes at every reboot?

Assuming (dangerous, I know) that the (seemingly top secret) LAN7515 is similar to the LAN7500, the MAC address is either stored in an external EEPROM or is configured by the driver. I cannot see an EEPROM anywhere near the LAN7515, so in the absence of any other clues must assume it's done by the d...
by NGC6543
Sun Apr 07, 2019 6:53 pm
Forum: Raspberry Pi OS
Topic: getting gps to work on raspberry pi 3
Replies: 23
Views: 4238

Re: getting gps to work on raspberry pi 3

OK.... Get a spare SD card, install Raspbian afresh, and start from scratch. Once you have the Pi running, run raspi-config and do the following: ..Go to the interfaces ....Select serial ......turn off the shell access ......leave the hardware enabled ..save and reboot. Then try my two lines from ab...
by NGC6543
Sun Apr 07, 2019 5:58 pm
Forum: Raspberry Pi OS
Topic: getting gps to work on raspberry pi 3
Replies: 23
Views: 4238

Re: getting gps to work on raspberry pi 3

rpdom wrote:
Sun Apr 07, 2019 5:51 pm
They are both hardware UARTS.
Thanks for the correction :)
by NGC6543
Sun Apr 07, 2019 5:28 pm
Forum: Raspberry Pi OS
Topic: getting gps to work on raspberry pi 3
Replies: 23
Views: 4238

Re: getting gps to work on raspberry pi 3

I'm on Stretch (with recommended software). I'm new to the RPi and Linux in general, so if anyone else wants to step in they can probably help more. However, the second thing I did with mine, last week, was set up a GPS module and configure the Pi to use the PPS output for the time source for ntp. I...
by NGC6543
Sat Apr 06, 2019 9:37 pm
Forum: Raspberry Pi OS
Topic: getting gps to work on raspberry pi 3
Replies: 23
Views: 4238

Re: getting gps to work on raspberry pi 3

Did you follow any guide on setting it up? Have you disabled the console access on the serial port? Have you installed gpsd? Most of the instructions on the 'net work for most GPS modules. You should be able to cat the NMEA strings without installing anything, as a first test, once you've disabled s...
by NGC6543
Fri Apr 05, 2019 10:13 pm
Forum: Automation, sensing and robotics
Topic: How best to control higher voltage relays with 12v/24v coils?
Replies: 26
Views: 3546

Re: How best to control higher voltage relays with 12v/24v coils?

Just to add: you could make do with much cheaper MOSFETs than the one I put in the diagram. That was just an example really to get us going, given that I didn't know much of your requirements (and I'm not up on MOSFET part numbers any more but was using that exact part myself that day). You just nee...
by NGC6543
Fri Apr 05, 2019 9:09 pm
Forum: Automation, sensing and robotics
Topic: How best to control higher voltage relays with 12v/24v coils?
Replies: 26
Views: 3546

Re: How best to control higher voltage relays with 12v/24v coils?

I would not do this without optocouplers to the Pi and I don't see why they are 'best avoided'. They are there to protect the Pi from the 12V switching a lot of relays circuit. The relay isolation protects the switching board (and everything else) from the mains side. Still, I worked in high availab...
by NGC6543
Fri Apr 05, 2019 3:59 pm
Forum: Troubleshooting
Topic: I suspect My Pi is bricked, due to a failed PSU, but how do I check?
Replies: 25
Views: 1469

Re: I suspect My Pi is bricked, due to a failed PSU, but how do I check?

:oops: Thanks guys, I got confused between polyfuse and TVS. :oops: I blame morning caffeine deficiency. :D I had to call the doctors as soon as I got up this morning. The receptionist asked my date of birth... it took me a good fifteen seconds to remember it! And then I wondered momentarily if I w...
by NGC6543
Fri Apr 05, 2019 11:10 am
Forum: Troubleshooting
Topic: Can I get back the flashing green light?
Replies: 8
Views: 575

Re: Can I get back the flashing green light?

All that did was stop the poweroff from completing. Thanks anyway. What makes you think it didn't complete? (ETA: You did disable your script when you tried the other method, didn't you?) The Pi doesn't power off as such - it just halts*. Either method produces exactly the same result as far as I c...
by NGC6543
Fri Apr 05, 2019 11:00 am
Forum: Troubleshooting
Topic: I suspect My Pi is bricked, due to a failed PSU, but how do I check?
Replies: 25
Views: 1469

Re: I suspect My Pi is bricked, due to a failed PSU, but how do I check?

davidcoton wrote:
Fri Apr 05, 2019 9:49 am
The polyfuse is on the top side of every Pi I have checked (B+ 2B 3B 3A+) except the original B. Not fitted on Pi0 of course.
Note that the component number varies between models.
This is it underneath on the 3B+
polyfuse2.jpg
polyfuse2.jpg (124.27 KiB) Viewed 1067 times
by NGC6543
Thu Apr 04, 2019 1:58 pm
Forum: Troubleshooting
Topic: Can I get back the flashing green light?
Replies: 8
Views: 575

Re: Can I get back the flashing green light?

Can't help with the light, but you don't need a script for that on the 3B+. Just add the following line to /boot/config.txt dtoverlay=gpio-shutdown,gpio_pin=3 You can change the GPIO pin, but leaving it at 3 means the same button will start the Pi up again too. Of course, if you use I2C which uses t...
by NGC6543
Wed Apr 03, 2019 9:35 pm
Forum: Troubleshooting
Topic: I suspect My Pi is bricked, due to a failed PSU, but how do I check?
Replies: 25
Views: 1469

Re: I suspect My Pi is bricked, due to a failed PSU, but how do I check?

Imperf3kt wrote:
Wed Apr 03, 2019 8:40 pm
This is one of the reasons I prefer to step up the voltage
You know, I never thought of that! Not that it's an option for what I'm doing right now, but next time...
by NGC6543
Wed Apr 03, 2019 7:38 pm
Forum: Automation, sensing and robotics
Topic: Know where I can get reasonably priced DPST/DPDT 240v/8a to 240v/10a relays?
Replies: 16
Views: 1906

Re: Know where I can get reasonably priced DPST/DPDT 240v/8a to 240v/10a relays?

Those little relays are nice, but (1) are only single pole (we really need two) and (2) will not cope with the inrush current of the big SMPSs it's going to be switching. They can have an inrush measured in tens of amps. A Dell server I know with a similar power requirement is specified to have not ...
by NGC6543
Wed Apr 03, 2019 7:21 pm
Forum: Troubleshooting
Topic: I suspect My Pi is bricked, due to a failed PSU, but how do I check?
Replies: 25
Views: 1469

Re: I suspect My Pi is bricked, due to a failed PSU, but how do I check?

For a through hole, SA5.0A is pretty close or maybe a 1N6373.

I'm going to be buying some myself for my PSU soon, along with some fuses :D
by NGC6543
Wed Apr 03, 2019 4:34 pm
Forum: Automation, sensing and robotics
Topic: Know where I can get reasonably priced DPST/DPDT 240v/8a to 240v/10a relays?
Replies: 16
Views: 1906

Re: Know where I can get reasonably priced DPST/DPDT 240v/8a to 240v/10a relays?

Do you know the inrush current of the SMPS you are switching? It should be on the specifications from the manufacturer. Anyway, one thing to consider is how you are going to mount the relays. Are you making a PCB that you can cut slots in for relay tags and mains side isolation distance? Most relays...
by NGC6543
Tue Apr 02, 2019 7:29 pm
Forum: Networking and servers
Topic: Raspberry Pi Router not Resolving DNS
Replies: 5
Views: 2176

Re: Raspberry Pi Router not Resolving DNS

You probably know this, but just to make sure: 127.0.2.1 is what DNSCrypt is listening on. BIND is configured to use 127.0.2.1 as its upstream server, but BIND itself listens on 127.0.0.1. So, 127.0.0.1 is what you want to set as the Pi's nameserver. Why it would change back after you edited /etc/dh...
by NGC6543
Tue Apr 02, 2019 3:41 pm
Forum: Beginners
Topic: rasberry pi controlling 50 relays
Replies: 8
Views: 679

Re: rasberry pi controlling 50 relays

Yes, there are a few ways to tackle this. A bank of 74HC595 can be daisy chained. A possibly useful aspect of those is the Output Enable, to keep the outputs high impedance while the data is clocked in and then all fired together by setting the OE pin. I would throw a MAX EPM7128AE CPLD (or similar)...
by NGC6543
Tue Apr 02, 2019 10:54 am
Forum: Graphics, sound and multimedia
Topic: Blender
Replies: 8
Views: 1156

Re: Blender

You have Blender installed on a Pi???

I think it runs slowly sometimes on my 3.4Ghz i7 laptop with 32GB RAM... and go onto my main system to work on it instead.

Try adding Avastar as well... you'll melt the poor thing.
by NGC6543
Tue Apr 02, 2019 3:18 am
Forum: Advanced users
Topic: To much of a good thing? Using a AMS1117-3.3 regulator?
Replies: 2
Views: 612

Re: To much of a good thing? Using a AMS1117-3.3 regulator?

I'm not sure exactly what you are doing but... The tachometer output on fans is usually an open collector or open drain, but might have an internal pull-up to the fan supply voltage. The transistor pulls the tach output to ground to give 1, 2 or 4 pulses per revolution (depends on the fan). The outp...
by NGC6543
Tue Apr 02, 2019 2:27 am
Forum: Networking and servers
Topic: Raspberry Pi Router not Resolving DNS
Replies: 5
Views: 2176

Re: Raspberry Pi Router not Resolving DNS

Your Pi/router should be able to resolve locally. What happens if you enter (on the router): dig @127.0.0.1 google.com If it works, BIND is listening locally and probably all you need to do is tell the rest of the Pi what its DNS resolver is... 127.0.0.1. In Raspbian that's done in /etc/dhcpcd.conf ...
by NGC6543
Sun Mar 31, 2019 5:12 pm
Forum: Automation, sensing and robotics
Topic: How best to control higher voltage relays with 12v/24v coils?
Replies: 26
Views: 3546

Re: How best to control higher voltage relays with 12v/24v coils?

...then add another relay to supply the other load then the contact ratings aren't exceeded per contact. That makes sense now. No more nightmares about welded contacts on one leg of the supply causing havoc :lol: I agree on using known quality relays from a reputable supplier, especially for an SMP...
by NGC6543
Sun Mar 31, 2019 1:33 pm
Forum: Automation, sensing and robotics
Topic: How best to control higher voltage relays with 12v/24v coils?
Replies: 26
Views: 3546

Re: How best to control higher voltage relays with 12v/24v coils?

you can use those relays direct (240V/10A contact rating) or parallel them up (10A x n) Do you mean to connect multiple relay's contacts in parallel to increase the current handling? Don't do that! There will always be one contact that closes a bit quicker than the others and takes the hit... it wi...

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