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by achrn
Thu Aug 15, 2019 12:22 pm
Forum: General discussion
Topic: PoE Power
Replies: 2
Views: 139

Re: PoE Power

A full standards-compliant PoE injector won't send power to a device that isn't standards-compliant (or nearly so), so in that case nothing bad. A passive injector that just imposes voltage on the wires regardless, I don't know - there are still lots of variables. The voltage is clearly a variable (...
by achrn
Tue Jul 30, 2019 2:12 pm
Forum: General discussion
Topic: Raspberry Pi 4 Thread - general discussion
Replies: 861
Views: 88365

Re: Raspberry Pi 4 Thread - general discussion

I could add all that up for you, but I think you are smart enough to see its surly not free. Why not claim you need to buy a house to keep the Pi in so you can use it when it's raining? That would make about as much sense as the claims you're making, and then you could say that a Pi costs hundreds ...
by achrn
Fri Jul 05, 2019 12:03 pm
Forum: General discussion
Topic: RP4 without ESD protection shipped
Replies: 15
Views: 758

Re: RP4 without ESD protection shipped

Ignoring ESD is not professional, it just a stupid way to invest a lot of time to find strange errors. So, when you read "It uses a specially conductive material to prevent ESD damage" and "The boxes have a conductive coating", you understood that to mean "we just ignored ESD"? Presumably you've te...
by achrn
Thu Jun 27, 2019 11:47 am
Forum: General discussion
Topic: Raspberry Pi 4 Heatsink vs Fan vs Flirc Case
Replies: 66
Views: 14084

Re: Raspberry Pi 4 Heatsink vs Fan vs Flirc Case

I'm actually pretty worried about the Flirc Case. I pre-ordered the new case for the rPi4 and I'm not sure it's going to be enough. ... I'm not sure if the extra mass is going to be enough by itself. But, I'm not a hardware engineer, so I don't really know. It's not the mass that helps, it's the su...
by achrn
Sat May 04, 2019 8:19 pm
Forum: General discussion
Topic: Power fans to cool Rpo 3B+
Replies: 6
Views: 387

Re: Power fans to cool Rpo 3B+

I have read in several places that's a bad idea to plug a fan to the rpi pins (at least directly). How could I power those fans? I guess I need an extra power supply for them. You can't run a (useful) fan on the actual GPIO pins directly, but there are power pins in among the other header pins on t...
by achrn
Fri Apr 26, 2019 3:05 pm
Forum: General discussion
Topic: Will Arduino nano and RPI get Damaged on Supplying 5V 3A DC?
Replies: 29
Views: 1143

Re: Will Arduino nano and RPI get Damaged on Supplying 5V 3A DC?

I happen to have a bunch of 5v 4A power supplies, so this is what I typically use, even for just a Pi alone. Ok, So I can Provide it 5.1V and 3 or 4A. Can you Please Show me your schematic for making 5V 4A Power Supply? He says he has a bunch of 4A power supplies, not that he made his own power sup...
by achrn
Thu Apr 25, 2019 12:39 pm
Forum: General discussion
Topic: resolv.conf automatically deleted from etc in raspberry pi 3
Replies: 6
Views: 276

Re: resolv.conf automatically deleted from etc in raspberry pi 3

Files looking OK until the system reboots and then either disappearing or reverting to a previous version is a bad SD card, in my experience. It doesn't have to be fake - genuine but faulty will do it too. I've had this a few times (I had one Pi that was prone to making cards do it, but I've scrappe...
by achrn
Thu Mar 28, 2019 2:09 pm
Forum: General discussion
Topic: How long will it stay on with a external battery?
Replies: 33
Views: 1341

Re: How long will it stay on with a external battery?

20100 / 500 = 40.2 hours You're assuming this battery outputs 5V. If it doesn't, your trivial calculation is clear, simple and wrong. OP: We need more detail, like: 1: Do you really mean battery, or do you mean powerbank? 2: If battery, what chemistry and what voltage (or how many cells)? 3: Is it ...
by achrn
Sun Mar 10, 2019 5:26 pm
Forum: General discussion
Topic: LiPo Battery Voltage Drops
Replies: 7
Views: 411

Re: LiPo Battery Voltage Drops

If you're trying to draw 0.7A, you'll be taking 0.7 x 5.2 / 3.2 / 0.85 = 1.3A from the battery (if we assume an 85% efficiency) I was hoping to get some math for my setup. Since I would like to read up on the theory (I am quite uneducated in electronics), could you point me to some sources? A switc...
by achrn
Sun Mar 10, 2019 8:17 am
Forum: General discussion
Topic: LiPo Battery Voltage Drops
Replies: 7
Views: 411

Re: LiPo Battery Voltage Drops

This setup draws around 0.7V, Is that supposed to be 0.7A? If I only connect the RasPi without Display the system boots up, drawing around 0.2A. Where? From the battery, or from the powerboost? Presumably from the powerboost (ie into the Pi) , so (given that you've told us it's dipping below 3.2V) ...
by achrn
Sat Mar 09, 2019 2:45 pm
Forum: General discussion
Topic: Under voltage detected - revisited
Replies: 26
Views: 1391

Re: Under voltage detected - revisited

Anyhow, I still don't understand the purpose of diode D1 on the expansion board. It may very well be drawn wrong. That block is just input filter and protection for the board, specifically D1 is so if you connect your power supply backwards (relatively easy to do with screw terminals), you won't da...
by achrn
Fri Mar 08, 2019 9:19 pm
Forum: General discussion
Topic: Under voltage detected - revisited
Replies: 26
Views: 1391

Re: Under voltage detected - revisited

take the Pi off the board, connect a (say) 10 ohm resistor between pins 2 and 6 on the board GPIO jumper (just poke the resistor wires in the holes) and measure the voltage across the resistor. It will be drawing 0.5A but should still give you 5V. It occurs to me that I should point out (in case it...
by achrn
Fri Mar 08, 2019 4:09 pm
Forum: General discussion
Topic: Under voltage detected - revisited
Replies: 26
Views: 1391

Re: Under voltage detected - revisited

Possibly the schematic is not quite true, and the board is putting the 5V supply to the board through D1 before passing it to the Pi, so your Pi is actually getting 5.02V minus a diode drop. I am not seeing that. I think you are looking at it backwards. To me it looks like you plug the Pi into this...
by achrn
Fri Mar 08, 2019 12:40 pm
Forum: General discussion
Topic: Under voltage detected - revisited
Replies: 26
Views: 1391

Re: Under voltage detected - revisited

Because the 5V are fed through the rpi 5V pins and not trough its USB port, I'm not sure if it's the reason of the following messages: I don't believe it is. If anything, you'll get lower voltage by feeding to the usb than feeding to the GPIO header, since the latter bypasses some protection ciruci...
by achrn
Tue Mar 05, 2019 8:17 pm
Forum: General discussion
Topic: RPI 3 B+ running on Battery 200mAh
Replies: 21
Views: 802

Re: RPI 3 B+ running on Battery 200mAh

I don't think I've seen a PP3 that can give you 600mAh at 200mA - you only get those sorts of capacities out of that sort of battery if you're drawing only 1 or 2 mA and/or only for an hour a day with long recoveries in between. (Indeed, the data sheet cited shows 2mA for 300 hrs (to 6V) = 600 mAh,...
by achrn
Tue Mar 05, 2019 4:08 pm
Forum: General discussion
Topic: RPI 3 B+ running on Battery 200mAh
Replies: 21
Views: 802

Re: RPI 3 B+ running on Battery 200mAh

Well, I looked up the datasheet for my particular battery: https://d2ei442zrkqy2u.cloudfront.net/wp-content/uploads/2016/03/MN1604_6LP3146_US_CT1.pdf I didn't see where it talked about a maximum output current, but it does show a particular chart of interest to me at 200mA ( 1000mW ? ), because it ...
by achrn
Sun Mar 03, 2019 9:47 pm
Forum: General discussion
Topic: Weatherproof Enclosure...
Replies: 4
Views: 310

Re: Weatherproof Enclosure...

I had problems with a Pi in a plastic box in an ambient of a little over 50C. I've now done this: https://www.raspberrypi.org/forums/viewtopic.php?f=63&t=217627#p1431981 and it looks fairly promising, but I haven't had it in the high ambient conditions yet. Most of the Hammond cases can be had with ...
by achrn
Fri Mar 01, 2019 2:21 pm
Forum: General discussion
Topic: Layout of new official keyboard
Replies: 47
Views: 2553

Re: Layout of new official keyboard

>> Ah yes, I do like a keyboard with out the stupid redundant num pad. I've found that accountants like them - they can bash numbers in quicker than on the horizontal keys. But why do the rest of us get lumbered with them just because one teensy tiny part of the workforce wants them? In my company ...
by achrn
Fri Mar 01, 2019 10:14 am
Forum: General discussion
Topic: Operating 24/7
Replies: 15
Views: 1358

Re: Operating 24/7

Yes, 24/7 is fine. My first Pi has been running basically 24/7 since mid 2013 (though it generally doesn't get much more than a year uptime at a time, because it's on my central heating, and that occasionally gets switched off for things like boiler servicing - right now uptime is 127 days, that shu...
by achrn
Thu Feb 28, 2019 6:52 am
Forum: General discussion
Topic: Best way to power 4 x Raspberry Pi
Replies: 31
Views: 1350

Re: Best way to power 4 x Raspberry Pi

When using 5V from an ATX power supply, do you need to wire up dummy loads to the 12V, 3.3V, -12V and -5V rails to keep it happy? It used to be necessary to draw a couple of amps from the 12V line to get a stable voltage on the others. However, the last power supply I had that required that was dec...
by achrn
Wed Feb 27, 2019 10:38 pm
Forum: General discussion
Topic: Best way to power 4 x Raspberry Pi
Replies: 31
Views: 1350

Re: Best way to power 4 x Raspberry Pi

I disagree that shorting a 5V 50W power supply is "a lot more dangerous" than shorting a 12V 60W supply... Remember that under short circuit conditions the voltage dissappears, you are left with just the current. In the absece of foldback protection (not necessarily the case) a 12V 60W supply will ...
by achrn
Wed Feb 27, 2019 10:11 pm
Forum: General discussion
Topic: Best way to power 4 x Raspberry Pi
Replies: 31
Views: 1350

Re: Best way to power 4 x Raspberry Pi

How do I know how many amps a 12v PSU need to be, if I convert it to 5v? I have a 12V 5A somewhere around here that I don't use - would that be enough? Can you recommend a 12v-5v circuit? Probably 12V 5A will be enough, yes, though it does somewhat depend on what circuit you use to step it down. Pe...
by achrn
Tue Feb 19, 2019 7:29 pm
Forum: General discussion
Topic: IP6x case highish temperature ambient
Replies: 11
Views: 805

Re: IP6x case highish temperature ambient

OK, I'm resurrecting an old thread, but I've only just implemented my solution. I've made a 'homebrew' FLIRC-like case. I used a Hammond diecast enclosure, glued in a small block of aluminium (using a glue intended for bonding heatsinks together) and mounted the Pi on that. It's a little delicate in...
by achrn
Tue Feb 19, 2019 3:59 pm
Forum: General discussion
Topic: All my RPIs 3 are underpowered, all the time
Replies: 23
Views: 1029

Re: All my RPIs 3 are underpowered, all the time

I am running Arduino with some Dallas DS18B20 and from time to time, the temperature in the living room drops in 5 seconds from 20 Celsius to -85 Celsius. The Dallas sensors usually give +85°C if they have an error, not -85°C. Most times I have encountered this it was because of bad wiring causing ...
by achrn
Wed Feb 06, 2019 10:10 pm
Forum: General discussion
Topic: How change user name of Raspberry Pi
Replies: 5
Views: 1071

Re: How change user name of Raspberry Pi

https://www.raspberrypi.org/forums/viewtopic.php?f=63&t=227620#p1396338 It works fine for Raspbian Lite - I think there are things in the full desktop that assume the user is called pi - certainly someone further down the thread had a certain amount of trouble taking this approach, but I never use a...

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