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by davidcoton
Tue Dec 12, 2017 10:53 pm
Forum: Troubleshooting
Topic: How big is Rasbian supposed to be?
Replies: 7
Views: 137

Re: How big is Rasbian supposed to be?

It should be just over 4GB when installed. Possibly it's too big for whatever unzipper you are using. Try 7-zip.
by davidcoton
Tue Dec 12, 2017 10:27 pm
Forum: Beginners
Topic: 1MOhms
Replies: 9
Views: 268

Re: 1MOhms

Even if you find a spare pair of contacts that work (low closed resistance), you really do not want to mix low voltage wiring with mains in that environment. If you do, all the wiring must be insulated to mains standards. But you are asking for an accidental connection of mains voltage to your Pi (a...
by davidcoton
Tue Dec 12, 2017 3:41 pm
Forum: General discussion
Topic: Distance using u'sonic sensor
Replies: 13
Views: 314

Re: Distance using u'sonic sensor

Thanks. Tried this one but get error "missing parentheses in call to print". Does not do anything That's because it's a Python2 program and you are running on Python3. Probably the only change required is to do what it implies: Add parentheses around the argument part of each print statment. For ex...
by davidcoton
Tue Dec 12, 2017 2:12 pm
Forum: General discussion
Topic: How to execute program on server without breaking security issues ?
Replies: 51
Views: 1350

Re: How to execute program on server without breaking security issues ?

May I supply the emphasis on the most important part? One method is to set up port forwarding on your router. To do this, you must change the configuration of your router to forward all inbound traffic from the internet on a specific port to the local IP address of your Raspberry Pi. Most routers ha...
by davidcoton
Tue Dec 12, 2017 2:09 pm
Forum: Beginners
Topic: battery pack question
Replies: 7
Views: 254

Re: battery pack question

If you power pack fully charged only gave 4.92v I suspect it soon reaches a low enough voltage for things to start not working correctly. while you are developing your project why not just use a mains psu to power your pi, that will also give you time to source a better power pack for the final pro...
by davidcoton
Tue Dec 12, 2017 1:53 pm
Forum: General discussion
Topic: Physical Computing
Replies: 11
Views: 389

Re: Physical Computing

Red LEDs only require 1.8 volts or so. Blue, green and white LEDs may need 3.3v You should test that at least your LED still works by connecting it, with resistor in series, across an AA, or AAA cell. That will also confirm that you have the LED the right way around. They will not light up the wron...
by davidcoton
Mon Dec 11, 2017 11:16 pm
Forum: Troubleshooting
Topic: Setting the time zone
Replies: 4
Views: 128

Re: Setting the time zone

Reboot after setting (not sure if that's it, but worth a try)?
by davidcoton
Mon Dec 11, 2017 10:59 pm
Forum: Beginners
Topic: Connecting Relay with Pi
Replies: 10
Views: 212

Re: Connecting Relay with Pi

If you are not experienced in working with mains voltages please seek help from someone who is as mains can kill you destroy you pi or burn down you house if you get things wrong. +1. You need to be familiar with your national wirng codes and practices before undertaking this sort of connection. Th...
by davidcoton
Sun Dec 10, 2017 9:21 pm
Forum: General discussion
Topic: Something changed
Replies: 23
Views: 559

Re: Something changed

I'm not certain that it's necessary, but did you reboot after changing the password?
by davidcoton
Sun Dec 10, 2017 2:17 pm
Forum: Troubleshooting
Topic: Internet connection sharing over USB wont work
Replies: 18
Views: 489

Re: Internet connection sharing over USB wont work

I'll never understand the obsession with static IP addresses I see on this forum. Why does everyone try to do that? Because when things aren't working - for whatever reason(s) - setting a known IP address removes one variable from the equation, usually making debugging the real problem(s) easier. O...
by davidcoton
Sun Dec 10, 2017 11:47 am
Forum: Advanced users
Topic: High pitched noise when fading LED's via PWM
Replies: 4
Views: 162

Re: High pitched noise when fading LED's via PWM

It could be that the PWM frequency is radiating from the LED strip. You may need to screen all the audio circuits so they don't pick it up (the sulution is really to avoid radiating the PWM frequency in the first place, but that might be tricky).
by davidcoton
Sat Dec 09, 2017 11:15 pm
Forum: General discussion
Topic: Powering multiple pi and boards
Replies: 8
Views: 354

Re: Powering multiple pi and boards

jcyr wrote:
Sat Dec 09, 2017 8:35 pm
Supplies aside, I'm curious where you guys hook up the power. Via micro-USB, or via power pins on the header?

In other words, with or without fuse?
OP concerns a Pi Zero which has no power protection. For other models use the micro-USB whenever possible, it might save your Pi one day.
by davidcoton
Sat Dec 09, 2017 9:50 am
Forum: General discussion
Topic: Problem with relay and resistive load
Replies: 18
Views: 533

Re: Problem with relay and resistive load

The Songle relay consumes 60 mA each. 180 mA and maximum for the gpio bank is 50mA. That is not the issue. The supply fior the relays is not coming throught the GPIO pins, but from the 5V rail. This could possibly overload the supply (which is why it's worth trying a separate one), but it's not rel...
by davidcoton
Fri Dec 08, 2017 11:02 pm
Forum: Beginners
Topic: How to efficiently power 5x 3535SMD LED?
Replies: 8
Views: 277

Re: How to efficiently power 5x 3535SMD LED?

Sorry this posting is a bit late...my ISP crapped out just as I was writting it last evening. What you don't know is how consistent (or not) the 3535smd is from part to part, or even if you would get LEDs off the same die. Trying to drive all 5 off the same power bus is going to be a problem for th...
by davidcoton
Fri Dec 08, 2017 4:44 pm
Forum: General discussion
Topic: Powering multiple pi and boards
Replies: 8
Views: 354

Re: Powering multiple pi and boards

I haven't tried it, but there's no reson why you can't do exactly the same as with audio components. Just be careful that your PSU can provide a stable 5-5.25V at the maximum total load, wires as short as possible and thick enough to avoid excessive voltage drop. You can power your Zero through the ...
by davidcoton
Fri Dec 08, 2017 4:37 pm
Forum: Beginners
Topic: Multiple RPi using a Single External HDD for Data Storage
Replies: 1
Views: 85

Re: Multiple RPi using a Single External HDD for Data Storage

Your basic scheme sounds right, depending on which model Pis you are using and therefore whether they have ethernet ports, wireless, neither, or both): connect the Pis by wired or wireless LAN (the fourth Pi could run as an AP and provide DHCP for the network, or use a separate hub), then share the ...
by davidcoton
Fri Dec 08, 2017 4:22 pm
Forum: Beginners
Topic: Random.Choice and while loop
Replies: 6
Views: 188

Re: Random.Choice and while loop

This is better: ... Yes, that should work. Now we can clean up the logic (just one condition, at the expense of erepeating the random.choice line), the naming of variables (meaningful and consistent style), and the diagnostic prints (so we know what is being printed): #!/usr/bin/env python import r...
by davidcoton
Fri Dec 08, 2017 3:32 pm
Forum: Beginners
Topic: Safety Instructions
Replies: 18
Views: 622

Re: Safety Instructions

If you make a mistake building a circuit live, it will go bang immediately (or whatever the consequence). If you turn off and build a circuit with a mistake, the bang happens when you switch back on. The latter provides time for review and correction before the bang. Saves money, and time in the lon...
by davidcoton
Fri Dec 08, 2017 3:21 pm
Forum: General discussion
Topic: Should I move to Ubuntu
Replies: 10
Views: 431

Re: Should I move to Ubuntu

And use apt-get update and apt-get upgrade to keep up to date. That will work, but note that the newer, shorter commands apt update and apt upgrade may be better optimised for interactive use, while the longer form is optimised for script use. My guess is that the performance of the two versions wi...
by davidcoton
Fri Dec 08, 2017 2:07 pm
Forum: General discussion
Topic: Maximum drives?
Replies: 4
Views: 217

Re: Maximum drives?

Linux has a very high limit, I've operated servers with near to 100 drives connected. Maybe, but Raspbian has a soft limit of 8 active USB channels (see link others have quoted). So an array of 12 drives might work, 16 probably won't. With independent library drives (or several smaller arrays) the ...
by davidcoton
Fri Dec 08, 2017 2:02 pm
Forum: General discussion
Topic: High Precision AD/DA board ADS1256
Replies: 7
Views: 288

Re: High Precision AD/DA board ADS1256

Go back to basics. From the example you quote, full scale input voltage range is about 10V. This represents the differential range +/-5V, with +5V giving 7FFFFF, 0V gives 000000, and -5V gives 800000. Each step is therefore 10/2^24 = 0.6uV. You need to get a very stable reference voltage, derived fr...
by davidcoton
Thu Dec 07, 2017 9:08 pm
Forum: Troubleshooting
Topic: Painfully slow performance
Replies: 28
Views: 772

Re: Painfully slow performance

Yeah but is that caused by the cable being unable to handle the voltage or the cable being unable to handle the current, resulting in voltage sag. The problem detected by the Pi is undervoltage, not undercurrent. Undervoltage can have two (common) causes: The PSU itself cannot generate enough volta...
by davidcoton
Thu Dec 07, 2017 6:01 pm
Forum: Beginners
Topic: Random.Choice and while loop
Replies: 6
Views: 188

Re: Random.Choice and while loop

If I've got it right, the problem is the second break statement. The first one is right: exist the "while true" loop when the new bottle is different. But the second one is executed outside the "if not" code, so it exits even when the bottles are equal. Just delete the second break line, without cha...
by davidcoton
Wed Dec 06, 2017 8:16 pm
Forum: General discussion
Topic: Three Pi's "On My TV" (Just for fun ...)
Replies: 3
Views: 256

Re: Three Pi's "On My TV" (Just for fun ...)

mikerr wrote:
Wed Dec 06, 2017 7:07 pm
If your TV has Picture in Picture you could view 2 at once too ?
Isn't that known as Pi in Pi? :lol:
by davidcoton
Wed Dec 06, 2017 8:14 pm
Forum: General discussion
Topic: OK. This is ridiculous!
Replies: 34
Views: 1551

Re: OK. This is ridiculous!

Burngate wrote: So, hopefully, Turbojoe will still be exited by his next Pi when he gets it. I'm certainly still exited
Exited by a Pi? We always warn people about the dangers of mains electricity, but is there some other danger lurking? That could be exciting. :lol:

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