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by Mortimer
Thu Nov 01, 2018 11:32 am
Forum: Beginners
Topic: Detect current on Raspberry pi
Replies: 88
Views: 8628

Re: Detect current on Raspberry pi

Hmm! the microphone might be polarised (is it an electret mic?). Try swapping the speaker wires instead.
by Mortimer
Wed Oct 31, 2018 11:04 pm
Forum: Beginners
Topic: Detect current on Raspberry pi
Replies: 88
Views: 8628

Re: Detect current on Raspberry pi

Because the audio circuitry of the handset by its self was carefully designed so that the microphone audio and speaker audio were 180 degrees out of phase and at an amplitude that any locally fed noise would cancel itself out. The audio circuitry of the USB audio dongle was likely in-phase and ther...
by Mortimer
Wed Oct 31, 2018 9:53 pm
Forum: Beginners
Topic: Detect current on Raspberry pi
Replies: 88
Views: 8628

Re: Detect current on Raspberry pi

Interesting, it sounds like it might be it but then I don't understand why this Larsen effect didn't occur at all without the Pi. Because the audio circuitry of the handset by its self was carefully designed so that the microphone audio and speaker audio were 180 degrees out of phase and at an ampl...
by Mortimer
Tue Oct 30, 2018 1:10 pm
Forum: Beginners
Topic: Detect current on Raspberry pi
Replies: 88
Views: 8628

Re: Detect current on Raspberry pi

Wouldn't it be easier to look for the signal that triggers the oscillator circuit driving the ringer speaker, because that will be a simple Voltage level change surely? Much easier to interface to a GPIO. If not : I would take the speaker feed, AC couple to a rectifier, and then a simple smoothing c...
by Mortimer
Fri Oct 19, 2018 11:01 am
Forum: General discussion
Topic: SD card write count?
Replies: 15
Views: 1574

Re: SD card write count?

LOL! reminds me of the time way back when I was working in the avionics industry, we got in a bubble memory device to try out. Someone thought it a good idea to try it out as a hard-drive in a computer. I think it lasted less than an hour!
by Mortimer
Fri Oct 19, 2018 10:46 am
Forum: HATs and other add-ons
Topic: PoE HAT - USB Ports not working - over-current (FIXED - New Hardware Release)
Replies: 327
Views: 91013

Re: PoE HAT - USB Ports not working - over-current

Surely it's up to the sales outlets how they present information about a product and what they say. If their online sales engine and website doesn't have any other appropriate item status than "out-of-stock", then what are they to do? It is technically correct.
by Mortimer
Fri Oct 19, 2018 8:19 am
Forum: Other projects
Topic: making a digital piano : is the rpi fast enough ?
Replies: 13
Views: 2811

Re: making a digital piano : is the rpi fast enough ?

So you have 8 digital outputs and 23 digital inputs. I'll go out on a limb and guess that the digital inputs are the piano keys, but I'm at a complete loss trying to figure out just what in the heck the outputs are actually for and why you would want to write "1" to them in a loop. It's quite a com...
by Mortimer
Fri Oct 12, 2018 1:57 pm
Forum: Mathematica
Topic: Matematica removed from raspbian image
Replies: 39
Views: 22230

Re: Matematica removed from raspbian image

Looks like someone (DrYak) has stepped up to counter the mis-information post at Phoronix.
by Mortimer
Thu Oct 04, 2018 3:21 pm
Forum: Other projects
Topic: making a digital piano : is the rpi fast enough ?
Replies: 13
Views: 2811

Re: making a digital piano : is the rpi fast enough ?

I would recommend taking a look at Julian Ilett's channel on Youtube. He has done a series of videos on a penny organ project which might give you an ideal starting point to have a tinker. Doesn't use a RPi, but will give you a way of getting something going quite quickly and as you're understanding...
by Mortimer
Mon Oct 01, 2018 12:47 pm
Forum: Automation, sensing and robotics
Topic: Motor torque and gearing
Replies: 6
Views: 729

Re: Motor torque and gearing

Lego is pretty powerful stuff : https://youtu.be/slv5fvS6e9Q

The chap in the video builds a Lego machine that gave a measured pull of 102kgs!
by Mortimer
Mon Oct 01, 2018 9:41 am
Forum: Troubleshooting
Topic: microUSB power problem
Replies: 18
Views: 1032

Re: microUSB power problem

I did suggest that it might be the cable. What is OK for a RPi 1, is not necessarily going to be OK for RPi 3+. I was always able to run RPi 1's off very low power outlets. E.g. headless using the USB port on a BT HomeHub, or directly off the USB port on a Motorola Lapdock. My RPi 3 and 3+ would not...
by Mortimer
Sun Sep 30, 2018 4:04 pm
Forum: Troubleshooting
Topic: microUSB power problem
Replies: 18
Views: 1032

Re: microUSB power problem

Are you sure the Pi is. the problem and not the cable?
by Mortimer
Fri Sep 28, 2018 9:17 am
Forum: Off topic discussion
Topic: Speaker Wattage and Resistance Questions
Replies: 14
Views: 2697

Re: Speaker Wattage and Resistance Questions

Is it worthwhile mentioning that a speaker is not 8 Ohms 'resistance' (or 2 Ohms or whatever), it is 'impedance'. Series connection of speakers of the same type will in all likelihood work in the way suggested, but different speakers might not. The Impedance figures are at a specific frequency, usua...
by Mortimer
Tue Sep 18, 2018 10:20 am
Forum: General discussion
Topic: RS485 module
Replies: 7
Views: 707

Re: RS485 module

Yup, I concur that the use of UART-TXD to control the driver state seems odd. There should be some sort of delay so that the state doesn't change for every transmitted bit, but decays after the end of the packet/message.
by Mortimer
Tue Sep 18, 2018 9:55 am
Forum: General discussion
Topic: Techmoan on Youtube - VinylVideo - Playing video from a 45rpm record
Replies: 3
Views: 399

Techmoan on Youtube - VinylVideo - Playing video from a 45rpm record

Does anyone watch Techmoan videos on YouTube.

You might find this one of some interest, particularly the fact the product is built around a Raspberry Pi:

Techmoan on Youtube - VinylVideo - Playing video from a 45rpm record
by Mortimer
Mon Sep 17, 2018 11:17 am
Forum: General discussion
Topic: RS485 module
Replies: 7
Views: 707

Re: RS485 module

The SN65HVD driver has two pins for enable/disable writing and listening. In the abelectronics module the pins for enabling writing are connected to the UART TX pin. So, when we write a logic '1' in the UART, the write mode is enabled and it is written a logic '1' in the RS485 line. But when a '0' ...
by Mortimer
Thu Sep 13, 2018 11:38 am
Forum: Beginners
Topic: How to password protect a folder in raspbian ?
Replies: 12
Views: 1686

Re: How to password protect a folder in raspbian ?

Aren't all folders in Rasbian protected by passwords?

A folder created by one user isn't necessarily accessible to another, unless the first user grants permission, or the second has access to super-user password.
by Mortimer
Sat Aug 04, 2018 10:36 am
Forum: Networking and servers
Topic: how do i connect to my cisco router/switches
Replies: 3
Views: 912

Re: how do i connect to my cisco router/switches

I don't believe Cisco do a USB-RJ45 (RS-232) cable, although there are many 3rd party suppliers of such cables, and they all contain a RS-232 converter inside the USB plug. The RJ45 end is still RS-232 serial. Many of their later models have a mini-USB console port that uses a normal male Type A to ...
by Mortimer
Tue Jul 31, 2018 5:38 pm
Forum: Beginners
Topic: PuTTY connection
Replies: 13
Views: 735

Re: PuTTY connection

I'm not understanding how PuTTY fits into this. SFTP just needs an SFTP client on the Windows machine and an SFTP service running on the Pis. It looks like you're using the SSH.NET library. As the connections are secure, I see no reason to close the connections between reads for security reasons. Pe...
by Mortimer
Tue Jul 31, 2018 3:28 pm
Forum: Beginners
Topic: PuTTY connection
Replies: 13
Views: 735

Re: PuTTY connection

I can do Samba, my wife is Brazilian and a good dance teacher, however : What is Samba
by Mortimer
Tue Jul 31, 2018 11:36 am
Forum: Beginners
Topic: PuTTY connection
Replies: 13
Views: 735

Re: PuTTY connection

I don't know quite what you're trying to do. But from the sounds of it, you are just retrieving a text file from each of the three Pis. I would either: (1) If the Win10 PC is on all the time, create a shared folder and have the Pis use Samba to write the text files directly into the share, then the ...
by Mortimer
Mon Jul 30, 2018 2:09 pm
Forum: HATs and other add-ons
Topic: Looking for a converter for 230V > 12V and 12V > 5V
Replies: 4
Views: 804

Re: Looking for a converter for 230V > 12V and 12V > 5V

You mean something like this for mains to 12V?: https://media.rs-online.com/t_large/R1618273-01.jpg For 12Vdc to 5.1Vdc, I think the consensus would be to look for a 12V-to-5V UBEC (Universal Battery Eliminator Circuit): https://www.modmypi.com/image/cache/catalog/electronics/voltage-regulators/DSC_...
by Mortimer
Sun Jul 29, 2018 12:39 pm
Forum: Automation, sensing and robotics
Topic: Relay Module KY-019 5V
Replies: 488
Views: 87970

Re: Relay Module KY-019 5V

The worst thing is that Nano is not WYSIWYG GUI. WYSIWYG is pointless and unnecessary for pure text files as they retain no visual formatting information, and line wrapping can cause confusion in my opinion. Luckily Rpi recently provides the Geany IDE for python. I sometimes use Geany in Windows 10...
by Mortimer
Fri Jul 27, 2018 3:54 pm
Forum: Automation, sensing and robotics
Topic: Relay Module KY-019 5V
Replies: 488
Views: 87970

Re: Relay Module KY-019 5V

Ah but all of that relates to the accuracy of the real time clock circuit. So "+/-2ppm from 0 to 40degC" tells you that between those temperatures the accuracy of the RTC is better than 2ppm. It says nothing about the accuracy of the temperature sensor. The +/-2degC temperature accuracy is more like...
by Mortimer
Fri Jul 27, 2018 1:23 pm
Forum: Automation, sensing and robotics
Topic: Relay Module KY-019 5V
Replies: 488
Views: 87970

Re: Relay Module KY-019 5V

What are the specifications of the modules?

I would imagine there would be a tolerance range to the accuracy. If it was +/-10% say, then all of your modules would be within spec for a temperature reading of 30C, i.e. 2 are bang on, one reads high and one reads low.

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