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by Earlton2
Fri Jun 18, 2021 10:12 pm
Forum: Other projects
Topic: Monitoring a Heat-Recovery Ventilator in a Home Control System
Replies: 4
Views: 536

Re: Monitoring a Heat-Recovery Ventilator in a Home Control System

I use the RD serial port on a Pi to capture dial pulses from and old telephone. In this case they come in as an '@', which I count to determine the number dialed. Dial zero gets you 10 pulse or '@@@@@@@@@@'. The ASCII character consists of a START bit followed by up to 8 DATA bits so the character l...
by Earlton2
Sat May 22, 2021 1:06 am
Forum: Automation, sensing and robotics
Topic: Foursquare Referee OpenCV
Replies: 2
Views: 675

Re: Foursquare Referee OpenCV

I've been looking at OpenCV OAK of late. This camera can detect depth. If your camera was above the court, might a flip in depth indicate where the ball hit the ground. Even with periodic video samples you might be able to create the mathematics of the flight path and from that determine if the grou...
by Earlton2
Fri Apr 30, 2021 1:06 am
Forum: Automation, sensing and robotics
Topic: Controlling 6 24VDC Sensors with RPI
Replies: 2
Views: 213

Re: Controlling 6 24VDC Sensors with RPI

[*]Are the relays intended to control the transmitters. i.e. only ON for a short period, or to somehow select the receivers. As I read it BOTH will run from 10V so on my systems I'd be using a raw 12V to run he devices. So let's say you have the transmitters ON all the time, each receiver can be wir...
by Earlton2
Tue Dec 22, 2020 2:22 am
Forum: Other projects
Topic: Control a Hornby Train Set With a Raspi
Replies: 18
Views: 7727

Re: Control a Hornby Train Set With a Raspi

Below you will find a Youtube of my Pi Train Interface (PITI) in action, which I later called "Dial-D for Diesel". There is more of a description in on the web-site but I'm afraid the circuits are pretty old now. The original dual track was just straight but later I modified it to run the ...
by Earlton2
Sat Nov 07, 2020 3:03 am
Forum: Graphics, sound and multimedia
Topic: Playing a sound from a script
Replies: 2
Views: 258

Re: Playing a sound from a script

Instead of ./... maybe you need to spell out the full path.

In another 'place' (C) I build up a system() call string using sprintf() and include' aplay' (I think), and the appropriate path and sound file.

DW
by Earlton2
Sun Oct 25, 2020 5:13 pm
Forum: Advanced users
Topic: How to power Raspberry Pi 4B 8GB from 12 volt battery
Replies: 24
Views: 4960

Re: How to power Raspberry Pi 4B 8GB from 12 volt battery

For smaller Pi I've been using a v7805-1000x from cui-inc. digi-key. Normally fed into the gpio pin. I like 12 volts available for powering motors and amplifiers.
by Earlton2
Fri Sep 25, 2020 2:10 am
Forum: Automation, sensing and robotics
Topic: Opening a Cabinet Sized Door
Replies: 14
Views: 804

Re: Opening a Cabinet Sized Door

Is there any chance you have used a thin gauge of wire between the battery and solenoid and it's turn on current is being limited? Would it be of any use pulsing the solenoid, say three 1-sec ON/OFF? Do you add a reverse diode across the solenoid to take care of the reverse voltage pulse? If the dri...
by Earlton2
Sat Aug 22, 2020 12:46 am
Forum: Beginners
Topic: 4B headless start
Replies: 4
Views: 410

Re: 4B headless start

This has helped me with a headless PiZero sound system for a bolly truck. I have redirected audio to two GPIO pins and am using aplay to output various tones and sound 'bytes' selected via push buttons. This was all working downstairs until I invoked systemd for auto startup and later unplugged the ...
by Earlton2
Wed May 27, 2020 2:17 am
Forum: Advanced users
Topic: 160 Watt 4 ohm speaker with pi zero
Replies: 20
Views: 2069

Re: 160 Watt 4 ohm speaker with pi zero

I've been happy with this 20W Stereo Class-D unit from Ada Fruit: https://www.adafruit.com/product/1752 I don't use any of the fancy controls as my GPIO was busy enough, but it plugged into the audio output and happily played music, sounds and also talked under program control. 4 ohm 12V in the spec...
by Earlton2
Wed May 27, 2020 2:03 am
Forum: Beginners
Topic: Which of the schemes is the correct to power a relay?
Replies: 6
Views: 483

Re: Which of the schemes is the correct to power a relay?

With regard to the GND connection I would use the second schematic however there is no indication of what the VCC and JD-VCC requirements are. Are they both inputs? Is there a chance their current requirements exceed the Pi 3V3 source level. What does the specification of the relay device list for V...
by Earlton2
Sun May 10, 2020 2:22 am
Forum: Beginners
Topic: [SOLVED] How to run a gphoto2 command on start up?
Replies: 9
Views: 542

Re: How to run a gphoto2 command on start up?

I use systemctl to start up a program via a script call and a systemctl timer to periodically send a signal to the latter for data capture. The script with the embedded Signal can also be called from the Terminal so it makes it useful for testing. I'm not saying you need Signals or even program star...
by Earlton2
Mon May 04, 2020 12:14 am
Forum: Teaching and learning resources
Topic: Car nut would love some guidance for a car computer. Not sure where to look
Replies: 4
Views: 1504

Re: Car nut would love some guidance for a car computer. Not sure where to look

The 5/3.3V conversion just works as a ratio so 2.5V in would simply give 1.65V etc. It's normal intent is to prevent a 5V device from hurting a 3.3V Pi or peripheral chip. If your sensors generated 12V then a 12/3.3 ratio would be required. I'm presently using an Analogue to Digital device with an I...
by Earlton2
Tue Apr 14, 2020 9:30 pm
Forum: Assistive technology and accessibility
Topic: Where do i start
Replies: 4
Views: 1727

Re: Where do i start

DietPI, PI-Top, Noobs_V3 ? As an example I use "C" with system calls to espeak. static char sEmerg[200] /* a string for the emergency message */ ... /* build up the espeak command and throw the resulting file at aplay */ sprintf(sEmerg, "espeak -ven-uk-north -a50 -p10 -s150 --stdout&q...
by Earlton2
Mon Apr 13, 2020 10:49 pm
Forum: Beginners
Topic: Anemometer
Replies: 38
Views: 2481

Re: Anemometer

For calibration don't you just stick it out of the car window and take a few regulated runs down a country lane. A co-pilot might be a good idea!
by Earlton2
Sat Apr 04, 2020 2:08 pm
Forum: Automation, sensing and robotics
Topic: Values in the ADC are fluctuating and incorrect.
Replies: 9
Views: 1526

Re: Values in the ADC are fluctuating and incorrect.

Does this have anything to do with big-endian, little-endian interfacing. I had to swap bytes when doing A2D on my RaspberryPi. I am using WiringPi to run the i2c not a Python driver or such.
by Earlton2
Thu Mar 26, 2020 8:25 pm
Forum: Beginners
Topic: emulate a Printer
Replies: 1
Views: 273

Re: emulate a Printer

I'm hopeful you get some answers to your query as we have an old LED display which I've interface to a RPi over the serial lines. If the Pi would look like a printer to an Ethernet line then we could add it as a teaching aid to a library network . At the moment it 'speaks' ASCII, EBCDIC and Baudot. ...
by Earlton2
Tue Jan 28, 2020 10:28 pm
Forum: Weather station
Topic: Rainfall Sampling
Replies: 6
Views: 2174

Re: Rainfall Sampling

The rainfall detector appears to toggle both ways so the switch will be on or off for the time taken to fill the 'bucket'. You read the switch in one of your loops (say 5-min) i.e. ON or OFF. When the new reading is different from the old one increment the rainfall count, after which you save old = ...
by Earlton2
Sun Jan 19, 2020 3:09 am
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: Serial on RPi B works; won't work on RPi Zero W
Replies: 4
Views: 817

Re: Serial on RPi B works; won't work on RPi Zero W

In raspi-config I set: 1. Interface > Serial > ... login .. accessible over serial > NO 2. ... serial port hardware to be enabled > YES I'm using WiringPi to access serial: if (wiringPiSetup() == -1) .... if ((ftmp = serialOpen ("/dev/serial0", baud)) < 0) << part of set-up, int ftmp - fil...
by Earlton2
Wed Jan 15, 2020 11:05 pm
Forum: Automation, sensing and robotics
Topic: Device to measure angle for input to RPI
Replies: 3
Views: 793

Re: Device to measure angle for input to RPI

Inclinometers et al: https://www.digikey.ca/products/en/sensors-transducers/motion-sensors-inclinometers/533?FV=-8%7C533&quantity=0&ColumnSort=1000011&page=1&k=tilt&pageSize=25 C$35 ++ over here. Also used in game controllers so maybe some much cheaper parts are available. You'll...
by Earlton2
Tue Jan 14, 2020 1:50 am
Forum: Beginners
Topic: UART Alarm system control suggestions
Replies: 7
Views: 921

Re: UART Alarm system control suggestions

10 cents: DETECTING SIGNAL LEVELS 1. The driver/receiver of RS232 is an inverter so the TTL level is the inverse of the RS232 levels. 2. A serial line is usually marking unless there is data or something sending break. 3. Marking on the TTL line is +ve, (Pi GPIO-14/15 = 3.3V), spacing on the TTL lin...
by Earlton2
Thu Jul 04, 2019 12:44 am
Forum: General discussion
Topic: A question about power
Replies: 7
Views: 748

Re: A question about power

Might be of interest but not supporting the amps required for a Pi-4: My supply for a CNC machine uses two 12V PC power supply boards in series and I use the first 12V to provide 5V through a 7805 regulator (1.5A). This tends to get a tad hot but is surviving. The stepper driver circuit was doing th...
by Earlton2
Tue Jun 04, 2019 10:08 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: Is it possible to communicate with my ultrasonic flow meter
Replies: 1
Views: 599

Re: Is it possible to communicate with my ultrasonic flow meter

I have used wiringpi to set-up drive the serial port. The actual wiring usually needs an inverting driver between the pi logicand the device rs232. Nominally the latter is +/- 12v but more often than not it uses 0 to 5v levels. You might check the device TD pin when marking (idle) to see if it is 0 ...
by Earlton2
Wed Apr 17, 2019 1:15 am
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: I2C RTC DS1337 1Hz clock on SQW/INTB RS1 RS2 EOSC
Replies: 1
Views: 812

Re: I2C RTC DS1337 1Hz clock on SQW/INTB RS1 RS2 EOSC

I am still using a DS1337 for my RTC but using rtc-ds1307 inside /boot/config.txt There are still additional registers available on the chip and specifically for me 0x0E with the RS1/2 bits at 0x18. To my surprise I now find I can set these with i2cset -f -y -m 0x18 1 0x68 0x0E 0x00. This outputs a ...
by Earlton2
Sun Mar 17, 2019 1:49 am
Forum: Other projects
Topic: Power for outoor enclosure
Replies: 4
Views: 1626

Re: Power for outoor enclosure

I'd use a 12V line if that will power both devices with 7805 regulator to generate 5V into the Pi on the GPIO lines. There are also pin compatible switchers with the same footprint but less heat. My set-up uses a 12V trickle charged battery to provide power for several devices scattered around the h...
by Earlton2
Fri Mar 01, 2019 4:04 pm
Forum: Automation, sensing and robotics
Topic: Cat Home DIY Q&A - Solenoid How To
Replies: 35
Views: 6808

Re: Cat Home DIY Q&A - Solenoid How To

its likely of no significance in this circuit but the led diode in the transistor base will slow down the base discharge and delay the turn off. i.e. placing the transistor in linear mode. if anything i would suggest adding a 4k7 to gnd at the base.

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