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by Earlton2
Tue Jan 28, 2020 10:28 pm
Forum: Weather station
Topic: Rainfall Sampling
Replies: 5
Views: 218

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: 283

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 - file descript...
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: 258

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 have to go hunt for...
by Earlton2
Tue Jan 14, 2020 1:50 am
Forum: Beginners
Topic: UART Alarm system control suggestions
Replies: 7
Views: 489

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: 429

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: 354

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: 441

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: 1001

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: 3746

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.
by Earlton2
Thu Feb 28, 2019 6:38 pm
Forum: Automation, sensing and robotics
Topic: Water Depth Sensing
Replies: 10
Views: 3144

Re: Water Depth Sensing

on sonar units we used a pressure sensor. these were analog current loop so we had to use a converter inside the unit. a loop allows you to have a long cable but the sensor has to be fixed on the bottom not just hung over the side. arduino is the usual suggestion here but i would tend to wire up an ...
by Earlton2
Thu Feb 14, 2019 1:31 am
Forum: General discussion
Topic: Is Raspberry Pi capable of replacing 2 wire thermostat
Replies: 8
Views: 974

Re: Is Raspberry Pi capable of replacing 2 wire thermostat

then again you could use a standard thermostat in the control circuit and use a relay closure or ac switching device across it. the thermostat could be set at a safe default minimum e.g. 10c while the new circuit runs the weekly sequence. the pi needs to get time from either the web or an rtc.
by Earlton2
Thu Feb 14, 2019 1:10 am
Forum: General discussion
Topic: Powering RPi inside of PC case
Replies: 17
Views: 3873

Re: Powering RPi inside of PC case

i would mount the pi on a piece of wood that slides into an empty harddrive slot. the nuts on db25 and de9 connectors make a good standoff with 4-40 bolts. re power i tend to run 5v and ground into the gpio connector using a 10-pin header at pos-1 . for simple projects this gets me i2c and tx/rx whi...
by Earlton2
Mon Feb 11, 2019 9:38 pm
Forum: Advanced users
Topic: EMULATION HELP REQUEST
Replies: 13
Views: 1369

Re: EMULATION HELP REQUEST

I don't understand a word of it but having started with a PDP-8 in the 1960's with a DMA college project, I'm enjoying the ride. The other computer was a LEO with a door on the back so you could get inside and change the valves!
by Earlton2
Wed Jan 30, 2019 10:07 pm
Forum: Wanted
Topic: RPi, 26 pin GPIO and Mounting Holes
Replies: 9
Views: 2979

Re: RPi, 26 pin GPIO and Mounting Holes

Would it help to simply purchase a Pi-Zero sans pins and solder in the 26 you need? Or purchase a 40-pin Pi and chop off the unwanted pins. The Pi's don't care. I often just solder in a 10-pin header on a Pi-zero. The top position (pin-1) gets you power, I2C and serial data which is sufficient for s...
by Earlton2
Tue Jan 29, 2019 3:04 am
Forum: General discussion
Topic: What is the temperature range of model A?
Replies: 16
Views: 4841

Re: What is the temperature range of model A?

No idea but I presently have a Zero-W running in an unheated building where outside temperatures of late have reached -41C. The processor shows 2C while the plastic case it sits inside is down to -16C. Other than the CPU, all probes are TMP107s with the outside units attached to a bat house. Data ca...
by Earlton2
Mon Jan 21, 2019 2:10 am
Forum: Beginners
Topic: Detect electrical current of external device
Replies: 13
Views: 1247

Re: Detect electrical current of external device

The attached schematic shows two opto-couplers, two 2.2K resistors and two 1N914 diodes wired to the bell circuit and interfaced with a Pi. There are separate inputs for FRONT and REAR which need limiting to around 10mA for the opto device. The diodes are to protect the opto devices from reverse vol...
by Earlton2
Mon Dec 10, 2018 4:58 pm
Forum: Beginners
Topic: how to increase the raspberry pi 3 wifi range
Replies: 9
Views: 12522

Re: how to increase the raspberry pi 3 wifi range

My simple reflector antenna is cut from cardboard with aluminum foil strip stuck to the inside. It is 400 mm across and 50 mm high with no attempt to make the short vertical parabolic. The equation I used was y = x*x/4f with x from 0 to +/-200 mm and focus f at 100 mm. The f value was chosen so the ...
by Earlton2
Fri Nov 30, 2018 2:20 am
Forum: Assistive technology and accessibility
Topic: Dementia clock/picture frame and audio suggestion for my mum, best practice?
Replies: 7
Views: 7234

Re: Dementia clock/picture frame and audio suggestion for my mum, best practice?

Could you split the code into separate tasks which could be called by system control timers. i.e an 8 a.m. call to whatever needs doing then. I have several systemctl 'functions' one of which starts a program and another which periodically sends a signal to trigger a data sample. I'm afraid it would...
by Earlton2
Fri Nov 30, 2018 2:04 am
Forum: General discussion
Topic: High Wattage Remote Relay
Replies: 12
Views: 1073

Re: High Wattage Remote Relay

I've pulled many a relay from old microwave ovens and furnaces. Much of these have the power lines on top as spade lugs while the low voltage coil lines were soldered to the board on the bottom. Early on the coils were 12V but of late they are more likely 24VDC. In either case I have used a 2N2222 t...
by Earlton2
Wed Oct 24, 2018 9:03 pm
Forum: Off topic discussion
Topic: Tea Time
Replies: 6
Views: 4487

Re: Tea Time

The cottage pi is now recording negative temperatures while the one in Beckwith his heading that way. Both have probes inside and outside a bat house and neither shows any significant delta. We returned from the North to find the modem dead, along with the HiFi, three light timers and my CNC linux c...
by Earlton2
Thu Aug 02, 2018 1:45 am
Forum: Off topic discussion
Topic: What was your 1st game?
Replies: 49
Views: 19110

Re: What was your 1st game?

My thanks to Burngate for the Adventure references.
by Earlton2
Tue Jul 24, 2018 1:42 am
Forum: Off topic discussion
Topic: What was your 1st game?
Replies: 49
Views: 19110

Re: What was your 1st game?

So we had a 110 baud 20 mA Teletype and you were led to a cave... << You see a stick >> >> Pick up stick << You see a bird cage >> >> Pick up cage << You see a canary >> So obviously the bird was supposed to go in the cage but it wouldn't, not until you typed ... << Drop stick >> << The bird is in t...
by Earlton2
Thu Jul 19, 2018 2:08 am
Forum: Python
Topic: Charts from logged data
Replies: 6
Views: 800

Re: Charts from logged data

I presently use gnuplot on my debian system to generate a png graph from temperature data captured on a RaspberryPi. I'd hope it would also work on the Pi but can't verify that at the moment. The graph shows four temperatures over two weeks and repeats two of them over two days. i.e. time scales top...
by Earlton2
Tue Jul 10, 2018 4:18 am
Forum: Automation, sensing and robotics
Topic: Multiple Ultrasonic Sensors Over Long Distances
Replies: 3
Views: 1056

Re: Multiple Ultrasonic Sensors Over Long Distances

1) power the sensors effectively? While I've used the same sonar sensor I have not done it at any distance, I have however run digital temperature sensors over 50ft of telephone wire with no problems. For that I wired +5v, data and two ground wires. One experiment you could test is to wire one of th...
by Earlton2
Mon Mar 26, 2018 12:04 am
Forum: Off topic discussion
Topic: Tea Time
Replies: 6
Views: 4487

Re: Tea Time

The WiFi has now settled down after the last update and my farm Pi-Zero-W installation is busily capturing temperature logs every hour and e-mailing me the days findings at midnight. This is last nights effort: 2018-03-24 19:01, 12.1, -2.4, 0.0, 0.0, 2018-03-24 20:01, 11.0, -3.6, 0.0, 0.0, 2018-03-2...

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