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by JohnsUPS
Thu Dec 05, 2019 4:10 pm
Forum: Java
Topic: How can you run a Java Applet in Raspbian Buster?
Replies: 4
Views: 100

Re: How can you run a Java Applet in Raspbian Buster?

Unfortunately I am in this same predicament. There are status web pages hosted by small servers installed to monitor the HVAC in buildings where I work. These devices are old, and are using NPAPI still. I can pull them up in my Chrome browser (via a JNLP file/Java Webstart), but have had no success ...
by JohnsUPS
Tue Dec 03, 2019 12:52 am
Forum: Automation, sensing and robotics
Topic: Detecting an appliance is in use
Replies: 30
Views: 649

Re: Detecting an appliance is in use

I made a monitor for my sump pump that simply counts the number of times that the pump has energized. All that was necessary was to connect a small step-down transformer across the motor leads. This pump has two cords coming from it - one for the pump and one for the switch, so the motor connections...
by JohnsUPS
Tue Nov 19, 2019 10:50 pm
Forum: Automation, sensing and robotics
Topic: Smart Coffee Machine Pump Controlled by Raspberry Pi & HC-SR04 Ultrasonic Sensor
Replies: 3
Views: 167

Re: Smart Coffee Machine Pump Controlled by Raspberry Pi & HC-SR04 Ultrasonic Sensor

Great project!

You could get a reverse osmosis filter setup and remove the bottle altogether. No pump needed either.....
by JohnsUPS
Mon Nov 18, 2019 11:56 pm
Forum: Automation, sensing and robotics
Topic: How to turn on Multiple TVs using a raspberry Pi?
Replies: 4
Views: 225

Re: How to turn on Multiple TVs using a raspberry Pi?

If the TVs are on a network, they may respond to a wake on LAN broadcast..... Otherwise, (as was previously mentioned) it would be perfectly feasible to configure a Pi with an IR LED connected to a GPIO pin and modulated with the "turn on" remote control code bit banged by a snippet of code. For tha...
by JohnsUPS
Thu Nov 14, 2019 1:22 am
Forum: Advanced users
Topic: Is it possible for RaspberryPi 3 B+ to power a 6V device
Replies: 14
Views: 513

Re: Is it possible for RaspberryPi 3 B+ to power a 6V device

I have contemplated doing this myself, but my solution was to connect an optoisolator across the switch of the remote. This way, all that needs to be done is to drive the LED of the optoisolator from a GPIO pin. Any general purpose opto should work, so long as the current requirements of the LED are...
by JohnsUPS
Wed Nov 06, 2019 2:54 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: DS18b20 and Relay
Replies: 4
Views: 736

Re: DS18b20 and Relay

What transistor are you using? Not all transistors have the center pin as the base.....
by JohnsUPS
Sun Nov 03, 2019 8:58 pm
Forum: Other projects
Topic: Messure AC current
Replies: 5
Views: 611

Re: Messure AC current

When working with mains voltages, please observe all the applicable precautions first....... To measure anything off the mains, you should really use a transformer for isolation. For measuring current, you could go with something like this: https://www.amazon.com/HiLetgo-Current-Ammeter-TA12-100-Ard...
by JohnsUPS
Sun Nov 03, 2019 12:21 am
Forum: Automation, sensing and robotics
Topic: Flow meter question
Replies: 4
Views: 646

Re: Flow meter question

I looked at the data sheet for the flow meter, and there is a 10k pullup on the open collector output to the V+ pin. Because the data sheet lists the working voltage as 5 - 24 VDC, the data line will be pulled up very close to 5V (if the meter is powered from 5V). The GPIO pins cannot tolerate more ...
by JohnsUPS
Fri Oct 25, 2019 1:37 pm
Forum: Advanced users
Topic: Multiple DS18B20 temperature sensors
Replies: 37
Views: 20242

Re: Multiple DS18B20 temperature sensors

I assume this has to do with the fact that the temperature sensors are on a long wire. I have them now on a 5 wire direct bury cable. Red carries the positive, black negative and yellow, white and orange carry a signal back. Each signal has its own resistor and gpio. The cable is about 50 ft long a...
by JohnsUPS
Fri Oct 25, 2019 1:01 pm
Forum: Advanced users
Topic: Multiple DS18B20 temperature sensors
Replies: 37
Views: 20242

Re: Multiple DS18B20 temperature sensors

I do not understand your last comment from your setup..."the data line comes back to a driver chip". I understand the single wire setup but what is your driver chip? Do you mean the internal PI I2C? In the temperature measurement setup that I have deployed, the data line does not come back to a GPI...
by JohnsUPS
Thu Oct 24, 2019 1:24 am
Forum: Advanced users
Topic: Multiple DS18B20 temperature sensors
Replies: 37
Views: 20242

Re: Multiple DS18B20 temperature sensors

I assume this has to do with the fact that the temperature sensors are on a long wire. I have them now on a 5 wire direct bury cable. Red carries the positive, black negative and yellow, white and orange carry a signal back. Each signal has its own resistor and gpio. The cable is about 50 ft long a...
by JohnsUPS
Mon Oct 21, 2019 11:59 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: One wire DS18b20 sensors disconnected when reading too fast
Replies: 8
Views: 1279

Re: One wire DS18b20 sensors disconnected when reading too fast

Thank you both for your valuable tips. I made some further debbuging. With one sensor at a time running for at least 30mins reading the temperature every 5 seconds. One of my four sensors dies after circa 10 minutes. I haven'm made another test run to confirm or another run with those remaining 3 t...
by JohnsUPS
Mon Oct 21, 2019 11:47 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: One wire DS18b20 sensors disconnected when reading too fast
Replies: 8
Views: 1279

Re: One wire DS18b20 sensors disconnected when reading too fast

It sounds like you are using a water proof ds18b20 sensor, there are many low quality/factory seconds being sold on line on various line on sales sites, these often fail after some use or randomly , I have experienced this myself. You could try testing your setup using just the ds18b20 chip obtaine...
by JohnsUPS
Thu Oct 17, 2019 3:12 am
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: DS18B20 Max Distance
Replies: 44
Views: 49585

Re: DS18B20 Max Distance

@JohnsUPS Hello, first of all let me thank you for your careful post. I'm sure it has provided countless people (like myself) with inspiration on how to extend the scale of their 1-wire designs... I have a couple of questions: First, I was quite surprised to see how you are using the CAT6 wire, bun...
by JohnsUPS
Thu Oct 17, 2019 1:45 am
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: One wire DS18b20 sensors disconnected when reading too fast
Replies: 8
Views: 1279

Re: One wire DS18b20 sensors disconnected when reading too fast

If your sensors are located in such a manner that running one cable and daisy chaining them together isn't practical, you can run each sensor back to a separate GPIO pin. However, each pin must have its own pullup resistor to 3.3v. This will eliminate the star topology that was created when the data...
by JohnsUPS
Sat Oct 12, 2019 1:26 am
Forum: Beginners
Topic: Trouble reading DS18B20 one wire through 16 relay board on RPi
Replies: 20
Views: 796

Re: Trouble reading DS18B20 one wire through 16 relay board on RPi

Thanks for the post, I have six pieces of ULN2803A chips, will that work? Or I have to get the Dallas DS2482-800 ? For either, would you mind to show me how do I connect it with the one wire sensor and the pi? The ULN2803A driver and the DS2482-800 driver are chips with completely different target ...
by JohnsUPS
Thu Oct 10, 2019 10:37 pm
Forum: Beginners
Topic: Trouble reading DS18B20 one wire through 16 relay board on RPi
Replies: 20
Views: 796

Re: Trouble reading DS18B20 one wire through 16 relay board on RPi

You probably shouldn't attempt to switch the sensors on and off. They will be perfectly happy running all the time. Besides, if the sensor is off, you will miss any temperature swings that may have happened. The relay board isn't needed. If you want to run 32 sensors, no problem. The way I would tac...
by JohnsUPS
Mon Sep 09, 2019 2:00 am
Forum: Troubleshooting
Topic: Help with 4-20mA and Raspberry Pi 3B+
Replies: 6
Views: 359

Re: Help with 4-20mA and Raspberry Pi 3B+

If you still want to use the current to voltage converter board, then you don't need a resistor in series with the output of the sensor as the board provides this series resistor for you. The board is expecting to be connected to a current source directly. It appears as though you're making sure tha...
by JohnsUPS
Sat Sep 07, 2019 5:04 am
Forum: Troubleshooting
Topic: Help with 4-20mA and Raspberry Pi 3B+
Replies: 6
Views: 359

Re: Help with 4-20mA and Raspberry Pi 3B+

You didn't provide any details about the pressure transmitter. I am referencing this two wire pressure sensor wiring diagram, using the "4-20ma Output Wiring Diagram with Integral Cable", which appears to be wired similarly to what you have shown: https://cdn.automationdirect.com/static/specs/prosen...
by JohnsUPS
Tue Sep 03, 2019 3:18 am
Forum: Automation, sensing and robotics
Topic: Car clutch sensor
Replies: 3
Views: 306

Re: Car clutch sensor

Other than tapping off an existing switch (such as the one tied to the cruise control), you could add your own switch to the clutch pedal. Where the switch resides would depend on how the clutch is set up. The switch could either reside under the dash by the pedal, or if there is a lever somewhere (...
by JohnsUPS
Fri Aug 30, 2019 12:26 am
Forum: Other projects
Topic: Pushbutton multiple inputs
Replies: 12
Views: 671

Re: Pushbutton multiple inputs

So basically you are saying if the button was wired to 3.3V and GPIO from the beginning with PD resistor enabled via SW, I should not see random inputs triggered on that pin? Not exactly. With the way you stated that this push button is wired, with one side going to +5V, then pushing the button wil...
by JohnsUPS
Thu Aug 29, 2019 11:35 pm
Forum: General discussion
Topic: pics - how are you using your Pi?
Replies: 18
Views: 1335

Re: pics - how are you using your Pi?

Recent project....Temperature and rooftop data center chiller monitor.

Image
by JohnsUPS
Tue Aug 27, 2019 10:13 pm
Forum: Automation, sensing and robotics
Topic: Motor Sensing Circuit help
Replies: 5
Views: 615

Re: Motor Sensing Circuit help

Does the motor operate at full on and full off or does it operate at variable speeds? Knowing the answers to those questions will help to identify how sensitive the sensing circuit needs to be. Because the output of the CT transformer is 0-1V @ 0-15A, you could feed it to a comparator circuit, but n...
by JohnsUPS
Fri Aug 09, 2019 1:30 am
Forum: Other projects
Topic: How to read 4-20mA signal input
Replies: 20
Views: 27673

Re: How to read 4-20mA signal input

What can also be used to keep the current loop isolated while still being able to precisely read the voltage across the scaling resistor used in the loop is a switched capacitor building block, like the LT6943: https://www.analog.com/media/en/technical-documentation/data-sheets/6943f.pdf The output ...
by JohnsUPS
Tue Aug 06, 2019 10:18 pm
Forum: Automation, sensing and robotics
Topic: Phone hang-up sensor
Replies: 9
Views: 488

Re: Phone hang-up sensor

I wasn't able to see the pic, but what could also be used is a reed relay within the phone, actuated by a magnet attached to the receiver.

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