Go to advanced search

by JohnsUPS
Tue Jan 01, 2019 11:59 pm
Forum: Automation, sensing and robotics
Topic: DS18B20 randomly missing connection
Replies: 3
Views: 1096

Re: DS18B20 randomly missing connection

The mixed topology wiring is part of the problem here. Per Maxim and other testimonials that I have read, the 1-Wire protocol does not like a star topology. My suspicion is that it isn't very tolerant to reflections on the line, and with a star topology these reflections are going to happen at sligh...
by JohnsUPS
Tue Jan 01, 2019 11:27 pm
Forum: Automation, sensing and robotics
Topic: Relay Line out voltage causing voltage on line in
Replies: 31
Views: 3424

Re: Relay Line out voltage causing voltage on line in

What is happening is that you are getting coupling from the mains back to the input from within the relay, and this is largely the result of the high voltage AC connection. Bear in mind that the input impedance on your multimeter is very high, and that any coupling will show up because there is no l...
by JohnsUPS
Sat Dec 22, 2018 12:23 am
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: Backlight Control on Waveshare 5" Touchscreen
Replies: 23
Views: 17289

Re: Backlight Control on Waveshare 5" Touchscreen

I'll try to post my schematic.... My standard practice is to buffer a GPIO pin with a small value resistor, then to the base of a transistor. This is done to protect the GPIO pin. The transistor then does the heavy lifting for whatever I'm wanting to drive. https://i.pinimg.com/originals/6a/cf/2e/6a...
by JohnsUPS
Mon Dec 10, 2018 3:19 am
Forum: Automation, sensing and robotics
Topic: How to power and read multiple DS18B20 temperature sensors
Replies: 18
Views: 11714

Re: How to power and read multiple DS18B20 temperature sensors

Have you considered using a 1 wire driver chip? I am using the DS2482-100. It is connected to the PI via I2C. The chip is powered from 5v, and there are level shifters in the two I2C lines to the PI. The chip also protects the GPIO line/PI from transients from the outside world. The 5v supply to the...
by JohnsUPS
Mon Dec 10, 2018 2:24 am
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: Backlight Control on Waveshare 5" Touchscreen
Replies: 23
Views: 17289

Re: Backlight Control on Waveshare 5" Touchscreen

I bought an inexpensive 5" LCD panel for a recent project, and I needed a way to turn the backlight on and off. The display had an on/off switch on it, so instead of cutting traces, I added a couple of mosfets. I measured the backlight currrent, which was ~107ma. The mosfets I used were rated higher...
by JohnsUPS
Mon Oct 08, 2018 11:10 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: DS18B20 Max Distance
Replies: 44
Views: 57442

Re: DS18B20 Max Distance

Just an update to my earlier post about the data center temperature monitor. The monitor has been installed, and everything is working perfectly. I wanted to share some of the installation details, as this installation technique is now proven to work in an electrically noisy environment and should b...
by JohnsUPS
Sun Sep 09, 2018 12:32 am
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: DS18B20 Max Distance
Replies: 44
Views: 57442

Re: DS18B20 Max Distance

The setup is still working perfectly (and has been for weeks now), but a 1 wire bus master is not a "booster". It is just a proper driver. If someone has a distance requirement, using a driver is the logical place to start. The common method I see is by using a GPIO pin with a pullup, which may be O...
by JohnsUPS
Tue Aug 14, 2018 12:32 am
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: favorite replacement for 8-channel Bi-directional Logic Level Converter - TXB0108
Replies: 3
Views: 1712

Re: favorite replacement for 8-channel Bi-directional Logic Level Converter - TXB0108

In the past, I purchased several 4 bit bidirectional level shifters, all nice surface mount assemblies, but they were not very reliable. Instead, I have opted for a larger through-hole solution. It may be a bit more work if you need to shift many lines, but I have found the simple level shifter made...
by JohnsUPS
Sat Jul 07, 2018 2:28 am
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: DS18B20 Max Distance
Replies: 44
Views: 57442

Re: DS18B20 Max Distance

JohnsUPS That's are very good news, please check you PM inbox. BR, YV1HX, I wanted to post my test results because the search results I got when researching the distance were not too inspiring. I am the type that will test something like this for myself. Because I know that my previous post is sear...
by JohnsUPS
Fri Jul 06, 2018 3:15 am
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: DS18B20 Max Distance
Replies: 44
Views: 57442

Re: DS18B20 Max Distance

I am in the process of building a data center temp monitor for my work, and have settled on the DS18B20's for the sensors. However, I was concerned about the 1 wire protocol distance, until tonight when I was able to test this. I have five sensors at the end of 470 feet (143 meters) of Cat6 working ...

Go to advanced search