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by JohnsUPS
Fri Nov 26, 2021 9:46 pm
Forum: Automation, sensing and robotics
Topic: 12v heater for miniature green house?
Replies: 11
Views: 549

Re: 12v heater for miniature green house?

An alternate idea..... I used to work on a device that needed a heater, and so there were two 330 ohm (in series) chassis mounted resistors attached to a metal plate (to evenly spread the heat) with thermal compound. The connecting wires were teflon insulated for heat resistance. A relay or SSR turn...
by JohnsUPS
Fri Nov 19, 2021 1:16 am
Forum: Other projects
Topic: Building temperature sensor network for greenhouse
Replies: 13
Views: 692

Re: Building temperature sensor network for greenhouse

You might be able to arrange a more reliable setup by leveraging the 8 channel driver DS2482-800. This will give you a way to break up some of the stubs/branches. You can run multiple temp sensors off of each channel. Any remaining channels on the IC could be reserved for future expansion. If done t...
by JohnsUPS
Tue Nov 16, 2021 12:25 pm
Forum: Other projects
Topic: Building temperature sensor network for greenhouse
Replies: 13
Views: 692

Re: Building temperature sensor network for greenhouse

Yup. Just string a few DS18B20 sensors around (literally). They are tiny, and easy to protect from moisture and humidity. Although it's called a 1-wire bus you need three wires. I use 4-core flat telephone cable and RJ11 or RJ12 6P4C connectors (6 pin 4 conductor). I use ESPeasy with Wemos D1 Mini ...
by JohnsUPS
Tue Nov 16, 2021 12:31 am
Forum: Beginners
Topic: Raspberry Pi 4 wifi will only connect to 5g
Replies: 13
Views: 411

Re: Raspberry Pi 4 wifi will only connect to 5g

There could be a couple of reasons for this. One that was already mentioned was interference on the 2.4 band. The other could be from what is called band-steering. On the wireless network that I work on (~5000 access points or so), we have band steering turned on to force 5Ghz capable devices to use...
by JohnsUPS
Fri Nov 05, 2021 12:50 pm
Forum: Off topic discussion
Topic: Just out of curiosity...
Replies: 11
Views: 582

Re: Just out of curiosity...

Hopefully alowing just the one post won't invite others to do the same in order to get their message out there. I would be in favor of seeing the glossy pic deleted and replaced with the sellers info in text form, and having it moved to the For Sale section as was mentioned. Doing so may act as some...
by JohnsUPS
Mon Nov 01, 2021 10:00 pm
Forum: Automation, sensing and robotics
Topic: Voltage sensor using ADC0832
Replies: 18
Views: 1234

Re: Voltage sensor using ADC0832

Indeed....you would need a load regardless. The INA260 seems like it would be a lot less hardware to deal with. Being I2C, it would do all of the math for you and interfacing that is very easy. The ADC is 16 bit, but it looks like the conversion time isn't as fast though, but that should be expected.
by JohnsUPS
Thu Oct 28, 2021 2:13 pm
Forum: Other projects
Topic: Raspi 0 W reboots/crahses when switching Relay.
Replies: 2
Views: 302

Re: Raspi 0 W reboots/crahses when switching Relay.

Because you are powering the relay coil from the same power supply as what is powering the Pi, what is probably happening is that the power supply voltage is drooping below the operating threshold of the Pi when the relay switches. Try powering the relay coil from a different supply and/or adding a ...
by JohnsUPS
Fri Oct 22, 2021 12:13 pm
Forum: Automation, sensing and robotics
Topic: Voltage sensor using ADC0832
Replies: 18
Views: 1234

Re: Voltage sensor using ADC0832

It seems like an INA260 would make this monitoring task much simpler.......?
by JohnsUPS
Sun Oct 17, 2021 1:26 am
Forum: HATs and other add-ons
Topic: Linear power supply HAT?
Replies: 2
Views: 361

Re: Linear power supply HAT?

I also work with a lot of UPS units, and there are times when it would be nice to characterize so-called "bad" batteries based upon capacity. Usually there is only one or maybe two truly bad ones when they are replaced, and these marginal/used batteries can be used in non-critical UPS unit...
by JohnsUPS
Mon Oct 11, 2021 1:12 am
Forum: Off topic discussion
Topic: To Director of Communications, Raspberry Pi
Replies: 14
Views: 1474

Re: To Director of Communications, Raspberry Pi

The nice thing about this forum is that the majority of posters are (or were at one time) professionals in their area of specialty, and for the most part, that professionalism, civility and understanding flows over to how posts are responded to. I have found the mods to be fair and firm when necessa...
by JohnsUPS
Thu Sep 30, 2021 9:27 pm
Forum: Off topic discussion
Topic: cable chaos
Replies: 21
Views: 2149

Re: cable chaos

My upstairs "code bench" has a scattering of Pi's and related stuff also (hardware design is done in the basement). :-) Let's see - as I look around....stuff just waiting for a project or spares in case I get neanderthal-ish with the voltmeter probes....... 3 ea 3B+ & cases 3 picos 2 z...
by JohnsUPS
Thu Sep 30, 2021 2:20 pm
Forum: Off topic discussion
Topic: cable chaos
Replies: 21
Views: 2149

Re: cable chaos

Around the holidays where I used to work, people were sending a little executable around (back when it wasn't such a problem) that would open the CD tray. We all had tower PCs then, so this worked. The accompanying note would say something like "Look! I got you a coffee cup holder for Christmas...
by JohnsUPS
Tue Sep 28, 2021 1:36 pm
Forum: Off topic discussion
Topic: cable chaos
Replies: 21
Views: 2149

Re: cable chaos

Oh, there is a special reserved spot for the coffee :D
by JohnsUPS
Mon Sep 27, 2021 12:43 pm
Forum: Off topic discussion
Topic: cable chaos
Replies: 21
Views: 2149

Re: cable chaos

I feel so much better now.....not alone in the workbench overflowage syndrome...... My workbench isn't too far removed from the on pictured for Jim Williams - stuff everywhere. I occasionally clear a spot to make room for a new project, but as one might guess, that spot gets filled up and the cycle ...
by JohnsUPS
Mon Sep 27, 2021 1:24 am
Forum: Automation, sensing and robotics
Topic: Hardware suggestions for battery monitoring
Replies: 26
Views: 1660

Re: Hardware suggestions for battery monitoring

When reading this, I was wondering about the possible application for a LTC1043 switched capacitor building block. It isn't cheap, but it would be ideal for sampling a voltage from points without a common ground. However, the maximum supply voltage is 18v........
by JohnsUPS
Mon Sep 27, 2021 1:01 am
Forum: Troubleshooting
Topic: Troubleshooting DS18B20 sensor on Raspberry 3 A+ with Buster Lite
Replies: 26
Views: 901

Re: Troubleshooting DS18B20 sensor on Raspberry 3 A+ with Buster Lite

Unless its just the picture, the resistor appears to be 470 ohms, not 4700.
by JohnsUPS
Wed Sep 15, 2021 12:50 am
Forum: General discussion
Topic: Need an alternative for 2 x DS18B20 parallel wired to Rpi
Replies: 9
Views: 542

Re: Need an alternative for 2 x DS18B20 parallel wired to Rpi

Thanks for the update. Good to hear that your problem was solved, especially considering that your installation didn't leave much room for wiring changes....
by JohnsUPS
Wed Sep 08, 2021 6:01 pm
Forum: Networking and servers
Topic: Enable static IP address allocation for clients with wireless access point
Replies: 12
Views: 983

Re: Enable static IP address allocation for clients with wireless access point

In this situation you should constrain the range of addresses to be handed out to something less than the full class-C subnet, and then assign your static addressing to be outside of this range, but still within the same subnet. Alternatively, you could assign reservations instead of setting statics...
by JohnsUPS
Sun Sep 05, 2021 9:35 pm
Forum: Beginners
Topic: Why cant i connect to web sites in Chromium?
Replies: 19
Views: 890

Re: Why cant i connect to web sites in Chromium?

How is your Pi obtaining its IP address? If DHCP, then usually the policies will provide all of the necessary configuration items.
If static, be sure that you have configured valid DNS servers.
by JohnsUPS
Tue Aug 10, 2021 1:32 am
Forum: General discussion
Topic: Need an alternative for 2 x DS18B20 parallel wired to Rpi
Replies: 9
Views: 542

Re: Need an alternative for 2 x DS18B20 parallel wired to Rpi

Signal reflections are probably the biggest problem with the typical "GPIO with pullup" deployment of the 1 wire protocol, especially as the wires get longer or the sensors are wired in such a way as to cause competing reflections back. In this situation, especially because rewiring the se...
by JohnsUPS
Tue Aug 03, 2021 1:15 pm
Forum: Beginners
Topic: Weird power issues
Replies: 20
Views: 1054

Re: Weird power issues

On one Pi (3B+ I think) that I was running a SSD on as well as a keyboard, mouse and some other electronics on the GPIOs, I got the little lighting bolt voltage warning. I was using a generic 5V 4A switcher for a power supply. The switcher used the common TL431 reference to set the output voltage, a...
by JohnsUPS
Fri Jul 23, 2021 11:08 am
Forum: Troubleshooting
Topic: pi 4 cannot ping gateway but can connect to internet
Replies: 5
Views: 346

Re: pi 4 cannot ping gateway but can connect to internet

Your school may have ICMP blocked. This is the protocol that ping uses. Sometimes ICMP is turned off as a security measure.
by JohnsUPS
Tue Jul 20, 2021 11:22 am
Forum: Other projects
Topic: How could I loop this python code??
Replies: 4
Views: 398

Re: How could I loop this python code??

Alternatively, a CRON job could be set up to execute the code every 5 minutes.

Please use code tags. It will preserve the indentations (especially for Python) also as pcmanbob pointed out.
by JohnsUPS
Tue Jul 20, 2021 11:01 am
Forum: Troubleshooting
Topic: Could a Pi create high bandwidth usage? [SOLVED]
Replies: 9
Views: 462

Re: Could a Pi create high bandwidth usage?

Are you sure that your LAN is seeing only one DHCP server? What you describe could be a multiple DHCP server (when the servers don't know about each other) problem. When a device is needing an IP address, it will send out a broadcast, and a DHCP server will respond to this broadcast. If there is mor...
by JohnsUPS
Sun Jul 18, 2021 8:16 pm
Forum: Automation, sensing and robotics
Topic: Need Help: Simple Home Power Status Detector
Replies: 13
Views: 1013

Re: Need Help: Simple Home Power Status Detector

A simple way of detecting the presence (or not) of mains voltages is to use a USB power supply with a voltage divider to drop it down from ~5 VDC to just under 3.3VDC. Most people I know have several laying around. They're fairly reliable, but usually noisy, so a small cap and series limiting resist...

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