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by JohnsUPS
Fri Oct 16, 2020 1:05 am
Forum: Beginners
Topic: Fixed IP address problems
Replies: 8
Views: 268

Re: Fixed IP address problems

If you need to connect to the Internet, make sure that the DNS server address(es) are configured.

Also, without a default gateway configured, you may get unpredictable results/odd behavior. Whenever I configure a static IP address on anything, I always configure a default gateway.
by JohnsUPS
Tue Oct 13, 2020 12:28 am
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: 1-wire Temperature Inaccuracy
Replies: 12
Views: 2169

Re: 1-wire Temperature Inaccuracy

Bear in mind that there are a lot of fake DS18B20 sensors out there. I purchased some that were way out of calibration also, from overseas vendors. Spend a little more and order your sensors from a reputable chip house like Digi-Key, Mouser, or the like. Basically you're looking for a vendor that wi...
by JohnsUPS
Tue Oct 06, 2020 12:42 am
Forum: Beginners
Topic: What do you install on your RPi?
Replies: 8
Views: 260

Re: What do you install on your RPi?

Whenever I do something with a Pi, there is usually a goal in mind, so for me it would be "whatever is necessary". For the most part I don't remove anything from the stock OS (whichever flavor that may be).
by JohnsUPS
Sun Sep 13, 2020 2:37 am
Forum: Automation, sensing and robotics
Topic: My temp sensor ds18b20 doesn't seems accurate
Replies: 19
Views: 4818

Re: My temp sensor ds18b20 doesn't seems accurate

All these answers, and not one suggestion on how to calibrate the sensor? Who care which device he owns is the most correct? All he wants is to calibrate the readings and make them read the same number. DS18B20,1 - Reads 18c DS18B20,2 - Reads 21c DS18B20,3 - Reads 22 All in same vessel to calibrate...
by JohnsUPS
Thu Aug 27, 2020 12:37 am
Forum: Advanced users
Topic: ds18b20 network
Replies: 1
Views: 123

Re: ds18b20 network

You may want to take a look at this:

viewtopic.php?f=44&t=36163

viewtopic.php?f=37&t=231164
by JohnsUPS
Thu Aug 27, 2020 12:24 am
Forum: Beginners
Topic: Using an external psu
Replies: 18
Views: 733

Re: Using an external psu

Typically in this situation I would go with a 3V3 regulator (such as an LM1086-3.3) fed from your 5V rail. This will provide about 0.55 volt overhead above the regulator's internal 1.25V reference which should not cause much warming at all with your 30ma or so current draw. As a rule of thumb for f...
by JohnsUPS
Wed Aug 26, 2020 12:04 pm
Forum: Beginners
Topic: Using an external psu
Replies: 18
Views: 733

Re: Using an external psu

Typically in this situation I would go with a 3V3 regulator (such as an LM1086-3.3) fed from your 5V rail. This will provide about 0.55 volt overhead above the regulator's internal 1.25V reference which should not cause much warming at all with your 30ma or so current draw. As a rule of thumb for fi...
by JohnsUPS
Sat Aug 22, 2020 8:25 pm
Forum: Beginners
Topic: Networking Over Ethernet Issues
Replies: 3
Views: 132

Re: Networking Over Ethernet Issues

Make sure ICMP is enabled, especially if the PI is pulling an IP address and gateway...
by JohnsUPS
Wed Aug 19, 2020 11:38 pm
Forum: Other projects
Topic: Advice / feasibility of borehole inspection idea
Replies: 10
Views: 593

Re: Advice / feasibility of borehole inspection idea

You could potentially use an analog security camera (rebuilt into an enclosure that will fit into a 50mm hole) with an analog encoder at the top to digitize the signal. I have been part of a project recently that is upgrading video security systems to digital. To preserve the existing coverage/reuse...
by JohnsUPS
Wed Aug 19, 2020 11:04 pm
Forum: Automation, sensing and robotics
Topic: Joining multiple DS18B20 sensors
Replies: 21
Views: 3095

Re: Joining multiple DS18B20 sensors

VirenS, These are the two guides that I used for reference when planning out the network. I found the Springbok document helpful. With regards to your network, look at the bottom of page 30 where it talks about reflected signals and the placement of the sensors along the trunk (avoid placing them at...
by JohnsUPS
Mon Aug 17, 2020 12:12 pm
Forum: Automation, sensing and robotics
Topic: Joining multiple DS18B20 sensors
Replies: 21
Views: 3095

Re: Joining multiple DS18B20 sensors

I see this as doable, however my first concern would be to try to limit the length of the stubs that run off of the main trunk line, especially because there will be so many of them. In the data center, I wanted to provide a service loop for each sensor. Instead of running an extended stub off of th...
by JohnsUPS
Sun Aug 16, 2020 11:10 pm
Forum: Automation, sensing and robotics
Topic: Joining multiple DS18B20 sensors
Replies: 21
Views: 3095

Re: Joining multiple DS18B20 sensors

Thank you VirenS for the kind words.... I frequent these forums on a regular basis to keep up with whats new, and to also learn from those with much more experience. There is a wealth of information on this site. With that said, I would encourage you to post here where others can assist you as well....
by JohnsUPS
Sun Aug 16, 2020 10:37 pm
Forum: Beginners
Topic: Leds with relays
Replies: 43
Views: 1406

Re: Leds with relays

When there are only a couple of channels required, one could use the MPSA13/MPSA14 darlingtons.
by JohnsUPS
Wed Aug 05, 2020 12:27 pm
Forum: Automation, sensing and robotics
Topic: sensor recomendation for garge door state
Replies: 3
Views: 210

Re: sensor recomendation for garge door state

I have installed sensors/switches on my garage doors for the alarm system, and a yet-to-be installed door status indicator for the inside of the house. What I did was utilize magnetic door switches. I mounted the magnet portion on the door, and used two switches per door. One is mounted at the top a...
by JohnsUPS
Mon Aug 03, 2020 10:08 pm
Forum: Beginners
Topic: Pizza Oven - Digital temperature monitoring :)
Replies: 4
Views: 265

Re: Pizza Oven - Digital temperature monitoring :)

Fortunately the MAX31855 has a chip select. What could be done instead is to multiplex ten MAX31855's using something like a CD74HC42 4-to-10 line mux to select a chip, read/store the data, then move on to the next one. Because temperature is generally a slowly changing value, reading them only peri...
by JohnsUPS
Mon Jul 27, 2020 2:16 am
Forum: Automation, sensing and robotics
Topic: DIY Temperature Sensor
Replies: 6
Views: 525

Re: DIY Temperature Sensor

I have used the Dallas/Maxim DS18B20's a bit and have experience sourcing them from various vendors. The first two batches I purchased were from Banggood.com (trying to go cheap - bad move), but from two different vendors who sell on that site. These sensors varied quite a bit from each other. Well ...
by JohnsUPS
Sat Jun 06, 2020 2:38 am
Forum: Beginners
Topic: Case FAN : should it suck, or should it blow ?
Replies: 18
Views: 2024

Re: Case FAN : should it suck, or should it blow ?

Usually I see fans pulling the air out of a case, but not always. In the case of some of the larger Cisco Catalyst switches, the big fans on the front of the power supplies pull air in and exhaust it out the back. In the case of some of the smaller switches, the fans are in the back and air is pulle...
by JohnsUPS
Wed Jun 03, 2020 7:28 pm
Forum: Automation, sensing and robotics
Topic: Water Tank Monitoring System
Replies: 8
Views: 843

Re: Water Tank Monitoring System

The most simple (and probably reliable over time) would be a magnetic float/reed relay setup. Reed relays are sealed, so the contacts are protected. An elegant solution that I read about (don't recall the original author), consisted of a small watertight tube with reed relays within it and a magnet ...
by JohnsUPS
Wed Jun 03, 2020 7:14 pm
Forum: Beginners
Topic: Monitor GPIO inputs
Replies: 22
Views: 1321

Re: Monitor GPIO inputs

From the OP's description, it was said that the two inputs would never be high at the same time, but with two separate monostable circuits, this is a non-issue. I would tackle this with a CD4538 dual monostable. Fewer parts than a 555 for just a 10 second delay circuit. Also, depending on just what ...
by JohnsUPS
Wed May 06, 2020 8:21 pm
Forum: Other projects
Topic: Struggling to understand voltage drop
Replies: 8
Views: 634

Re: Struggling to understand voltage drop

The circuit appears like it should work, but what I am suspecting is that the coil of your relay is loading down your power source (the source isn't able to supply the necessary current), and as a result, the voltage is dropping. How big is this relay (what is the coil voltage/coil current rating?) ...
by JohnsUPS
Wed May 06, 2020 8:09 pm
Forum: Beginners
Topic: Need help measuring the speed of a small ball
Replies: 10
Views: 905

Re: Need help measuring the speed of a small ball

Ahhhh....reminds me of times past - played my share of foos back in the day..... If I get what you are describing correctly, you basically just want to measure the speed of the ball during a penalty kick or such as the ball enters the goal. Because the ball won't loose any significant amount of spee...
by JohnsUPS
Mon Apr 20, 2020 2:54 pm
Forum: Beginners
Topic: Lathe tachometer
Replies: 4
Views: 328

Re: Lathe tachometer

I did something similar to that. The object of the project was to flash a strobe light at a given time in the rotation to "freeze" the motion of the stock. This was designed for a wood lathe, however it would work on a metal lathe too. There was an adjustable timer delay between the sensor and the s...
by JohnsUPS
Mon Apr 13, 2020 8:58 pm
Forum: HATs and other add-ons
Topic: prototyping board w/o strips ?
Replies: 5
Views: 483

Re: prototyping board w/o strips ?

For making one off projects and prototyping, using the 0.1" on center, 0.040" dia plated through hole boards with point-to-point wiring, does the trick for me. The wire is usually 26 ga Kynar insulated wire wrapping wire that is stripped, formed and soldered as necessary to make connections. I never...

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