That hard to describe vibration feeling when you rub your hand over something electrical

[rkhanso]

I'd put this in the big CraftbrePi thread here, but I don't think this is a CraftbeerPi problem.

You know the feeling you sometimes get on your hand when you move it along a piece of metal of an electrical device plugged into the wall outlet? I'd describe it as maybe the electrical "feeling" of a 60Hz hum. I'm sure we've all felt it at some time or another. I can feel it when the vacuum is plugged into a specific outlet in my house. I've always assumed it might be from a poor or incorrect ground, bad component in whatever device I'm touching, or just not known what caused it.

I recently made a homemade PCB to plug a Raspberry Pi Zero W into, which interfaces with plugs that I connect three 1-wire temp sensors, a 2-channel Arduino-type relay module, and a flow meter that I'm using with CraftbeerPi3 to control a Kegerator. I'm having some what I think are freeze-ups on the Raspberry Pi, where something will stop the temp sensors from updating the Web GUI. Sometimes the sensors are not seen by CraftbeerPi on the Hardware Settings page, but not always. The Raspberry Pi appears to be still be somewhat responsive, but that could be just because of web pages being cached in the browser. But when the temperatures stop changing in the web GUI, I can still navigate the web pages and make changes to the beer name, etc. If I power off/on the Raspberry Pi, it'll work again for a varying amount of time.

I'm powering the Raspberry Pi from a 12V, 2A Wall Adapter connected to a 12v to 5V DC/DC convertor. I'm using the 12V to run a couple fans in the Kegerator. One 12v circulation fan is always on. The other 12v fan is controlled by CraftbeerPi for cooling the Tower.

When I touch the back of the PCB, I get that vibration feeling. I'm wondering if that's dangerous, if I can stop it from happening and if it might be the cause of CraftbeerPi to stop updating the temperatures.

I originally used to use the same components (minus the homemade PCB and the flow meter) connected loosely with Dupont wires, but thought something more secure would be better. There obviously wasn't the PCB to feel the vibrations, but the Controller seemed to run pretty well before.

To throw another wrench in, I made an attempt to convert over to Keg Cop but had weird issues and I suspect might be related to this current problem.

The obvious answer would be to look what has changed (The homemade PCB and addition of a flow meter). Any suggestions on if this vibrating feeling I get is the cause or something to just ignore? I might be able to try a different power supply if I can just use one from a laptop (but that runs at 19v, so I wouldn't be able to connect the fans in the Kegerator).

 

[rkhanso]

The vibration feeling may be coming from the Kegerator, not the PCB.
When I touch the sides of the Kegerator itself, I can feel it there also. Not on the front door (I suppose it might be more insulated because of the door seal?) or the back.

If the temps stop updating when they are higher than the set/control temperature, the solenoids will just stay on and running the compressor or fan.

One thing I found that is probably not related to the vibration feeling, but could be about the temperatures stop updating in the GUI -- I do have the DS18B20s power wire connected to 3.3v instead of 5v. I know the CraftbeerPi3 website says to connect the power to 3v3. But somewhere in the big CraftbeerPi3 thread on Homebrewtalk, someone mentions they are more stable when connecting the power to 5V, but keeping the data on 3v3 with the 4.7k ohm resistor.
Or maybe they stop updating the GUI because of the physical hum I feel?

When all else fails, a removal of DC power to the DC/DC converter gets everything working again. Until the next time the temps don't change.

When the temps don't change in the GUI, when looking at the Developer Mode of the browser, I can see the updates coming through to the browser, but the temps just don't change. Isn't this telling me it's trouble on the 1-wire system of the Pi?

 

[rkhanso]

It could be that the electrical vibration feeling is not at all related to the unresponsive temperatures. I removed all temp probes and installed them one-at-a-time and let the controller run for a long time in-between. I bet there's just a bad temp sensor. I've had some not work brand-new out of the bag.

The first two worked fine together for a long time. I connected a completely different temp sensor in the last spot/connector on the PCB and after a while, the temp readings froze up again - no changes. And the new temp sensor unique address can't be seen in CraftbeerPi. In fact, all the sensors unique IDs are not seen again.

Doesn't this seem to be a problem with the 1-wire bus, connectors, sensors then? If I do a simple reboot from CraftbeerPi, the temp sensors still won't work. It is only able to work again when I cut and restore power to the Pi/controller.

 

[balrog]

First thing I think I would do is measure with a good voltmeter between what you are touching that gives you that "feeling" and a known, good and righteous, absolute, ground.

 

[rkhanso]

I will try that.
I'm wondering if my power supply may be too weak. When I connect the 3rd temp sensor is when the trouble seems to happen.

 

[day_trippr]

but keeping the data on 3v3 with the 4.7k ohm resistor.

fwiw, I run a bunch of different machines that utilize ds18b20 sensors, most on 3 meter pigtails, and wrt host devices that use 3.3V IO (RaspberryPi, esp32 and 8266) the most reliable mode is to run the sensor VDD at 5V, and use a 2.2K pull-up to 3.3V on the data line...

Cheers!

 

[rkhanso]

Voltage across the 5V line on the PCB is 5.05v
Voltage across the 3v3 line on the PCB is 3.23-3.24v whether I have 2 or 3 temp sensors connected.

 

[day_trippr]

fwiw, the Dallas Semi spec for the ds18b20 claims a max idd of 1.5 ma per device, so current is rarely going to be a limiting factor (network capacitance, otoh...)

Cheers!

 

[rkhanso]

Would having the 1-wire sensors on 3.3v instead of 5v have them disappear from the device list in the Pi OS?
With temp working/updating on the top - Temp not working/updating on the bottom. The CraftbeerPI web GUI and ssh session still work fine. It appears just the 1-wire data/sensors are gone.

pi@raspberrypi:~ $ ls /sys/bus/w1/devices/
28-3ca1f648dfe9 28-3cb7f648a909 w1_bus_master1
pi@raspberrypi:~ $ ls /sys/bus/w1/devices/
w1_bus_master1
pi@raspberrypi:~ $

 

[Kickass]

I always thought raspberrypi was some sort of computer thing. I’m beginning to wonder if I’ve misunderstood this whole time. What happens to your eyes when you

get that vibration feeling

?

 

[rkhanso]

I've removed the power supply I was using and went to powering the Pi with a USB Phone Charger (1A) to see if there's any difference. I'm not using the 12v at all so the fans aren't running, but the AC compressor is running to cool the Kegerator. Still have 2 temp probes connected for now.

 

[rkhanso]

I've removed the power supply I was using and went to powering the Pi with a USB Phone Charger (1A) to see if there's any difference. I'm not using the 12v at all so the fans aren't running, but the AC compressor is running to cool the Kegerator. Still have 2 temp probes connected for now.

Nope - still the same issue when powered by the Phone Charger to the usb-type power connector on the Pi.
I suppose the next step is to remove the PI from the homemade PCB and Dupont wire it all up and run it that way to see if it stops updating the temps and I can't see the DS18B20s in the Pi command line.

 

[rkhanso]

One last try before I wired up everything without the PCB --- I have just a single temp sensor connected to the PCB going the keg.
It's been working for about 6 hours and still going. I'll let it run this way for a few days to ensure it's not going to give anymore trouble. If it's OK, I'll replace that 1-wire temp sensor with a different one and see if it might have been a bad sensor.

EDIT - It didn't help after adding a second, different temp sensor. It still stopped updating temperatures. But if I just connect a single 1-wire temp sensor up, it'll run and run - no trouble at all. I guess I'll have to remove the Pi from the homemade PCB and wire everything up manually to see if it will work with more than 1 temp sensor.

 

[rkhanso]

I figured out what caused the vibration feeling. It was what I used for supplying power to the controller.
At first, I used a 12v DC adapter that powered both the 12v DC computer fans in the Kegerator as well as a 5v DC/DC convertor to run the ESP32 (or Raspberry Pi) through the homemade PCB. I tried another USB phone charger on just the 5v stuff (leaving the 12v devices disconnected and not powered) and I still felt the vibration. This made me think it was my homemade PCB or the power coming through the outlet/house. But then I connected just the Pi and then the ESP32 to the same USB phone charger and still felt the vibration. That got me to try a different USB phone charger, and I didn't feel the vibration then.

I connected everything back up, using Keg Cop and the Homemade PCB, but with the second USB charger running the 5V side and there's still no vibration felt. The 12V DC is not connected to the homemade PCB anymore.

And the temperatures that didn't update on both Keg Cop and CraftbeerPi3 - I think were both related to a bad 1-wire temp sensor. I replaced all three of them and haven't had any trouble with the updates or sensors not seen by either software.

Hopefully this will make a reliable Keg Cop installation.