Yet Another Parasitic Draw Case

[hexibot43]

Alright. I'm giving up on the Raspberry Pi for now. Sounded like a great idea. The footprint on my bench is small. But I just can't get the PicoScope 4423 I have working with it. Usb permissions?!? My Imac will be running the show for now. Honestly, I just plugged my scope into my Imac and everything just works. A little bit to learn still but it is logging data like a champ.

To be continued as the data accumulates in my Imac.

Running Picolog 6 to record data. What would be the easiest way to add temperature data to my logs? We've just started getting colder here, and it seems to be effecting my recordings.

[Steve Smith]

Hello and thank you for the feedback

The Raspberry Pi adventure looks to be a disappointment at this stage and I want this to work for you.

I must apologize as i mentioned in my previous post I would liaise with colleagues and this completely slipped my mind. I will try for you ASAP, did you try the support line?

Regarding temperature monitoring, a thermocouple sounds like the solution but we are going to need an interface which will require a battery and here lies the problem as we want to get around the dependence upon batteries .

I guess the good news is the demand of a thermocouple on a temperature transducer battery is minimal and will suffice through your battery monitoring.

I will take a look at Pico T & M options and feedback

Take care......Steve

[Steve Smith]

Hello again, sorry no joy on a thermocouple adapter/interface for your scope (4223)

This has now been resolved thanks to the introduction of the 4x25A scopes, however, this does not help us here!

No doubt a quick Google search will find you a battery powered temperature interface/transducer (e.g. 1 mV/Degree C/F) in which we can connect a thermocouple and then convert the 4 mm outputs to BNC.

It sounds like a bit of a mission but it will allow you to then log temperature alongside battery voltage

I hope this helps, take care......Steve

[Martyn]

For the installation on the Raspberry Pi can you try

Code: Select all

sudo apt-get purge wget
sudo apt-get install wget
wget -O - https://labs.picotech.com/debian/dists/picoscope/Release.gpg.key | sudo apt-key add -

and if it still hangs cut and paste the console output so we can take a look.

[Martyn]

Further to this to check versions type these three commands

[hexibot43]

I really want to thank you all for helping me. I am a dog with a bone. Not giving up. In the picotech forum for picolog, I got some help too.

I have my Raspberry Pi 3b+ up and running well with Picolog6 beta. I set it up as I had it set up with the Imac. Saved where I left off on the Imac. And copied the file to the picolog folder on PI. I really loved how Picolog had no problem when I paused the recording on Imac, to take some time with scope on the Pi. And then when I plugged it back in. Just un-pause it And continued logging as if nothing has changed. The Annotation (notes) feature is great too. I enjoy using picoscope6 software, but I'm really loving this picolog.

So much of the time I want to use the scope so that I don't have to sit there hoping to get a glimpse of the problem. I just want to hit record and walk away. For example, last week I had a car that would just suddenly die. And of course, I tired of waiting for it to die. Walked away. Came back to a dead car. And when I go to start it back up, it just starts. No answer because I didn't sit there waiting. Perfect place to use the picolog. When I come back to the dead car I can just rewind and look at the data. Even if it took hours to catch it. looking forward to trying my hand at that. Usually working on three cars at the same time. That is the kind of tool that can really help out.

Thanks Again Everyone,

Mab

Don't always need crazy hi resolution data. Just a slow methodical look at the problem.



I

[hexibot43]

So where was the issue with connecting the scope to the Pi. A file needed to be embedded in the software for the usb connection of the Scope. It was missing. And once I was able to write that file into the rules directory everything was right as rain.

From the command line
"lsusb " gave me a glimpse of all USB devices connected to the Pi. And you could see my scope show up when plugged in.

But no connection between Picolog and Scope. There was not a rule to the interface to allow the 2 to communicate. A rule was missing stopping this communication. Once in place the communication simple happens.

https://www.picotech.com/support/topic40687.html


Seems so simple now that it works. But I alone did not have the skills to figure it out.

[hexibot43]

Hello again, sorry no joy on a thermocouple adapter/interface for your scope (4223)

This has now been resolved thanks to the introduction of the 4x25A scopes, however, this does not help us here!

No doubt a quick Google search will find you a battery powered temperature interface/transducer (e.g. 1 mV/Degree C/F) in which we can connect a thermocouple and then convert the 4 mm outputs to BNC.

It sounds like a bit of a mission but it will allow you to then log temperature alongside battery voltage

I hope this helps, take care......Steve

Hopefully this is very simple solution to Temperature input. Found an Analog Devices, tmp35,36, 37 device would give me a simple voltage output that I could read in on one of the 3 channels I still have left on the Pico 4423. Do some simple math to it, and be able to log it with my other data. Ordered a couple and should see it by Wednesday. I should not have to worry about issues of power isolation. I am thinking of just using an(is that right?) USB cable cut open to power the circuit. Or run it off the rail of the Pi. There will be no physical contact to any anything other than the case of the battery. Hmmm. No need to even touch the case. Just a reading of Ambient Temperature. No special units to use.
Am I mistaken? Maybe if I only had a two channel scope that might no be a smart way to go. But I'll still have two left over channels for now.

[hexibot43]

Two Steps forward, and one step back! Story of my life.

I had this thing working flawlessly. And honestly much to my amazement. I could never get my Pico Scope to work well with any of my laptops. Randomly loosing the scope, and/or Crashing running Pico Scope software. When I moved to the IMAC all those problems seemed to go away. So when I switched to a Raspberry Pi I thought I would surely have the same issues I did with the laptops. Initially I did, but realized I was not using a top notch power supply. I bought a 3 Amp power supply specifically for the Raspberry PI 4, which has more stringent power requirements. Now my Pico Scope is running like it does on the IMAC; like a champ.

NOTE: So anyone running a RPi get the best power supply you can.



My next problem was the datasheets for the Temperature sensor I was going to use

https://www.analog.com/media/en/technic ... _36_37.pdf

The Picture of the TO-92, from my point of view had ambiguous pin alignment. I think it could be taken 2 ways. And of course I choose the wrong way. And basically shorted out my RPi. And now I have a dead Raspberry PI 3b+. At least it is cheap to replace. So honestly not a big deal. Just an annoyance.

https://en.wikipedia.org/wiki/TO-92

Much better, and clear view of pin arrangement. No way that I could see to mistaken pin positions. And with that I could see my mistake. I inverted pins 1, and 3. So inverted the pins connection, and now the chip is working perfectly. Maybe that is why they sell the chip is sets of 5. It took me 2 to realize my mistake.

Now the big question is should I upgrade to the Rpi 4 with more memory? And should I get all the memory I can? Or is the 3b+ with 1g enough? I realize I will have to get an adapter cable for the hdmi cable to micro hdmi. But other than that? Am I missing anything else to get? Or other considerations.

Gotta say, I'm having fun with this project. Even with the bumps in the road. I can see lots of other things to use the rpi. Looking forward to seeing my data in with the added temperature data. I'm guessing that the drain of the battery will be close to linear with the correction for temperature.

And PicoLog rocks! Made my Pico Scope usefull all over again. I think I have 4 DSOs, and a couple analog scopes. None of the others are capable of what the Pico Scope is with the advent of Picolog.

[Steve Smith]

Just following up on a battery voltage logging exercise:

Below we have logged the voltage of a fully charged (healthy) 12 V conventional lead acid battery.

The battery has been standing on a workshop bench with no load applied and monitored using a Raspberry Pi as described above

Channel A (blue) is the channel of interest, please ignore channel B (red) as this was another experiment monitoring a 7.2-volt Ni-Cd battery.

I guess the message I want to relay is how a healthy, charged battery standing on a bench with no consumers attached will slowly but surely discharge.

Here we have the battery on the 9th of November 2020 @ 12.706 V

Image 1

Now below we have the same battery on the 21st December 2020 @ 12.516 V

Image 2

The 12 V battery (Channel A, blue) does appear to have plateaued but I will continue to monitor over the coming months and report back on the battery condition.

Let’s put the battery discharge into perspective from 12.706 V to 12.516 V.

 Battery voltages greater than 12.6 V are considered as 100% SOC
 Battery voltages at 12 .5 to 12 .6 V are considered as 80 % SOC
 Battery voltages at 12.4 to 12.5 V are considered as 70 % SOC and re-charging is recommended!

If we bear this in mind, it’s no wonder a number of vehicles suffer discharged batteries if we add into the mix parasitic drain.

In the parasitic drain training article here https://www.picoauto.com/library/traini ... in-testing we discussed “Battery Reserve” and how to estimate the amount of time a battery can sustain parasitic load before requiring a recharge!

I had not considered battery self-discharge as witnessed above and so we should add a buffer into this “reserve” calculation to allow for the battery itself.

I must add, I am relatively new to PicoLog but for this work it is simply perfect and forgiving too! What I mean by “forgiving” is that I accidently disconnected the USB cable from the scope on or around Monday 23rd November (hence no data drawn) and did not realize for over a day! However, upon reconnection and re-opening PicoLog we picked up with logging where we left off, how cool is that?

I hope this helps, take care…..Steve