PiicoDev Precision Temperature Sensor TMP117 (CE07502)

Hello,

Conceptions about how hot or cold something feels are always tricky, reminds me of this classic from Veritasium.

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This is my first post so forgive any errors - I hope that this is the right place to ask but if not please tell me. In setting up this post I find that:

  1. I cannot input code
  2. I cannot input images

Could you suggest how to do this?

I have recorded and measured temperature using

  • A Polymer Lithium Ion Battery (LiPo) 3.7V 2000mAh SKU: CE04378|
  • A RP pico
  • the PiicoDev Expansion Board For Raspberry Pi Pico
  • the PiicoDev Precision Temperature Sensor TMP117 SKU: CE07502
  • The PiicoDev OLED Display Module (128x64) SSD1306 SKU: CE07911.

I have programed this to output the values to a file and tested this by measuring the temperature of my freezer and the result was fantastic.
Unfortunately I left the battery / piico development board connected for a week and flattened the battery.

I now want to measure (in the freezer the freezing point of a salt solution.

  1. Is there ANY way to switch off the battery other than remove the battery from the circuit? (The joiner seems a little delicate)
  2. Is there any way of measuring the charge on the battery? I believe that this can be done by measuring the voltage of the battery by monitoring VSYS. Is this correct? AND Is there any published data on volts with % charged?
  3. Will putting the TMP117 in a plastic bag in the solution cause any problems? Obviously if the TMP117 is put in a solution will short the sensor but if the ice contracts on freezing will it harm the sensor?.

Any hints comments would be helpful

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Hi Laurie,

Welcome to the forums :slight_smile:

Re the posting difficultes, here’s a post I’ve made previously about how to paste your code in:

And you can upload/insert images by clicking on the

icon, or you can just copy and paste them in.

We’ve got some good articles on powering a project from a battery:

Cold is very hard on batteries, and they often won’t be designed to work down at sub-zero temperatures as it will freeze the electrolyte. I’d recommend keeping your batteries outside the freezer and running a wire in to power your device. It shouldn’t affect the seal on your freezer much.

I’d also suggest taking a look at our recently released Makerverse Nano-Power timer:

Yes, monitoring the battery voltage is the usually way. A fully charged LiPo will be around 4.2v, and dead flat below 3.0v. Here’s an article I found with a quick google that gives some good advice on understanding the discharge profile of a typical LiPo battery:

Hard to say. If there’s enough air and the bag is sealed, and the ice has somewhere else to expand it might be ok. If the sensor gets frozen into the ice it might get crushed. You also run the risk of condensation and ice forming on the PCB, which may also result in damage - it’s not the best choice of temperature sensor for what you’re doing.

You might be better off with a waterproof sensor, like one of the more common DS18B20s:

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Hi Trent.
Interesting. Like a fan. the air temperature has got to be the same behind and in front of it but the front feels cooler due to the air movement evaporating moisture off your skin.

Personal experience demonstrating how it is all relative.
I had been residing in PNG for some 3 years at this time. Friday night at Lae Golf Club at the movies. Auditorium was termed a Haus Wind, that is closed at each end but open to fresh air at the sides. We were experiencing a bit of a weather event. Heavy rain which was not unusual but pretty high wind which was extremely unusual.
I was in the bar in shirt and shorts having an ale (or two) and my wife and 3 children out in the hall. They were huddled together trying to keep warm under a blanket and I was freezing in the bar with goose bumps on arms and legs, felt really cold.
THE THERMOMETER SAID 29ºC. Like I said, how you feel is all relative. Normal would be about 38ºC 24/7.
Cheers Bob

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Guys,
fascinating to see the comments above regarding temperature measurement.

My use case is the ongoing measurement of temperature in a few different locations inside and outside of the house. The TMP117 accuracy and precision is more than adequate for this. Allegedly.

I’m also interested in considerations such as cost, ease of use, consistency, repeatability, and interchangeability.

A quartet of piicodev TMP117s and a raspberry pi would not be definitive. But I’m curious to know just how close the readings are “out of the box” and how well they track over a period of time. Plus any insights gained in the process.

Anyone?

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Hi Allan
See the other post re my thoughts on all of this.

Compare piicodev TMP117 and BME280 temperature sensors

Cheers Bob

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Is it OK to use the PiccoDev TMP117 inside a fridge, that will have a brew fermenting? The fridge temperature will be about 18 degrees, and it will be relatively humid.

Thanks

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Hey @David148064 - In general circuit boards shouldn’t be exposed to high humidity/condensation. Your use case is fine for a maker-scale low stakes test. If there’s any chance of condensation on the sensor it’d be best to avoid - perhaps seal the sensor in a bag or conformal coat it?
You might slow down the time-response of the sensor, but reduce the likelihood of damage, or contamination.

What did you go with in the end?

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Hi. I have the Pimoroni Automation 2040 W and would like to use the PiicoDev TMP117 with it. Several questions:
Will it work on the Automation 2040 W? Can I run your Micropython example code on it?

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Hey @Pete56180,

PiicoDev gear should work fine via the QW/ST connector along with the PiicoDev TMP117 code examples for RPi Pico

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Thanks.
Would also like to know if your Piicodev RTC module will work with it.

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Hi Pete,

All the PiicoDev modules use the same JST SH / Qwiic / STEMMA QT connector (that connector has a different name for every manufacturer that uses it). So you should be able to add the PiicoDev RTC to the daisy chain just fine, you’ll just need to check that nothing is using the same I2C address and change the from the default address if you do wind up with two modules using the same address.

Hi, I have version 1.2 of the board with the DIP switch for address selection. I am going to be permanently mounting this to another board with 10mm standoff to enable good airflow. The holes for the pins though are not in the same alignment as the “standard” on PiicoDev Mounting Guide - Tutorial Australia. Can I please get confirmation that the holes for the pins are the same distance from the mounting holes as per the standard and that instead of straddling the centre line, the SCL pin is on the centre line? I just want to make sure it is perfectly aligned on my board. Thanks.

Hi Doug
I bought this up last Nov 22 in this thread

New video by Michael; The Factory | Design A Product With Us Part 3: PCB Design In KiCAD

The short answer is no, I don’t think they will line up. Unfortunately this seems to be a universal problem and can be quite a nuisance. I think someone must have has some sleepless nights thinking up a way to make things as awkward as possible. I think there may be one or two manufacturers that align any pins AND the mounting holes on a standard 2.54 (0.1") PCB grid but it is very rare.
Cheers Bob
PS
The solution I have found is to mount the small board then connect the pin positions with a slightly smaller tinned copper wire so they can be bent half a hole to mate with your larger board holes. A nuisance but it is a neater solution than butchering boards to get the mounts to line up.

Thanks Robert, however I was hoping that they would stick to their standard as they discuss the mounting holes and provide information on the pin spacing in the link I shared. @Michael may have some information… I do not use KiCad, so I can’t just load it up and see.

Hi Doug
I don’t think there is a standard". True the header pin holes conform to the 2.54mm grid and the mounting holes conform to a 2.54mm grid BUT NOT THE SAME GRID. They seem to be half a hole out in both directions.
Bewildering what???
Cheers Bob

Hi Robert, Core Electronics have their Piicodev products and have documented the size and position of the mounting holes and the pins in the link I posted. That is why I’m asking - I’m not worried about other boards, I’m asking about a Piicodev board designed by Core (hopefully) to their layout standards.

Hi Doug
I have already had this discussion with Michael as in that link above.
I am sitting here looking at 2 boards. One PicoDev and one Adafruit. Neither have the header pin holes and the mounting holes on the same grid.
I would respectively suggest you purchase the board you are interested in and try it. You will find I think that I am correct.
Cheers and good luck. Bob
Edit.
Just had a look at that link. All the dimensions are there. It stands out like a neon light that the mounting holes and header pins are not on the same 2.54mm grid. For instance one dimension shows the header holes 1.27mm from the edge of the board and the mounting holes 22.4mm from the same edge. Now subtracting 1.27mm from 22.4mm leaves 21.13mm. This is not evenly divisible by 2.54 so cannot be on the same grid. I don’t think they are even on the same 1.27mm grid. This is all good if your connections are cables but is a bit iffy when you are trying to use header pins and mounting stand offs as you want to do.

Hi Robert, I have three of the Piicodev TMP117 boards and I don’t really care what grid they’re on as I can put holes anywhere I want on my board. I just need confirmation that the TMP117 board has the pins the same distance from the mounting holes as specified in their standard for Piicodev boards with the referenced pin on the centre line. It would be nice to have everything on a 0.1” grid, however it isn’t always that easy when designing boards. Core have chosen their layout, and that’s fine with me. I just need the clarification I mention. If I used KiCad, I could just load up the board and check, but I don’t use it and I’m not sure I trust conversion programs to get it right.

Hey @DougM - I can confirm the vertical distance is the same and the SCL pin is centred.
Uploading: image.png…

The rev20 board introduced the 4-pin DIP switch to make addressing easier / solderless.

The Mounting Guide is slated for a major update. In the meantime I’ll update this line:

1-unit modules all have similar outer dimensions, mounting hole, and PiicoDev connector placement. The number of pins in the breakout header differs module-to-module, but is always centred.

To read something to the effect of:

1-unit modules all have similar outer dimensions, mounting hole, and PiicoDev connector placement. The number of pins in the breakout header differs module-to-module. The breakout is usually centred. Download the PCB source files to check a specific board.

@Robert93820 hindsight, eh? :woman_shrugging: It turns out most of the long-term decisions in a project get made (or not made) right at the beginning - when you have the least benefit of hindsight and experience.

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