Small portable thermometer, 7-segment display.

Discussion in 'The Projects Forum' started by jsandb, Jan 12, 2014.

  1. jsandb

    Thread Starter New Member

    Jan 12, 2014
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    Hi folks! New here :)

    I'm just starting out and my knowledge of electronics are very limited.

    My idea is to build a couple of small thermometers that i can use for homebrewing. Ranges are from 0 to 100C, but the most important is 50-80C during the mash.

    Is it possible to get better precision than +-0,5C?
    How small is is possible to build a portable thermometer, can i use a smaller battery than 9V that seems to be the most common?
    I've seen some projects using attiny, what do you think of that? Is using an IC the most simple way to build a thermometer?

    My main goals are:
    - As small as possible.
    - Easy to read 7-segment display.
    - Waterproof probe so i can measure temp in liquids.
    - Precise (is under +-0,5C possible?)

    I hope a project like this can be a great learning process.
     
  2. #12

    Expert

    Nov 30, 2010
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    The simplest way is to take a $10 bill to the hardware store and buy one. Oddly, you seem to want a learning experience.:confused:

    OK. You have a lot of choices, but "smallest" and "hand made" are not going to happen at the same time. Those Asian factories have hobbyist people completely whipped in the "tiny" department.

    You can make a thermocouple probe. That is really small. A thermistor comes in second, an LM34 comes in third. The digital display will have to be separate from the probe if you want the business end small.

    There's a start. I have to go put the laundry in the dryer now.

    ps, 1/2 C is easy enough. All the retail products can do that.
     
    Last edited: Jan 12, 2014
  3. jsandb

    Thread Starter New Member

    Jan 12, 2014
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    The size is not that important, but ut would be fun if it could be done smaller than using a Arduino.

    Probe-size is not important so the easiest to begin with is the best for me.

    This is mostly for fun and learning so retail is not an option :)
     
  4. tracecom

    AAC Fanatic!

    Apr 16, 2010
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    Have a look here before you make up your mind.
     
  5. #12

    Expert

    Nov 30, 2010
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    Arduino? I'm the local crank on, "Y U put MPU in everything?"
    Look at these datasheets. If you don't want to build the display yourself, you can get the ICL7107 already mounted to a display for $10.50 the last time I bought one. If you're a serious masochist, you can build the ICL7107, one amplifier at a time.
     
  6. #12

    Expert

    Nov 30, 2010
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    tracecom had a good idea. $4 for a Harbor Freight meter (if you catch them on sale) and one chip. Same chip I named.

    I hope you are beginning to realize this can be as difficult or as easy as you want it. I remember when we made these out of one transistor at a time and the 8088 was the most advanced chip on the planet.:rolleyes:
     
  7. jsandb

    Thread Starter New Member

    Jan 12, 2014
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    Looks fun, i'll try that too :)

    That looks great! My plan is to build a few so maybe i can start with the mounted kit and build more stuff myself as my knowledge grows.

    ICL7107 + LM35 feels like a good starting point, maybe a bit too hard but thats better than too easy :)

    You don't happen to remember where you bought ICL7107 + display?
     
  8. #12

    Expert

    Nov 30, 2010
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    Yeah, I'll look that up. BRB.
    What country are you in?

    Kind of like this. It's called a panel meter. I'm looking for one with the digital volt meter chip in it.
     
    Last edited: Jan 12, 2014
  9. jsandb

    Thread Starter New Member

    Jan 12, 2014
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    Thanks, i live in Sweden.

    Another thing, what battery do you recommend for this project?
     
  10. #12

    Expert

    Nov 30, 2010
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  11. jsandb

    Thread Starter New Member

    Jan 12, 2014
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  12. #12

    Expert

    Nov 30, 2010
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    You went from, "I don't know" to "That's the plan" in less than 2 hours.
    Not bad for a beginner.:)
     
  13. jsandb

    Thread Starter New Member

    Jan 12, 2014
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    I'm so eager to get this started!
    I have some time now to read this site and "the art of electronics" until my parts arrive :)
     
  14. spinnaker

    AAC Fanatic!

    Oct 29, 2009
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    Look at the DS18S20 or DS18B20. Very easy to interface to with an mcu.


    What is "during the mash"???
     
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  15. Brownout

    Well-Known Member

    Jan 10, 2012
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    That's the step that converts grain starch into sugar, which is subsequently fermented into alcohol. Mashing is the hardest part of the process ( as I understand, never did it before ) and anyone who can get consistant results is a brew master.:cool:
     
  16. #12

    Expert

    Nov 30, 2010
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    Minor problem..there is no MCU in this design.
     
  17. THE_RB

    AAC Fanatic!

    Feb 11, 2008
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    HomeBREWing?

    Alcohol producing yeast are killed in that 50-80'C temperature range.

    However it's an ideal temperature range for home DISTILLING. ;)
     
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  18. takao21203

    Distinguished Member

    Apr 28, 2012
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    I made a 6-digit 7seg LCD display some while ago- with 2 controllers.
    Each 3 digit display has serial 3-wire interface.

    The PCB is small, but no so small, after all.

    And it is not totally cheap. A character LCD module would be cheaper.

    [​IMG]
     
  19. jsandb

    Thread Starter New Member

    Jan 12, 2014
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    No yeast involved in the mashing process, my fermentation temperature ranges from 18-24'C for ale.

    Neat! Do you some more documentation on that build? :)
     
  20. takao21203

    Distinguished Member

    Apr 28, 2012
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    Yes, there will be a new blog entry soon.
    There are two controller chips under the displays (for 7seg decoding/LCD drive)

    For a thermometer, you'd need a 3rd chip on a extra PCB.

    [​IMG]

    The controllers can use 2v to 5v. PIC32 which I use here is 3 volts only.

    What about i2c temp. sensors? They are small.

    I already have c code to drive the display pcb with a master controller. it is an easy spi-like protocol (serial data transfer).
     
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