# Small portable thermometer, 7-segment display.

#### jsandb

Joined Jan 12, 2014
12
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.

#### #12

Joined Nov 30, 2010
18,223
Is using an IC the most simple way to build a thermometer?

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#### #12

Joined Nov 30, 2010
18,223
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. Thread Starter #### jsandb Joined Jan 12, 2014 12 Have a look here before you make up your mind. Looks fun, i'll try that too 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.
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.

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.
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?

#### #12

Joined Nov 30, 2010
18,223
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.

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#### jsandb

Joined Jan 12, 2014
12
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.
Thanks, i live in Sweden.

Another thing, what battery do you recommend for this project?

#### #12

Joined Nov 30, 2010
18,223
You went from, "I don't know" to "That's the plan" in less than 2 hours.

#### jsandb

Joined Jan 12, 2014
12
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

#### spinnaker

Joined Oct 29, 2009
7,835
Look at the DS18S20 or DS18B20. Very easy to interface to with an mcu.

What is "during the mash"???

#### Brownout

Joined Jan 10, 2012
2,390
What is "during the mash"???
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.

#### #12

Joined Nov 30, 2010
18,223
Look at the DS18S20 or DS18B20. Very easy to interface to with an mcu.
Minor problem..there is no MCU in this design.

#### THE_RB

Joined Feb 11, 2008
5,438
...
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.
...
HomeBREWing?

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

However it's an ideal temperature range for home DISTILLING.

#12

#### takao21203

Joined Apr 28, 2012
3,702
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.

#### jsandb

Joined Jan 12, 2014
12
HomeBREWing?

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

However it's an ideal temperature range for home DISTILLING.
No yeast involved in the mashing process, my fermentation temperature ranges from 18-24'C for ale.

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.

Neat! Do you some more documentation on that build?

#### takao21203

Joined Apr 28, 2012
3,702
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?
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.

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).