ICL7101 & LM34 temp. meter

[dacflyer]

i have the ICL7107 led display driver and the LM34 temp sensor.
i am looking for help to make a temp modual.
i like to know the temp outside before getting up inthe cold mornings. so i can have a idea of how to dress for the day..
my thing is..its always dark when i get up. so looking out the window or seeing a LCD display is useless in the dark, thats why i'd like a led version. can someone help out with a schematic?

i think i just need this to be in a voltage mode since the LM34 says 10mv = 1 degree.
also what scale should be used? 20mv? 200mv?
i'd like it to also indicate -degrees for them really cold days :p and the decimal point for tenths of a degree.. ex. ---> -15.4
and just to be fancy, i'll have a 5th led segment to indicate the "F"
this might be a neet project for some others out there..
i'd like to learn more about this ic. as far as setting it up for what one whould need.. id there a cook book for this ic somewhere? (ICL7107)
thanks....

<small>[ January 26, 2006, 08:41 AM: Message edited by: dacflyer ]</small>

[Engineer1138]

You can find a schematic for a panel meter based on the 7107 at http://www.electronics-project-design.c ... ivers.html. If you search around you may find an entire panel meter (assembled) for about $20 based on this chip; they used to be quite popular.

But: if it's going to be outdoors, be sure all your active components are industrial or military/automotive rated. Commercial ICs generally are rated only down to 32F.

Also be sure the LM34 can output negative voltages for subzero temps. I seem to remember that in order to read temps below 0F, it needs an offset voltage, which will complicate the circuitry.

[philba]

Funny, I have one of those that I've been wanting to play with.

Have you looked at the datasheet? http://www.intersil.com/data/fn/fn3082.pdf It's pretty complete and also calls out a number of app notes that are pretty helpful. I think with those resources, you should be able to get your questions answered.

Note figure 18 which is for a centigrade thermometer. should be pretty easy to adapt to the LM34.

[dacflyer]

i have studied the sheet some. found it earlier.
i canot find definitions for all the pins.
perticularly pins from 27 to 40.
the rest is self explanitory

[Will]

If you want to play with electronics assembly that's fine - I do it myself all of the time - however - If you just want to measure the temperature - Heartland of America - somewhere in Florida (If you are further interested DacF I can get you the full detail) Sells digital thermometers with remote temperature measurement for about $20 (Sometimes on sale for about $15) for which you get the receiving unit and a remote (radio) transmitter - which you just stick outside to measure the temperature. The receiving unit (Which is capable of accepting signals from two more transmitters) also displays room temperature and is a so-called Atomic Clock - which receives radio signals from WWV in Denver Colorado and, from that, displays precise time. It also changes the time automatically at Spring and Fall as desired. If you buy two of them ($40 or $30 on sale - I have three) then you can place receivers and transmitters in different locations and both receivers will display both remote temperatures and each local temperature. I can get you one if you wish

[philba]

check this carefully but I think +Vs goes to +V (pin 1), Gnd to pin 32 and Vout to pin 30. You may need to pull Pin 30 to +V - the DS shows a 22K pull up. By connecting Vout to IN LO, an adjustable ref to IN HI and the Ref divider trimpot, you can 2 point calibrate your thermometer as the text with fig 18 says.

Pins 27-40 seem to be, for the most part, discussed though its kind of scattered around. Not the clearest data sheet in that regard.

[dacflyer]

Will >> i am very well aware of them types of units etc,,but they are mostly all LCD displays
you cannot read them in the dark,,
mine will just be a LED unit in the house with the wired sensor sticking out the window..that all, nothing to be complicated. thanks

[jwax]

Crazy I know, but how about a flashlight to read the LCD in the dark?
Couldn't resist!

[ecerfoglio]

Crazy I know, but how about a flashlight to read the LCD in the dark?
Couldn't resist!

Or a "permanent" backlight behind the LCD?

Could be just a couple of leds and a power supply. Of course it will need a wallwart if you don’t turn the leds off...

[MrAl]

Hello there,

I picked up an LCD temp measuring unit at
WalMart a few months back for $8 and it has
a back light built in.
Also has features like min/max and
indoor/outdoor readings.

I also picked up a wireless at KMart a month
or so ago and it was about the same price.

It's just too simple to buy one and use it

If you need to light one up yourself, use a
very small wall wart and white LED perhaps.


Take care,
Al

[Dave Dixon]

Ray,
Would you believe that I have a box sitting here at work right now, that I was wanting to find a home for! It is the Intersil ICL7107EV/KIT. PCB, manual, and all the discrete components ready to be built. Four segments, but the first one is "+1." It's yours for the cost of shipping. (Okay, I'll take an extra dollar for it!). Let me know if you want it, and how/where to ship it, if you are interested.
I can't believe this thing has been in a cabinet for 15 years or so, and just surfaced last week. What timing! My private email is ddixon at aeromach dot com.
Good luck,
Dave

BTW The manual is about 200 pages, with a bunch of applications notes. It's probably worth the cost of shipping alone! If you are still on Mountain Dr. I already have your address.

<small>[ January 27, 2006, 07:33 AM: Message edited by: Dave Dixon ]</small>

[dacflyer]

Jwax how can you say that and then boast about "leds lighting the future".
Sure i'll take it !
i already have all the parts i basically need.
i just need to figgure out how to interface the LM34 to the 7107..and what/how to set the meter up to read it. as far as which components i need to set up the ref level , osc. etc..
that 200 pages should answer my questions..
send it, and let me know the cost, and i'll send you a check thanks....

[Dave Dixon]

Hi Ray,
It's shipping today via Airborne Express. I'll advise of shipping costs today or on Monday. I figure that had been in storage since around '85.... and just happened across my bench last week! That's too strange. Have fun,
Dave

[Ron H]

I have two remote thermometers with WWV clocks. One projects the outside temperature onto my ceiling in my bedroom. The other projects the time, and the temperature in my garage, onto the ceiling in my bedroom (I watch my garage temp because my un-winterized motorhome is in it).
Neither was astronomically expensive, but I can see why you would want to build one for the experience, and maybe to save a few bucks.

[dacflyer]

RonH >>
ya, buying somehting ready made is not as fun or exciting.

i mean thats what hobby electronics is all about,,enjoying something you made and being able to say " i made this! "

i have all sorts of neeto stuff around here, like the 216 led clock powered by 4017's and i also have made some cool hard drive clocks.
and many other things