looking for schematic / plans

[dacflyer]

i am looking for a schematic or plans for a temperature meter , led 7 segment display type
3 digits so i can read 100+ degrees
doesn't have to have celcius converter..unless its something simple to do...i have (3) 2.5"
led 7 segment displays..common cathode that i'd like to use..
anyone have plans that isn't PIC controlled
i was thinking to use a thermister as the sensor
like the one that radio shack uses
someone show me i am anxious to get this made soon.<p>radio shack sold a lcd modual once but it was limited to 120F i am looking for something to go at least 200F high and as low as -20F is this possible ? thanx

[dacflyer]

Hmmmm wonder if anyone has even peeked at this post yet....
i am still looking for help on this one
it has to be a NON-PIC version,i know the main temp part has to use a AD CONVERTER but i need the BCD driver section for common cathode..
i found one long ago but it is designed for common anode...for the led display..might have to bugg Edd on this one :p

[Mike]

<blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr>Originally posted by dacflyer:
[QB
i was thinking to use a thermister as the sensor
like the one that radio shack uses
someone show me <p>Anyway, i think the reason nobody responded is because you specifically said no PIC, and there is no real easy way to do that without a pic. Think about it, you need to have one chip detect the temperature, another calculate what to display on the LCD and another to turn the binary code to analog that your 7-segment display can handle. A single PIC can connect directly to the sensor and LED screens and it would calculate the temp, and change it to the screen. And, with a PIC it would be easy to setup to display celsius.<p>
-Mike

[wd5gnr]

Well, I'll bite. How about using an LM34? This outputs 10mV/degree and 100 degrees would be 1V. Then you could use one of the cheap LED panel meters and set the decimal point in the right place with a divider:<p>http://www.web-tronics.com/test-equipme ... -led-.html<p>These meters usually read 200mV and for some reason the built-in dividers will scale for 20V but not 2V. But if you built an external divider to cut the LM34 voltage by a factor of 10 that would give you 1mV/degree. A 3 1/2 digit display would show 1999 for 199.9mV or 199.9 degrees. You can select the decimal point so it would show 199.9 and there you go.<p>No PIC included! Not that I don't like the PIC.

[k7elp60]

I assume you are looking to monitor up to 100 degrees F and a little beyond. You could use the LM34 series of temperature sensors, they have an output of 10Mv per degree F. If you are willing to switch to Common anode displays you could use the ICL7107, set it up as a 0-2V DPM and you would
be done.

[dacflyer]

mike >> i hardly think one would go broke...
i have a schematic here from an old old old
"radio electronics magazine july 1990"
they show a digital water temp guage that can be built for your car..as well as many other guages..all use basically a A/D converter "CA3162E"
and a BCD 7 segment decoder for 3 digit disply
"CA3161E"
but..the BCD decoder is for common anode display... i am looking for a such circuit that will let me use the common cathode display i already have...which is 3> 2.3" tall displays
the LM34 doessound interesting..is there a way to use this ? i have looked to find me a BCD 7 segment decoder for 3 digit disply , but i am unable to find such...anyone got advice?
only reason i do not want ti use a pic is cause i do not know anything bout programming...and i also like off the shelf parts..

[jollyrgr]

Here is a kit if you are interested:<p>http://www.electronickits.com/kit/compl ... /ck101.htm<p>For something along the lines of wd5gnr's idea you can use a panel meter and silicon PN junction. I don't have the schematic presently but there is a way to use an OP amp and standard PN junction device (diode, Bipolar transistor) to convert the temperature/current in the PN junction to a voltage. Using this circuit you can then use a standard volt meter or even one of the panel volt meters to create a digital thermometer. It would take some searching through the data sheets or experimentation to find the temperature/voltage curves though. This would be a bit harder but I wanted to suggest it anyway.<p>Using the LM34 sensor, and its known 10mV/Degree, would be the way to go. Based on the LM34's data sheet:
http://www.national.com/ds/LM/LM34.pdf<p>you get 10mV per degree F. Thus at 75F you get 750mV.<p>Input voltage to the LM34 is anywhere from +5 to +20 volts. If you want to measure below 0F, you have to offset the ground of the LM34 or go with a split power supply. But you must be careful with the panel meter used. Some do not like to measure voltage from their own source. Thus you would need two independent sources; one for the meter and one for the LM34.<p>Some panel meters have a maximum base voltage reading of 200mV. This may or may not be a problem. The simple solution would be a high impedance divide by ten voltage divider (such as a 9M Ohm resistor in series with a 1M Ohm resistor) when you want to read at the 200+ F range. With a 3 1/2 digit panel meter you would still see three digits, just not the decimal's value when measuring above 200 F.<p>[ June 02, 2004: Message edited by: Jolly Roger ]</p>

[Mike]

<blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr>Originally posted by dacflyer:
mike >> i hardly think one would go broke...
<hr></blockquote><p>not exactly what i meant, he said he was thinking about buying something from RadioShack which is why i said that.<p>[ June 02, 2004: Message edited by: Mike ]</p>

[dacflyer]

mike > no problem,,,<p>anyway....i am not worried about any decimal point
i only have 3 digits to use..
so maybe something comes along soon....

[russlk]

The MC14543B is a BCD to 7-segment decoder that can drive either common anode or common cathode. It is available from Digikey.

[dacflyer]

thanx russ , i will look into it..

[dacflyer]

hey russ, i just looked up the chip you mentioned..it is a single LCD driver...not for LEDS. or multi-led display.
did you make a error?
would like to find the common cathode version of the CD3161E display driver
or find a way to make CD3161E work with a common cathode display driver............

[k7elp60]

Russ, is correct. The Ph pin determines the polarity of the segment drive. I am using several of them to drive common anode displays. In each case the displays are multiplexed. I am using 560 ohm resistors in series with each segment. Driving the individual anodes with 2N3906 transistors from a 9V source. The bases of the 2N3906 transistors is are driven thru a 4.7k resistor from a 4553 3 digit counter.

[Edd]

Hey Dacflyyyyyyyyer…wanna buy a duck???.
Seems like either suggestion on the display /counter would be ok, especially with ICL7106/07 series of DVM chips only being 2 bucks now or complete digital panel meters available for $7.95. Seems like your desired use of a "CA3162E"/"CA3161E" combo made by RCA may be cramped by a NLA situation now. Maybe as a second sourced NTE but I imagine that they would be pricey there.
As far as building up from CMOS ‘ the chip that hasn’t been mentioned is this 3 digit 14553 counter chip all in a single chip…along with its ancillary digit/seg driver chip.
http://rocky.digikey.com/WebLib/On-Semi ... 553B-D.pdf
See page 7…. Only three digits would be needed…it is duplicated for 6.
It so happens that I have some surplus 1 ½ inch square boards utilizing it, being a complete 3 digit counter with its small 3 digits display(red) with their magnifying lens molded on the led end caps…..like used to be used on the first generation of TI Datamath, Corvus, National and H/P pocket calculators. Seems like these boards were on some equipment for fatties, they were supposed to chew their food, 25,50 ? times between “timed” counts. One has your name on it per gratis if you so desire to use as is, or to strip for parts or scale up to larger display LED’s.
This would only require a D/A converter in front of this counter. Plus whatever sensor media that you decided on in front of that with its appropriate scaling.
As for your units use, will it be for a calibrated referencing to some specific temperature, or in a differential mode, such as you might use in AC work on monitoring temp shift on a refrigerants hi /and/or/ low side lines tubing or air over condensing temp variance. ????
I have so many different types of thermometers that I got non working for a mere pittance from pawn shops, and then repaired and cal, that construction of one has never been a need of mine.
Addenda: Mikes dicesting/digesting/or/dissecting of a wall thermostat should work but ONLY for their u/p's programmed limited temp range. Sensing agent is a 1N914/4148 diodes junction.
I have cal corrected (switched indoor/outdoor temp) with a variable small value series resistor to find its fixed value.I have one in my van and one in the lab just for their LCD thermometers use, with the only internal relay...(50 ma hog) disabled to get about 1 yr batt life. Cast off units for about a buck from amongst garage sale items.<p>73's de Edd
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<p>[ June 05, 2004: Message edited by: Edd Whatley ]</p>

[Mike]

I was just thiking, you could always dicest a digital thermostat...