A simple digital thermometer circuit with out a micro controller and having a seven segment LED read out is shown here. The IC has an internal timing circuitry and hold function. When the hold function is enables, the output IC latches itself to the present state. It can directly drive a seven segment display and there is no need for current limiting resistors. LM35 is a three terminal precision temperature sensor IC from National semiconductors.
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A simple digital thermometer circuit with out a micro controller and having a seven segment LED read out is shown here.
The IC has an internal timing circuitry and hold function. When the hold function is enables, the output IC latches itself to the present state. It can directly drive a seven segment display and there is no need for current limiting resistors. LM35 is a three terminal precision temperature sensor IC from National semiconductors. IC LM35 is used for sensing the temperatures. A voltage proportional to the temperature will be available at pin 2 of the LM35 and this voltage is coupled to the high input pin pin11 of the CA CA does the job of converting this analogue voltage in to a BCD format.
The time taken for the charge to restore to its original value is noted and the number of clock cycles elapsed during this time will be a measure of the charge induced by the input voltage voltage applied to pin The point of restoration is sensed using an internal comparator which latches the counter and the count is then multiplexed into the BCD outputs and the entire cycle is repeated.
The hold pin CA pin6 can be used for running the IC in different modes. When the hold pin is grounded or left open the IC runs in low speed mode sampling rate is 4Hz. When the hold pin is held at a fixed 1. C1 is the power supply bypass capacitor whose job is to bypass noise if any from the power supply line. The next section of the circuit is the BCD to seven segment decoder plus display driver section.
For that purpose CA is used. Transistors Q1, Q2, Q3 common anode terminals of the corresponding seven segments displays. Q1, Q2, Q3 are driven by the 4, 3, 5 pins digit driver pins of the CA respectively.
I think 0. If it does not work then use a parallel combination of 0. I have tried this circuit and it worked! But, there is a huge error in the datasheet, pin 3 of CA should be floating not grounded. Looks good but how do you Exactly calibrate it? How to connect the all seven segment display….?? If we connect the all seven segment display in parallel with IC means all display showing the same value or what???????????
I have understood. Put all display pins in touch a with a, b with b, c with c and so on. Hi i made this project on project board but when i put 0. What is it mean and how can i solve this issue.
For CA you can use CD CA available from ebay. Yes, i have tried this circuit it works very nice. You have to do a little bit calibration after assembling the circuit using two POT.
Is there any substitute for ca????. Actually I could not find it. I am making this circuit so any one who knows substitute of ca plz help…………. Does this circuit indicate temperatures below 0 Celsius? Author admin. Audio oscillator circuit February 22, Simple function generator circuit October 25, Water level Controller January 22, Vijay Kumar 2 years ago.
What is the use of transistors and how to connect three seven segment display together. How could connect the displays The output of displays are not numbered. Aldrin 4 years ago. Jerry Van Cleeff 5 years ago. Abdulaziz Qwb 6 years ago. Can I use for C2 the value 0. Abdulaziz Qwbaiban 5 years ago. Tom 6 years ago.
Vicky 6 years ago. I have a doubt on this circuit…… How to connect the all seven segment display….?? Naveed 6 years ago. Seetharaman 6 years ago. MAsaood 7 years ago. Dharmendra thakur 7 years ago. Abdullah Zohaib Kiani 7 years ago.
R 6 years ago. Hi I m just a beginner. Do we need a software to be burnt in the IC to make the circuit work. No they are A to D converters no need for any software. Atchyut 6 years ago. Can we use any other BCD decoder other than Ca?? Seetharaman 7 years ago. It is common anode type. AZ 8 years ago. Keith 8 years ago. Are there substitutes?
Prateek Birthare 9 years ago. S;;D 9 years ago. Scientific topics in a simple beautiful. Submit Type above and press Enter to search. Press Esc to cancel.
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Digital thermometer circuit