# High and Low Temperature Alarm Circuit Prototype

Discussion in 'The Projects Forum' started by John Rickson, Oct 7, 2014.

1. ### John Rickson Thread Starter New Member

Oct 7, 2014
2
0
Application is for example, in a pipe running a fuel oil, I need to maintain the temperature between 50-70 deg. Celsius:
Dear Sir,

Greetings!
I would like your kind assistance regarding my Project.

The Project is about High Temperature and Low Temperature Alarm prototype.

Example:

Normal Operation: 50 deg. Celsius to 70 deg. Celsius
Below 50 deg. Celsius --> Low Temperature Alarm
Above 70 deg. Celsius --> High Temperature Alarm

I am wondering if this will do using the logic gates in this manner:

Input is 1/0: Singl input in a 3-state

Input is 1 : H.T.--Alarm (LED Red Light)
Input is 0 : H.T.--Alarm (LED Red No Light)

Input is 1: Normal--(LED Green Light)
Input is 0: No Light

Input is 1: L.T.--(LED Red Light)
Input is 0: L.T.--(No Light)

If there's an alarm, a reset button is available.

Thank you and I hope to receive positive feedback.

Regards,
John

2. ### #12 Expert

Nov 30, 2010
16,664
7,311
I don't see why you need to use logic chips. Input is 1? Apply that to an LED. If there isn't enough current, apply it to an npn transistor and have the transistor light the LED. Input is zero? Apply that to the same circuit and the LED won't be on.

If you have some reason to use logic chips, please tell about it.

3. ### John Rickson Thread Starter New Member

Oct 7, 2014
2
0
Dear Sir,

Thank you and appreciate your message. I just have the idea by using logic gates. If this will do by using the transistors/Op-amps, would it be alright to ask the diagram please?

Regards,
John

4. ### #12 Expert

Nov 30, 2010
16,664
7,311
First you have to tell what kind of device you are using to measure 50C to 70C. The output of your measuring device will dictate how to get it to turn an LED on.