What's a Simple Design for this Circuit Description?

[Thingamajig]

Simple circuit design for this description?

It's been a long time since I've designed a circuit...

The input to the circuit is a temperature readout from a thermometer or temperature sensor. I guess you could think of the temperature as a voltage (?). When the temperature is above a particular point, I want a first high voltage light to be on and a second high voltage light to be off. When the temperature is below that particular point, I want the first light to be off and the second light to be on.

 

[dougy83]

You can use an opamp as a comparator & drive the LEDs from the output. The set point is adjusted via the pot, R1.

 

[Thingamajig]

Thanks! That was fast! What software allowed you to draw that so nice and fast?

The only change I have to make is that lights are not LEDs, but rather are regular lights. I'm not sure how exactly the circuit would look for that. I know that's super basic, but I haven't designed a circuit in about 20 years.

 

[ADWSystems]

Lights, as in 120V light bulbs? What wattage?

 

[Reloadron]

OK as to the beginning, I am guessing you do not yet have a temperature sensor or transmitter scheme? If not, what is the approximate temperature range you are looking at?

The rest isn't that difficult. I would think about a comparator circuit to drive a simple relay configuration. I would use a DPDT relay with contacts rated to handle the lamps. Temperature exceeds setpoint and lamp A is on with lamp B off. Temperature below setpoint and lamp B is on with lamp A off. I believe that is what you are after? I would add some hysteresis likely in the comparator circuit so the relay isn't freakig out as the temp hovers around setpoint.

Ron

 

[Thingamajig]

Lights, as in 120V light bulbs? What wattage?

The lights are 120V light bulbs and 100W or more.

OK as to the beginning, I am guessing you do not yet have a temperature sensor or transmitter scheme? If not, what is the approximate temperature range you are looking at?

The rest isn't that difficult. I would think about a comparator circuit to drive a simple relay configuration. I would use a DPDT relay with contacts rated to handle the lamps. Temperature exceeds setpoint and lamp A is on with lamp B off. Temperature below setpoint and lamp B is on with lamp A off. I believe that is what you are after? I would add some hysteresis likely in the comparator circuit so the relay isn't freakig out as the temp hovers around setpoint.

Ron

I don't yet have the temperature sensor. I'm thinking the sensor will be a laser thermometer but could easily be something else. The temperature range is about 0F to 100F. The "particular point" is about 50F or so. Your re-wording of my description is correct.

 

[Reloadron]

The lights are 120V light bulbs and 100W or more.



I don't yet have the temperature sensor. I'm thinking the sensor will be a laser thermometer but could easily be something else. The temperature range is about 0F to 100F. The "particular point" is about 50F or so. Your re-wording of my description is correct.

It all starts with the sensor and where and how it gets mounted. Each type and design of sensor best is used for different applications in the scheme of things. IR sensors for example like this sensor for example have some merit. Nice features like output scaling and signal processing is done for you. The downside of any LASER IR type sensor can be for example emissivity. All alloy surfaces do not reflect the same.

Nice sensors are those that do the signal conditioning and scaling for you.

Another question becomes is this for an industrial work project or something you wish to toss together around the house? There can be considerable difference between something that will be used in an industrial application and something that I will shove above the kitchen sink. Additionally there is budget.

The better you can describe the application the better people here may help and provide suggestions and ideas.

Ron