doncarlosalbatros
Full Member level 2
I was doing on-off temperature control for around 40°C for an enclosed big enclosure manually by switching on and off a 1100W heater(with a fan) with my hand. The accuracy is not very important roughly 40°C is fine. Now instead me doing this, I want to automate this on-off process. Basically 40°C corresponds to 8V output of the temperature transducer.
Here below is raw voltage output of the temperature transducer when it is heating and cooling around 40°C(sampled at 4kz):
Here is a close view of the raw data:
Now I tried the following comparator circuit(with LM2903) where I set the threshold to 8V with a hysteresis of around 35mV, and fed the 4kHz above sampled input to the circuit as PWL.
Here the comparator triggers **broken link removed**.
Below shows the input as the sampled voltage from the transducer, the non-inverting input which shows the hysteresis level, and the heater current in order.
Here is my question:
Here is the datasheet for the transducer.
Now this sensor is set to 0-10V output and I wondering how would floating input turns off heater for this circuit. Is connecting 560k or 1Meg to Vcc load the transducer or damage it? Transducer output can be anything between 0 to 10V.
If there's no fundamental problem with this circuit, I just need to control something better than or same as a human doing. Normally when I see the temperature exceeds 40°C I turn off off the heater with my hands and when lower than 40°C I turn on on heater. I act like a comparator and SSR. So I need to automatize it instead of staying there for one hour. And it is fine for my purpose. Then I turn off the heater after making a measurement .
How can I obtain heater off when the input is floating? I'm not sure if the R5 connected to Vcc is a good idea. Because if the input floats the heater will run forever.
Here below is raw voltage output of the temperature transducer when it is heating and cooling around 40°C(sampled at 4kz):
Here is a close view of the raw data:
Now I tried the following comparator circuit(with LM2903) where I set the threshold to 8V with a hysteresis of around 35mV, and fed the 4kHz above sampled input to the circuit as PWL.
Here the comparator triggers **broken link removed**.
Below shows the input as the sampled voltage from the transducer, the non-inverting input which shows the hysteresis level, and the heater current in order.
Here is my question:
Here is the datasheet for the transducer.
Now this sensor is set to 0-10V output and I wondering how would floating input turns off heater for this circuit. Is connecting 560k or 1Meg to Vcc load the transducer or damage it? Transducer output can be anything between 0 to 10V.
If there's no fundamental problem with this circuit, I just need to control something better than or same as a human doing. Normally when I see the temperature exceeds 40°C I turn off off the heater with my hands and when lower than 40°C I turn on on heater. I act like a comparator and SSR. So I need to automatize it instead of staying there for one hour. And it is fine for my purpose. Then I turn off the heater after making a measurement .
How can I obtain heater off when the input is floating? I'm not sure if the R5 connected to Vcc is a good idea. Because if the input floats the heater will run forever.