How do I get my Sensor Switch transistors

cmartinez

Joined Jan 17, 2007
8,218
Alright Rod, I think I got it. I was able to add about 50mV of hysteresis to the circuit. Which is roughly 1.5% of the sensor's complete range... I think that value should be about right. What I did is eliminate the 4.7K pull ups at the comparators' outputs, and then placed a 1M feedback resistor into its negative input. This should drop the voltage at the negative input just enough to add hysteresis.

So no... no Op Amps or expensive extra pieces are needed anymore!

Capture.JPG

It is very important that you tell me what you intend to do with this circuit, since maybe we need to invert the way it works at this point due to the nature of your process.

Can you explain to me the sequence of events that you want to control?
 

Thread Starter

RodneyB

Joined Apr 28, 2012
697
Alright Rod, I think I got it. I was able to add about 50mV of hysteresis to the circuit. Which is roughly 1.5% of the sensor's complete range... I think that value should be about right. What I did is eliminate the 4.7K pull ups at the comparators' outputs, and then placed a 1M feedback resistor into its negative input. This should drop the voltage at the negative input just enough to add hysteresis.

So no... no Op Amps or expensive extra pieces are needed anymore!

View attachment 89347

It is very important that you tell me what you intend to do with this circuit, since maybe we need to invert the way it works at this point due to the nature of your process.

Can you explain to me the sequence of events that you want to control?
Basically to start off I want to monitor the humidity and temperature. This is second stage the temperature. At certain temperature and humidity levels I will get a notification. I will be using the wilsarm to send me the notification. Depending on the humidity I may want to either switch in a fan to blow air, a humidifier, or sprays. At extreme cases I will need to switch all three on fan sprays and humidifier. I also want to have a low humidity and high humidity alarm. Thus the need for 5 outputs.
 

cmartinez

Joined Jan 17, 2007
8,218
Basically to start off I want to monitor the humidity and temperature. This is second stage the temperature. At certain temperature and humidity levels I will get a notification. I will be using the wilsarm to send me the notification. Depending on the humidity I may want to either switch in a fan to blow air, a humidifier, or sprays. At extreme cases I will need to switch all three on fan sprays and humidifier. I also want to have a low humidity and high humidity alarm. Thus the need for 5 outputs.
Yes... but are you turning the fans on to lower the humidity? And I assume, of course, that the sprays and humidifiers are there to increase the humidity (of course!)
 

Thread Starter

RodneyB

Joined Apr 28, 2012
697
Yes... but are you turning the fans on to lower the humidity? And I assume, of course, that the sprays and humidifiers are there to increase the humidity (of course!)
the fan is to lower the Humidity. It is essential that only one output is on at a time
 

cmartinez

Joined Jan 17, 2007
8,218
I think I understand...

These are your outputs, and their functions the way I understand them:
  • Fan output to lower humidity
  • humidifier to increase humidity
  • sprays to increase humidity
  • low humidity alarm
  • high humidity alarm
Is this correct?
 

Thread Starter

RodneyB

Joined Apr 28, 2012
697
I think I understand...

These are your outputs, and their functions the way I understand them:
  • Fan output to lower humidity
  • humidifier to increase humidity
  • sprays to increase humidity
  • low humidity alarm
  • high humidity alarm
Is this correct?

Yes that's correct for the alarms I am going to use sirens with different pitches. I will pickup an output for the notify unit from the comparator.
 

cmartinez

Joined Jan 17, 2007
8,218
Yes that's correct for the alarms I am going to use sirens with different pitches. I will pickup an output for the notify unit from the comparator.
Ok, let me tweak the circuit a bit and then I'll get back to you... at what voltage will the alarms be working?
 

cmartinez

Joined Jan 17, 2007
8,218
They 12 volt sirens
Ok... now I've got enough information to configure every output of your circuit.

You said that:
It is essential that only one output is on at a time
The thing here is that your circuit will sometimes have several outputs on at the same time, for instance:

In the case of extremely low humidity you will have:
  • Low humidity alarm activated
  • Humidifier activated
  • Spray activated.

In the case of extremely high humidity you will have:
  • Fan activated
  • High humidity alarm activated

Is this correct?
 

Thread Starter

RodneyB

Joined Apr 28, 2012
697
Ok... now I've got enough information to configure every output of your circuit.

You said that:


The thing here is that your circuit will sometimes have several outputs on at the same time, for instance:

In the case of extremely low humidity you will have:
  • Low humidity alarm activated
  • Humidifier activated
  • Spray activated.

In the case of extremely high humidity you will have:
  • Fan activated
  • High humidity alarm activated

Is this correct?
Ok I see from the diagram that each individual piece of equipment is independently switched. So this will not be a problem.

Is my understanding correct that as the voltage increases or decreases from the sensor, the corresponding outputs go on or off.
 

cmartinez

Joined Jan 17, 2007
8,218
Ok I see from the diagram that each individual piece of equipment is independently switched. So this will not be a problem.

Is my understanding correct that as the voltage increases or decreases from the sensor, the corresponding outputs go on or off.
So far, yes. The circuit will start turning on the outputs as the sensor detects more humidity. That's why I needed to know the logic behind your design. Because you want some outputs to turn on as the humidity decreases...
But with what you've just told me, I have enough information to draw you a more complete circuit.

Last question, do you have the siren alarms yet? do you know how many amps they'll consume? What's the working voltage of the valve that will control the sprays?
 

Thread Starter

RodneyB

Joined Apr 28, 2012
697
So far, yes. The circuit will start turning on the outputs as the sensor detects more humidity. That's why I needed to know the logic behind your design. Because you want some outputs to turn on as the humidity decreases...
But with what you've just told me, I have enough information to draw you a more complete circuit.

Last question, do you have the siren alarms yet? do you know how many amps they'll consume? What's the working voltage of the valve that will control the sprays?
One siren is 420mA the second is 190mA

The pump sprays I don't know at this stage as I am still trying to source a suitable unit
 

cmartinez

Joined Jan 17, 2007
8,218
One siren is 420mA the second is 190mA

The pump sprays I don't know at this stage as I am still trying to source a suitable unit
No problem... your pump can be any voltage you want, but I suggest you look for a 220VAC pump unit, just to be consistent with the rest of the circuit.
 

Thread Starter

RodneyB

Joined Apr 28, 2012
697
No problem... your pump can be any voltage you want, but I suggest you look for a 220VAC pump unit, just to be consistent with the rest of the circuit.
Once we have this up and running I would like to start working on a Humidity Monitor using an LCD
 

cmartinez

Joined Jan 17, 2007
8,218
Here's the latest circuit, if I understand your logic correctly. Both high and low humidity alarms work at 12V and employ transistors instead of triacs for their switching.

Feel free to ask any questions.

Capture.JPG
 
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