Try to use Li-ION battery (3,7V) and MAX865 chip to get 5V.
Do you think it will work if I just use Li-ION battery (3,7V) with the micro-controller and transmitter.. and when I want the trigger the sensor, I just connect DC-DC convert to pump my digital output from micro-controller to 5V to sensor?
Or should I use the converter to get 5V to the micro-controller and also make a switch between 5V and sensor which can be controlled by digital output(High/Low signal)?
the sensor is using a heating coil for butane detection. its the main problem here, the batter will be drained in matter of minutes. an alternative may be , switch the sensor on for 5 secs, turn it off for maybe 15 secs and use PWM to control the heat to an optimum level.
Hmmm...interesting idea...but why to do that, use the pump all the time, efficiency is quite good.
you can control the heater temperature by driving it with a transistor. the base of the transistor can be connected to the pwm pin of the controller. You can turn on and off the sensor and can prevent overheating the sensor.
Like you said, it will drain the battery life so I am planning to turn the sensor on for 15-30s only (From my tested, it needed almost 30s to get to optimum heat level), then take sample and turn off the system including sensor pin for 20 minutes. That should prolong the battery life right? I'm not sure what you mean for the PWM to control the heat part though.. Please kindly explain..
The reason I also want to try with 1st option is because I have to turn on/off sensor in order to save battery but the the digital output from micro-controller is not 5V. So if I can just insert a DC-DC pump there, it would save the space from implementing another switch. However, I don't know if it will work or not.
So you mean I should go for 2nd option which is pumping the voltage direct from the battery to 5V and use it to supply the micro-controller. Then inserts a switch (BJT will do?) between 5V and sensor which can be trigger by digital output from micro-controller? (I have to turn on/off sensor in order to save battery)
If my understanding is not wrong, you said that the efficiency is good if I use the pump all the time? I will then go with the 2nd option then. Please suggest if the 1st option also work cause it would save space in the circuit.
Ok, I checked typical supply current of MAX865 pump and it is 0,6mA and it is quite large for this system. So, using the pump only for reading sensor is not bad idea. But, you have to know next: uC can work with Li-ION battery only if you implement sleep mode, next...you have to use analog switches for turning on transsmiter and sensor (easiest just allow power to pump and sensor)...my recommendation for switch is MAX890LESA because of 0,1uA conssumption, and the most important thing, you have to set refference for ADC of uC, if you use LI-ION direct on uC, reference will be variable.
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