I'm building a breathalyzer using the mq303a , and I'm not sure how to wire it for preheat
Use it in a normal way, with heater and analog output connected.
It needs 0.9V for the heater. Do you have that ?
Then keep it on for at least two days. That is the preheat time.
It is said in the datasheet that if i give 2.2±0.2V high voltage for 5-10secs it is enough ,
since i couldn't get the 2.2 I gave it 1.8V but i didn't tested it yet
I read in that datasheet that it must have 0.9V and that the Preheat time is over 48 hours.
That is how the preheat should be used, the normal circuit with the normal voltage for many hours.
The datasheet is confusing. They should have called the 48 hours: “burn-in”, and the heating up to get stable data should be called: “heating up”, or something like that.
The 48 hours should be done just once after buying it.
That must be done with the 0.9V, not with the 2.2V.
Something else is that the sensor needs to heat up for the output to be stable. That is a few minutes.
Under Fiq.2 is a note that it can be reduced to 5-10 seconds with 2.2V.
Are you sure you want to try that ? If the make a mistake and keep the 2.2V on for a longer time, perhaps the sensor could get damaged.
Is your question how to get 0.9V and 2.2V ?