IR sensor in car climate system..any experiences ?

[valeolan]

I have to implement an IR sensor for a car climate system.
I feel it quite sensitive, do you have any experiences on:
-where to locate the sensor
-errors not to do

etc..

 

[BigAl1956]

you need to be a little more spacific.

 

[SolidStateAutomotive]

Hi Valeolan,
For Infrared IR temperature measurement in the automotive environment, especially automotive interior, there are 2 main approaches in the market today.
- Mount the IR sensor in the dashboard. (Toyota compact car)
- Mount the IR sensor in the overhead module e.g. near the dome light or the rear view mirror (Dodge Durango)

The advantage of having the IR sensor in the dash is simple. Low cost! The wiring is very easy because the control unit usually sits behind the facia/dashboard in the centre unit and so the IR sensor can be directly wired.
The disadvantage is that the lower the IR sensor sits in the vehicle, the more susceptible to stray reflections it will be.

The advantage of having the IR sensor mounted higher is that it will have no problems with reflections and as it is facing downwards there is less likelihood of any dirt ingress. Typically this application uses a tunnel aperture as this is most cost effective.

If the IR sensor is aimed directly at the centre of the person then this will give a good regulation performance. The part of the signal coming from the surrounding will give a very stable feedback.

Because the IR sensor directly measures the temperature of the person, and does so immediately – well at the speed of light anyway - a good air conditioning regulation algorithm can be implemented in a very small code space. Things like solar load are automatically compensated. It’s a very elegant solution. It is even possible to make a good regulation without regulation algorithms at all – there is no need to calculate air mass transfers and volume flows as in a traditional thermistor based system.

You can easily prototype a regulation scheme by taking a multiple comparator IC e.g. ALD4302 and combining it with some trimming pots e.g. Bourns 3296 series dropped across supply voltage to give switching points. The IR sensor input to the system e.g. SSR1002 should be compared as the high input.
Driving the output stages through FETs will then allow you to control the fan, switch the compressor and regulate coolant flow via a solenoid valve – or what ever you system requirement is.
Or of course add the inputs to a standard micro. You will not need anything too powerful as there are basically no algorithms to write! That’s the beauty of IR.

IR is also used in many industrial applications where it’s required to measure temperature of a moving target e.g. in the paper and printing industry – you can’t let a thermistor scrape along freshly printed wet ink to see if it is warm enough to dry out properly.
IR sensors have also been used in tire temperature monitoring very successfully.

A single sensor mounted adjacent to the tire surface can ‘see’ the rubber temperature and if multiple sensor are employed per wheel, the temperature gradient can be seen across the surface – useful to check suspension geometry set up, tire performance and wear as well as tire pressures on the race track.
I even read an article about an Astromega F3000 car using IR sensors to do ride height set up based on the plank temperature.

Hope the above helps – there is a lot more to tell. Contact me if you need more info!