In my project I am using a temperature sensor (LM35) whose analog o/p is being signal conditioned by psoc. The psoc design is working fine as long as the i/p signal given to it is from a potentiometer on the board. When I am giving the Vout of the temperature sensor to the psoc emulator board, it is not working. The UART is displaying default garbage values. Can anyone tell me what to do? (I have also given a common ground for the sensor and psoc kit). One more thing is, I would like to transmit the data collected from the sensor wirelessly. Preferrably a zigbee module low power and high range. Any suggestions for modules that are compatible with psoc?
What supply are you providing to the sensor? You can give the following circuit a try (as recommended in LM35 datasheet)-
You might need an amplifier stage before routing the input to the ADC to account for the input impedance. Add a PGA usermodule before the ADC and set its gain either to 1 or > 1.
This appnote might help in giving cleaner ADC readings - http://www.cypress.com/?rID=2894
thanx for the suggestions, I checked everything (connections) but there is one thing i observed. Initially i had set the adc full range at 2, for calculation of scale factor and displaying voltage value. ( since the full range o/p of my sensor is just 1.5 v ) but the values i got in the UART were wrong. It was sampling all right and if the temperature is increasing the UART value was also increasing but the adc count and voltage values are not correct. ( example: I am getting a 0.296 v sensor o/p which i am giving to the adcinc through a buffer- resolution is 12 bit so total of 4096 counts for full scale of 2 v- for 0.296 the count value must be around 606, but I was getting only 230 in UART) I checked the v out till the o/p of pga and everything seemed to be fine. then following trial and error i found that if iam varying the full scale range, my adc o/p is coming closer to the correct value. I have set the full range as 5.24 and now m getting an accurate value in the UART. Please tell me what happened and how? I dont understand at all.
ADC is working enough within voltage of Vss to Vdd.
Near Vss or Vdd that will become inaccurate.
That range is said rail to rail.
Cause from characteristics of transister.
See this picture.
This picture from ADC datasheet of PSoC3 and 5.
You have to add Bias voltage to sensor output,
That should be subtract from ADC output value.
This Bias voltage is called as Analog Ground.
You might consider posting a project here for forum top look at. "File", "Archive Project"
and post it.
Look at your global resources, ref mux setting, and the DelSig signed vs unsigned
setting. Signed is in twos complement, so your calculation of LM35vout is not a
simple bit weight calculation.
An antenna can make a big difference.
For example I am doing a Wireless Lan connection over 1.5 miles, 1W RF, with a
high gain antenna, usb port powered.
Just a thought.