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PSoC 5, 3 & 1 MCU

Anonymous
Not applicable
        Hi, I've got a 5v microcontroller relay module, im using an external 5v supply for the transistor circuit of the relay. I also have an lm35 temperature sensor reading the temperature in the same project. The relay input seems to be active low as it seems that writing a 0 to the control pin of the relay will activate it. The problem is that when i activate the relay the temperature reading changes by a few degree. I see that the voltage supply to the temperature sensor drops slightly when activating the really changing the output temperature. Any advice on how to remedy this? Thanks Guys   
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Honored Contributor II
        Without a schematic of the relay and the power supply it is just a guess as to the cause. But it appears to be a drop in the voltage. You could try a larger cap on the supply or a larger current supply. Maybe some diodes to shunt voltage spikes from the relay coil. Post your project so we can analyze the issue.   

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Honored Contributor II
        Without a schematic of the relay and the power supply it is just a guess as to the cause. But it appears to be a drop in the voltage. You could try a larger cap on the supply or a larger current supply. Maybe some diodes to shunt voltage spikes from the relay coil. Post your project so we can analyze the issue.   

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Honored Contributor II

Post your schematic also. You didn't  mention which direction temperature changes when relay activated. I suspect that PSoC's ADC setting used is  Vref=Vdda/2, affecting voltage measurement.

Honored Contributor II

I second @oddisey1 - use one of the internal reference voltages as ADC reference. E.g. using 1.024V Vref, which will even give you higher resolution and precision.

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