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5v relay module advice | Cypress Semiconductor

5v relay module advice

Summary: 3 Replies, Latest post by hli on 03 Apr 2016 01:18 PM PDT
Verified Answers: 2
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Cfcorp's picture
33 posts

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

user_242978793's picture
969 posts

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.

user_342122993's picture
530 posts

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.

user_78878863's picture
2553 posts

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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