pic PIC16f877A resets due to external noise

Posted on Feb 5, 2014

Connect Relay with pic microcontroller and whenever I put Load on Relay`s Contacts PIC16f877a resets. I some time solve this problem by triggering another relay from basic relay attached to PIC. But this is not a solution. Can any one describes Why pic is affected with this relay spark. And what is really happening which causes pic to reset. Following things I have kept in mind while building circuit I never faces such

pic PIC16f877A resets due to external noise
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problem in Atmel 89c51 microcontroller with same relay interfacing circuit. It is PIC who goes reset every time. But if do not connect any load to relay the circuit works fine. No reset occurs. Can any-one describes what is the issue with PIC 1. A schematic helps visualize what has been implemented, far better than a series of textual bullet points. 2. Replace the 1n4148 with a Schottky barrier diode like the 1n5819. 3. Try putting a capacitor (try 10 uF) across the diode. Anindo Ghosh Mar 12 `13 at 11:08 I have had this problem before. It was because of the collapsing on the power supply. Put a 10 uF capacitor on the Vdd power rail, and most probably your problem will be solved. Also, to avoid SR latch-up, as @Kaz noted, Microchip suggest an RCR network. Look for this information in the datasheet of your microcontroller. abdullah kahraman Mar 12 `13 at 11:23 @AbdulRehman Try increasing the capacitor to 100uF. For the replacement on 1N4148, search for "Flyback diode". About grounding. Every cable/trace has a resistance, but very small. However, with sufficient current, there can be a voltage drop. This means the ground will be at a higher potential than 0 volts. abdullah kahraman Mar 12 `13 at 12:41 @AbdulRehman While several excellent inputs have been provided already, hence my prior comment may be irrelevant, my suggestion for a Schottky comes from trying to alleviate flyback pulses from the relay coil at the source....

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