Pic 16F887 resets when 2nd relay opens

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runman_up

New Member

• Jun 16, 2011

• #1

I have an application with a microcontroller activating two 5V relays through transistors - they activate fine from transformer/bridge rectifier regulated power no problem - I just get the problem when they turn off - after the second relay turns off it resets the pic chip! Do i need extra diode or something in there? The relays each have a protection diode on them.

Help

 

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Pommie

Well-Known Member

Most Helpful Member

• Jun 16, 2011

• #2

Do you have decoupling capacitors? Can you post your schematic.

Mike.

 

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runman_up

New Member

• Jun 16, 2011

• #3

Yes - a 0.1 mf capacitor at the ground to positive at the pic - I have a smoothing capacitor before the regulator of 1000mf. Sorry schematics pretty poor currently so bear with me.- I am new to this - how do I post a picture from my hard drive?

 

Last edited: Jun 16, 2011

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KeepItSimpleStupid

Well-Known Member

Most Helpful Member

• Jun 16, 2011

• #4

use "Go advanced/Manage attachments". It may take a day or so to be able to post pics for new members.

 

aljamri

Member

• Jun 16, 2011

• #5

Hi runman,

your picture has to be somthing like .gpj or and put say on desktop, press Go Advanced button, scroll down and find 'Attachments Managments' where Browse for your picture and upload it.

thats it

 

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Wp100

Well-Known Member

• Jun 17, 2011

• #6

Hi,

Apart from a schematic, what load is the second relay switching ? - are you using any supressors ?

Also do you have any input switches on long wire leads or a reset switch on Mclre ?

 

Mosaic

Well-Known Member

• Jun 17, 2011

• #7

A snubbing/freewheel diode rev. biased (1n4001) across the relay coil is essential!

 

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runman_up

New Member

• Jun 17, 2011

• #8

Supressors/MCLRE

Thanks!!!
I am using a reversed diode across the activating relay coil.

what load is the second relay switching ? probably 2 or 3A on the AC side - Using any supressors ? No - not sure what they are

Any input switches on long wire leads? Yes a foot long 22 ga- or a reset switch on Mclre ? No I did not seem to need it.