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Topic: 230V AC controll with arduino and relays (now dead arduino) (Read 5 times) previous topic - next topic

Fuge

Most of the arduino circuitry I've seen that interfaces with relays include some protection circuit that includes transistors (to help limit the current requirement at the arduino pins and still let it talk to the relay) and diodes for back EMF current protection. One of the first results that just showed up in my google search is this http://arduino.cc/playground/Main/ArduinoPinCurrentLimitations

You should check to make sure that something in your system is not pushing the current above that specified for the pins - check this http://arduino.cc/playground/Main/ArduinoPinCurrentLimitations

dc42


Sounds like a snubber network is needed across the relay contacts - large inductive spikes could be causing the problem at switching times.


I think he needs to determine whether the problem ocurs when switching the relay on or when switching it off. If it occurs when switching the relay off, then i think your suggestion of a snubber network is a good one. If it occurs when switching the relay on, then the problem is more likely to be inrush current due to capacitors in the load charging. In this case, the solution would be to add inductance in series with the relay contacts, or (preferably) replace the relay with a zero-crossing SSR.
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terryking228

Hi,
Many modern power devices like the charger have switch mode power supplies and big input power filters with large capacitors across the line.  Inrush current can be really high and cause transients that lock things up..

Plugging my laptop power supply in often makes a loud POP and sometimes a spark. Some BIG capacitor across the line.

See if the problem is the same with relay on-off and the units "power switch" on-off. Some units have their own on-off switch located AFTER the line filter capacitors so less inrush current (for THEM..).. You might dig inside and put you relay across their existing on-off switch.

Might be good here to use opto-isolated relays like these: http://goo.gl/Hu1I5

DISCLAIMER: Mentioned stuff from my own shop...
Regards, Terry King terry@yourduino.com  - Check great prices, devices and Arduino-related boards at http://YourDuino.com
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fca

5 Months later and another arduino gets "crazy"  switching on/off my ups grrrrrrrrrr i will have to check what went bad this time....
it seems that was the pin the the controlled the relay...
Im changing the relay with optoisolated with optocoupler 817c ...
what else can i do protect the arduino ?

thanks

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