Capacitor help!!

Good day everyone! I was wondering how would i use a capacitor with arduino. I am currently working on a project that uses a 24VDC supply , regualted to 12Volts .The 24vdc is used to supply current to my relay, which then activates a solenoid. Now here's the problem: I have a LCD connected as well, which displays a changing variable like weight(using load cells) and when the relay is activated, the lcd screens have weird characters popping up. It happens some time and sometimes not. I have also connected a diode through the pin and gnd for the relay but it dosent seem to help. I was wondering if a capacitor near before the Vin pin and after the Powersupply would help, but if so, how do i do this?

Post schematic of what you have now, so we can be sure we're all on the same page.

This is the only schemtic i have for now , ( kinda makeshift), but my full schemtic is too large and cant be seen clearly.

Look like you're trying to drive a relay directly from an Arduino pin? That's definitely a bad idea.

[u]Here is a MOSFET driver circuit[/u]. It could be used to drive a relay coil, or in your case it could drive the solenoid coil and you could ditch the relay. (Just make sure the MOSFET has a higher current rating than the solenoid.)

...The diode suppresses the high-voltage back-EMF when the relay (or solenoid) switches off. So if the display only glitches when relay or solenoid is switched-off, that's a clue.

BTW - Probably not related to your problem, but the solenoid coil should also have a fly-back diode. (In your circuit it would prevent arcing of the relay contacts, which could shorten the life of the relay.) Just about any time you power a coil with DC you should have a diode.

MarkT:
Look like you’re trying to drive a relay directly from an Arduino pin? That’s definitely a bad idea.

DVDdoug:
[u]Here is a MOSFET driver circuit[/u]. It could be used to drive a relay coil, or in your case it could drive the solenoid coil and you could ditch the relay. (Just make sure the MOSFET has a higher current rating than the solenoid.)

…The diode suppresses the high-voltage back-EMF when the relay (or solenoid) switches off. So if the display only glitches when relay or solenoid is switched-off, that’s a clue.

BTW - Probably not related to your problem, but the solenoid coil should also have a fly-back diode. (In your circuit it would prevent arcing of the relay contacts, which could shorten the life of the relay.) Just about any time you power a coil with DC you should have a diode.

hello! thanks for the reply. And yes the LCD only glitches when the solenoid goes off… anyway do you reccomend changing to the MOSFET driver and ditching the relay?

If you want isolation, keep the relay and drive it with the Transistor.

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