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Discussion Starter · #1 ·
I know what you're thinking. Really Dustin? Another Arduino post? Yes, sadly I do have another problem that I need some help with. I built my Arduino and it works just fine till I apply power to my relays. Without 12v DC connected the relays trigger just fine every time but with 12v DC connected sometimes they will miss fire (not open for as long as programmed to) or the Arduino will reset itself. So sometimes in the middle of a scare cycle it will just stop and then start back up again a moment later. The funny part is that I built 2 Arduinos and they both do this.

Secondly, only one of my Arduinos does not work correctly when running off a power supply. With the Arduino connected to my PC all the relays fire correctly but when connected to my 5v 2a power supply only relay 1 and 3 work. All of the LEDs light up but the internal switches in relay 2 and 4 don't engage. It's funny how it works just fine when getting power from the PC.
 

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In the first part of your post, it sounds like more of a power supply issue. Are you powering the wiper motor? What's the rating of your power supply?
 

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Can you use an LED with a resistor in place of the wiper motor just to check the operation of the relays?
 

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BTW, RoHS is not a brand, it's a compliance guideline. Some power supplies don't live up to their stated rating.
 

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Are you using pullup/down resistors in your circuit? Floating pins can cause this exact issue. Are you able to post a diagram?
 

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Your second issue, would the arduino you are using happen to be an UNO? If it is, you need a separate power supply with a higher voltage than 5 volts. While the usb connection is rated for 5 volts, the DC jack input needs 7-12 volts due to the on-board regulator circuit. The problem you are having may be caused by the voltage being too low. Try a 9 volt supply and see if that fixes it.
 

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Discussion Starter · #11 ·
BTW, RoHS is not a brand, it's a compliance guideline. Some power supplies don't live up to their stated rating.
lol Learn something new every day.

Are there snubber diodes across the relay coils on that shield?
Sorry man I'm an Aircraft mechanic that's still trying to lean electronics. I have no idea.

Your second issue, would the arduino you are using happen to be an UNO? If it is, you need a separate power supply with a higher voltage than 5 volts. While the usb connection is rated for 5 volts, the DC jack input needs 7-12 volts due to the on-board regulator circuit. The problem you are having may be caused by the voltage being too low. Try a 9 volt supply and see if that fixes it.
Yeah they both are an UNO. Ok I'll drive by goodwill and see what I can find. Funny, the other one works fine with 5v of power.
 

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Discussion Starter · #12 ·
Well that was a fun trip to goodwill! I got a fog machine for $7.

I got a 12v 1.5a power supply. Will that work?
 

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Funny, the other one works fine with 5v of power.
Component tolerances are lenient on this arduino stuff. If the circuit is under-powered and one relay shield is drawing more current than the second, it could cause your problem on the first unit and not the other. You could always swap relay shields from one uno to the other to test that theory.

Sounds like a cool project you are working on!
 

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Discussion Starter · #15 ·
It should work fine, just make sure the polarity is correct.

That's a steal of a deal for a fog machine!
You sir are correct! That fixed my problem with the relays. Now if I can just find out they my board likes to reset its self from times to time.

Sadly the fog machine is not working. Ill have to crack it open later tonight.

Thanks for all your help!
 

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As I've mentioned, I don't use Arduino's but Ski0204 is spot on with the voltage input. There's a regulator on the UNO that supplies 5v to the processor. The input voltage needs to be at least 7v or the regulator can't supply 5v to the processor. If the processor voltage drops below what is required for it to function, it will reset.
 

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Discussion Starter · #18 ·
I'll try running the Arduino that I'm using on sitting Zombie with the 12v power supply and see if that helps. I get this same problem even when connected to my PC.
 

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Discussion Starter · #19 ·
I ran it a bunch of times with the 12v power supply and it never reset once. Guess that fixed both of my problems!
A quick google search shows that the USB on your PC only puts out 5v. Guess that's why I was having same same problem powering it both ways.
 
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