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I have built a stand alone Arduino type board. It will run all day long as long as no actuator is hooked to the relays, the voltage on a voltmeter shows when the motor changes direction properly. The problem is when I actually hook up an actuator (9amp), I'm using a 10amp relay it will run for a bit (no set time, it changes) then just stop. I have hooked up a Oscilloscope to the 5v vcc line of the 168P chip and when the relays change state I get quite a bit of garbage on the scope when the relays change state, it shows the min voltage spikes anywhere from +8 to -12 volts, sometimes this freezes the board, sometimes it resets the board. Could someone look at my schematic and give me some clue as to what to look for? and any input to make it better? I am pretty new at this, so please, be easy on me. :)

The board runs off an Arduino sketch which is nothing more than a switch that tells the actuator to go up, wait 5 secs and go back down and wait until the button is hit again. Like I said, works perfect as long as no actuator is hooked up to the relays.

The board is setup with a jumper J56 and J70 that puts the relays connected to I/O 5 and 6 on the processor.

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mScientist
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  • Try it with a separate power supply for your actuator. Is this design well-implemented physically, eg, are your bypass caps right at the chip power pins? It kind of looks like you used *thing traces* instead of *power planes* for supplies, which is unfortunate. – Chris Stratton Oct 02 '20 at 17:30
  • Switching 9A motor, on that PC board, really? Yes, no wonder. The traces are far too thin for 9A load, I am surprised they did not melt already. And no snubber of any kind over the motor pins or relay contacts. The relay contacts would arc and spark during switchover, radiating electromagnetic interference, affecting the nearby AVR directly, or the I2C buses so the AVR actually is just waiting for some I2C transaction to complete. What is the relay type and coil voltage? Will the VD provide enough current when relay is actuated? – Justme Oct 02 '20 at 17:48
  • Have a read of [Switching HV DC relay on crashes microcontroller](https://electronics.stackexchange.com/questions/308379/switching-hv-dc-relay-on-crashes-microcontroller/308416) – TonyM Oct 02 '20 at 18:00
  • That is for a relay that sends the voltage one way. Plenty of people talking about snubbers etc but my relay changes the polarity of the 12v to bring the actuator back down – mScientist Oct 02 '20 at 22:14
  • Very confused by your comment. (1) 'That is for a relay' - what's the 'that' you refer to? (2) Two of us mentioned snubbers - but what's your point there? (3) Do you understand the suggestions put forward to you? – TonyM Oct 02 '20 at 22:26
  • The snubbers conversations only talk about when the relays are not switchng from 12v to -12v. Only for just supplying positive voltage. The traces for the 9 amps for the relays are a lot larger, i used a trace calculator to determine the width for those. I do have smaller traces but only for the 5v lines. I will post the relays im using in a bit. They are 10 amp relays. The max amps for the actuator under full load is 9 amps max. – mScientist Oct 02 '20 at 23:52
  • Either that or i still dont understand what a snubber is. I do have a diode across each relay. – mScientist Oct 03 '20 at 00:56
  • the relays I am using are g5le. The bypass caps are actually taken straight from the Uno Rev 3 schematics so I figured they have to be right. – mScientist Oct 03 '20 at 01:27
  • Well, Googling snubber before you posted long comments doesn't sound exhausting, does it :-) The site isn't a discussion forum and this is a lot of comments getting nowhere. So, let's continue the start that got skipped: please can you Google 'snubber circuit relay' and read and learn that, read the linked answer I posted and answer each of my questions briefly and directly. *"and any input to make it better? I am pretty new at this"* I'm not so let's use the methodical, engineering approach and get solid progress and results. – TonyM Oct 03 '20 at 09:06
  • Okay, i did Google it but isn't it the same as the diode i have across the relay coil? I have the schematic, couldn't it have been easier to look at it and help with some constructive criticism instead of the type of comments your posting? I know it's a 12v coil in there relay, I'm turning it on by a transistor, i see when the videos and Google talk about the mH produced by the coil but i don't see that info in the datasheet for the relay (g5le) – mScientist Oct 03 '20 at 15:58
  • *"couldn't it have been easier to look at it and help with some constructive criticism instead of the type of comments your posting"* Look, you've got a bit silly, I've offered constructive and clear direction but you're posting replies on everything but what I'd suggested. The site's for helping you solve it yourself, not a personal tutorial to solve it for you, nor a free design house. Anyway, there's no sign of progress after 7 comments so I'll wish you well and leave you to it. – TonyM Oct 03 '20 at 16:36
  • Im sorry, but you just linked to another question whose answer was install a snubber. – mScientist Oct 03 '20 at 16:50
  • Oh, and "that" was referring to the like you sent. After re-reading, i take it i was thinking the snubber went on the swich side of the relay, not the coil sure. – mScientist Oct 03 '20 at 17:02

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