Relays needed in the PCB design for my smart car

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Relays needed in the PCB design for my smart car

Postby mantosa » Mon Jan 09, 2017 11:28 pm

Hello
I am in the process of designing a PCB that incorporates a microcontroller, LEDs, capacitive sensors and relays to control light in my smart car. I have taken this picture as my reference.I have the little stuff worked out and have it prototyped and working, but I want some outside input on the relays on the board.
The relays are S2-L2-24v 4A NAIS relays. They are triggered by the microcontroller when it receives a certain input.(I take this datasheet as my reference: http://html.alldatasheet.com/html-pdf/132762/NAIS/RA-RELAYS/98/1/RA-RELAYS.html)
I want to make sure that I have adequate trace widths to support the relays when an auxiliary component is triggered. Right now I plan to use 1 oz copper for the board when I have it printed (trace width is 150 mil on the relays and power). I have attached the PCB design to this post.
Each individual relay would have a max of 1A /30V on it, and all power lines on the board are fuse protected. In all reality, it is likely that only one relay would be on at a time.
I am new to incorporating these things in to a PCB, so I may be approaching this completely wrong. Am I using the right relays? So any suggestion will greatly be appreciated!
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Re: Relays needed in the PCB design for my smart car

Postby davep238 » Tue Jan 10, 2017 8:10 am

mantosa wrote:Hello
I am in the process of designing a PCB that incorporates a microcontroller, LEDs, capacitive sensors and relays to control light in my smart car. I have taken this picture as my reference.I have the little stuff worked out and have it prototyped and working, but I want some outside input on the relays on the board.
The relays are S2-L2-24v 4A NAIS relays. They are triggered by the microcontroller when it receives a certain input.(I take this datasheet as my reference: http://html.alldatasheet.com/html-pdf/132762/NAIS/RA-RELAYS/98/1/RA-RELAYS.html)
I want to make sure that I have adequate trace widths to support the relays when an auxiliary component is triggered. Right now I plan to use 1 oz copper for the board when I have it printed (trace width is 150 mil on the relays and power). I have attached the PCB design to this post.
Each individual relay would have a max of 1A /30V on it, and all power lines on the board are fuse protected. In all reality, it is likely that only one relay would be on at a time.
I am new to incorporating these things in to a PCB, so I may be approaching this completely wrong. Am I using the right relays? So any suggestion will greatly be appreciated!

S2-L2-24v appears to be a _latching_ relay with a 24vdc coil. I found a datasheet here: http://www.newark.com/panasonic-electri ... dp/24M8044.
The datasheet you linked to is a SMT _microwave_ relay, which is not what you want. Neither relay bares any resemblance to your PCB layout. BTW, you can run some red traces to the RJ45, instead of all blue traces. can you also post the schematic diagram?
-Dave Pollum
programmer / digital designer
PCBs designed for low cost
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Re: Relays needed in the PCB design for my smart car

Postby DanV » Tue Jan 10, 2017 9:47 am

@davep238 - the Newark part is 12VDC (not 24VDC)

"S2-L2-12VDC Power Relay, DPST-NO, DPST-NC, 12 VDC"
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Re: Relays needed in the PCB design for my smart car

Postby DanV » Tue Jan 10, 2017 10:42 am

The closest Newark part I found was at
http://www.newark.com/omron-electronic- ... chDocsHook
But it has blade looking pins (0.8 x 2.8 mm (0.030" x 0.109") (although it says through-hole, solder) and current rating is not shown.
The datasheet:
http://www.farnell.com/datasheets/18302 ... 1377176169
says "Min. Carry / Switching Current DC12V 1A"
also "Continuous carry current 15A"
Some discrepancy in the ratings.
I would think a silver composite contact rated for 15A could switch less than 1 A without an issue.
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Re: Relays needed in the PCB design for my smart car

Postby n1ist » Tue Jan 10, 2017 5:37 pm

The minimum current is to clean the contacts and break down any oxide buildup. Otherwise, you can end up with a higher contact resistance at low currents.
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Re: Relays needed in the PCB design for my smart car

Postby mantosa » Tue Jan 10, 2017 8:39 pm

davep238 wrote:S2-L2-24v appears to be a _latching_ relay with a 24vdc coil. I found a datasheet here: http://www.newark.com/panasonic-electri ... dp/24M8044.
The datasheet you linked to is a SMT _microwave_ relay, which is not what you want. Neither relay bares any resemblance to your PCB layout. BTW, you can run some red traces to the RJ45, instead of all blue traces. can you also post the schematic diagram?

Thanks for reminding. It's mistake for posting a wrong datasheet link.
And with your recommendation,I found another one with 12 VDC: G8VA-1A4T-R01-DC12
Reference here: http://www.kynix.com/uploadfiles/pdf882 ... 1-DC12.pdf. Do you think this one will also be suitable?
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Re: Relays needed in the PCB design for my smart car

Postby mantosa » Tue Jan 10, 2017 8:44 pm

DanV wrote:The closest Newark part I found was at
http://www.newark.com/omron-electronic- ... chDocsHook
But it has blade looking pins (0.8 x 2.8 mm (0.030" x 0.109") (although it says through-hole, solder) and current rating is not shown.
The datasheet:
http://www.farnell.com/datasheets/18302 ... 1377176169
says "Min. Carry / Switching Current DC12V 1A"
also "Continuous carry current 15A"
Some discrepancy in the ratings.
I would think a silver composite contact rated for 15A could switch less than 1 A without an issue.


I also found one as same as you recommended.(http://www.kynix.com/uploadfiles/pdf882 ... 1-DC12.pdf.)
I will take your words as reference. Thank you very much. :wink:
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Re: Relays needed in the PCB design for my smart car

Postby DanV » Wed Jan 11, 2017 8:27 am

n1ist wrote:The minimum current is to clean the contacts and break down any oxide buildup. Otherwise, you can end up with a higher contact resistance at low currents.

Well, I am familiar with that concept, just seems like 1 A is fairly high.
Most relay contacts have a bit of wiping action as they flex during make/break to assist in such matters.
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