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My first schematic of a 2-channel relay board

StealthRT

Sep 4, 2010
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Hey all this would be my first try at creating a schematic in KiCad.

The schematic is a basic 2-channel relay.

The inputs are automotive 12v and gnd. This gets converted to 5v by the K78L05-1000R3.

The Wemos D1 mini has 2 digital pin outs that are 3.3v going to the LTV-356T with a 200 kOhms resistor in between.

From there it goes to a 1k resistor and then to the PMBT3904. Between that and the G5LE-1 relay is a 1N4007F.

In that same area is another 200 kOhms resistor that’s connected to an LED.

The outputs and inputs are the 2pos and 4pos 3.5mm Pitch Terminal Block Connector 300V 8A.

Just want to make sure my values are good and the components I have selected are suitable for my application. Please let me know if I am missing anything or have a value incorrect. Thanks!
1696104012538.png

Question also asked on:
electronics-lab, allaboutcircuits, kicad, Elec. Stackexchange, electro-tech-online.
 
Last edited:

Kiwi

Jan 28, 2013
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Jan 28, 2013
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471
Left end of R5 and R12 need to go to pin 5 on the relays.
 

Bluejets

Oct 5, 2014
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As an exercise probably ok but I don't see the point in the whole arrangement.
A lot of gear that is unnecessary to make a relay activate.
Don't like the bias arrangement on the opto outputs either.
 

StealthRT

Sep 4, 2010
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Final schematic:
1) Removed LTV-356T Opto.
2) Added 10k between Base and Emitter of the PMBT3904.
3) Connected LED to 5v line instead of the collector line on the PMBT3904.
4) Replaced 200R with 220R.
5) Replaced normal fuses for blade fuse holders.
6) Replaced 18v G5LE-1 relay with the correct 5v relay G5LE-1A4 DC5 model.
7) Added a solder pad for the always on (AO) +12v line.

1696195262431.png
 

Bluejets

Oct 5, 2014
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At 3v3, 1k base resistor will more than likely be too high a value.
What is the purpose of the uC...???
 
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