Arduino PLC v0.20

The design for the Arduino PLC shield is coming together now.

I’ve removed the “flywheel” diodes from the relays as the ULN2803 already has them. I’ve added a simple +5V power supply and changed the Arduino footprint to the Seeedstudio clone so we get an extra two analog inputs. The standard Adrunio Duemilanove will work as well but you won’t get the extra two analog inputs. I don’t think the TLP521 can sink sufficient current to illuminate the input LED’s so I might added some transistors to do that or just remove the input LED’s completely.

The updated schematic is here:

arduino_plc 0v20

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2 Responses to Arduino PLC v0.20

  1. Tom says:

    Hey, great PLC schematic! I can’t wait to see the final version.

    I would love to the the resistor values on the analog input circuits and a description of the input jumper. Also, what types of inputs are they capable of receiving? Does the 4.7V zener limit it to 4.7V? What if I wanted to use a 0-5V input?

  2. Massimo says:

    hello. I love your schematic, but after realized, the optoisolator for the input do not function. I mean that I sobstiture the Resistor for the input with a 1K resistor and I remove the zener. I put the tlp521 pin number 2 to ground. When I give 12Vdc to the pin number 1 (thrue the 1K resistor) the ouput led switch ON, but if I connect the input pin of the Arduino, the led stay ON (also when the 12Vdc input are off) and the Arduino seems not to have a input selected. Do you have some ideas? What do not function? thanks a lot

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