Do I need resistors?

Hi everyone

I'm building a temp sensor and thermostat for 4 reptile cages It's pretty simple

I'll connect 4 lm35 temp sensors (0-100ºc) to the analog pins, each monitoring different reptiles terrariums. At the same time, i'll connect a 4 relay module (octocoupler) that will turn on/off 4 different 110v heat tapes in each terrarium.

Do I need resistors somewhere in this circuit? Where? And how many ohms?

Thank you a lot

No resistors needed.

just be sure to wire those relay's correctly

|500x164

I've noticed that a 1k resistor between LM35 output and analog input pin helps with "jitters", also a 100nF ceramic capacitor from analog in pin to GND doesn't hurt. You would get better resolution using the internal 1.1V analog reference than the default VCC. @Hutkikz: Good point on the relays.

Hutkikz: No resistors needed.

just be sure to wire those relay's correctly

|500x164

Thank you all for the answers

I can't understand this diagram. Do I need to connect the separate DC supply AND the VCC connection to the Arduino?? Not only one?

Since you are dealing with 'life' make sure you have a fallback circuit.

.

Internal connections are probably similar to this:
Typical relay module connections.jpg

Do I need to connect the separate DC supply AND the VCC connection to the Arduino?

No, VCC goes to the Arduino 5volt.

JD-VCC goes to the separate 5 volt power supply.

Do not connect the ground from the relay board to the Arduino.

As CrossRoads picture shows This keeps the load power isolated from the Arduino.

CrossRoads: Internal connections are probably similar to this:

Or a trifle neater, |500x205