driving 2 12v 2A DC motors with Mega

Did you follow the instructions to zero both ends of the scale first?

What is your interpretation of the indicated value?

yes I zeroed in both ends of the scale. it seems like it is 1.8 ohms.

1.8 Ohms sounds reasonable, in which case the start/stall current, operating from a 12V supply, would be around 6.7 Amps. A 10 Amp motor driver should work.

Or, follow this tutorial for a MOSFET driver bildr High-Power Control: Arduino + N-Channel MOSFET - bildr

Contrary to the advice given in that tutorial, you should use a logic level MOSFET, like the one recommended.

jremington: 1.8 Ohms sounds reasonable, in which case the start/stall current, operating from a 12V supply, would be around 6.7 Amps. A 10 Amp motor driver should work.

Or, follow this tutorial for a MOSFET driver http://bildr.org/2012/03/rfp30n06le-arduino/

Contrary to the advice given in that tutorial, you should use a logic level MOSFET, like the one recommended.

Ok so the tutorial makes good sense and all. Now On one of the motors I need to be able to connect the Optical sensor to the Single-head pump. This is what will controll on/off. So I would need to run the sensor in-line with the mosfet between the gate and the arduino?

Optical sensor to the Single-head pump

What optical sensor? I see no optical sensor in any of the links.

Is this a sensor that counts motor rotations or something else?

There are many types of "optical sensor". We need more information about your sensor. What is the sensor sensing?

So I would need to run the sensor in-line with the mosfet between the gate and the arduino?

No, you would connect the sensor to the Arduino, read the sensor with the Arduino and control the motor based on the data from the sensor and some rule(s).

So the sensor can be found at this link. And if I understand correctly I attach that separately to the Arduino and use the Arduino to read the optical sensor and then based on the reading of the sensor the Arduino talks to the motor?

https://www.amazon.com/Optical-Infrared-Sensibility-Controller-Marinecolor/dp/B00Z9NUJWW/ref=pd_nav_hcs_rp_t_1?_encoding=UTF8&psc=1&refRID=5TAZMG4NSD6FTGK8DA06

And if I understand correctly I attach that separately to the Arduino and use the Arduino to read the optical sensor and then based on the reading of the sensor the Arduino talks to the motor?

That is right.

Have you connected the sensor and can you read it?

I really don't have any idea how to properly connect the sensor. The 4 wires are all different. This is why am looking for advice on here. I honestly know nothing about how all of this is supposed to work.

For wiring and usage instructions, consult the technical or user manual that comes with the sensor.

Part of the issue is that I have contacted the manufacturer and they haven’t gotten back with the wiring diagram or anything

I buy only sensors that come with technical data and instructions.

I think that the sensor is wired like this:

OPTO SENSOR.jpg

Google "Optical Infrared Water Liquid Level Sensor " and this is a common 4 wire diagram.

TwinkleToes: yes I zeroed in both ends of the scale. it seems like it is 1.8 ohms.

It's been a very long time since I used an analog meter BUT

On the X10 range that would be 18 ohms

groundFungus:
I think that the sensor is wired like this:

OPTO SENSOR.jpg

Google "Optical Infrared Water Liquid Level Sensor " and this is a common 4 wire diagram.

Wouldn’t that mean that I would need some resistors off the yellow and red wires before going to ground? Im new to reading schematics and the like.

Yes. Blue wire and white wire to +5V. Red wire to one end of 390 Ohm resistor. Other end of resistor to ground. The yellow wire to one end of 4.7K resistor. The junction of the yellow wire and 4.7K resistor to a digital input. Other end of resistor to ground. The resistor values are not critical. One value higher or lower will still work.

So if I understand correctly the sensor would be connected in a similar manner to what I have diagramed in the attached image? the wheel will stand in as the sensor. I think that the only modification would be grounding the circuit to the Arduino and powering the + rail with the Arduino.

I still need help understanding how to add in the transistor... I currently have the part #LM7805 however, I can not find anything telling me if this is a PNP or an NPN configuration. Is there any way to tell?

LM7805 is a voltage regulator, not a transistor. An LM7805 cannot be used in place of a transistor.

groundFungus: LM7805 is a voltage regulator, not a transistor. An LM7805 cannot be used in place of a transistor.

What part would you recommend that I use?

Hi,

two 12V dc motors (2A) independently of each other. I am looking for the best Shield/drivers to do this.

i suggest you to use adafruit motor shield v2

its have 3 L293D IC motor driver, you can controlled 4 DC motor with 12V and 2A of each motor supply.