Guidance on Transistor and Diode Strength Needed for 2 Windshield Washer Pumps

hi,

i want to preface this by saying i am a newbie, but i am completing this project for a class, and so the general idea of the project will not be changing.

my project is this:
i am connecting two 12v windshield washer pumps i recently bought to two separate water bottles in order to have them spray water based on input from a photocell. my project is very similar to this instructable: http://www.instructables.com/id/Squirt/?ALLSTEPS

however, there are some differences. i will have TWO water pumps, and at the ends of the tubing, i will have some nozzle type ends (to create a spray). i will also be using TWO servos to control the direction of the tube ends (left-right in a limited scope, up-down as well). also i will be using a photocell to determine when the pumps will spray and in what direction (probably 'random'ized). i am also maybe considering having an on and off switch so that it doesn't just start spraying willy-nilly when i plug it up.

I am aware that I will need both a Transistor and a Diode. The instructable lists a 1N4004 diode, and my instructor told me I would need a Schottky diode.

My questions are in relation to which type of diode and Transistor I should by (like total voltage, etc). When i looked to buy these items, i saw various versions with different voltage levels (40v, 50, ++++ to like 500v etc) how do i calculate which one i'll need? Will I need multiples of either for my circuit, or just one of each?

Also, I have a question about powering my project. I am aware that I will need at least 12v of power (or will this be more since there are 2 pumps?) :cold_sweat:

i have the following 12v plug: http://www.amazon.com/gp/product/B006GEPUYA/ref=oh_details_o00_s00_i01?ie=UTF8&psc=1

however, this connects to my arduino, but i know that the arduino only uses 5v when it is connected to this. Can this be used to power my project somehow, and if so, how should it be connected?

i also am thinking i will need to do something like this: http://itp.nyu.edu/physcomp/Tutorials/HighCurrentLoads
but i don't understand how to adapt it for my circuit.

if you could either help me or direct me to helpful guides, i'd appreciate it. i have been searching and still am, but sometimes hearing a reply directly from someone helps me better make sense of what i'm being told. i just don't want to misunderstand and burn out my board etc.
Thanks for the help, :grin: :sweat_smile:

You need to know how much current those pumps draw (i.e. double the figure for a single pump to get the total for both pumps), and use a 12V power supply capable of providing that much current with a suitable margin.

You will need a driver circuit between the Arduino and the motors. The link you posted gives you complete details for the circuit - I don't see how you can be in any doubt about how to connect it.

If you want to power the Arduino from the same 12V supply used to power the pumps then you will need to connect the supply to the DC input socket of the Arduino, and to the circuit powering the motors. That will probably involve getting suitable connectors and wiring them up to your supply.

If you aren't required to design that circuit yourself then you could use a standard motor shield or relay shield which would save you a lot of work, but cost more.

Schottky diodes simply have a lower forward voltage drop so less power is dissipated in the diode junction.

Replacement washer pumps are about $12 in tybhe U.S.

Relay shield for pump motors:
Relay Shield - DEV-12093 - SparkFun Electronics Try and find one with 2 relays in a similar price range.

petalpure:
I want to preface this by saying I am a newbie, but i am completing this project for a class, and so the general idea of the project will not be changing.

You might as well cut the "newbie" stuff - I think we immediately figured that's a "given". :smiley:

petalpure:
I am connecting two 12v windshield washer pumps I recently bought to two separate water bottles in order to have them spray water based on input from a photocell. my project is very similar to this instructable.

Cute!

petalpure:
however, there are some differences. i will have TWO water pumps, and at the ends of the tubing, I will have some nozzle type ends (to create a spray). I will also be using TWO servos to control the direction of the tube ends (left-right in a limited scope, up-down as well). also I will be using a photocell to determine when the pumps will spray and in what direction (probably 'random'ized). I am also maybe considering having an on and off switch so that it doesn't just start spraying willy-nilly when I plug it up.

If it is wired correctly, the motors only operate on Arduino command, and the program should include start-up stabilisation provisions.

petalpure:
I am aware that I will need both a Transistor and a Diode. The instructable lists a 1N4004 diode, and my instructor told me I would need a Schottky diode.

What is (s)he smoking? There is no reason to use a Schottky diode, a 1N4004 is quite correct.

petalpure:
My questions are in relation to which type of diode and Transistor I should by (like total voltage, etc). When i looked to buy these items, I saw various versions with different voltage levels (40v, 50, ++++ to like 500v etc) how do I calculate which one I'll need? Will I need multiples of either for my circuit, or just one of each?

One transistor or FET for each motor, with one diode across each motor terminals. These have to be "logic level" if FETs, so that they will switch on properly from just 5V.

petalpure:
Also, I have a question about powering my project. I am aware that I will need at least 12v of power (or will this be more since there are 2 pumps?)
I have the following 12v plug: Amazon.com

Pretty useless for the motors. I'd hazard they draw at least 1A running, if not two (and are not by the way, designed for continuous use), and double that to start up. I'd look at 5A rating for the power supply.

petalpure:
however, this connects to my Arduino, but I know that the Arduino only uses 5v when it is connected to this. Can this be used to power my project somehow, and if so, how should it be connected?

While you want 12V for the pumps, you want about 7V for the Arduino and 6V for the servos. You could use a properly regulated 5V supply ("plug-pack") fed to Vcc on the Arduino. One approach would be to use a 12V 5A supply, with a switchmode regulator rated at 2A to supply 6V to the servos and two diodes to reduce that to 5V for Vcc on the Arduino. Actually, a 5V 2A switchmode regulator for them all as the servos probably will work OK on 5V if the supply is well regulated.

petalpure:
I also am thinking I will need to do something like this but I don't understand how to adapt it for my circuit.

Not sure it is helping.