Resistance to water pump

Hello!

I wonder what the most appropriate resistance to a water pump with these features: -Power: 3.5 ~ 12V DC, 65mA-500mA -Pumping: 40-220cm -Capacity: 100-350L / H -Consumption: 0.5W-5W -Dimensions: 38x38x29mm

Thank you!

No resistor needed. You need a power supply with enough voltage and current. To switch the pump on and off use a transistor or mosfet. See: Digital Logic Transistor Switch http://www.electronics-tutorials.ws/transistor/tran_4.html

could tell me the name of some transistors, is suitable for pump, please?

I like to use a relay. You can find shields with relays.

Relays are never ever the correct part to use, they have no place in digital electronics and don't even make good door stops!

Mark

Good thing that pumps are not digital electronics. Relays are great for on off of motors.

transistor for a 13 volt, 500 ma pump could be a multitude of parts. TIP-120 is about as common as you get id you want to use a transistor.

holmes4: Relays are never ever the correct part to use, they have no place in digital electronics and don't even make good door stops!

Mark

I disagree with that statement. Relays offer total galvanic isolation and for some applications/projects the best component to use. There are probably more relays sold now then in any time in history.

holmes4: Relays are never ever the correct part to use, they have no place in digital electronics and don't even make good door stops!

Mark

I like to suggest them to those who are starting because there are cheap and easy to use shield for Arduino that don't need great amount of knowledge to get it ready to use. Only need supply (5V and GND) and the signal from the Arduino.

holmes4: Relays are never ever the correct part to use, they have no place in digital electronics and don't even make good door stops!

Mark

In the mid 1980's I was an engineer at a medical device manufacturer. We had an 8 position turntable with RF heat sealing presses to make vinyl bags.

The engineering manager had hired a local university professor and his flunky graduate student to design and build a solid state sequencer to operate the turntable (rotate the table, operate the RF heat sealing presses, interlock various parts for safety, etc...).

Well, if you don't know, RF heat sealing machines are basically radio transmitters in the multi-kilowatt power range. The RF field in their vicinity is strong enough to light a florescent tube that is hand held.

Suffices to say, the doc and his student couldn't make op-amps work in such an environment.

I was asked to "make the thing work", so I ripped out all the solid state crap and built a sequencer / controller out of relays, timers and microswitches.

It worked flawlessly, and from what I've been told by people who are still there, the turntable and it's "never the correct parts to use" relay and timer controller is still working today.

There are, indeed, MANY applications where a relay or an electro-mechanical device is superior to solid state due to it's simplicity and ruggedness.

could give me an example of a transistor for this project

dave-in-nj: transistor for a 13 volt, 500 ma pump could be a multitude of parts. TIP-120 is about as common as you get id you want to use a transistor.

pc5_costa:
could give me an example of a transistor for this project

dave-in-nj:
transistor for a 13 volt, 500 ma pump could be a multitude of parts. TIP-120 is about as common as you get if you want to use a transistor.

is this what you are asking ?

or a schematic ?

put power on your pump. this would be the 12 volts.

bring the ground of your pump to the collector of the TIP-120
read the data sheet for what pins are what.

Note: the TIP120 is an N type. it MUST be placed between the device and ground. it ONLY brings power to ground. a P type is used at the high voltage side and allows power to pass into your device. in the electronical world, we use N type about 95% of the time. that means the parts are more common and more common means lower cost AND more people can help you with them. best of all three worlds !

connect the emitter to ground. this ground has to be tied to the 12 ground AND the arduino ground. this is a common ground.

for a transistor you much ties the grounds together. the pump is not a digital elecronical circuit, so it falls out of the concept that relays do not belong in digital circuits.

a note : tying different power lines together can cause problems and some people prefer isolation. the relay is, by the very design, an isolated device between the signal and the power end.

put a resistor between your arduino output pin and the transistor base. the calculation of this resistor is based on the power that the device uses.

the calculation of the resistor is partly based on the power the device you are powering will use. i will be partly based on the need of the transistor. the transistor can be thought of as a dimmer switch. if you feed it a tiny bit of power, it will pass a much larger amount of power. feed it more and it will pass more. there is a point where you have fed it enough that it acts like a switch. this is called saturation. in this case you most definitely WANT to drive it into saturation.

alas, you cannot just connect it to the output pin of the arduino. the transistor ‘sees’ the current at the base input and drains that to ground. so, if you tie your arduino output pin directly, it will act like a power robbing short. you need to throttle it back, but also keep it into saturation. learn ohms law to determine values. the maximum output of the arduino is based on two values. the maximum for any one pin, but also the maximum for all pins combined which comes first ? you have to figure that out.

if you drive the transistor into saturation, it will act like a switch and pass power and consume a tiny bit. if you do not drive it into saturation, it will allow some power to pass and in some cases it will get HOT. this is bad. if you do not drive it into saturation, the device will get less power, like a dimmer would do. so you have to decide what you need. act like a dimmer and get hot, or turn it on like a switch.

since we are talking about slower running of the device, you have a much better option, use a PWM output. that turns on the transistor fully for tiny slices of time. this has the effect of keeping the transistor cooler AND allowing you t run your motor at slower speeds. something you cannot do with a relay.

to complete your circuit, start with a 330 ohm resistor. you could use around 470 or so. btw, for this sort of circuit, you could use 200 to 500 ohms. but, since I recommended relays, and got wordy, I will let someone else help you calculate how to select the resistor.

tip120.png

johnwasser: No resistor needed. You need a power supply with enough voltage and current. To switch the pump on and off use a transistor or mosfet. See: Digital Logic Transistor Switch http://www.electronics-tutorials.ws/transistor/tran_4.html

John,

reading between the lines, it would appear that english is not the OP's native tongue. no problem and he is very good at asking and is pretty clear. it seems that he is asking for the thing he cannot figure out.

in order to calculate the power through the transistor, one needs to know the data about the motor. in any device there is an equivalent resistance.

in order to calculate the power on the base of the transistor one needs to know the power in. many of the sites that do the calculation for your want voltage and resistance. all the OP has is voltage and current. so he is missing that elusive resistance.

I would highly recommend using a cheap relay board with opto isolator that you can buy very low cost for the project, but that is not what was being asked, the OP has specifically asked for a transistor.

reading between the lines, he needs help on using a transistor for this project. or how to use transistors in general.