Windshield washer pump "pulses"

Hello,

I'm researching through the forum and trying to make my own plant watering system. However I have a small puzzle. I have the following 12v windshield washer pump ( Taap 5-741). Which is a 12v cheap pump from the local auto parts place. I figured they would all be the same. However if I hook it up directly to a wall wart power supply at 12v 1A - then it pulses on briefly about once a second. It's not a continuous pumping action. Does the input need to be some kind of PWM signal? I'm not sure why it would pulse. Are there different types of these pumps? This post ( http://forum.arduino.cc/index.php?topic=284943.0 ) shows I probably need a bigger PSU - but I would appreciate some help as to what would be sufficient. I guessed that with not enough amperage (I've seen up to 3A recommended in various forum posts) - then it would just pump slowly? But I guess not :) I know code, not electrons - sorry for the repeat question!

Thanks, Wilks (edit: forgot link)

Find out the stall current of the motor by measuring its winding resistance. Stall current = supply voltage divided by winding resistance. Your supply should be happy to either supply this amount of current or else overload gracefully - your supply is tripping out and reseting every second because it doesn't meet such requirements. SMPS's seldom handle overload gracefully, they trip out.

Hi Mark - thanks for helping. I looked up what winding resistance is - and it says to measure the resistance "between the 2 armature wires". The windshield pump I have is a sealed unit. I can't get at the motor inside, only the power leads. But I understand now that the power supply is tripping - that makes more sense than a pulsing motor :) The other forum post mentions measuring the required current drain - maybe I can figure out how to do that. Then I'm hoping a supply like this: ( 12V 3A Wall Supply ) might work...

wilks: Hello,

I'm researching through the forum and trying to make my own plant watering system. However I have a small puzzle. I have the following 12v windshield washer pump ( Taap 5-741). Which is a 12v cheap pump from the local auto parts place. I figured they would all be the same. However if I hook it up directly to a wall wart power supply at 12v 1A - then it pulses on briefly about once a second. It's not a continuous pumping action. Does the input need to be some kind of PWM signal? I'm not sure why it would pulse. Are there different types of these pumps? This post ( http://forum.arduino.cc/index.php?topic=284943.0 ) shows I probably need a bigger PSU - but I would appreciate some help as to what would be sufficient. I guessed that with not enough amperage (I've seen up to 3A recommended in various forum posts) - then it would just pump slowly? But I guess not :) I know code, not electrons - sorry for the repeat question!

Thanks, Wilks (edit: forgot link)

Most wall warts these days are switch mode , they do not work well with inductive loads like motors , its probably just shutting down.

wilks: Hi Mark - thanks for helping. I looked up what winding resistance is - and it says to measure the resistance "between the 2 armature wires". The windshield pump I have is a sealed unit. I can't get at the motor inside, only the power leads.

Measure the resistance between the power leads. You never know, they just might connect to the armature via the brushes. ;) Then, as Mark says, the current I =V/R.

wilks: Hi Mark - thanks for helping. I looked up what winding resistance is - and it says to measure the resistance "between the 2 armature wires". The windshield pump I have is a sealed unit. I can't get at the motor inside, only the power leads. But I understand now that the power supply is tripping - that makes more sense than a pulsing motor :) The other forum post mentions measuring the required current drain - maybe I can figure out how to do that. Then I'm hoping a supply like this: ( 12V 3A Wall Supply ) might work...

The power leads are the motor leads.

Take a look at this.

http://www.sdcsecurity.com/docs/eblasts/choosing-right-power-supply.pdf

I can only relate my own experience though.

Small wallwarts are generally poor at driving motors whatever the current rating.

Pulsing being typical behavior.

Ones that work are generally brick type like laptop supplies with a cable.

Linear work fine generally.

Switchmode supplies can be had from the likes of flojet for the purpose.

I have tested several laptop supplies, some work some do not.

Those that do not exhibit the pusling behavior you experienced.

Using a 3 A rated supply i was barely able to run a 1 A rated 12 v brushed motor, extending the connection wires then caused it to fail to pulsing mode.

I experimented with many supplies as i had a lot, in the end i spent 70 on one designed for the job. I think its just a case of do you feel lucky.

One trick i have sucessfuly used however is to use a small LA battery as a “capacitor” but extra electronics are needed to control charging etc.
But its easier than using say a lipo.