DC Motor pulling too much current, how to limit this - Page 1
Forum section: electronics / beginners

author: 3cHeLoN
author_rank: Newbie
timestamp: March 28, 2016, 01:43:36 pm
content: Hi, my name is Folkert and I'm new at the forum. Hope you guys can help me with my electronics project for automatically watering my plants.I bought this motor:http://www.dx.com/p/hsyy01-water-pump-motor-w-hose-white-silver-236808to pump water from a container to my plants. I don't mind at what rate the water flows, it will water the plants at night.The motor works fine (and very fast) when connected to 4 AA batteries of 1.2V. Not so much when I connect it to a 1A 12V power supply, or a 5V 1A power supply. The motor starts but stops immediately and does this over and over again. As the motor is rated for 800mA I couldn't see what was wrong. Then I measure the current when running the motor from batteries, a whopping 3.2 Amps!I then connected the motor through a motor controller (http://www.lightinthebox.com/nl/l298n-dual-h-bridge-stepper-motor-driver-controller-board-module-voor-arduino-uno-mega-r3-mega2560-duemilanove-nano-robot_p1638643.html?currency=EUR&litb_from=paid_adwords_shopping&utm_source=google_shopping&utm_medium=cpc&adword_mt=&adword_ct=87561882434&adword_kw=&adword_pos=1o1&adword_pl=&adword_net=g&adword_tar=&adw_src_id=1810908567_301588514_21687237914_pla-117284547555&gclid=CjwKEAjwrOO3BRCX55-L9_WojHoSJAAPxcSPUensY5cGbFx6NDL0oQ62ffdWub7iJFLOYTZZ2QlYnBoC6_3w_wcB)When connecting 12 V to the input (onboard regulator brings it down to 5V) it works when setting PWM on the input pin of the motor controller (about 50% duty cycle). It draws 800 mA, but I get nowhere near the specs of 1.2 liter per minute (more 100ml per minute).And then the smoke starts to come from the motor controller... I quickly removed the power supply.I really have no idea what I'm doing wrong and how I can reliably and safely use this pump to water my plants. It seems other people were able to do it. Unfortunately, my knowledge of electronics is quiet limited, so any help would be very much appreciated!Thanks.- Folkert

author: dferyance
author_rank: Regular Contributor
timestamp: March 28, 2016, 08:49:41 pm
content: Probably either a defective motor or just incorrect specifications. A motor has windings for the electromagnet that are laminated. It is possible there is a short in the windings. DC motors can draw a lot of current but that page shows it should be under an amp. So I would suspect it is just busted and not break anything else trying to power it. Your power supplies are probably shutting down due to over-current or temperature protection.

author: mikerj
author_rank: Super Contributor
timestamp: March 28, 2016, 09:35:00 pm
content: Could be the pump itself has been badly machined or assembled and is putting a lot of load on the motor. Is it possible to remove the pump and run the motor by itself?

author: Ian.M
author_rank: Super Contributor
timestamp: March 28, 2016, 09:37:42 pm
content: +1 for excessive friction in the pump chamber, or its outlet may be restricted, leading to excessive motor current. It looks like the cover plate may be removable - a cautious investigation to see if anything is fouling the impeller is indicated. If you've ever run the pump dry, it may have burnt the impeller vane tips or the shaft seal, increasing friction.