Continue to Site

Welcome to our site!

Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

  • Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

Could someone explain this?

Status
Not open for further replies.

hantto

Member
Hi, i have an 2A water pump and a 1A powersupply. I wanted to limit the current to 1A that is going to the pump beacause it was pumping to fast (and the powersupply is only 1A).

So i calculeted 12/1=12ohms and 12*1=12W. And the nearest one i found in my personal stock was 10ohms 5W. (i will go and buy a 10W one soon)

And when i measured the current with only the resistor and it was 1,05A but when i had both the pump and the resistor the current was 0,61A. With only the pump the current was 1,23A.

So that the pumps resistance should be 12/1,23=9,7ohms, then I measured the resistance of the pump and it was 4,5ohms.

So could someone explain this to me? :) And how many ohms resistor should i have to get the current to 1A, should it be 12-4,5=7,5ohms or 12-9,7=2,3ohms?
 
4.5 Ohms is the off-state resistance of the pump which increases during run time because of generation of back-EMF in motor armature. And you want to limit the on-state current to 1A so use the on-state resistance in your calculation i.e. 9.75 Ohms. The final resistance value would be 12 - 9.75 = 2.25 Ohms.
 
Status
Not open for further replies.

Latest threads

New Articles From Microcontroller Tips

Back
Top