Let's Make Robots!


Stall Current & RPM

So I'm looking at what motors to buy for my next project, I'm struggling to find many retailers in the uk that sell them but one that I've found have some that I'm interested in. The specs they supply are 390mA stall and RPM of 250, but these figures are based on a 6v supply. I however will be using a 4.5v supply, is there any way to calculate how these numbers will be affected by a lower voltage supply? Also I will be running these motors in parallel (sets of 2 motors) will this also affect the RPM? Thanks :)


Right, back again with an update on my idea for a kick-ass fanctroller. So far, I've been coding away and right now, I'm up to the point where the actual fan control is implemented (I've already written the LCD-commands, several input functions, a setup and a menu.) But I'm having some problems.

The mother of all fancontrollers... Hopefully

So, I'm the process of making the -in my opinion- ultimate PC fan/pump controller for use with a water cooling system.

The idea is to make a bracket which fits into a 5.25" bay and holds an LCD, some type of input (probably joystick) and an arduino, so the temperature responses are completely programmable. It should have three fan/pump channels and 3-6 (however many ADCs I have left, at least 3) temperature sensors.

motor selection......



the weight of my robot is 12-14kg.....i am having a serious problem in selecting motors...


motors must must have good rpm

must have torque 

must  have feedback (for differential drive , positioning and controlling)

must have power to drive 12-14kg.....


plz provide me guidance.......... 


Lowest RPM of an electric bike motor?

What is the lowest possible RPM of an electric bike motor?  It seems to be the cheapest alternative to a slow gearmotor.  Thanks.