creating a 3v d.c. supply

Thread Starter

matttiger22

Joined Dec 7, 2014
1
Hi all,
I am making a little winding railway that moves a cart up and down the slope automatically using a simple 12v d.c. relay logic circuit. the only problem I have is powering the 3v d.c. motor. I could wire a separate supply in the way of a battery to it but I would rather use the same 12v d.c supply from the mains. How would I get a voltage drop to power the motor? The motor speed will be controlled with a pot
 

bertus

Joined Apr 5, 2008
22,266
Hello,

Where and how will the speed of the motor be controlled?
It can not be controlled over the 12 Volts when you use a LM317 regulator.

Bertus
 

wayneh

Joined Sep 9, 2010
17,495
You could use the LM317 but use a fixed resistor to limit the maximum voltage to 3V, and let the variable resistor control from 1.2 to 3V. Do the math for the resistances so you set this up right.
 

spinnaker

Joined Oct 29, 2009
7,830
Won't thatLM317 get mighty hot dropping 9V? A switching regulator might be a better way to go. The 34063 is a bit old school but easy to wire up with lots and lots of support on the internet. One can be had from one of those cheap USB chargers. A simple mod and the OP has his 3 V. Only problem getting the right sensing resistor.
 

Wendy

Joined Mar 24, 2008
23,408
True enough, but OP is not likely to be able to build anything too complex. The LM317 will need a heatsink though.
 
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