How do I power an arduino and 12v dc motor off an eighteen volt battery?

How would I go about powering both an Arduino and a 12v DC motor off one eighteen volt battery? Right now I use two voltage dividers which effectively split the voltage to 12 and 8.99 v, but the resistors only let the components (motor + Arduino) draw 17.9 mAH. I don't know what the [salvaged] motor needs to draw, but the Arduino needs 1 amp. I'm pretty sure I would damage the Arduino if I directly connected it to the 18v [also salvaged] battery.

Thanks in advance,
David

For the Arduino I would use one of these converters DC-DC-Buck-Step-down

It may even power your motor but I can say as we don't know the motor current requirement.

Do you have a multimeter that can measure amps? If so, connect your motor to a 12 Car battery and measure the current.

The above suggest converter is not anything special, its just the first one I came across on ebay.

Resistor dividers won't work because they change voltage when you start to draw current into your arduino. This converter measures the output and if it is below the goal voltage (12v in your case) it will turn on more to keep the voltage constant.

With difficulty is the short answer......

The Arduino doesn’t take 1amp, far less.

You need to know the spec of the motor and what you are doing with it to decide how to reduce the voltage, as the method very much depends on its current rating. ( see prev post)

A resistor divider cannot be used to power the Arduino.

I would be tempted to use either a buck convertor ( if you can get one to take 18v input ) to power the Arduino or voltage regulator.
I expect you want to drive the motor from the Arduino , if you use a suitable transistor to switch it from a analog output set at an output level of (1024*12/18) it will power the motor at 12v.

TBH - I suspect this is going to be hard for you , get a better battery , more suited to your needs .Probably cheaper in the long run.

You need two of the abovementioned buck converters, one for the motor (given that you have checked its stall current with an actual 12 V power supply) and one to give 5 V for the Arduino.

Note the Arduino runs from 5 V to the 5 V terminal, not "8.99 V".

dmalexander185:
How would I go about powering both an Arduino and a 12v DC motor off one eighteen volt battery? Right now I use two voltage dividers which effectively split the voltage to 12 and 8.99 v, but the resistors only let the components (motor + Arduino) draw 17.9 mAH. I don't know what the [salvaged] motor needs to draw, but the Arduino needs 1 amp. I'm pretty sure I would damage the Arduino if I directly connected it to the 18v [also salvaged] battery.

Thanks in advance,
David

If you are going to control the motor with PWM, you can just give it 18V and use a smaller duty cycle,
avoiding inefficiency of any power conversion between battery and motor (always a good idea).

Using a voltage divider for power is plain wrong, it will end in fried components and very hot resistors.
Voltage dividers are for signals.

For the Arduino you can use a cheap LM2596 buck converter from 18V down to 7V into Vin, or down to
5V straight into 5V pin. This will do a great job of isolating the Arduino from voltage fluctuations of the
battery due to the motor.