Boost 5V (4.7v) to 9V

Hi Tim,

How about a boost converter like this?

http://www.ebay.com/itm/DC-DC-2A-Adjustable-Boost-Power-Supply-Converter-Step-Up-Module-2-24v-Input-New-/161650445447?hash=item25a31e0c87

John

Cheaper to buy than build.

Tim

John is quite right.

There is one thing to consider though.

You haven't specified what the ratings are for the 9v motors.

All motors will tend to draw twice the running current when starting, and this spike on the voltage line can cause the Arduino to reset.

You may wish to consider separating the motor voltage (9v) from the 5v for the Arduino.

I'd also add a large capacitor to the 9v side, and fit 0.1uF caps across the motor.

Mark

Thanks for your answers!

The motors don't run from the 5V connection from the Arduino ;-)

But no capacitor is there for the motors. I'll try to add them.

Btw, the motors sort of run at 5V, but I might still be buying the step up module soon!

Thanks!

Tim

It is probably not a good idea to run the motors from the Arduino 5 volt power. Motors usually take more current than the Arduino  can supply. Also it will be a good idea to put a diode across the motor to protect the rest of your circuit from Inductive spikes. Check out "Flyback Diode or Freewheeling Diode". The Capacitor that Mark recommended will not help the motor run but it will help prevent the motor from resetting the Arduino. Your best approach is to use the Arduino to control a MOSFET or a Transistor and use the Transistor to control a higher voltage that is being used to drive the motors.

John

Tim

You haven't specified how you are intending to control the motors.

Are you using a H Bridge, or just connecting them so they operate in one direction only.?

A little more detail and we can provide a couple more suggestions.

As john said connecting a motor to the 500mA 5v regulator on an Arduino is not a good idea.

Even when its across the Vin terminal, it usually causes issues.

Mark

Sorry,

I'm using a custom build H-bridge, powered directly from the powerbank.

EDIT:

Is a 10uF capacitor rated at 50V big enough for the whole? and two 0,1 uF capacitors rated at 50V for the motors?

Hi Tim,

Could you share more detail on the custom H-bridge (e.g. schematic) and the motors (datasheet, or voltage and power requirements).

Phoefff, that's a damn good question

The input voltage is (as I assume 9V)

That's all I know

The ULN2803 can't easily be used for bidirectional motor control without additional complexity. It can't reverse the current to the motor on its own. There are better alternative ICs, and probably some pre-built boards that are low cost. But it all depends on the motors. Are these small hobby/toy motors (in which case we can guess current consumption)? Otherwise some more information is needed on the motors unfortunately.

The motors are these yellow ones (this is not the exact robot I'm using)

http://www.makershed.com/products/makeit-robotics-start-kit

Maybe this is going to help you. To be very honest, I know exactly as much about the motors I'm using as you do. I've borrowed the robot skeleton from someone.