Amplify DC Voltage (from 5v to 12v)

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Hi, I use arduino board which supply 5V output, but i need to operate 12V Motor.
I know that i could connect the arduino to 12V power supply and to solve the problem by this, but i cannot do it from some of reasons so i have to build a circuit which will get 5v DC input from the arduino and will supply 12V DC in the output.

Someone can help me with this? just give me some direction...
 

Hi, I think it's called a boost converter. Maybe in conjunction with a PWM IC/subcircuit could work.

Does the motor draw more current than the Arduino can provide? - Might be an idea to check that aspect; it may be necessary to use an external (12V) supply to handle the motor current.

Besides which, possibly a suitable interface to not damage anything when the motor turns off.
 


I think yes but after i will amplify the voltage i could use uln or some current amlifier not?
 

Hi,

What's uln, please? Do you mean like the L293 or ULN2000 or whatever it's called to shield the Arduino from the motor?

Also: Excuse my ignorance - Wouldn't the amplified current still come from the Arduino?

I'm still marvelling at not really understanding aspects of applying Ohm's Law to real circuits, so still think that what goes out can only be what goes in and it all has to balance out...
 

Hi,

What max motor current?

Do you want to control motor speed?
Or switch it ON/OFF?

Klaus
 

ULN2003A has seven darlington transistors with series input resistors. The input is from 5V TTL or Cmos logic and the output goes low with 500mA maximum.
ULN2803A has eight darlingtons the same.

Since they have saturation voltage loss of about 2V if the output current is 500mA then for the motor to get 12V the power supply must be 14V at whatever current the motor needs but not more than 500mA.

The current from the Arduino is not amplified, it simply switches the ULN on and off.
 

A simple transistor can switch a larger current, by controlling it with a small current.



The schematic is simplified. It is all right if you were to power the arduino with 5V, and also boost the 5V to create the 12V power supply.
 

PC power supplies with 5,12V are used for this reason.

Then you can decide if you want open drain control with motor coasting or a full bridge with fast start stop or PWM speed control, then stop change direction using logic level full bridges to switch 12V instead of half bridge.

Choose RdsOn much less than your motor coil resistance which defines your max surge current in one direction, usually up to 8x the max average rated current. Then use twisted pairs, and ferrite common mode chokes to reduce EMI and use start grounds with good conections and cap decoupling on all slow signal lines acting as antenna with low impedance differential for high speed data lines. Consider a PTC for stalled motor protection, just like power window motors.
 

KlausST said:
Hi,

What max motor current?

Do you want to control motor speed?
Or switch it ON/OFF?

Klaus
Click to expand...

Is it is on/off

BradtheRad said:
A simple transistor can switch a larger current, by controlling it with a small current.



The schematic is simplified. It is all right if you were to power the arduino with 5V, and also boost the 5V to create the 12V power supply.
Click to expand...

The problem is that i use something like 4 or 5 motors so i think that IC component is better(ULN 2003A etc..)
 

Audioguru said:
But you still do not tell us the maximum current (the stalled current) of the motors so we do not know if a ULN2003A will melt.
Click to expand...

it doesn't matter for me know, i still don't know how to make a circuit which will convert the 5v I/O output to 12v...
 

You simply use a 14V power supply for the ULN2003A to drive 12V motors that have a maximum stalled current of 500mA.

It sounds like you want the Arduino to somehow generate 12V at the high current. Impossible. If the maximum output of an Arduino is 25mA at 4V then its output power is 25mA x 4V= 0.1W.
If you convert the 4V to 12V then the 12V has less than 0.1W (inefficiency of maybe 80%) so 0.08W at 12V allows a maximum output current of only 0.08W/12V= 6.7mA which will not run a motor.
 

As i told you before i can't use in a power supply, the arduino connected to usb..
 

Hi,

i can´t find the word "USB" in this thread before.

You still don´t specify current.
In post#2 d123 recommended a boost converter. Isn´t this a solution for your problem?

What do you expect? What help do you need?

Klaus
 

KlausST said:
Hi,

i can´t find the word "USB" in this thread before.

You still don´t specify current.
In post#2 d123 recommended a boost converter. Isn´t this a solution for your problem?

What do you expect? What help do you need?

Klaus
Click to expand...
Ok only one more question please, i want to use ic called LT1073-12
Does it is ok to connect the vcc(5v) of my arduino directly to the input pin of the LT1073-12 or should i make pwm signal?

i mean like this:
 


I think that is okay so long as the Arduino has (protection) diodes on the input and output pins. I may be wrong, but it could help to read about H-bridges or flyback diodes and checking the Arduino in/out protection before connecting anything inductive or a largish capacitor...

Why do you need to use USB? What is the Arduino powered by, a laptop or desktop computer? There are USB power hubs that provide a fair amount of power (within reason) to each device connected. People connect Pis (and I imagine Arduinos) to USB power hubs to connect the peripherals they need to communicate with and to power the Arduino, etc., this is a way of "not using" a power supply for your motors.

4 - 5 motors that only need 130mA between them (ignoring start-up current) must be 5V solar motors or something similar?
 


I can't buy what you have suggested, i need to buy only the ic compenet and to connect in myself all the other components to it, i can't buy some finished board that makes the operation of dc-dc booster.
 
Last edited:

Hi,

Does it is ok to connect the vcc(5v) of my arduino directly to the input pin of the LT1073-12 or should i make pwm signal
Click to expand...

I can't figure out why PWM? Where did you read about PWM?
No pwm at all.

It says 5Vin..

Klaus
 

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