amount of electricity with multiple components

Hi everyone, I think my question is somehow basic.

I have a stepper motor that requires a 12V source which is plugged into the Arduino. In the same project I also have a servo motor which requires 5 volts and a few buttons and sensor.

Now, assuming that I bring the 24V from the arduino Vin pin to my breadboard, how can I make sure that all the components receive the correct amount of electricity?

For example, I don't wanna waste my servo provinding more than 5V to it, and the same for my stepper, so how can I eventually reduce it?

for the stepper motor I am using this board

If you know detailed tutorials please link..!

thanks :)

You need a 12V stepper motor driver, that the arduino can send control signals to. You also neeed a 12V to 12V switching stepdown regulator to efficiently make 12V. And a 24v to 5V regulator for the servo. Check pololu.com for the driver, and mouser.com for switching regulators.

For example, I don't wanna waste my servo provinding more than 5V to it, and the same for my stepper, so how can I eventually reduce it?

You need a voltage regulator to bring 12V down to 5. If the servo is rated for 5V (or 6V) it will probably be fried by 12V.

What's the current rating (mA) for the 5V servo? If it's a very small servo rated for 100mA* or so, you can use an LM7805 regulator (which only requires two additional capacitors). Otherwise, you'll need a switching regulator (which you can buy or build). Switching regulators are more efficient than linear regulators (like the 7805) so they don't waste as much energy or get as hot and in general they can handle more current without burning-up.

  • The LM7805 in an TO220 package can handle up to one amp. But it needs to be properly heatsinked, and even with a heatsink it may overheat with 12V applied and 7V dropped across it.

leech:

Now, assuming that I bring the 24V from the arduino Vin pin to my breadboard, how can I make sure that all the components receive the correct amount of electricity?

Yikes! Don’t put 24 volts on your Arduino! Here is the Vin spec:

Operating Voltage
5V
Input Voltage (recommended)
7-12V
Input Voltage (limit)
6-20V

ChrisTenone:
Yikes! Don’t put 24 volts on your Arduino! Here is the Vin spec:

Operating Voltage
5V
Input Voltage (recommended)
7-12V
Input Voltage (limit)
6-20V

good…so at this point I guess the best solution is using the 12V from the vin and add external batteries for the other components

DVDdoug:
You need a voltage regulator to bring 12V down to 5. If the servo is rated for 5V (or 6V) it will probably be fried by 12V.

What’s the current rating (mA) for the 5V servo? If it’s a very small servo rated for 100mA* or so, you can use an LM7805 regulator (which only requires two additional capacitors). Otherwise, you’ll need a switching regulator (which you can buy or build). Switching regulators are more efficient than linear regulators (like the 7805) so they don’t waste as much energy or get as hot and in general they can handle more current without burning-up.

  • The LM7805 in an TO220 package can handle up to one amp. But it needs to be properly heatsinked, and even with a heatsink it may overheat with 12V applied and 7V dropped across it.

now…I understood how voltage regulator works (more or less) but, let’s say I have a 9V battery. If I apply a voltage regulator I will be using 5V…but I would be wasting 4V right? What if I need 5V somewhere and the other 4V somewhere else?

I don’t have knowledge of electricity so I guess I might be wrong…?

thanks :slight_smile:

and add external batteries for the other components

No, please no.

If I apply a voltage regulator I will be using 5V..but I would be wasting 4V right?

Well it is the voltage times the current that you would be burning off. That is why we suggest a switching regulator not a linear regulator.

What if I need 5V somewhere and the other 4V somewhere else?

Then there is nothing you can do about it.

Grumpy_Mike: No, please no.

mmm..why not?

Because you have a power supply you can hang it all off that. Adding batteries to a system that plugs into the mains is just plain silly and ecologically criminal, not to mention a rank bad idea.

What happens when that bit powered by the batteries goes dead or drops in voltage. What happens is that then signals are being applied to un-powered or under powered chips. This can cause them to latch up and burn out.

ok..so what do I do? I can't power Arduino with more than 20V..I have 12V for the stepper, a couple of servos which would be 10V..I'm already 22....?

thanks

Use more than 1 switching regulator. - one to make 12v or 9V or 7.5V for the Arduino - one to make 5V or 6V for the servo - one to make 12V for the stepper motor. All are fed in parallel from the 24V supply.

good..thanks..can you tell me which switching should I buy? If I got it right they are not these ?

cheap More expensive, probably better build quality Board mount units, from digikey

I just use cheap ones off ebay personally, though....

ok thanks..!

leech:
ok…so what do I do? I can’t power Arduino with more than 20V…I have 12V for the stepper, a couple of servos which would be 10V…I’m already 22…?

I don’t think you have got the hang of voltages. If you have two servos that need 5V that does not mean you need 10V to supply them. You just need 5V and connect each servo between the 5V and ground. They are in parallel they have the same voltage across them.
On the other hand if each take say 200mA then to power two you need a supply capable of at least 400mA.
Basically in a parallel circuit current adds up but voltage doesn’t.