May I replace Voltage regulator, C5, C6 and battery with one Regulated adapter (Output: 5v / 1.5A) ?
My bad, I should call Power Supply instead of Transformer.
Absolutely not.
You should instead use a "transformer" to feed the + line of your servos and neopixels modules.
Remember to connect GND and - feed on all devices together (as already shown in your schematic)
The reason is, that Arduino must have a pretty precice 5V, which is not disturbed by any other amperage consumers.
You servos an neopixels are not that stringent on power requirements, as long as it does not exceed the maximum specifcations, and that your transformer can supply the amperage of all the devices connected.
Example :
if your servos each consumes 200mA on normal load (not stall), they should be provided a supply of 600mA (0.6A) total.
Add to this the amperage of your 2 neopixels.
The total should be within the spec on your transformer.
And to follow suit on Awols answer :
My answer will only be correct, if we both agree on the term "transformer" as being a complete transformer + rectifier unit, which usually is defined as a wall outlet charger, for mobiles or labtops.
Perhaps by "transformer" you mean "Adapter".
In electronics, you should be pedantic to avoid misunderstandings.
This is a transformer:
Perhaps you mean a regulated 5V adapter like this:
In which case, yes. But keep C6 in there. You will be driving the Arduino from the same 5V powering the servos, and servos are electrically noisy so you may find you need more bypass capacitors.
Pay attention to ground layout.
So, Anders53 what is your solution to provide separate voltage source? One "wall outlet charger" to Arduino board and other "wall outlet charger" to amperage consumers?
Yes, polymorph. indeed regulated adapter with output 5V 1.5A.
The big problem with servos is the stall current. If all three servos draw maximum current at the same time, it can overload your power supply.
This can happen because your Arduino moves them at the same time, -or- if something outside disturbs the servo's positions.
polymorph, so what the solution for my case...?
It's will look weird with two Regulated adapter in the wall.
Obviously you will need a small 9V adapter, for the Arduino external power input and a larger 5V adapter for the servos and neopixels.
I'd say that a rechargeable 9V battery would last pretty long, if it only needs to feed the Arduino.
I am not sure on the good idea of dimensioning the 5V adapter for all the servos stall current, as that could lead to a burn out of the stalling servo, if it is jammed mechanically.
Your decision.
A good switching regulator wallwart will do.
Servos can typically draw 1A of current to start moving or make sudden changes of direction, so your situation would call for a 4A capable power supply.
Example:
http://www.mpja.com/5-Volt-DC-Plug-Power-Supply-4A-Regulated/productinfo/18520%20PS/
Cut off the, make a triple splitter cable - power/Gnd to the servos, power/Gnd to the neopixels, power/Gnd to the 5V header on the Arduino. Place large electrolytic caps near the servo & neopixel connections.
If the servos are really power hungry, then you may need to have separate supply for them, in which case connect their Gnd to the Arduino Gnd.
You could also put a resettable PTC fuse, or a regular inline fuse holder even with perhaps a 1A fastblow fuse, in series with each servo power feed if you are worried about it jamming and drawing excess current.
Thank you guys,
We are talking about small servos Micro Servo SG-90
Read the datasheet on the servo.
It should state the stall current.
Though it wont be "much" as a 9g servo is not exactly a power puller.
It is aimed at lightweight applications where small size is a must.
I don't see a big problem using a single regulated 5volt supply, as long as it does not "dip" when loads kick in.
What if you feed an Arduino from USB. Is that clean?
The only thing could be the Aref for the A/D.
Maybe wise to leave C6 in, and make C4 a bit bigger.
Just try, and report back.
Leo..
Anders53:
Read the datasheet on the servo.
It should state the stall current.Though it wont be "much" as a 9g servo is not exactly a power puller.
It is aimed at lightweight applications where small size is a must.
Operating Speed (4.8V no load): 0.12sec/60 degrees
Stall Torque : 1.2kg / 42.3oz(4.8V);1.6 kg / 56.4oz (6.0V)
flash_os:
Operating Speed (4.8V no load): 0.12sec/60 degrees
Stall Torque : 1.2kg / 42.3oz(4.8V);1.6 kg / 56.4oz (6.0V)
OK, so while the specification sheet should quote the stall current, in practice they do not tend to consider it sufficiently important to do so.
Generally because they are are most commonly used with rechargeable batteries which have a quite substantial capacity for impulse currents. And because they are often cheap "knock-offs" of more durable designs and not intended for review by engineers.
Seems to be determined by testing then.
My GUESstimate is 250mA for such a small motor.
Remember that the motor is driven by transistors in a bridge (a complete chip), which would quickly burn out, unless a current limt circuit is added to the driver stage.
Which means the current limiter sets the stall point.
Anders53:
Remember that the motor is driven by transistors in a bridge (a complete chip), which would quickly burn out, unless a current limt circuit is added to the driver stage.
Which means the current limiter sets the stall point.
This Quite so! works better.
Why is it, do you suppose, that manufacturers refuse to make their datasheets available?
I wasn't saying use two power supplies, but that you need a power supply rated for more than the maximum current that everything could possibly draw at once.
So, for instance, three servos with stall current of 300mA each and an Arduino that can draw no more than 250mA maximum, would mean 3x300mA + 250mA = 1.15A. So I'd get a 5V 2A regulated power supply.
You can measure the stall current with your DMM on the current setting simply by fixing the servo so it cannot move, then sending a signal to move it.