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My link (client blocked??) was the PDF for the SG90 datasheet.
It's odd that you cannot purchase 5V supplies from amazon.in
Even if you need several, to me, that would be better than messing around with a horde of 'buck convertors'.
I am. You can't drive servo from your board if pulse doesn't have return path.
And I repeat, your setup is no sense. If you really can't find psu for all 30 servos, divide it in two groups and use two 5-6V 12+A psu.
Finding 5V is easy yes, but not 6V
I did try a 5V 10A PSU to run 10 servos and there was some jitter so I did not want it to get less voltage or current as I was facing issues. I thought if I meet the voltage requirement it will be 1 less thing to worry about. Hence the decision to go for next higher voltage available.
@kmin I understand I am not doing this optimally, but in my past project I did try that approach of splitting servos in cluster of 5 servos and powered them by 1 wall charger each cluster also had a 1 capacitor Per cluster. So 4 cluster total 20 servos but it was jittery and jerking a lot. So I thought of not cluster\ splitting power circuit this time around.
Maybe "wall charger" wasn't able to supply 4amps, maybe you didn't have common ground or maybe there was another issue.
All grounds were shared.
Wall charger was 5V 6A phone charger.
And still may be something went wrong then...
I am learning... so let me get through this project and I will be better at !!
5V is within the operating range.
SG90datasheet.pdf (167.9 KB)
Agreed
I was just being safe !
It's not that I dnt agree with you, I was just letting you know my thought process...
True that buck converter makes it more complex.
You're complicating the matter.
I won't trouble you with practicalities any further.
I understand your concern
Let me see what I can do !
I already have 12V 33.3A I will try and replace it by 5V 20A for 20 servos + 5V 10A on separate circuit for 10 servos. Both PSU to have shared ground.
Yes you are if each servo gets its power from a different, or even a few buck converter. The output of the buck converter IS a power supply, no matter what you think.
That is exactly why you can't do this.
Driving that board from USB can not supply enough power
Why "in this case"? Without connecting all power supplies to ground nothing associated with that diagram will work.
Which is why we are trying to help you, but you seem reluctant to learning new stuff, and you keep sticking to your own misunderstanding of this project.
Yes this is correct, but you are missing something very important. A 400W supply is very unforgiving, so if you do make a mistake you can vaporise tracks and cause a lot of damage.
Sorry for chiming in ( unrequested ), but I'd stay away from 'max specs' of any circuit.
For example 6V on servos is asking for troubles.
Regarding current consumption of sg90 I measured mine with a scope and it draws bursts of 400mA at a frequency of 100Hz ( which is the frequency of the servo pwm generated by my esp32 board ) while sweeping servo back and forth continuously.
Doing this the servo became hot and I fried it. So I'd say also that the 'average sg90' is not good for continuous operation.
Good general advice but for a servo this is not relevant.
How did you measure that? Normally a scope will only measure voltage. Where did the 400mA come from? You can't get that much from a esp32.
I am sorry if I came across as unwilling to learn..
I am away from all the hardware till day after tomorrow.
I will have to return \ exchange my PSU and mini buck converter to get a 5V PSU then I can setup correctly.
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I powered the servo with a bench power supply and measured the current with a 1ohm resistor in series with the +5V to the servo.
Thanks for the one answer.
It's stationary, I take it? Like plugging into a wall?
If so, consider a PC ATX PSU. Has 5V rail and you can use separate buck converters to step the +12V rail down to 5V.
Over spec by 30-50%, so 600 watt supply or even 800 watt and you'll have power all day long.
Here's a guide I found very useful. It's really easy.
https://www.dimensionengineering.com/appnotes/atxguide/atxguide.htm
Circuit - Servo(32) - PCA9685 (2) - PSU 5V 20A (2) - Nano (1).pdf (116.9 KB)
This is the overall scheme, but I will be testing only half of it 8+8 servos on 1 PSU 5V 20A with 1 PCA9685 16 channel driver and 1 nano. I have put capacitor values based on my research please let me know if it is correct. not sure if I should also be using ceramic caps too along with electrolyte caps, if yes what specifications? I have planned to shared ground of both PSU do I need to share nano ground as well ?
I will be adding 2 servos at a time and scaling up gradually
any other component to be added in circuit?
B&W Circuit - Servo(32) - PCA9685 (2) - PSU 5V 20A (2) - Nano (1).pdf (116.0 KB)
here you go