I have a 12V 5A Power supply which is connected to DC DC buck that steps it down to 6V this is connected to 7 Servo SG90 via 32 channel servo driver so no uno is needed.
If I increase the servo motor to 8 -10 servos then there is jitter\ motor heating \ uncontrolled rotation in some motors.
I am using a 32 channel servo motor driver for signalling & power delivery, am sure this driver can handle signalling of 32 servos am not sure if it can deliver power to 32 servos without burning it's traces. Find datasheet is extremely difficult and the 1 I found for similar chip by different manufacturer doesn't mention Max ampere it can deliver. I have seen videos which show power delivery of upto 18 to 15 servos is possible simultaneously.
First step is to power 10 servos simultaneously then 20 servos then ultimately 30 servos.
Now I have considered 1A per servo so I need 10A at 6V (60W)
PSU is 12V 5A (60W) converted in buck to 6V at 10A (60W)
I can run only 7 servos on this set up I know the conversion will not be perfectly efficient so this is expected that I may get only 7A and not 10A.
So I am changing to new power supply to 12V 33A which will be stepped down to 6V via DC DC buck converter and since it has 8A Max output I will buy 3 more buck converters.
I need to know if this is the right approach to continue.
Eventually for further projects I need to be able to control large arrays of like 100 to 500 servos without jitter and smooth movements. I think I will have to power them in sets of 30 or so and also code accordingly.
During testing with old power supply 12V 5A I connected 10 servos and 2 servos stopped after working for sometime 1 of which had heated and other just started uncontrolled rotations.
I suspect as all motors start simultaneously all were at peak draw and may be there some imbalance in current and that caused 2 servos to fail. DC buck has Max output of 8A so not sure how the servo got heated.
In old power supply even with 7 servos the servos look stable when making a wave like motion and they have smooth movements but I have observed that the speed of all servo increase slightly when some servo changes direction. So my understanding is when any servo is at peak draw other servos also get slightly more current and their speed increases.
Would it be better idea to have a individual step down buck for each servo ?
I guess I may need some over current protection on each servo individually with buck converter I am less worried about over voltage.
I am from non engineering background so my knowledge is quite limited. I am using python to send commands over serial port and make this work fortunately this part seems to work fine.
Since you need to buy new PSU, why don't you buy 6V supply. No need for buck converters. Calculate 0.7A for every sg90, so for 30 you need 6V20+A PSU. 6V 150W would be perfect.
Finding a 6V supply with higher Ampres is quite difficult.
And now I have received (new)12V 33.3A power supply.
My next plan is to power the 32 channel chip via usb and use new PSU to power 15 individual step down chip for 15 servos...
This I can test this after 2 days as some parts are yet to be delivered
Individual chip can handle input of 12V so no worries here and Max output is 3A sustain output is 1.8A which I want to limit to 1A which I don't know how...
My other concern is when so many servos pull current from PSU do I need to worry about ensuring equal and balanced distribution of current ?
Any other precautions to avoid instability in circuit \ jerking of servos etc
As I have mentioned before 2 of my servos stopped working and 1 was heated so my guess is somehow the servo managed to pull more amps which in turn heated it and caused damage which I want to avoid.
Servos were under no load and no obstruction to servo horns \ lever.
They don't if they are in working condition. Let your servos draw what they need.
While technically ok, your setup is no sense to me. For 30 servos you want 12V psu and 30 buck converters instead of one single 6V psu.
Agreed but where I stay I couldn't find a 6V PSU with enough Ampres. 6V 2A is what I get. I do have a 5V 10A that runs 10 servos but at peak draw voltage drops to below 4V so not using it.
Servo will pull as much current as it requires yes agreed
But with 10 servos running on DC buck that can't output more than 8A at 6V how did servo heat up and stopped working..
I am from non engineering background and learning as I go so it may not be a optimal setup !
@kmin thank you for your patience though any thoughts on the video and why servo speed is changing
From the data sheet of that buck converter you have:-
Regulator IC: MPS MP2307 buck regulator IC
Input voltage: 4.75V to 23V
Output voltage: 1V to 17V (adjustable)
Surge current: 3A
Rated output current: 1.8A (continuous)
Output ripple: 30mV (no-load)
Maximum conversion efficiency: 95% (5Vin, 3.3Vout~200mA)
Switching frequency:340KHz
Load regulation: 0.5%
How does this square up with your statement:-
Maybe I am getting confused with what you have?
However, what ever is the specification of the buck converter, with that board you can't use more than one buck converter, because you can't connect the outputs of more than one power supply to this board.
You should never connect the outputs of more than one power supply together. This causes great instability as each power supply fights the other for control. So your basic design criteria will not work at all.
So your questions are answered:-
NO
A servo gets overheated if it is supplied with more voltage than is needed. Your buck converters are not very good, as are most of the cheap buck converters. The specification of buck converters are not easy to decode as they want to show the product in the best possible light, and so all the maximums are quoted as "up to" and you will not get all these at the same time.
No not current, it is voltage. This shows you voltage supply has too much ripple voltage. This can be cured by adding capacitors across the power and ground to smooth the voltage. (reduce the ripple).
Yes but as I said you can't use more than one power input to that controller board, without surgery. That means cutting the motor power supply tracks every few servos and feeding each section with a different voltage. But I am not sure if even that would work as I can't see the schematic of the board.
No you require a stable voltage, over current protection is not needed, nor is it feasible.
Now in new setup I will be using PSU 12V 33.3A that goes to 15 individual mini buck converter which will power 15 servos. only signalling will be done through 32 channel driver. As I am not sure if that driver can handle power deliver for so many servos.
I did think to add capacitor but not sure where do I add them as in between mini buck & servo or between 12V 33.3A PSU and mini buck.
Also I am not able to find any 6V capacitor can I use 25V capacitors?
Very limited experience, not an electric engineer by training. Lot of reading and some logical thinking along with guidance from forum. I have did upto 8 servo motors before this project, but now I wanted to scale up.
400W supply because eventually I plan to run 30A (1A per servo x 30 Servos)
right now I will try out 15 servos. If my understanding is right that PSU will only provide 33.3A if there is demand.
I am assuming
It will run at 12V and around 15A because I am connecting only 15 servos now
also that 15A will be divided among 15 mini buck convertors and hopefully not fry them
Can anyone confirm these assumptions? and if it is wrong what would be the solution.
