Hi guys i am searching for stepdown converter. I need 5V 12 A and I would like to use an akku 7,2V 30A 6000mAh LI Ion. Its a hexapod with 18 servos which needs 5V 12A So i need to convert the voltage to 5V but I don't know which converter I should use. I thought about using the LM2596S with 3A max. So i would use 4 or 5 of them to provide my voltage. I am not sure about my decision! Maybe some of you might know better stepdowns or have completly other ideas. Maybe using 12 V Akku Thank you for answers (You can answer also in german if you want) Cheers Max
: Moved by Moderator
A 7.2V battery has ~6V minimum, so you'd better choose a step down, having a correspondingly low dropout.
You should look for two baords with LTC3611.
Hi what do you mean? The LM2596S is a step down converter.
a) 12A switching regulators with integrated MOSFETs are rare. b) is 12A really the highest current that ever occurs, for instance if something is stuck ? c) as you have multiple servos, you can use multiple step down converters, but you should not connect their outputs together (in parallel) but each one supplies his set of servos. d) if you use for instance 1 converter for 1 servo, the converter needs to handle the current that is required when the servo is stuck, which may easily be 3A. In the sum the converters will of course not draw 18*3/(5/12)A e) if 5V/15A is really all you need https://www.pololu.com/product/2881
Max A. wrote: > Hi what do you mean? The LM2596S is a step down converter. There's not much left to step down when the input is at 6V, the output at 5V, and the saturation voltage is 1,5V.
: Edited by User
Use servos designed for up to 8.4V.
Thank you for your answer. I think this Pololu is a good idea. Did you use it before? Do you think I need a cooling? The problem is that I use a PCA 9685 so I would have to use some stepdowns in parallel. So I think this Pololu is the best.
Max A. wrote: > think this Pololu is a good idea Because it requires 6.5V at least, and you supply is not 7.2V as you told but 5V to 8.4V, it will not allow full use of the battery.
Sorry I don't know what you mean
Max A. wrote: > Hi what do you mean? The LM2596S is a step down converter. Yes, but it has too much drop-out voltage. The efficiency at the minimum input voltage of 7V is about 70%. But your battery goes down to 6V or even less. I would use a linear low-drop regulator with a drop-out voltage of 600mV or less. However I cannot recommend any LDO because all that I used are for the range below 1A.
Do you have a link for me. Cause that what I found can only handle with 1A but I need 12A. And I don't want to use so many
You might want to try a buck-boost converter. there are modules available, like this one: Ebay-Artikel Nr. 254169431168 some further information about it is available here: https://www.eevblog.com/forum/projects/reverse-engineeringdeciphering-mystery-buck-boost-circuit/ You might want to replace the Mosfets, as they are not logic level but only driven with 5V at the gate (at least in the one I got). The FETs will begin to enter the linear mode (and heat up quickly) when the input voltage drops slightly below 5V, so make sure this never happens. At 12V input (this is what I tested) and a few amps this module runs fine.
In case your 5V range is 4.9 to 5.2 you could simple built your own low drop linear regulator with discrete transistors. Two out of three mostly do not need all power regulated because PWM supplied consumer can live without it.
I think I will use 3 Li Ion Akkus in Serie for 10,8 V and convert them with 2 buck converter to 5V. Each of them has to handle with 6Amps and they are built to handle with 9Amps so I think this will work. Also I won't have the problem with too low drop-down voltage. Do you think this is a good Idea?
Max A. wrote: > Do you think this is a good Idea? Better than using 2 cells. With 2 cells you need a SEPIC converter. They are not so common and less choices.