Help Request: Regulators.

 
#1

DJ Sures, I need your expertise to finalize my LeXI Project. Here's my question, Her HD-7 arms each have 7 servos. That's a total of 14 servos that need external power. How many regulators do I need to power them right? they will have a power source of 2 x 12v power sonic batteries at 9a each connected in parallel. the batteries will be only for the arms. Also connected to the batteries will be the 2 dc motors. any help would be greatly appreciated so I can complete my robot.

#2

@aameralis you have already asked the question on this thread. Maybe you can continue over there.

DJ has lots of other things to spend his valuable time on. There are people like Rich on this forum who will be able to help you just as well Grin

#3

You can work it out.

Find the maximum current draw of the servos.
Multiply it by the number of servos.
This is the maximum all servos will draw if they all start up at the same time or are at peek load at the same time, which basically means it's enough power for any circumstance.

Your regulators will need to be rated higher than the maximum demand. So, for instance if each servo had a maximum demand of 2A, that would be 14A. So you would need a 14A regulator for these servos or put 3 x 5A in parallel, or use one 5A for every 3 servos (one will have 1 servo on, or do a 3, 2, 2 configuration).

You will also need to check the batteries can give out the required current. A 5Ah LiPo battery with a 20c rating will give out 100Amps (20x5) but a 9Ah battery with a 1C rating (if they exist) wouldn't be able to supply the necessary current and the servos would fail regardless of the regulators.

Don't forget to allow for the DC motor's current draw too.

#4

@aamerlis , there are devices called BEC ( servo battery elimination circuits) designed to drop battery voltage down to a set voltage for your servos. These are lliterally designed specifically for what you want and are switching regulators that don't burn off voltage as heat. Castle creations is a reliable brand used in high end RC planes , heli and jets. They are programmable to the specific voltage you want 4.8 v to 9v output.

I will post one rated 10 amp continuous current.

#5

http://www.ebay.com/itm/Castle-Creations-CC-BEC-10A-6S-Switching-Regulator-/360703623085?pt=Radio_Control_Parts_Accessories&hash=item53fb9c7fad

This is a 10 amp model that I would run no more than 4 high torque servos from to keep it cool. No more than 8 standard ( 200ma to 600ma) servos

#6

UC285 LDO Regulator 5A Adjustable 1.2-6V TO220


http://www.ebay.com/itm/UC285-LDO-Regulator-5A-Adjustable-1-2-6V-TO220-/181052292299?pt=LH_DefaultDomain_0&hash=item2a278ebccb


If you do want the DIY route instead of using a premade regulator like I posted you can use an adjustable 5 amp regulator for each servo as well. Remember the gold rule of power regulation - the stall amp load of the servo needs to be less than the continous rating of the regulator- here are some low drop out cheap regs you can use to power 1-2 servos each to keeps the regs running cool. You just use a resistor jumpered on pin 4 and 5 to control the voltage output. This way you can give the individual servo the voltage it needs 4.8 to 6v

Just a note on Rich's suggestion - he's right you can parallel regulators but when you put multiple loads from different servos the load does not like to balance between the regulators and one can run hotter than the others and in the event it gets too hot it could fail. That's a possible situation and I just want you to know all your options. Two things can be done to remedy multiple loads. You can put a diode on the emitter of each regulator and a heatsink is a must. Pranav used parallel regs for lower amp loads on his project. The other obvious option is having a switching regulator like the one I posted that is premade for the job or individual regulator for every 1-2 high torque servos.


Personally I'm a DIY guy and I'm fine with a reg for every servo , it means if a reg overheard or goes bad that the damage is isolated to only that one regulator and servo and maybe the power fuse. It keeps larger oops moments from happening. I hope you found this informative. - Josh

#7

That would cost over $84 for 16 servos. 12ARM plus two NECK. Then, would we be done? This project is eating my lunch. It is my own fault. I always think BIG.

*eyeroll*

#8

@josh how to you program the first one( BEC)?

#9

@Mel , talking to aamerlis a while I know he likes to get the most from his equipment. You can use 5 volt reg which are much cheaper but you will get a little less torque rating than 6 volts would give you.

LM1084 5v regulators , 1 per servo and these handle 5 amps continous each. On eBay they are 10 for $5

Since these are cheap and handle 5 amp they are a great choice to regulate each of your servos Mel. They just want get you max potential of the servo at 5 volts but you could get the job done for around ten dollars. Smile

#10

@aameralis , you buy the castle creations usb cable to program them. Download software from their website. They are switching regulators so they are much more efficient and cooler than a analog regulator.