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Asked — Edited

Recommendations For Buying Additional Servos

Hello,

I would like to expand my kit and buy a few more servos. What do you recommend?

I have noticed a couple different price levels.

Hitec 33322S for $11.41
Hitec 33322S Amazon

or

Hitec 35485S $19.88

Hitec 35485S Amazon

Are these good servos to work with the EZ-B? Why is there a difference in price? What are the benefits of more expensive servos? How much should I be paying for one standard servo?

Thanks!

United Kingdom
#1  
They will have different torque ratings.

33322S Torque oz./in. (4.8V/6.0V): 42 / 51
35485S Torque oz./in. (4.8V/6.0V): 72 / 89

Depending on their use you may need high torque or you may get away with a cheaper one.

Prices, I don't know since I'm UK based.
#2  
What is the torque of the EZ-Robot servos that come with the kit?
United Kingdom
#3  
From the info on the store page around 2-3kg/cm but I'm not 100% sure, I'll have a proper look when I get home where I can see better:)

What do you need the servos to do? Ideally (although few ever do) you should calculate the required torque. Generally I just throw the high torques in everything now to be on the safe side, it costs more but I wasted too much on Melvin when I was going cheap.
#4  
Im not sure exactly, I just wanted to get some extra servos to experiment with various robots especially since I can start 3D printing various designs. I wanted to compare the torque of the EZ-Robot servos to the ones I listed from Amazon.
#5  
@feroze standard rated servos are approx 61 oz in. The standard can vary slightly from brand. There are servos with different specs that ate better at certain tasks. You first want to ask what exactly are you wanting the servo for? Then a little math will help you with choosing the specs you need. Two major points are max torque and speed. Speed is rated in the lowest possible time it takes for that servo to move a certain number of degrees. For example a .14 sec @ 60° means it take .14 sec to move from center to 60° in either direction. So ask yourself what you will be using a servo for and how much pressure in ounces it must pull or push. In most cases a standard servo in the Ezrobot store ( a private labeled futuba s3003) or the 995mg high torque will take care of your general needs.
#6  
Yah I just want to get like 2 more servos that are comparative to the EZ-Robot servos. Unfortunately ordering the servos from EZ-Robot located in Canada is not cost effective with shipping. So I am looking to get from Amazon.


HiTec 33322S Amazon

These servos seem to be comparative. Will they work with the EZ-B?
United Kingdom
#7  
Yeah they should work as far as I can tell. Pretty much any analogue or digital servo will work with ARC.

Personally I use the 995MGs Josh mentioned, they are high torque and metal gear so can handle pretty much anything I throw at them. I learnt when I was messing with Melvin's arms that cheap isn't good, I spent more on rubbish than the good ones cost in the end.

Also, be careful where you buy. There are a lot of counterfeit servos out there. By that I mean cheap knockoffs from China which aren't very good. I made the mistake of buying a bunch on ebay and, well, I wish I hadn't. If they are priced too cheap then be careful:)
#8  
I found some of those MG995 servos on Amazon:

MG995 Amazon

Do they require an alternate power source? Or can they be powered from the EZ-B? I know some metal servos need an alternate power source.

Which would you recommend the Hitec ones of the MG995, they are about the same price
United Kingdom
#9  
The EZ-B will power them but you get more out of them and avoid possible brownouts if you supply them with 6v, it depends on the robot at the end of the day, but supplying with 6v is pretty simple, I have covered it in my showcase for Melvin (I think it's called Project Hearoid) and plan to do a tutorial for a quick and easy method.

I have only used the MG995s so can't really compare them but I have no problems with the MG995s other than a browning out issue with the LCD screen (the EZ-B only supplies 5A I think, which was not enough for 2 servos and the LCD so I had to supply the power externally).
#10  
I found the post for Project Hearoid but couldn't easily find out how to power my servos with 6v instead of from the EZ-B.
United Kingdom
#11  
If your battery is 6v then it's very simple, basically just take a +ve and ground from the battery to the servo.

If you use anything else you need a 6v regulated circuit, I use an Etronix regulator. This connects on to the battery, from that you can take it to a distribution block, strip board or whatever and then on the servo, connect the red & black (or whatever colours the vcc and ground are) to the 6v supply.


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#12  
@feroze I would use alternative power like Rich is displaying on any high torque servo. You get much more holding power with 6 volts and there is the added benefit of keeping the brain of your robot , EZB, nice and cool.
#13  
HiTec Standard Karbonite Servo

I will use alternative power in the future, but for now I just got similar servos to the ones that came in the EZ-Robot kit. I compared the specs of the Hi-Tec servo with the Futuba s3003 and the specs were close to the same.

The torque at 4.8v was 42 for Hitec and 44 for Futuba. The speed was about the same too.

So I decided to go Hi-Tec servos because of prime shipping. They should work directly with the EZ-B right with no alternative power source. Also all standard servos should be the same size right? So these servos should fit the EZ-Bit mounts correct?