180 degree servo's

[Electro12321]

Hi,

I am new to servo's and i dont fully understand the specs that are given on remote control internet shops.

Does anyone know of any cheap servos that are capable of rotating at least 180 degrees?

The only one that i am able to find any decent amount of information about is the Hitec HSR-8498HB which was specially built for the Robonova-I that they have developed. This servo is too expensive at £40 each.


Rob

 

[jimlovell777]

How's this for cheap? **broken link removed**

I bought a few and the work well. Only concern being there is no protection for edge limits, it's up to you to make sure you don't over drive them in a direction. At that price I didn't care.

 

[Electro12321]

How's this for cheap? **broken link removed**

I bought a few and the work well. Only concern being there is no protection for edge limits, it's up to you to make sure you don't over drive them in a direction. At that price I didn't care.

How did you know that this was able to rotate 180 degrees from the specificaton?


Im a little confused with servo specifications when they say things like......
Operating Angle: 40°/ONE SIDE PULSE TRAVELING 400usec

Can someone please explain this to me?

 

[Chippie]

You can take a standard Futaba S148 servo and mod it to do 180.......

 

[Mr RB]

Most of the lower end Hitec servos will do 180', the HS311 and HS422 both will do it but you need to send a signal that is a little out of spec, like 0.9mS to 2.1mS or so instead of 1mS to 2mS.

 

[Electro12321]

Most of the lower end Hitec servos will do 180', the HS311 and HS422 both will do it but you need to send a signal that is a little out of spec, like 0.9mS to 2.1mS or so instead of 1mS to 2mS.

Cheers, is the input signal still linear outside of spec to rotate the output/horn?

For example.

Hitec HS-422.
It appears like its designed to rotate 90 degrees, 1100uS-1900uS.

I calculate that to rotate the output/horn, that 1 degree is 8.889uS.

So to rotate the output/horn the extra 90 degrees is still 8.889uS per 1 degree? So the signal range is 700uS-2300uS?

 

[Mr RB]

I have a few HS422 here and I know them pretty well. They will definitely do the 180' but I can't say exacltly what the uS timings are. From memory i don't think you will need to go as extreme as 700-2300 but it will be a little out of spec.

I didn't specifically notice any change in linearity near the ends of its travel so I guess the linearity is similar to what it is through the bulk of the range.

If you are going to work with servos there is a xtal controlled LCD servo tester project on this page;
Shift1-LCD Projects
you could build it for under $30, and it will move the servo under control of a pot then read the exact uS from the display.

What you are talking about is the exact use for a servo tester.