Marro

Does anyone have any suggestions on how to extend the range of motion of the HS-55 servo? The servo will move for about 180 deg, but once connected to the radio the max range is a little more than 90... I'm aware of the ServoMAX, but it's pricy... Any other clever alternatives?

Thanks,

Miro

alan0899

G'day Mate.
Longer servo arms, & shorter control horns, they will increase your control surface throw.
I am assuming this is what you require.

Marro

Good idea, but it's not the throw I'm after... I need 180 degrees of motion...

Miro

pilotpete2

Also you may be able to get more travel from the servo by increasing the ATV setting for that channel in the radio setup, this assumes your transmitter has adjustable ATV, or that you haven't already maxed it out.
Allans suggestion is good also, though be aware that longer arms on a sub-micro servo will make them more susceptible to stripped gears.
Good luck,
Pete

Marro

ATV is maxed out, but still nowhere near 180 deg...

Marro

To answer my own question:


To increase the range of motion on the servo, you
need to put a resistor in parallel with the pot that you have. If it's
a 5K pot then adding a 5K resistor in parallel will about double the
range of motion. Note that if the current range of motion is not
centered in the total ROMotion then adding another resistor could just
lock the rotor all the way to one side. I would suggest that you get
three of the miniuture 10 or 20 turn pots that Radio Shack sells and
put on in series on each side of the pot, and one in parallel across
the pot, then you can adjust range, span, and center to match your
needs. If that is the servo that I'm thinking of, you may be able to
put all three inside of the case with 3/32" holes to allow adjustment.



[link=http://groups.google.com/group/comp.robotics.misc/browse_thread/thread/541463ee67d349ec/ada18e197b962eb1?lnk=st&q=how+to+increase+the+motion+of+servo&rnum=1#ada18e197b962eb1]Original article[/link]



Has anyone tried this??

Miro

redfox435cat

Get one your willing to screw up. pop the case and look for the pot. It is the thing between the output shaft and the circuit board, with it plugged in you can turn it slightly either way and motor will turn. I forget the values, it has been 10 yrs but you can solder the same value 1/4 watt resistors on the two outside poles of the pot. cut one solder it in and cut the other and solder it in. DO not mess up the alignment with the output gear. . then on the top portion of the case cut out he plastic stops molded into the case. put it back together. if you get it right the output will have increased to 180 degree. I assume your trying to make a cheap retract servo since this is what I did mine for


whoops you got it

I did this in a tower sysem 3000 #53 servo and it worked very well. It wasn't very percise becuase it was outside it original desighn specs but it served it perpose well and used it in my super sport as a retract servo for 5-6 years with no problems

alan0899

G'day Mate,
Do you need 180 Deg servo motion for use in retracts? If so, you need a retract servo!

Marro

No retracts. I made the pan/tilt head for the camera, but the 90 deg of travel for pan is too limiting. It's ok for tilt, though. There is practically no force that servo needs to exert, it's just the range...

Miro

rob10000

Marro, here's my experiences. I've been flying FPV with pan/tilt for a few months now.
I looked inside a HS-55 with the idea of adding the resistors, then said "no way" when I saw how tiny everything was inside, with almost no extra space for anything. I bit the bullet and bought the Servomax and increased my travel that way.
BTW, I had to retire my HS-55 because even though the servo is not connected to any linkages, the mass of the camera (cased KX-131) and the tilt mechanism up high puts alot of leverage on the output shaft and it's bushing(in the case of the HS-55, that bushing is the case!) It got sloppy pretty quickly.
I've since moved up to a HS-81 that should be more tolerent. I don't know how critical weight is in your application, but another solution is to buy a HS-225 from ServoCity. They offer the option of 180* rotation for an extra $10.
However, it's 21g heavier than the HS-55.

Marro

Good to know. Thanks. How's your experience in FPV? Do you have some advice?

Miro

Tech-RCU

Marro,

We offer a device a called a servo stretcher. It plugs inline like a servo extension and will make any servo such as the HS-55 travel 180 degrees. It modifies the signal going to the servo. They are not on our site yet but just give us a call at 620-221-0123. They are in stock and about $14.00. Thanks

ServoCity
Tech

Marro

Hey, what happened to the post that said someone had the servo extender for sale for $14??

Miro

Tech-RCU

Our reply must have been deleted. We offer a device called a "servo stretcher" that plugs between a servo and the controlling device. It modifies the signal and makes a servo that normally operates 75- 90 degrees into 180 degrees. It is not on our site yet but will be very soon or you can call us at 620-221-0123. Thanks

Tech
ServoCity.com

davewallace

My Feedback: (29)

Marro,
Here is a link that I found to change to as much a you want. They have a bunch of other electronic projects for RC also.


Dave

http://www.uoguelph.ca/~antoon/gadge.../servomod.html

JGspeed

To get the servo to give a greater degree of throw with no changes in the variation of pulse width control signal, you would have to replace the pot with a value higher than the original. As an example, if the original pot were 10 Kohms and you wanted to increase throw by 30% you would have to go up to a 13 Kohm pot. Since pots are made in standard values, you would have to take a higher standard value and bridge it with a fixed resistor that would approximate the target value. I haven't dissected an HS-55, but I would expect it might be tough to find a source for the same physical size in different values. Mechanically there should be no problem. Any servo I've had apart since the 70's had stops on the output gear that would allow 180deg. of rotation.