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Model Forum / Radio Controlled / Water Models / December 2003Looking for 360 degree (only) Servo
I'm looking for a medium heavy servo (like Hitec 715 or 725) with a travel of at least 340 degrees. A winch servo like the 725 doesn't work because its designed to make about 7 full turns for a full range of pulse widths - making the position resolution pretty sloppy within one rotation. Yes, I can do gears or install an external potentiometer - I was just hoping to find a servo I could use without modification but my web surfing isn't turning one up. Any pointers to manufacturer/model would be appreciated. tnx mgg I've got an FP-S136G. Its a futaba retract servo. Will that work? > I'm looking for a medium heavy servo (like Hitec 715 or 725) with a > travel of at least 340 degrees. A winch servo like the 725 doesn't work [quoted text clipped - 7 lines] > tnx > mgg If you let us in on what you are trying to do, maybe someone here can come up with an elegant solution.  SignaturePaul McIntosh Desert Sky Model Aviation http://fly.mcintoshcentral.com > I'm looking for a medium heavy servo (like Hitec 715 or 725) with a > travel of at least 340 degrees. A winch servo like the 725 doesn't work [quoted text clipped - 7 lines] > tnx > mgg Go to servocity.com and look at Hitec servos. It is not listed in the chart, but if you pick a servo, the description lists whether 360 modifiable or not - example, HS-425BB, 700BB and 705MG servos are and HS-81 isn't. I do not know what's involved, but an email to Servocity will get you an answer. David >I'm looking for a medium heavy servo (like Hitec 715 or 725) with a >travel of at least 340 degrees. A winch servo like the 725 doesn't work [quoted text clipped - 7 lines] >tnx >mgg > Go to servocity.com and look at Hitec servos. It is not listed in the > chart, but if you pick a servo, the description lists whether 360 > modifiable or not - example, HS-425BB, 700BB and 705MG servos are and > HS-81 isn't. I do not know what's involved, but an email to Servocity > will get you an answer. tnx, but the common "360 servo mod" is to turn the servo into geared reversible DC motor, easily controlled via a standard RC receiver. the geard potentiometer is replace with a resister bridge. I want position controlled nearly 360 degree movement. That takes a specially built single turn potentiometer or a multi-turn potentiometer with just the right resistance range. As for the question about what I want to do - I've spent a lot of time thinking about good ways to do this - and finding the right servo if it exists is the simplest solution. Changing out the pot in the servo with a different multi-turn one with the right resistance range to get just over one turn would be the next best solution. What am I trying to make - well think light weight pan tilt zoom - except most PTZ units only rotate around 180 degrees. I'll pop servo city an email though and see if they can shed any light. tnx mgg > David > [quoted text clipped - 9 lines] > >tnx > >mgg > > Go to servocity.com and look at Hitec servos. It is not listed in the > > chart, but if you pick a servo, the description lists whether 360 [quoted text clipped - 22 lines] > > > David David, why not try changing the existing pot for a multiturn as you first thought (the resistance isn't that important it's the voltage that is used to sense the direction) and add in two fixed or variable resistors at either end so you can adjust the endpoints? Chris I am afraid that servos don't work like that. You need to get the right resistance /rotation ratio and adding resistors won't do that. His best bet is to get a tilt/pan setup designed for what he needs. Anything else will be a kluge. SignaturePaul McIntosh Desert Sky Model Aviation http://fly.mcintoshcentral.com > > > > > Go to servocity.com and look at Hitec servos. It is not listed in the [quoted text clipped - 37 lines] > Checked by AVG anti-virus system (http://www.grisoft.com). > Version: 6.0.551 / Virus Database: 343 - Release Date: 11/12/2003 I don't know about modern servo amps, but the amps I built for my Royal Classic system kit DID work that way. The servos could be modified to sweep up to 250 degrees by CHANGING the values of the fixed resistors on either side of the pot ! ! ! ! ! David >I am afraid that servos don't work like that. You need to get the right >resistance /rotation ratio and adding resistors won't do that. [quoted text clipped - 43 lines] >> Checked by AVG anti-virus system (http://www.grisoft.com). >> Version: 6.0.551 / Virus Database: 343 - Release Date: 11/12/2003 > tnx, but the common "360 servo mod" is to turn the servo into geared > reversible DC motor, easily controlled via a standard RC receiver. the [quoted text clipped - 10 lines] > - well think light weight pan tilt zoom - except most PTZ units only > rotate around 180 degrees. do you need control in the form of a servo? as most pan tilt units only have on off motor control and they stay were you put them using no power refer to http://homepages.ihug.co.nz/~atong/ = Alan's Hobby, Model & RC Web Links and scroll down the headers to "Servo & TX alterations, calculators, clonepacs, make an ESC or winch, FAQ." in particular "Servo mods to 180 and 360 degree operation.. Gang and Fit servos " http://www.amya.org/us1mpt4.pdf [16 page PDF download] regards Alan T. Alan's Hobby, Model & RC Links http://homepages.ihug.co.nz/~atong/ ............................................................. > I'm looking for a medium heavy servo (like Hitec 715 or 725) with a > travel of at least 340 degrees. A winch servo like the 725 doesn't work [quoted text clipped - 7 lines] > tnx > mgg > refer to http://homepages.ihug.co.nz/~atong/ > = Alan's Hobby, Model & RC Web Links > and scroll down the headers to > "Servo & TX alterations, calculators, clonepacs, make an ESC or winch, FAQ." > in particular "Servo mods to 180 and 360 degree operation.. Gang and Fit That might have been correct at one time, but it isn't today. I have a 715 - and the pot in it has its own internal travel limit. Turns about 200 degrees. If I added resistance to make the server want to travel 360, it would simply tear the guts out of the pot. The pot does look fairly standard though, so I expect I can replace it with something that will do what I want. tnx mgg > servos " http://www.amya.org/us1mpt4.pdf [16 page PDF download] > regards [quoted text clipped - 16 lines] > > mgg > SignatureReal Working Engineer What about a PIC between the receiver and servo that takes 1~2 ms input and outputs a suitable amount of steps for the pulse range that equals 360º? The PIC experimenters could probably code that up fairly readily. >I'm looking for a medium heavy servo (like Hitec 715 or 725) with a >travel of at least 340 degrees. A winch servo like the 725 doesn't work [quoted text clipped - 7 lines] >tnx >mgg John Hawkins - From Canada's Atlantic Coast http://rcalbum.rchomepage.com/Home.html Most servos I have looked into have mechanical stops at around 190-200 degrees of total travel. Same with the pots as most modern servos have direct drive pots. At best, those will allow about 250-280 degrees. SignaturePaul McIntosh Desert Sky Model Aviation http://fly.mcintoshcentral.com > What about a PIC between the receiver and servo that takes 1~2 > ms input and outputs a suitable amount of steps for the pulse range [quoted text clipped - 15 lines] > John Hawkins - From Canada's Atlantic Coast > http://rcalbum.rchomepage.com/Home.html I was thinking in terms of using only one revolution of a multi turn winch servo. In order to have full deflection of the transmitter stick equal only one revolution of the servo the input to the PIC would be translated to the necessary output pulses to the servo. For example say for the servo given pulse width from 1 to 2 ms = 7 revolutions so one revolution would be from 1 to 1.14 ms (or any similar range within 1~2ms) So for 1ms input the PIC output would be 1ms and for 2ms input, output would be 1.14 ms. Intermediate values would be proportionate. This is just a suggestion of the logic. I have only a brushing familiarity with the process. >Most servos I have looked into have mechanical stops at around 190-200 >degrees of total travel. Same with the pots as most modern servos have >direct drive pots. At best, those will allow about 250-280 degrees. John Hawkins - From Canada's Atlantic Coast http://rcalbum.rchomepage.com/Home.html I had a similar problem when installing the Hitec drum type servo winch into my sailboat. What I finally ended up doing was installing a physical stop on my transmitter stick to prevent the servo from overwinding. Limit the stick movement and you limit the servo movement. Cheap and effective. Bill McNeal http://nfloridaorcas.freeservers.com > I'm looking for a medium heavy servo (like Hitec 715 or 725) with a > travel of at least 340 degrees. A winch servo like the 725 doesn't work [quoted text clipped - 7 lines] > tnx > mgg http://servohut.com/HTML/s125fullt.htm May do the job... Gri - grizzlyon ---------------------------------------------------------------------------------- Posted from the RCGroups.com Discussion Forums Visit us at http://www.rcgroups.com <------- Win free R/C Gear View this thread at rcgroups.com: http://www.rcgroups.com/forums/showthread.php?threadid=17793 > http://servohut.com/HTML/s125fullt.htm tnx mgg SignatureI have better things to do with my time that worry who might make fun of my sig. I had this same problem with rotating gun turrets on a model warship. The solution I ended up using was to mount an arm on the servo with fishing line or similar tied to the ends to the ends, the loop formed is wound on a drum, the camera mounted on the drum, this has the advantage of being light. Another solution is to use a 3:1 or 4:1 gear ratio the larger gear mounted on the servo, but this requires much more precision, or maybe a large pulley on the servo driving a small pulley on the camera's rotation shaft. Regards Chris Signature------------------------------------------------------------------------- > I'm looking for a medium heavy servo (like Hitec 715 or 725) with a > travel of at least 340 degrees. A winch servo like the 725 doesn't work [quoted text clipped - 7 lines] > tnx > mgg |
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