Hello all!
anyone can provide me with informations about the Hitec HSR 1422-CR?
cant find any information on the web…
thanx
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I’ve never heard of that servo.
In fact, in it’s .pdf catalogue, Hitec doesn’t use the label “CR”.
The closest servo to that is the:
HS-422 (57 oz. in.) Standard Servo
Description -
Size = Standard
Voltage = 4.8 - 6.0vdc
Torque = 57 oz.-in.
Weight = 1.66 oz.
Speed = 0.16s / 60 degrees
Part# S2-01 ] $12.99
Woops!
Sorry Marc, I forgot about that one.
That’s just a 422 servo that’s modified for continual rotation.
I believe that Jim modifies them for continual rotation himself, which is why I didn’t find them in the catalogue.
You can find the tutorial here, if you want to see how it’s done, or do it yourself:
lynxmotion.com/images/html/smodh2.htm
I believe that almost all servos can be altered the same exact way.
However, you’re going to need a hacksaw or a metal abrasion cutter (i.e. dremmel tool) to get the metal gears cut, on the “MG” tagged servos.
I’m not sure what would cut the titanium gears on the 5995TG, but I doubt a hacksaw could do it.
Then again, you might as well just buy a regular motor and get way more torque for way less money, at that point.
CR servos are not the best form of locomotion for a bot, but they are probably the easiest to work with when your building a small non-violent bot.
Thanks Nick,
i am planning to use the CR as a head mount for a SRF05 ultrasonic sensor. this way, i can perform a full 360 degree sweep.
however: how do i control it? i found out, when pulsing eg. 1511ms (strange, isn’t it???), the motor stops. anything above (until about 2500ms) will make him turn CW, anything below will make him turn CCW. However: 0ms stops the bugger as well…
depending on the “distance” from the pules value to the “middle” (1511), the speed increases.
is that normal behavoir? can i center the bugger at exactly 1500?
looks bewildered
Aye, if you read the tutorial, that’s what it says is supposed to happen.
It outlines one way that you can center it, by changing the resistion (should be a word) of the internal pot.
The alternative method is to use the Visual Sequencer (you might be able to do it with the LynxTerm, but I don’t know, as I haven’t updated the firmware since I downloaded it in November) to set the pulse offsets and thresholds.
The pulse offset is 11 ms too much, in your case.
The thresholds for this servo are 500 as the min and 2000 as the max, but you’ll want to take a look at the tutorial that I linked you to, to make sure that my memory isn’t playing games with me.
I know that it’s a big NO-NO to tell the servo to turn more than it can when it’s not a CR servo (they heat up and die very quickly because they’re pushing against the physical stoppers that were cut off in the CR servo).
I’m not sure that you could hurt your servo by telling it to go to a 0 ms position, but I wouldn’t force the issue, if I were you.
I actually had Hitec make them up special for us. We don’t have time to do the mod in house. 
But then you can’t use the neeto servo erector set brackets.
I’m not sure what would cut the titanium gears on the 5995TG, but I doubt a hacksaw could do it.
actually titanium is quite easily abraised. meaning a grinder type cutting wheel on a dremel
nick
Once the servo is made continuous rotation, you no longer have the ability to move the final gear to an exact position. You need to implement some sort of feedback. You can implement a 2:1 gear increase (not reduction) to get about 360 from a normal servo at half the resolution and torque.
Ok,
that means i can only control direction and speed of rotation, am i right?
thus, i have to do something like this:
move left at speed X
pause <amount of time>
stop
the angle is then a function of X and , isn’t it?
You’ve got the right idea, but without the potentiometer (which has been ripped out as part of the modification) you can’t be sure. The duration and duty cycle (distance from center pulse) you’ll have to send to get it to move the same angle will increase with weight. If your weight is offcentered and the axis is not precisely vertical, you’ll have a changing load which will be tricky too.
What are you doing about the cable to the srf05?
hmmmm…
ok, the weigth should be (relatively) fixed. a multi purpose sensor housing and a srf05. i will give it a try.
if it dont work, i will dump the idea and do it with a standard servo like this:
- sweep from 270 to 90 degree
- turn around
- sweep from 270 to 90 degree
should be pretty the same…
i plan to do a sensor sweep from 181 to 179 degree (with 0 being the center) and then moving the head back to center. no continous rotation. no problems with the wire…
Hi Jim,
I have another question about this servo. I have purchased several from you and have noticed they seem to have a larger and more desirable dead band than a modified servo. They don’t have that “hunting or motion” tendency if being used in an RC application.
There must be something that the manufacturer does to put this feature into the servo. I have the need to put together a pan and tilt unit but need to use a metal gear trained servo with a coreless motor to accommodate a very smooth pan. I fear modding my own servo with the standard 360 degree hack just won’t do as well as your unit as far as standing still with no stick input.
Is there something they do in the voltage divider network or else where that you know of to increase the dead band of my unit?
Thanks Jim
Dan
I requested a larger deadband, but I do not know what thet did to make it happen.
Thanks for the quick reply Jim.
I’ll pull one of yours apart and see if they’ve done anything different with the voltage devider resistors than what we do with our hacks.
Dan
Hi, I was wondering if how I can implement the 2:1 gear increase. Is this a modification to the servo with gears that can be purchased from Hitec?
No the gears would have to be external to the servo. Sorry…