Servo Controll Help

Master_Gix

I was in my local hobby store the other day and I saw this tiny little servo made by Grand Wing Servo. Modle Naro STD. So I snatched it up, as it was only about 10 bucks. Well it came with little to no documentation, all it says is it is compatable with any system using 1500 us neutral. I was wanting to use it as a place to mount my IR sensors so I can get a nice Sweep reading without my bot having to move. So I plugged it in just like my Parallax servo and well... It doesnt work at all. It will spin only one direction and then get hot as hell.
Im not a electronic guru, or do I have the proper devices to try and measure the actual timing of the servo, but im guessing it runs on a diffrent PMW frequency than my other servos. I tried pluggin in some random Numbes to no avail. Or it could be that is needs some extra companents that my current servos dont.·I would really like to use this tiny little servo, as it is really really small, but if no one has any clue Ill just make my sensor sweeper out of a GIAGANTIC Parallax servo .

Thanks for any help.

allanlane5

Did you connect up a common ground?

And yes, the Parallax servo also uses a 1500 uSec (or 1.5 mSec) pulse to center the servo.

Note this is a 'positive' going pulse, repeated every 20 mSec. Thus you MUST do an 'LOW ServoPin' before doing anything.

It sounds like either you don't have a common ground, or you are commanding the servo all the way to the stop and leaving it there -- which would make it heat up.

I'm assuming it uses the 'standard' 3-pin servo connection, of course, or it probably wouldn't move at all.

Master_Gix

I have connected a Parallax servo and it works fine, not a single problem.
Im just using the folling simple code to test it, and it really freaks out.

x var word
output 1
here:
for x = 1 to 100
pulseout 1,500
pause 10
next
pause 500
for x = 1 to 100
pulsout 1,1000
pause 10
next
pause 500
goto here

Like I said the parallax servo works fine with the code above. But the little Grand Wing servo just spins to one extreme and starts to heat up. All I do is unplug the Parallax servo and plug in the GW servo. That is why I was assuming perhaps it runs on a diffrent timming. I know just enough about robot building and programming to really break stuff, but I do have fun. =D

allanlane5

1. You are only doing a 'pause 10', when the spec says do a 'pause 20'. Perhaps the Parallax servo's are more forgiving.

2. Nowhere do you say 'LOW 1'.

3. OK, let's assume it uses a different pulse width. Now you need to find that pulse width.


LOW 1
FOR I = 1 to 10
PULSOUT 1, 100
PAUSE 20
NEXT

Run that, and see where the Servo goes. Keep upping the PULSOUT parameter until you can center the servo.

It's also possible the little servo is defective, does not have its resistor hooked up.

It sounds like you've ruled out grounding problems, and polarity problems. Now you're in to new research. Good luck.

OH!· What voltage are you using?· The Parallax servo's should be good at 5 volts or 6 volts.· I don't know how forgiving the 'Wing' servo is.· Look it up on the web, if you want to make sure.

Master_Gix

Checked the voltage on the GW servo websit, it supposed to run between 4.8 - 6.0 v, so I think im alright there.
Although I did just run a program that has only one single line:

Low 1

Heh, it spun all the way to one side and started to heat up, just like when I run the above program. Im starting to think this lil servo is just defective. Because it shouldnt do anything at all with a Low 1 command.

BTW thanks for all the help so far. =D

Bruce Bates

Maaster_Gix -

Are you sure the servo is wired correctly per the GWS web site? Not all servos are wired alike, and not all servos are wired as the Parallax servos are, in terms of which color wires are used for which purpose. Here are two common wiring/color assignments:

signal positive negative

---

---

---

orange red brown
white red black


Regards,

Bruce Bates

Armored Cars

Is the third wire white or blue? White is negitive shift and blue is positive. Futabas (and most other companies) are always white, but Airtronics are blue and are not compatable. It drives me crazy because I have a radio system that doesnt work with any of my servos.

Look at www.towerhobbies.com and get a mini or micro Futaba if that one doesnt work. The extra money will be worth it.

Master_Gix

It has a Black red whit color pattern. I roamed around the GW servo website a while and couldn't find any wiring specs. So I did what any hobbiest would do.. I tried them all to see what works. The best pattern, well the only pattern that didnt make the little green led dim and the 5v regulator start to heat up on the stamps carrier board was, Vdd - red, Vss - white, Signal - black. But it still just spins all the way to the right and stops no matter what number I put into the pulsout command.

I var word
LOW 1
FOR I = 1 to 10
PULSOUT 1, 100 (I have tried everything from pulsout 1, 1 to pulsout 1, 20000)
PAUSE 20
NEXT

Wow and let me tell you the Parallax servo doesnt like that wire pattern at all.

Ah well, if it turns out to be a lost cause, ill just buy me another micro servo, this time from Futaba.

steve_b

Based on the colours, I'd assume (I know I know...don't ASSume!) that red is Vdd and Black is Vss leaving white as the signal.
Does that do anything?

The wiring colour would be VERY non-standard to use white as ground.

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Steve
http://members.rogers.com/steve.brady
http://www.geocities.com/paulsopenstage

"Inside each and every one of us is our one, true authentic swing. Something we was born with. Something that's ours and ours alone. Something that can't be learned... something that's got to be remembered."

Master_Gix

On this lil servo, when i apply red to Vdd, black to Vss and white to signal the 5v regulator on the stamps carrier board starts to heat up and that little green led goes real dim. I'm thinkin thats a bad thing, so i dont leave it connected like that for verry long. The Parallax servo i have works just fine with that configuration.

One day.... One day I will build a robot that does more than burst into flames.... Although that is quite a specital to behold.

I guess im prolly going to have to order me a micro Futaba. Which means that I have to wait DAYS for it to come in the mail. I guess im going to have to go back to holding my sharp IR range finder in my hand, spinning it around every now and then and making brrrrrrrrrrrrr noises with my mouth.

allanlane5

Oh -- you "tried them all to see what works"?

One of the pins needs to be +5. One needs to be ground. If you reverse these two, you burn up the Servo's control electronics.

I don't have a BOE in front of me, but I thought it was Black is ground, then Red is +5, then White is signal -- in that order.

When I get home tonight, I'll see if you can check this stuff with a voltmeter.

I HAD hoped that the Servo 3-pin standard was a STANDARD, you know, everybody does it ONE way? Instead it sounds more and more like the RS232 'standard', where you have three-wire, DB-9, DCE, DTE, RJ45, whatever. So many different ways to implement it, that this becomes the first problem you have to solve before you can make any more progress.

steve_b

Just looking at my parallax "standard" servo....and ya...red is +5; black is gnd and white is signal.

And it certainly sounds like you've shorted something out at some point and when you connect it normally it's drawing hard on the regulator (hence the dimming).



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Steve
http://members.rogers.com/steve.brady
http://www.geocities.com/paulsopenstage

"Inside each and every one of us is our one, true authentic swing. Something we was born with. Something that's ours and ours alone. Something that can't be learned... something that's got to be remembered."