RCCrawler Forums

jevyguy · 07-27-2009, 09:58 PM

I have a 4 channel futaba TX that does NOT have any EPA adjustments...

No big deal, I purchased a Hitec HPP-21 servo controler so I can fine tune the servo's

My issue is that when I program the servos, the TX is not capable of making the servo's rotate as far as they have been programed to go.

Can I add something to my TX pot's that will allow my servos to rotate the 180* I want them to?

SACCO · 07-27-2009, 11:41 PM

Pics of the Tx?

If you crack it open, you just might find a pot to give you more throw.

clockworks · 07-28-2009, 12:13 AM

Have you tried changing the servo resolution from high to normal, using the programmer? If you servo has this setting, it'll increase the throw.

Next option would be to fit a longer servo arm so that you need less servo movement.

I'll have a think about the Tx travel - not sure if there's an easy way to do it.

Narly1 · 07-28-2009, 05:54 AM

Quote:

Originally Posted by clockworks

Have you tried changing the servo resolution from high to normal, using the programmer? If you servo has this setting, it'll increase the throw.

Next option would be to fit a longer servo arm so that you need less servo movement.

I'll have a think about the Tx travel - not sure if there's an easy way to do it.

You could use something like these:

http://www.electrofex.tv/index.php?c...3e28f9989d2118

Do a web search for "servo stretcher" to find more similar items.

Narly1

jevyguy · 07-28-2009, 07:08 AM

Quote:

Originally Posted by SACCO

Pics of the Tx?

If you crack it open, you just might find a pot to give you more throw.

There are some odd pots in there but I dont dare turn anything.

Quote:

Originally Posted by clockworks

Have you tried changing the servo resolution from high to normal, using the programmer? If you servo has this setting, it'll increase the throw.

Next option would be to fit a longer servo arm so that you need less servo movement.

I'll have a think about the Tx travel - not sure if there's an easy way to do it.

I don't think I have the option of changing the resolution with the 5995/5955
I also want to be able to keep the pivot point as close to the center on the servo horn as possible... More torque!!!

Quote:

Originally Posted by Narly1

You could use something like these:

http://www.electrofex.tv/index.php?c...3e28f9989d2118

Do a web search for "servo stretcher" to find more similar items.

Narly1

That looks like it could work, but I really don't want to add any more electronics to an already cramped truck..
Do you think that I could still use the servo programer with this little guy?
http://www.rcdude.com/servlet/the-13...retcher/Detail

jevyguy · 07-28-2009, 02:23 PM

Quote:

Originally Posted by Narly1

You could use something like these:

http://www.electrofex.tv/index.php?c...3e28f9989d2118

Do a web search for "servo stretcher" to find more similar items.

Narly1

Thanks for the input.. I had no clue anything like this existed.

I just ordered 2 of these little guys

http://www.rcdude.com/servlet/the-13...retcher/Detail

Narly1 · 07-28-2009, 04:46 PM

Quote:

Originally Posted by jevyguy

Thanks for the input.. I had no clue anything like this existed.

I just ordered 2 of these little guys

http://www.rcdude.com/servlet/the-13...retcher/Detail

Glad to help.

Wow, nice price on those. Do note that there are no end-point adjustments on that unit, which means you may end up with too much travel. A servo sitting jammed against a physical hard stop is not a happy camper.... especially the digital ones....

Narly1

jevyguy · 07-28-2009, 05:28 PM

I am not worried because I can still adjust the endpionts with my programer.
It might take a little tunning, but I am sure it will work out

Narly1 · 07-28-2009, 06:57 PM

Quote:

Originally Posted by jevyguy

I am not worried because I can still adjust the endpionts with my programer.
It might take a little tunning, but I am sure it will work out

Cool, sounds like you have thought this through. Let me know how you make out.

Narly1

jevyguy · 08-04-2009, 01:15 PM

No go... They didn't even work.
It could be that I have digital servos, but I even tried an old anolog JR. For some reason it didn't work either. It could be something to do with the receiver, but who knows. Needless to say I will be sending them back

JeremyH · 08-04-2009, 01:32 PM

Quote:

Originally Posted by jevyguy

I don't think I have the option of changing the resolution with the 5995/5955
I also want to be able to keep the pivot point as close to the center on the servo horn as possible... More torque!!!

Yes you do. Here is the manual for the HPP-21:
http://www.hitecrcd.com/product_file..._Manual_US.pdf
Scroll down to the bottom of the first page....it tells you how to change the resolution/throw on the bottom right.

jevyguy · 08-04-2009, 04:48 PM

Quote:

Originally Posted by JeremyH

Yes you do. Here is the manual for the HPP-21:
http://www.hitecrcd.com/product_file..._Manual_US.pdf
Scroll down to the bottom of the first page....it tells you how to change the resolution/throw on the bottom right.

If you read the instructions, it clearly states: "This feature allows a choice of high or normal resolution for HITEC HS-7XXX series G2 digital servos".

If you read my post, it clearly states that I am using a 5995/5955, not anything with a 7

JeremyH · 08-05-2009, 04:19 AM

Quote:

Originally Posted by jevyguy

If you read my post, it clearly states that I am using a 5995/5955, not anything with a 7

Well, you are correct, I didnt read closely.

Which one of those servos do you have? Because one of the two numbers that you listed is already setup to have 180* throw...

oldhippie · 08-05-2009, 05:45 AM

Quote:

Originally Posted by jevyguy

No go... They didn't even work.
It could be that I have digital servos, but I even tried an old anolog JR. For some reason it didn't work either. It could be something to do with the receiver, but who knows. Needless to say I will be sending them back

I used one of those things for steering with a jr9100t/3pk and it worked great. Don't know what the problem is with your setup. I also used a servo city Servo stretcher:
http://www.servocity.com/html/180o_servo_stretcher.html
for a r2d dig with a futaba 3003/traxxas tq3 with good results.

jevyguy · 08-05-2009, 02:25 PM

Quote:

Originally Posted by JeremyH

Well, you are correct, I didnt read closely.

Which one of those servos do you have? Because one of the two numbers that you listed is already setup to have 180* throw...

It's all good, but you did get my hopes up a bit.

I use a 5955 in the front and the 5995 in the rear. The 5995 is programmed to throw 180*, but my steering pot in my TX wont allow for that much travel. This is the reason I got the servo stretcher

Quote:

Originally Posted by oldhippie

I used one of those things for steering with a jr9100t/3pk and it worked great. Don't know what the problem is with your setup. I also used a servo city Servo stretcher:
http://www.servocity.com/html/180o_servo_stretcher.html
for a r2d dig with a futaba 3003/traxxas tq3 with good results.

I don't know what my issue is either, I really wish they would have worked. The company I bought them from say that they have had great success so far.

I did see that unit. I dont know if your servo is digital, but the specifications say it is for anolog servos. Besides I was looking for something very compact because I already have very limited space

Narly1 · 08-05-2009, 03:21 PM

I would be inclined to do a couple of things:

1. Check that the wiring between the receiver, stretcher, and servo are all intact and correct. Is there a chance that you have either the stretcher or servo or both plugged in backwards such that the signal and -ve wires are reversed?

2. Hook an oscilliscope between the signal and ground pins on the channel of interest. The pulse width should be I think 120 msec. Move the transmitter control for that channel around to see if the pulse width changes. Then plug in the stretcher and verify that the new pulse width is 2x or aprox 240 msec.

Narly1

jevyguy · 08-05-2009, 05:02 PM

The servo actually worked, it just wouldn't throw it any further than it was already programmed to. Besides that if I would hold the TX in the full turning position the servo would turn, but then go back to center after a few seconds even though I was still against the stop on my TX

I already sent them back, and I have no sort of access to an osciliscope

clockworks · 08-05-2009, 05:11 PM

Sounds like the stretchers were suffering from a lack of voltage through the Rx. What ESC are you using, and do you have an external BEC?

jevyguy · 08-06-2009, 10:00 AM

Quote:

Originally Posted by clockworks

Sounds like the stretchers were suffering from a lack of voltage through the Rx. What ESC are you using, and do you have an external BEC?

2 tekin FXR-Pro's, and a CCBEC set at 6.5v

YJ_Driver · 08-06-2009, 10:52 AM

Assuming you're running the servo off the 6.5V BEC, is that stretcher rated to run at 6.5V? That circuit might not work well or may have been damaged if it wasn't designed for that high a voltage.

I had the same situation using an old radio but with a HS7955, so my solution was to set the servo to normal resolution and tune the endpoints.

For you I think the only solution is a stretcher. Don't mess with the pots internal to the TX, they are NOT for EPA and you'll just mess something else up. I don't think there's anything simple you can do to the TX either. You could add two resistors from the steering's pot middle pin to the end pins, but no guarantees and your steering won't have a linear response.

Richard

07-27-2009, 09:58 PM	#1
jevyguy Quarry Creeper Join Date: Jul 2005 Location: Utah Posts: 261	Epa... Fix??? I have a 4 channel futaba TX that does NOT have any EPA adjustments... No big deal, I purchased a Hitec HPP-21 servo controler so I can fine tune the servo's My issue is that when I program the servos, the TX is not capable of making the servo's rotate as far as they have been programed to go. Can I add something to my TX pot's that will allow my servos to rotate the 180* I want them to?

07-28-2009, 12:13 AM	#3
clockworks Rock Crawler Join Date: Feb 2008 Location: UK Posts: 818	Have you tried changing the servo resolution from high to normal, using the programmer? If you servo has this setting, it'll increase the throw. Next option would be to fit a longer servo arm so that you need less servo movement. I'll have a think about the Tx travel - not sure if there's an easy way to do it. Last edited by clockworks; 07-28-2009 at 12:26 AM.

08-05-2009, 03:21 PM	#16
Narly1 Quarry Creeper Join Date: Jul 2008 Location: Erin, Ontario, CANADA Posts: 471	I would be inclined to do a couple of things: 1. Check that the wiring between the receiver, stretcher, and servo are all intact and correct. Is there a chance that you have either the stretcher or servo or both plugged in backwards such that the signal and -ve wires are reversed? 2. Hook an oscilliscope between the signal and ground pins on the channel of interest. The pulse width should be I think 120 msec. Move the transmitter control for that channel around to see if the pulse width changes. Then plug in the stretcher and verify that the new pulse width is 2x or aprox 240 msec. Narly1 Last edited by Narly1; 08-05-2009 at 03:38 PM. Reason: clarity

07-27-2009, 11:41 PM	#2
SACCO I wanna be Dave Join Date: Jul 2006 Location: Moscow Mills MO Posts: 2,204	Pics of the Tx? If you crack it open, you just might find a pot to give you more throw.

07-28-2009, 05:28 PM	#8
jevyguy Quarry Creeper Join Date: Jul 2005 Location: Utah Posts: 261	I am not worried because I can still adjust the endpionts with my programer. It might take a little tunning, but I am sure it will work out

08-04-2009, 01:15 PM	#10
jevyguy Quarry Creeper Join Date: Jul 2005 Location: Utah Posts: 261	No go... They didn't even work. It could be that I have digital servos, but I even tried an old anolog JR. For some reason it didn't work either. It could be something to do with the receiver, but who knows. Needless to say I will be sending them back

08-05-2009, 05:02 PM	#17
jevyguy Quarry Creeper Join Date: Jul 2005 Location: Utah Posts: 261	The servo actually worked, it just wouldn't throw it any further than it was already programmed to. Besides that if I would hold the TX in the full turning position the servo would turn, but then go back to center after a few seconds even though I was still against the stop on my TX I already sent them back, and I have no sort of access to an osciliscope

08-05-2009, 05:11 PM	#18
clockworks Rock Crawler Join Date: Feb 2008 Location: UK Posts: 818	Sounds like the stretchers were suffering from a lack of voltage through the Rx. What ESC are you using, and do you have an external BEC?

08-06-2009, 10:52 AM	#20
YJ_Driver Quarry Creeper Join Date: Apr 2009 Location: Ottawa, ON, Canada Posts: 251	Assuming you're running the servo off the 6.5V BEC, is that stretcher rated to run at 6.5V? That circuit might not work well or may have been damaged if it wasn't designed for that high a voltage. I had the same situation using an old radio but with a HS7955, so my solution was to set the servo to normal resolution and tune the endpoints. For you I think the only solution is a stretcher. Don't mess with the pots internal to the TX, they are NOT for EPA and you'll just mess something else up. I don't think there's anything simple you can do to the TX either. You could add two resistors from the steering's pot middle pin to the end pins, but no guarantees and your steering won't have a linear response. Richard

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