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Author Topic: radio gear glitching with failsafe  (Read 3737 times)

pete_486

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radio gear glitching with failsafe
« on: November 12, 2007, 07:33:50 PM »

hi ive just put a 1/4 scale servo on my makara steering its a hitec hs-805bb complete with y lead.
when i operate the steering the throttle servo starts twitching.
when i do away with the failsafe (a new mtronics) its ok .
ive also tried numerous servo's on the throttle to no avail  >>:-(
please help.


Pete
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Stavros

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Re: radio gear glitching with failsafe
« Reply #1 on: November 12, 2007, 08:09:13 PM »

Pete without sounding rude I think you have answered your own Question by stating that you have tried numerous other servos maybee a faulty failsafe,give Mtronics a ring they will be the bets ones to advise you

Stavros
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glennb2006

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Re: radio gear glitching with failsafe
« Reply #2 on: November 12, 2007, 11:19:39 PM »

What size battery pack are you running Pete?

Glenn
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pete_486

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Re: radio gear glitching with failsafe
« Reply #3 on: November 13, 2007, 12:20:19 PM »

im running a 6v 3300mah nimh.

Pete
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ids987

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Re: radio gear glitching with failsafe
« Reply #4 on: November 13, 2007, 02:51:52 PM »

Pete,

When you say you are using a Y cable, do you mean that you have the battery and the steering servo on the Y cable, or the battery and the throttle servo (plus failsafe) on the Y cable ?
If the Y cable is on the steering channel, moving it to the throttle channel may cure the glitching. I personally prefer this arrangement, as I feel it gives slightly more protection.
If this is the case, I will explain my reasoning - although there is still more than one possible explanation.

Ian
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AC RAZOR 45

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Re: radio gear glitching with failsafe
« Reply #5 on: November 14, 2007, 11:46:32 PM »

you cant be for real the whole idea of the y lead is so the steering servo gets a full 12 volts and gives its max torque out,so what is the use of putting it on the throttle servo...pass.. :D
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scoop

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Re: radio gear glitching with failsafe
« Reply #6 on: November 15, 2007, 12:28:03 AM »

You might be getting radio glitching from your Mobile Phone, I always switch mine off when using radio gear, just a thought as some makes of radio gear are prone to interferance from certain types of Mobiles. Cheers Scoop
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wingertaz

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Re: radio gear glitching with failsafe
« Reply #7 on: November 15, 2007, 09:53:04 AM »

I have come across similar problems in the past. Using a particular make of failsafe when fitted to a perfect working radio set up, interference was caused. I used a different make and no problems. The original failsafe which was causing a problem in the first installation was used on another model with no problems.

Compatability could be the problem here.

Gary.
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w3bby

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Re: radio gear glitching with failsafe
« Reply #8 on: November 15, 2007, 10:40:06 AM »

Was it all working before you put the 805 in? End points adjusted OK, no binding or stalling at the end of travel?
Try another servo and see what happens.....

ids987

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Re: radio gear glitching with failsafe
« Reply #9 on: November 15, 2007, 01:40:14 PM »

you cant be for real the whole idea of the y lead is so the steering servo gets a full 12 volts and gives its max torque out,so what is the use of putting it on the throttle servo...pass.. :D
OK - I didn't think I'd get away without justifying this.

The failsafe is on the throttle servo, so by putting the battery on the Y cable with the throttle servo, there are less points of failure between the battery and the failsafe - ie the battery doesn't have to go through the receiver and the extra associated plugs/sockets to get to the failsafe. Most cases of complete loss of control (at least where a failsafe is installed), are caused by sudden loss of power. If the power gets through the harness, switch, and Y cable to the failsafe, and you remove everything else, the failsafe should still shut the throttle down.
I would guess that either the rudder servo is either causing enough voltage drop to trigger the failsafe, or it is modulating/spiking the power lines with noise. Another possibility is that it is interfering with the RF signal to the Rx.
With such a big battery, if the voltage is dropping enough to trigger the failsafe, I would say that either the battery may be faulty, or there is a slightly iffy connection (probably either the switch, or one of the plug/socket connections).
With the Y cable on the rudder servo, the servo (power wise) is effectively teed into the connection from the battery to the Tx, so it has a higher chance of inducing interference into the power supply going to the Rx and the failsafe - ie the Rx is not receiving a clean power supply or "ground". Again, this will be made worse if there is a problem with the battery or the switch / harness.
I can see your point, but the loss on the power lines, through the Rx PCB - between channel 1 and channel 2 (or 3), should be very small. The biggest benefit (at least in terms of voltage loss) from a Y cable, is in terms of bypassing any battery eliminator or regulator circuitry etc - which may be associated with the Rx battery socket.
You are right, in that the way you have installed the Y cable will give you slightly more voltage at the rudder servo - not sure whether this would be easily measurable or not, but it compromises the protection given by the failsafe more, and I think it may (only may), be causing the immediate problem - I see it as a relatively easy thing to try out.

Of course, the rudder servo may just be faulty, and draining too much current (or draining too much current due to mechanical obstruction), or causing interference......

Ian
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w3bby

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Re: radio gear glitching with failsafe
« Reply #10 on: November 15, 2007, 05:13:44 PM »

2 Ians barking at the same tree O0 The 805 is a brute of a servo and draws a lot of current (700mA no load running) when it's doing its stuff, I can't find the stall current for it but the 755 draws 1800mA. I suspect the 805 is the culprit as well, either through voltage drop or noise.

thedevil

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Re: radio gear glitching with failsafe
« Reply #11 on: November 15, 2007, 06:53:01 PM »

hi ive had numerous mtroniks fail safes and none of them have ever worked properly or they glitch all the time.
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ids987

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Re: radio gear glitching with failsafe
« Reply #12 on: November 15, 2007, 08:41:45 PM »

A less sensitive failsafe (or perhaps one which takes longer to trigger) may well cure the symptoms. I guess it depends whether it is showing up a problem, or just picking up noise or power dips which may be inevitable with such a big servo, and sub-optimal wiring. Maybe I'm overthinking it.
When I wrote earlier about Y cables, both scenarios are fairly poor compromises. Really, each servo, and the Rx should have a separate feed (power and ground), all the way from the battery - or even separate batteries. Failing that, a dedicated feed for the Rx, and a common feed for all the servos (I'm including the failsafe - power-wise, as part of the throttle servo. These scenarios would obviously make switching etc a bit awkward though - although the last one could be done with one dual pole switch.
I guess one concern would be that; presumably the twitching at the moment is with no load on the rudder servo. The current will obviously rise considerably under load, so if another failsafe cures the problem "on the bench", it may resurface in use.

Ian
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w3bby

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Re: radio gear glitching with failsafe
« Reply #13 on: November 15, 2007, 11:28:58 PM »

Here's how the car guys deal with it

Available ready-made from http://www.rc-car-online.de/htstarteng.htm

pete_486

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Re: radio gear glitching with failsafe
« Reply #14 on: November 16, 2007, 07:20:40 PM »

hi i got a new failsafe today and it's the same an mtronics, my mates all run them but it's still doing the same.
my mate Al has the same setup and it doesnt chatter  >>:-(
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wingertaz

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Re: radio gear glitching with failsafe
« Reply #15 on: November 16, 2007, 08:10:11 PM »

If both equipment and installation are identical in both you mates model and yours ? then there must be a fault with one or more components in your model. A process of elimination should show up the guilty item.  O0

Gary
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