PPM protection resistor

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MikeB
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PPM protection resistor

Post by MikeB » Sun May 01, 2016 11:17 am

On the 9Xtreme, the PPM/PXX output signal in the module bay is a direct connection to the processor. In hindsight, it would be better if this signal included a 100 ohm resistor in series to provide added protection to the processor pin. This will provide some protection against "unusual" events, such as shorting the output or plugging/unplugging a module with the radio powered on.

Such a resistor may be added to the back board. I had a 100 ohm surface mount resistor available, so I've added it. I cut the track close to the module bay pin and soldered the rsistor across the cut after scraping the green solder resist away from the track. In the picture below, this is outlined in dark blue.
An ordinary, through hole, resistor may be used, simply cut the track where indicated in red in the picture, then again after scraping the solder resist away, add a 100 ohm resistor, shown in light blue, to bridge the cut made.
9XT-100R.jpg
The black and white wires are the telemetry connections.

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Re: PPM protection resistor

Post by jhsa » Sun May 01, 2016 11:41 am

I think this mod is very important.. This one and the diode on the switch board..

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Re: PPM protection resistor

Post by bob195558 » Sun May 01, 2016 9:41 pm

I have added this PPM Protection (Resistor) Mod to the list of Optional 9Xtreme Radio Mods,
found here: (viewtopic.php?f=95&t=7182&p=98846#p98846).

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Re: PPM protection resistor

Post by jhsa » Sun May 01, 2016 10:13 pm

this mod should NOT be optional.. We've seen already a few boards with a fried PPM pin.. I think this is something that has to be done, or sooner or later we will make a little mistake and fry the board.. It seems that you just need to remove/insert the RF module with the radio ON for that to happen.. :(

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Re: PPM protection resistor

Post by Rad » Fri Jun 24, 2016 8:35 pm

Is there any tutorial of how to do it?

Im not very good at soldering and it would be great if I see in a video how to do it.

A video showing how to do in any kind of board should be enough.


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PPM protection resistor

Post by ShowMaster » Sun Jun 26, 2016 12:51 am

To add the resistor is actually real easy if you take these steps.

To do first before opening the to case!

First obtain the 100 ohm resistor. 1/4 watt size being the largest package and most common for most and easiest to DIY for this mod. Smaller wattage is ok but harder for some that don't solder a lot.
Once you have the resistor you'll need a small tip soldering iron. The idea is to not use a "barn burner size" that will melt everything. If you post a picture of what you would use, a thumbs up or down can be given.
Next you'll want some small diameter solder, maybe the size of a servo single wire size.
Leaded 60/40 type instead of unleaded.
Leaded for "rework" flows like hot butter where unleaded doesn't!
Finally a sharp hobby #11 blade knife and needle nose pliers and cutters.
You'll want to bend the resistor wires and cut them to length or not. It depends on you. Maybe cut one to start. The knife will be used to cut the piece of trace out and scrape the trace left to expose the copper at the gap ends for soldering.

When you have all this, it's time to DISCONNECT the Tx's battery as should always be done when you open the case. Next remove the case screws and open the case. What you did when you first added the 9Xtreme board. Carefully remove any connector wires to allow you to spread the case halves or fully disconnect them, what ever is better for you to do the next step.
ImageUploadedByTapatalk1466901722.216745.jpg
Then looking at the case back half, compare it to Mike's picture and cut the trace and make a gap as shown with the hobby knife. Firm pressure a few times will cut the trace. Then a sideways blade pressure will peel the unwanted trace away making the gap. It won't damage the board!
Maybe 1/16 trace removed? Not critical as it's purpose is to sever the trace to add the resistor.
Once cut and removed, use the blade to scrape the resist (green) off of the trace to expose the copper for soldering. Expose the copper at the points equal to the length of the resistor body.

Then bend the resistor leads to drop onto the 2 exposed trace areas. You'll cut the second lead to make it easier later.

Now heat up your soldering iron, clean the tip, add some solder to it to set it, and tin the exposed copper trace to prep the copper for the resistor. Not much, just flow some on it.
Now lay the bent resistor leads across the 2 tinned trace spots and tack solder one side you cut the lead short on. Then line up the other side and cut and solder it.
It's harder to work with a tiny resistor with short leads for some, so leaving one long makes a handle in this case.

Once happy with your work, or posting a picture for an opinion, reassemble your connectors and case and then connect the Tx's battery last!

My case open picture was before I added the resistor! I don't have a recent one.




ImageUploadedByTapatalk1466901722.216745.jpg
ImageUploadedByTapatalk1466900429.110627.jpg

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Re: PPM protection resistor

Post by Rad » Sun Jun 26, 2016 3:34 pm

Thanks for your help, I´ll try to do it this week. :)

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Re: PPM protection resistor

Post by Rad » Wed Jun 29, 2016 5:08 pm

Well, I think I did it. Not the best looking mod, but as far as it works...

And yeah, I burnt the battery case... No problem it can not be seen, lol.
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IMG_20160629_190611.jpg
IMG_20160629_180455843.jpg

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PPM protection resistor

Post by ShowMaster » Wed Jun 29, 2016 11:12 pm

Looks ok! You could have just removed the green resist on the cut copper trace to make shorter leads (same difference), but it all works either way. As long as your ohm meter says you now have 100 instead of 0 ohms between the module pin and he lower board pin you soldered your leads to after the trace cut, all good!
You also want no solder bridging the lower board connection pad. The pic is a little off axis to see but I'm sure you checked it.

You say it works after your mod, great!
Always remember to remove/disconnect battery power and double check your mod work, and you'll go far!
Welcome to the mod squad!
ImageUploadedByTapatalk1467241950.836244.jpg
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Re: PPM protection resistor

Post by jhsa » Wed Jun 29, 2016 11:30 pm

To me it looks like the wire is shorting both PPM pin and the one immediately to the left of it on the 12 way connector :o

But I'm looking at the picture on my mobile phone.

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Re: PPM protection resistor

Post by ShowMaster » Thu Jun 30, 2016 2:50 am

It does look that way and I mentioned it. Hopefully it's just the angle.
He says it works.
I would have liked him to scratch off the green resist as I suggested and solder where Mike's diagram shows it, but if nothing's shorted on the 12pin pads, it's electrically correct.

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Re: PPM protection resistor

Post by Rad » Thu Jun 30, 2016 5:51 am

ShowMaster wrote:As long as your ohm meter says you now have 1K instead of 0 ohms between the module pin and he lower board pin you soldered your leads to after the trace cut, all good!

Thanks to god is just the angle, no short circuit there. :)

I have not checked the new resistence, but I installed a 100ohm one. Just to be sure, it has 4 stripes. Black, brown, black and gold. Is that OK? What you said about 1K confused me. Im afraid I have no idea of electronics...

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Re: PPM protection resistor

Post by ShowMaster » Thu Jun 30, 2016 7:07 am

Sorry, my bad.yes 100 ohm. There's been many mods for different reasons to the 9x trace. Brain glitch. Fortunately you caught it. The 1k wouldn't have caused any damage and may have even worked, but 100 ohm is the choice Mike posed and is correct.

Yes
Brown black brown 100

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Re: PPM protection resistor

Post by Rad » Thu Jun 30, 2016 8:05 am

ShowMaster wrote:Sorry, my bad.yes 100 ohm. There's been many mods for different reasons to the 9x trace. Brain glitch. Fortunately you caught it. The 1k wouldn't have caused any damage and may have even worked, but 100 ohm is the choice Mike posed and is correct.

Yes
Brown black brown 100
Great, I thought I had to do something more. Pfew!

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Re: PPM protection resistor

Post by lancaster » Fri Oct 28, 2016 5:58 pm

Hi Guys
Some weeks ago I updated my firmware to EU LBT versions on the XJT module and my XR receivers with no problems (SP Extreme board installed in T9X)

The RX update requires leads to be connected between the SPort on the RX and the module pins numbers 3,4 and 5 in the TX.

But thinking back on this and Joaos strong recommendation to fit this PPM protection, it occurred to me that I might have been at risk of damaging my T9X whilst plugging in the necessary leads and switching the TX on with no module in place.


- could I be at risk of damaging the TX at this time ?
- will the PPM protection mod eliminate this risk?

Any thoughts ?

Regards
Hans

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Re: PPM protection resistor

Post by jhsa » Fri Oct 28, 2016 6:07 pm

lancaster wrote:
But thinking back on this and Joaos strong recommendation to fit this PPM protection, it occurred to me that I might have been at risk of damaging my T9X whilst plugging in the necessary leads and switching the TX on with no module in place.
Some boards did get damaged because of inserting and/or removing the RF module WHILE the radio is powered ON.

But, yes, it is a very good idea to do the resistor mod..

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Re: PPM protection resistor

Post by lancaster » Fri Oct 28, 2016 6:20 pm

Hi Joao
Hope you are well

Thanks for the super quick reply

I will do the PPM mod to be safe on both my T9XExtremes ( I recently bought a second Extreme board as the numbers are going down below 100!)

regards
Hans

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Re: PPM protection resistor

Post by lancaster » Tue Nov 01, 2016 8:17 pm

Hi Guys

I have installed the 100 ohm resistor on both my 9Xtreme TXs and everything appears to be working ok.

Am I correct in thinking that because the resistor is in line to module pin no 5, good values for the RSS1 and SWR value indicate that all is working as it should ?

regards
Hans

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Re: PPM protection resistor

Post by jhsa » Tue Nov 01, 2016 8:42 pm

You installed it on pin one of the module bay, right?
RSSI has nothing to do with the PPM connection. If you did it correctly you should be able to control a model or some servos.

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Re: PPM protection resistor

Post by lancaster » Tue Nov 01, 2016 9:35 pm

Hi Joao

I installed the resistor as shown on Mike photo

I thought it was pin 5 but now I see its pin 1

I will test for servo control as you say

thanks
Hans

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Re: PPM protection resistor

Post by jhsa » Tue Nov 01, 2016 10:03 pm

Yeah, that is Pin 1 :)

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Re: PPM protection resistor

Post by Rad » Sun Jun 18, 2017 3:19 pm

Hi! A bit of necroposting here. Im going to start flying so I discovered I can connect the radio to the computer and install a flight simulator, that's great.

But I think I need to remove the module or install a 1K resistor exactly where my 100 ohm resistor is. So, guys, do you know if the 100 ohm resistor is enough or should I replace it? Im using a 9xtreme board and Im planning to install the multiprotocol board inside.

I also have a turnigy 9xr pro. Do I need to do something extra to the radio?

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Re: PPM protection resistor

Post by silversurfer48 » Thu Jul 20, 2017 6:36 pm

Does this mod need to be done with AR9X board as well ?

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Re: PPM protection resistor

Post by jhsa » Fri Jul 21, 2017 9:51 am

No, you don't need to do anything. The radio does not use the module for connecting to the computer. It uses the trainer port on the back. Just plug the simulator cable to the radio while it is powered off. The cable will then power the radio on.
Or, with the 9xtreme turn the radio ON, then plug a USB cable between the radio and computer. The radio will then emulate a joystick. As simple as that ;) Depending on the simulator, you don't even need a simulator dongle :)

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Re: RE: Re: PPM protection resistor

Post by jhsa » Fri Jul 21, 2017 9:54 am

silversurfer48 wrote:Does this mod need to be done with AR9X board as well ?
Nope, the Ar9x already have a protection resistor on the PPM line. The post I wrote above also applies to it except the USB joystick capability.. I think Mike mentioned sometime ago that he probably would also implement it on the Ar9x, 9XR-PRO, etc. That would be wonderful.. :)

João

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Re: PPM protection resistor

Post by silversurfer48 » Fri Jul 21, 2017 4:58 pm

you think maybe since i swap out 9xtreme due to short on the board and installed a AR9X board the throttle hold switch is not working

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Re: PPM protection resistor

Post by silversurfer48 » Fri Jul 21, 2017 5:02 pm

this is what was done for 9xtreme board have the 1k resistor. what should I do to change out the resistor what do I replace the connection with once the 1k is removed to make that line work properly ?

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Re: PPM protection resistor

Post by ShowMaster » Sat Sep 02, 2017 2:39 pm

Reading that the AR9X board already has the protection resistor in line on its board, it would seem you will remove the 100 ohm added for the 9Xtreme board and replace it with a short across the trace gap.



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Re: PPM protection resistor

Post by Rad » Mon Sep 25, 2017 6:11 am

MikeB wrote:
Sun May 01, 2016 11:17 am
I had a 100 ohm surface mount resistor available, so I've added it.
Do you think this one would work?

http://www.ebay.com/itm/100pcs-SMD-Chip ... Sw0fhXjOha

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Re: PPM protection resistor

Post by MikeB » Mon Sep 25, 2017 7:59 am

Yes, I used a 0805 resistor myself.

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