Switch feedback and power wiring issues in 9XR-P case mod project

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BiggsDarklighter
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Switch feedback and power wiring issues in 9XR-P case mod project

Post by BiggsDarklighter »

My apologies for the long post. I have had some vexing issues past couple nights on this. I have spent so long staring at this particular issue, I have lost my starting point and confused myself... I HAD this working...

Background: (for those who somehow haven't stumbled across my other posts... LOL!)

I am stuffing a 9XR-Pro into a vintage Futaba FP Gold radio and modernizing it. Why? I got issues... :lol:

I am having a switch feedback issue. Swapping the Tunrnigy switch with the Futaba switch was pretty straightforward. Everything worked fine. I did some testing and managed to get the Futaba analog meter sorta working too, off the converted switch. Power up was pegging the meter though. Okay moving along...

Taking a closer look at the first Futaba donor radio mainboard, I noticed a trimmer pot. I needed a mounting board anyways, so I spent a few hours un-populating it, of course leaving that trimmer in place. I then flipped the input protection fuse over to the other side of the board (sticks up a LOT) so I could have double protection and hopefully safely slow charge the Futaba nicad pack maybe without involving the Turnigy charging circuit. Doing dumb stuff though so two fuses are probably still a good idea no matter what... I already popped the Futaba one once.

I am powering the radio off the Futaba transmitter pack. The Futaba pack plugs into original spot on Futaba mainboard. Constant b+ Power goes through Futaba fuse. Just two jump spots on the board, and to the trimmer pot for the analog meter. I have a JST plug off one of those points, with ground going to another jump point. I can put a diode here, but currently it is just jumped over to the ground plane. Removed the balance plug from the Turnigy RF and power board, and installed the JST mate there. Triple verified, polarity all correct and until I add meter back in, all works as it should.

The Futaba TX pack is a 9 cell nicad with charged voltage of 10.8v. This does appear to be kicking my low voltage alarms on, but that should be a simple matter to change in the radio setup (I haven't left anything powered up long enough to sort out since weird stuff is going on). I am wanting to run this pack due to how thin it is, and already the radio has a holder going for it. Room is at a premium. Pack appears to be fine, and I have a spare. So first question:

1) Is 10.8v good, or should I use a voltage booster circuit? The slight bump up I need shouldn't be too much of an inefficiency/power sink issue. Not my main issue though, more of a curiosity.

EDIT: Okay reading through one of the many many manuals available for this, YES I can use the 10.8 nicad pack. Well probably. Nimh is mentioned specifically, not nicad. Close enough. Voltage is WELL within tolerances so no need to bump it. Pretty sure my meter will fall off the scale well before TX stops working.

I am unsure as the wiring on the two donor radios is vastly different, but it appears that Futaba had the analog meter setup so that if the radio was off, but charging, the meter was powered up. I would have to buy a third complete radio to verify this (tempting, and cheap enough). They had negative side of the meter attached to the side of the charging jack that grounds when you plug in. And another wire to the the switched negative on power switch. Power is constant battery voltage, adjusted by the trimmer pot.

2) Should I continue with plan to charge the Futaba pack directly from the Futaba plug trying to get it working like original, or can I plug/wire Futaba power jack into the Turnigy mainboard charging jack? I figure the Turnigy charging circuit is set to cutoff at lipo cell voltage though...

Anyways before I added the Futaba mainboard power input and trimmer mod, the Futaba analog power meter was working (but hard pegging) with the negative on the black Turnigy switch lead. Radio powering on and off as it should. Ideally, if I have any chance of the meter showing when charging or just working safely, I need a safe switched ground point for the negative side of the meter when the system is powered up.

3) Any ideas what I should use?

I can likely pop a simple transistor into the Futaba board for this if I need to used a safe switched power source. If something pops the transistor, I only loose the analogue meter and not the actual system power. But just a simple switched ground would be nicer and easier....

Again, I had it working (before adding in the trimmer pot) using what I thought was switched ground on the switch. Mentero stated there is no switched ground though, and things were acting a bit off, so I figured I should post this up and get some guidance.

Oh as for the feedback problem I would have to verify again exactly what it was doing (and am real leery to do that now lol), but it wasn't powering back down right, or at all or something... If I plug it all back in and try again, I will edit this with exact specifics.

EDIT: Okay with the negative of the meter hooked to the black switch wire like it was, on initial battery plug in with the switch off, the meter powers up to basically full, although it is supposed to be off. Switch turns on, meter drops to zero and system powers up. Turn off, meter jumps up halfway, but system doesn't turn off. Unplug battery, plug back in, meter jumps up to full. I did this a few times to make sure of what was going on, then it booted up into bootloader mode. OOPS. Pulled battery, disconnected wire from switch. Powered up, all is good. WON'T do that again though LOL!!!

I REALLY want this analog power meter to work. Super big part of this radio's vintage feel.

BiggsDarklighter
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Re: Switch feedback and power wiring issues in 9XR-P case mod project

Post by BiggsDarklighter »

Hopefully my explorations hasn't caused any lasting issues. It just randomly went into boot loader mode again with things back to normal, ie not using the turnigy switch for a switched ground it obviously doesn't like... Now at the moment I don't have anything plugged into the mainboard, just the LCD and RD/power board. Weird. It went back to normal when I turned it off and back on.
BiggsDarklighter
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Re: Switch feedback and power wiring issues in 9XR-P case mod project

Post by BiggsDarklighter »

Alright I may have found the problem... I am rewiring and moving the Futaba plug slightly so I can utilize the through hole for mounting, and it looks like I had a weak short/leak to ground before the fuse. I was tracing bits down with a continuity test and was getting beeps on the power side I hadn't even hooked up yet. Looks like the short was between the Futaba battery connector pins.

In the process, I also lost my Futaba board power feed. I think I know where I lost that though, and can simply jumper it back in.

Okay got the powers and grounds clean, and tried again. I can power up the 9XR-P system normally now, until I add that meter backing grounding to the switch like before. Then everything seems exactly the same. Since I knew it probably wasn't correct, I only tried it for a second and just the once. I really need a safe switched ground... The search continues.
Last edited by BiggsDarklighter on Mon Aug 24, 2020 11:41 pm, edited 1 time in total.
BiggsDarklighter
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Re: Switch feedback and power wiring issues in 9XR-P case mod project

Post by BiggsDarklighter »

And nope. I can't find a single switched ground, at least not with the DVOM, and so far nothing staring at the schematics. I am going to give up on that I think and go digging through my electronics parts bin for a suitable transistor. I think I need an NPN, but my brain is fuzzy on that. Good thing for google and data sheets! Whatever I need, pretty sure I have it on hand.

I need to find a plug for the encoder, and then I think I will connect into that to grab switched (3.3v probably) power for the transistor. This should be a good way to isolate the meter issues from the power main power feed, and prevent the odd back feeding issues I have been having. Not sure why grounding through random c**p could possibly have caused problems? :geek:
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mentero
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Re: Switch feedback and power wiring issues in 9XR-P case mod project

Post by mentero »

I'm not sure I understand what you are trying to do.

As far as I understand, you are capable of using the switch on the old Futaba radio to power the Pro board, and everything seems to work. So far, so good.

Also you want to have a functional analog voltmeter, (for cosmetic reasons?) that works when charging the Nicd pack Indicating charge and also displays battery voltage when the radio is working.
I do not understand why you want to have an indication that the battery is charging, having the display on your battery charger.
I also do not understand why you want a battery voltage indicator when the radio is working, since you already have the data on the screen.

Maybe I got everything wrong ?
Miguel
We demand rigidly defined areas of doubt and uncertainty. Douglas Adams.

BiggsDarklighter
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Re: Switch feedback and power wiring issues in 9XR-P case mod project

Post by BiggsDarklighter »

No you got it right. Is there a good point? Not really. Cosmetic charm. I could put an i2c screen in the same spot if I was smart enough to figure out how to program the data going to it...

Old Futaba switch powering up the Pro board, check and done!

There is an analog meter in the Futaba radio. Taking it out would leave a hole, and it is a BIG part of the radio's vintage charm. I would like to have it work when the radio is powered on. I have it mostly working now, including tracing down the original circuits to get the stock trimmer back in. Now one odd thing I noticed in Vikar's thread, is the red power indicator LED inside the power meter. I have yet to find one that has that and it looks like Vikar did that. Now I also notice that his gauge is reading way off when the system is powered on... But he is powering it with only 7.6v from a lipo or something. These gauges seem to be 3v gauges, so obviously he has something left of the original circuits.

As for indication of charge, I "THINK" the way the stock charging jack was setup, it actually does ground the meter powering it on when the charger is plugged in. I can not charge this with my normal charger that has a screen and voltage etc. It times out. The Futaba packs like to be SLOW charged for 15-24hrs. I actually have an original Futaba charger coming with the third radio.

I don't really care if it does, or doesn't indicate during charging. Now if the last radio gets here and does indicate when charging, I will lean more towards trying to do that here. I mostly just want the meter to show the correct approximate battery state, and work while radio is powered up. Simple enough. You would think.

What I need to sort out is a way to ground the negative side of the Futaba meter circuit and complete it, hopefully using a switched 3.3v output from the Pro. Now we can come to conclusions from pictures posted that Vikar "probably" sorted this out since he shows the meter working when the radio is on. But I also see some, odd wiring to a hot glued switch. And he offers no explanations of anything, or operating video.

I have three options. A fairly complex transistor and mosfet circuit. I have tried both on their own and had problems. I popped a capacitor testing it the other night, and melted it into my finger. OWW. Oops... Unless I find the right circuit example to build, this is beyond my abilities to easily design myself. I couldn't solve the latching effect the mosfet has. Or get it to activate on 3.3v... My patience for 3-4 more days of sorting that out is beyond depleted.

Next, I find an appropriate micro octocoupler circuit, micro relay, os something else that just requires simple plug in wire it up kinda approach. A micro relay is truly the ideal here, but 3.3v ones are either far away, or not cheap. If I can scavenge one from something on hand, bam. Actually I know where I might just have one...

Finally. I cheat! Kinda like I suspect Vikar did. I can use a trainer switch as a momentary "battery check" to complete the circuit at anytime. Or I could use another switch to just turn it on/off. Or both...

I think I will use one of the trainer switches for a battery check no matter what else I do or don't do. Some of the higher end Futaba's of this day actually had a pushbutton battery check switch! The trainer switch would blend right in.
Last edited by BiggsDarklighter on Thu Aug 27, 2020 12:37 am, edited 1 time in total.
BiggsDarklighter
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Re: Switch feedback and power wiring issues in 9XR-P case mod project

Post by BiggsDarklighter »

Oh the initial reason I posted these sorta unrelated questions up here, is I actually had it all working (mostly) as intended at first using the Pro switch to ground the meter. All was happy, all was working. Then as I added stuff in and got it all into the Futaba case, something went sideways and it started preventing the Pro system from shutting down.

Again it is working now and adjustable as intended, if I manually ground the negative side of the meter circuit.
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mentero
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Re: Switch feedback and power wiring issues in 9XR-P case mod project

Post by mentero »

Screenshot from 2020-08-27 11-11-33.png
Screenshot from 2020-08-27 11-11-33.png (11.64 KiB) Viewed 6988 times
Maybe you can power the gauge circuit on RF-POWER_ON, with the ground permanently connected. You will get a functional voltage gauge and adjust with a simple two resistors voltage divider.
This will not work while charging though.
We demand rigidly defined areas of doubt and uncertainty. Douglas Adams.
BiggsDarklighter
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Re: Switch feedback and power wiring issues in 9XR-P case mod project

Post by BiggsDarklighter »

Mentero, your posts got me thinking! I went back to Vikar's few pictures he posted, blew them up and took a much closer look. So he used a Turnigy 9x for his conversion. Real similar to mine, but closer to a Taranis clone. And he did power his meter up right off the switch. Meter fed with a 100k resistor wired to positive side, and then grounded to somewhere else. While that might work sorta okay on that model, it isn't accurate and probably won't work with this one. As I looked closer, a lot of other details were less than ideal. Anyways the take away there is he defiantly cheated, and didn't worry too much about things like the meter's accuracy.

I decided to pick up another radio (this is becoming an obsession). But I found a 7ch one will all the options, AND it came with a charger too! But more importantly, it came with a solid back, no module cutout. I am not going to modify this one, much. I am stealing the back off of it, swapping in a module back, and try to get it fully working on the AM. I may setup a 2.4ghz module for it.

More importantly though, I have a fully operational radio I can check a few things out on. Nope, charging the battery doesn't register on the gauge.

I ordered some micro relays today. I have the circuit already working the way I want, minus the turning on and off bit. :lol: I am going to try out your RF module power idea to turn the relay on/off and complete the ground. Any questions that come up about the original Futaba setup, I now have a reference radio to look at.

The next question I have (I will post a dedicated thread for a little later) what on earth type of JST connectors does this 9XR-Pro take GAHHH?! I need a plug for the encoder.
BiggsDarklighter
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Re: Switch feedback and power wiring issues in 9XR-P case mod project

Post by BiggsDarklighter »

BTW, I GOT IT WORKING!!! I decided to stick with an electron plan of attack I am proficient in. I used a micro relay. I added a 3pin JST to the top of the 5v regulator and grabbed ground, switched battery, and 5v there (not using the 5v yet, but I probably will). I used that ground and the switched battery for the coil side of the relay. I then used the switch side to complete the ground side back to the original Futaba board. So any funky behavior on the Futaba side of things is electrically and mechanically isolated from the Turnigy side of things.

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