X24 Integrated Flight Control System - Page 15 - RC Groups
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May 26, 2018, 04:43 PM
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davidmc36's Avatar
I like ON.

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Jun 13, 2018, 11:30 PM
Registered User
Before I do this I thought I would ask.

I have a rxcel ignition kill switch. It's intended to connect to the rx and a separate battery. My thought was maybe to forgo the separate ignition battery and plug it into the bec port of the xps. So I would have a channel for the kill function but be picking up power on the second lead.

Any idea if this would work? I'm concerned about having both plugged into the xps.

In case your not familiar with the rxcel, here are some images.


Last edited by WR_Rider; Jun 13, 2018 at 11:35 PM.
Jun 14, 2018, 12:29 AM
You would plug the igntion directly into the X24. The X24 powers the ignition and acts as the ignition kill by turning on/off the power to the ignition. You don't use anything else, which is one of the many great features that the X24 has. It's a simple solution.
Jun 14, 2018, 10:18 AM
Registered User
Ya I thought about that but I find myself a bit worried about ignition noise feeding back in to the xps. While this might be ignorant of me I'm still not sure how the xps is doing any filtering due lack of tech info. With the the rxcel it is optically isolated and has worked good for me so I figured it would hurt to combine both.
Jun 14, 2018, 12:09 PM
The X24 was specifically designed to drive ignition systems. The BEC powers the ignition box directly, and provides isolation from the rest of the X24 circuitry. Everyone runs their ignition directly from the X24, that's one of its features.
Jun 16, 2018, 10:58 AM
OK, I found the issue with the power off not always working as expected. So everyone understands the issue, this is going to get a bit technical.

The problem is simple: you can not power off the X24 if there is power on the Match input. This input is used when you are setting up servos using the AutoMatch feature. However, this input can also be a 3rd redundant power input (for those of you who are freaky about redundancy). This input floats when there is nothing connected to it, but the A/D converter pulls it down (with microamps) when the A/D is on.

At firmware v1.4 I added a safety check that would not allow you to turn off the X24 if there was power in the Match power input. With the last version of firmware (v1.8) I added a message that pops up if you try to power down from the menu with power in the Match power input. However, there is no message or notification if you are trying to power down with one of the switch inputs (SW1 or SW2), again when there is power in the Match input. So, those that are having the problem with the X24 not powering down, it is due to having power in the Match power input. What? You say you don't have power in that port! Well, technically you do - but it's thousandths of a volt from atmospheric conditions and parasitic charges through the circuit board. On power up the X24 looks at the Match input and determines if the voltage is >0 by comparing to a value of 5 (out of 4096) and if the value is greater than 5 then it assumes there is power. 5 = .00016 volts. So a bit over 1.6 thousandths of volt. When the X24 gets hot (like 150 degrees), the resistance goes down and the value ends up being about 14. At normal (77 degrees F) temperatures the value is 1 to 2. So, indeed and as reported, a temperature increase can surpass the value of 5 and thus the system thinks there is Match power connected.

I have changed the firmware to compare the Match input voltage to a real usable voltage value (>4 volts) so the X24 knows when there really is power on the Match power input. This makes the problem with the X24 not always turning off under some circumstances go away. This problem did not exist when this product was first released. It only occurred after I added the safety check to prevent the X24 from powering off when there is power on the Match input. Those that have v1.3 or earlier firmware will never have this problem because there was no check being done.

There are 3 solutions to resolve this issue:

1) Send your X24 back and we will re-flash it and return it to you.
2 ) Use our Serial Link to update the firmware yourself.
3) Put a special binding plug on the Match power input. By special, I mean one that has power and ground connected together (not ground and signal like a normal binding plug). You can take any existing binding plug and move the signal connection to the power connection (center). Once this plug is inserted into the Match power input it will prevent the line from "floating" by grounding the match power input, which should stop the problem no matter what climate changes occur.

If you have firmware older than v1.6 you might want to consider either sending it in or getting our Serial Link. There have been a bunch of changes to support JETI customers. The latest version (v1.9) also has a new Diagnostics page that shows you the state of the buttons, SW1, SW2, the BEC voltage, BUS voltage, and Match input voltage.

OK... next issue... battery power usage. Someone has reported excessive power drain while in sleep mode (powered off).

If you use a slide switch or a pin and flag switch, the current draw can be as high as .00033A (330uAh). If you use the push button option (with a push button, slide switch, or pin and flag switch), the current draw is about .000020A (20uAh). I just tested an X24 to get these numbers. You can test the current draw yourself using any meter that has a current setting (most do).

Firmware v1.0 through v1.6 always turns off the LED on power off. v1.7 firmware always leaves the LED on, and v1.8 (and later) has the option to leave it on or turn it off on power off. If you have the LED on it will consume >7mAh.

24 hours at 330uAH is 7.92mA of consumption. 24 hours at 20uAH is 480uA of consumption. 24 hours at 7mAH (+330uAH) is 175.92mAH of consumption. Clearly you wouldn't want to leave the batteries connected with the LED on, but with the LED off even with a pin and flag switch you should be able to go months with a 2500mAh.

When the X24 powers off, the BUS is disconnected, the BEC is disconnected (by virtue of it being connected to the BUS), and the secondary voltage regulator is disconnected (that powers the OLED, external LED, and current matching harware). The primary regulator still runs but the CPU is in sleep mode. That takes around 20uA. If you use a pin and flag or slide switch and you are leaving the switch in the closed position, then that draws the 330uA of current. You are better off using the slide switch and pin/flag switch as a push button type. Where you slide the switch to turn on the X24 and slide the switch back. To turn off the X24 you slide the switch until you see the power off message and then slide it back. That will use the least amount of power, but realistically even a few mAh would mean months of stand by before you were concerned about the batteries.

I am going to spend the day going through all of the X24 features and protocols to make sure nothing was "broken", and then release the firmware updater.

Sunday is my day off - for Father's Day. I wish you all a happy Father's Day!
Jun 17, 2018, 02:43 PM
Registered User
Well, I now have 3 flights on the xps 24. I'm using the on board bec with my da60 and my jeti radio. I'm happy to report all is working as advertised so far. I'm still on vs 1.8. My only negative comment is its just on the verge of being a little big for my 60cc airframe but does fit.

Satisfied customer so far.
Jun 17, 2018, 02:44 PM
Registered User
My eyes are absolutely burning after reading all that !

Happy Father's Day !

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