Radio RSSI depth controller

If you have a programmable radio that runs opentx like a taranis or tx16 with telemetry or your running a RC system that does RSSI servo output then you can make this work.



Essentially what we can do is set one of the radio channels to change based on the signal strength of the radio, so as the sub dives the signal will be attenuated by the water, changing the rssi, therefore changing the servo position so that it starts to move the dive controls to level the sub out where the signal strong enough for control but still underwater.

Because its using the radio its self to set the max depth you should never loose signal since as soon as it gets too low it will immediately start to reduce its depth to increase the radio signal. you can also mix it with your normal diving controls as a backup.

this would actually work better with 2.4ghz as it should run just below the surface because the signal is attenuated so much.

https://oscarliang.com/rssi-ppm-channel-taranis/

reading the article by oscar, it sounds like the receiver he is using (and perhaps others) will output RSSi directly, just not in a very usable way... i need to see if any of my "submarine" receivers will output the RSSI directly. the method that oscar details in the article is basically "send rssi telemetry data from rx to tx. program tx so it sends a standard servo value for rssi back to the rx. use that value to move a servo". it really needs to remove the TX from the equation, if telemetry feed to the tx fails, no data.

tsenecal wrote:reading the article by oscar, it sounds like the receiver he is using (and perhaps others) will output RSSi directly, just not in a very usable way...  i need to see if any of my "submarine" receivers will output the RSSI directly.  the method that oscar details in the article is basically  "send rssi telemetry data from rx  to tx.  program tx so it sends a standard servo value for rssi back to the rx.  use that value to move a servo".   it really needs to remove the TX from the equation,  if telemetry feed to the tx fails, no data.

Most 2.4ghz telemetry RC systems have the same 100mw transceivers in the receivers and transmitters so the RC and telemetry always work together, infact it wont send telemetry if its lost RC plus you can always mix that to your dive channel so your selecting the attenuation level to hold, this lets you dial it in to run just under the surface or flick a switch and manually control it like you did before. With modern radios if the telemetry was lost your radio immediately starts shouting at you that your telemetry has stopped, so it's not something that can happen without you noticing, plus this is only relying on the receiver itsself not any external sensors or attachments so there is very little to go wrong if you program it right.


Some receivers can output rssi directly to a servo without telemetry, but then you lose the ability to mix it with other channels via the radio.

I have used the same setup to work the landing gear automatically on aircraft by using altitude data rather than RSSI so when the LIDAR detected the altitude was under 50m it would automatically deploy the landing gear and retract the camera using some logical switches programmed into the taranis handset, it worked reliably enough.

Geofrancis...


remember that i am using the 915mhz equipment... for that, all the RX output at max 100mw, while the TX can go up to 2 watts, so there can be quite a difference between the two, and telemetry may not reach the transmitter, but the sub still can be under control...

a pressure sensor connected to an arduino based failsafe is how i do my depth keeping... adding a feed of the rssi signal from the RX to that same arduino would definitely be a "good thing"...

tsenecal wrote:Geofrancis...


remember that i am using the 915mhz equipment...  for that, all the RX output at max 100mw, while the TX can go up to 2 watts, so there can be quite a difference between the two, and telemetry may not reach the transmitter, but the sub still can be under control...

a pressure sensor connected to an arduino based failsafe is how i do my depth keeping...  adding a feed of the rssi signal from the RX to that same arduino would definitely be a "good thing"...

yes it would still work with your setup. the whole point of it using the rssi is that it should never loose signal since it will already be trying to surface when the signal gets weak, it should only dive to the point where the rssi has been set to level the dive planes. by setting it very conservatively it should run just under the water. you can select the signal to the sub or the signal from the sub to run the dive control, that way its being controlled with the weakest signal.

I have done a simple setup for RSSI depth control using my taranis radio. Its basically a logical switch that is active if the RSSI drops below a set value. That is then used to add a 50% up mix to the pitch control.

Using TRSS would probably work better as that is the signal level from the receiver and the data is generated by the module so should be more reliable.

You will want to set it to a reasonable number like 40 or 50 I'm using 90 so I can make it loose connection just by moving it for bench testing.