Failsafe methods

Failsafe methods

Postby djrm » Sun Apr 29, 2012 10:39 pm

Today I decided to check the failsafe operation of my copter and I found it does not work at all.

What I did find is that when the receiver has once seen the transmiter signal then it continues to output the same outputs until it receives an update, i.e. if I switch off the transmiter then the receiver outputs remain in the last seen position. I think this fools the existing failsafe detection software into making the no failsafe decision. I've checked both the PPM and servo outputs of my receiver and they both have the same operation, this is not good.

I wonder if there is a method which could be used to achieve failsafe operation with my equipment like it is, I suspect not. There is no RSI indicator I can use, however there is a led on the receiver which lights when the radio signal is being received, I may have to open the box and connect a wire to this to trigger the failsafe when the led goes off.

btw my RC is the very inexpensive 7 channel T7AH system which seems ok in evry other way.
How do more sophisticated RC systems operate in failure conditions?
Anybody got any other ideas how I could have a failsafe system? David.
User avatar
djrm
 
Posts: 40
Joined: Wed Feb 15, 2012 11:32 pm
Location: North Yorkshire, UK

Re: Failsafe methods

Postby copterrichie » Sun Apr 29, 2012 11:39 pm

David, I do not know anything about the radio gear that you are using but if there is an indicator light that represents the present of the TX signal, maybe that light can be tapped into to open or close a relay switch shutting off power.
copterrichie
 
Posts: 2261
Joined: Sat Feb 19, 2011 8:30 pm

Re: Failsafe methods

Postby Hamburger » Mon Apr 30, 2012 8:33 pm

your are right - failsafe is ambiguous and misleading.
Most TX/RX today have a builtin failsafe - usually RX kicks in when signal from TX is lost and either RX continues sending last values or RX sends user-defined values on all channels. In these cases the MWii failsafe does not get triggered.
If you somehow kill the connection between RX and MWC, then the MWii failsafe will kick in - I once had a RX piggybacked onto the MWC board with simple connectors and the RX flew off during flight - that was the only occasion the MWii failsafe did safely increase gravity authority over copter.
User avatar
Hamburger
 
Posts: 2557
Joined: Tue Mar 01, 2011 2:14 pm
Location: air

Re: Failsafe methods

Postby djrm » Mon Apr 30, 2012 11:20 pm

I've opened the receiver, there are two LEDs which light when the signal is good. I'll diode OR them together and feed their output to the spare pin on the 3 pin DC power connector I would then have to modify the MWC software to use this signal to trigger failsafe operation mode. I'm thinking that perhaps I could also clamp the PPM output with the same signal to make the failsafe operate automatically with unmodified software but if I do that I'll loose the failsafe timer.
David.
User avatar
djrm
 
Posts: 40
Joined: Wed Feb 15, 2012 11:32 pm
Location: North Yorkshire, UK

Re: Failsafe methods

Postby djrm » Tue May 01, 2012 8:52 pm

The receiver LED voltage has been fed into the MWC A3 analog input, this is an unused input on my Crius lite FC board. The voltage is being tested as part of the failsafe software. The result is that failsafe now kicks in when the receiver gos off (or out of range).
I have called the new analogue input the rssipin, I guess if your receiver had RSSI then it could be used for this function.

I defined the RSSIPIN like this
Code: Select all
  #define RSSIPIN                    A3


and added a port initialisationto to the setup function
Code: Select all
  #if defined(RSSIPIN)
    pinMode(RSSIPIN,INPUT);
  #endif


the existing failsafe reset was disabled by testing for the new macro RSSIPIN
Code: Select all
      #if !defined(RSSIPIN)
      #if defined(FAILSAFE)
        if(failsafeCnt > 20) failsafeCnt -= 20; else failsafeCnt = 0;   // clear FailSafe counter - added by MIS  //incompatible to quadroppm
      #endif
      #endif


The new input test was added just befor the failsafe test in the main loop
Code: Select all
      #if defined(RSSIPIN)
       if((debug2=analogRead(RSSIPIN)) > 300) {
         if(failsafeCnt > 2)
          failsafeCnt -= 2;
         else
           failsafeCnt = 0;   // clear FailSafe counter
       }
       debug3 = failsafeCnt;
      #endif


It all seems to work, the motors spin at failsafe rate when the RC is switched off and then disarm after 20 seconds.
I'll be more confident that my copter will not be able to fly away now.
User avatar
djrm
 
Posts: 40
Joined: Wed Feb 15, 2012 11:32 pm
Location: North Yorkshire, UK

Re: Failsafe methods

Postby copterrichie » Tue May 01, 2012 10:05 pm

This is excellent!
copterrichie
 
Posts: 2261
Joined: Sat Feb 19, 2011 8:30 pm

Re: Failsafe methods

Postby Hamburger » Tue May 01, 2012 10:22 pm

Spektrum RX seem to change the constant-on LED to blinking LED in case of signal loss.
Not as easy to correctly interpret in code?
User avatar
Hamburger
 
Posts: 2557
Joined: Tue Mar 01, 2011 2:14 pm
Location: air

Re: Failsafe methods

Postby ajazz76 » Thu Aug 02, 2012 11:27 am

Hi guys, yesterday I tried my receiver from hobbyking AR6110B and I connected at throttle pin receiver to multiwii std se throttle pin but the motor immediately stop when I switch off the radio. So I decided to use the Aux 1 pin at the receiver and connected to my multiwii throttle pin.......and.....It works...... and complete all the failsafe procedure. Hopefully this information usefull who other got this type of receiver. Just to share...
ajazz76
 
Posts: 2
Joined: Wed Aug 01, 2012 5:41 pm

Re: Failsafe methods

Postby mahomedia » Tue Feb 05, 2013 11:03 pm

djrm,
how did you connect receiver led wire to the A3. Direct soldering with a wire or with a resistor? Can you provide details with photo. I want to try this in my copter.
mahomedia
 
Posts: 12
Joined: Tue Feb 05, 2013 10:59 pm

Re: Failsafe methods

Postby Andy7 » Wed Feb 06, 2013 1:28 am

Hamburger wrote:Spektrum RX seem to change the constant-on LED to blinking LED in case of signal loss.
Not as easy to correctly interpret in code?

My Hk6s RX also blinks on signal loss. But I guess it would be pretty easy to latch the fail safe in code if any "off" state is detected on that input.

Is it worth seeing if its worth cancelling fail safe if the signal return?

I might give this a go on my quad when I get time. I guess a0 or a1 are free on the NanoWii.
Andy7
 
Posts: 129
Joined: Fri Dec 28, 2012 5:09 pm
Location: Oxford, UK

Re: Failsafe methods

Postby Goetz » Mon Mar 18, 2013 1:50 pm

this sounds interesting for me, since I dont manage to tell my FrSky to send nothing in case of signalloss, but there is an RSSI-Pin. Can it direktly soldert to the defined Arduino-Pin or should there be an resistor in series?
Goetz
 
Posts: 82
Joined: Sun Mar 04, 2012 3:40 pm

Re: Failsafe methods

Postby Goetz » Mon Mar 18, 2013 3:04 pm

Goetz
 
Posts: 82
Joined: Sun Mar 04, 2012 3:40 pm

AW: Failsafe methods

Postby Lapino » Mon Mar 18, 2013 3:37 pm

Try to rebind your receiver, failsafe should be detected then ;)
Lapino
 
Posts: 84
Joined: Tue Aug 16, 2011 10:01 am

Re: AW: Failsafe methods

Postby scrat » Tue Mar 19, 2013 7:45 am

Lapino wrote:Try to rebind your receiver, failsafe should be detected then ;)


If you rebind receiver then you must set failsafe again between Tx and Rx.
scrat
 
Posts: 925
Joined: Mon Oct 15, 2012 9:47 am
Location: Slovenia

AW: Failsafe methods

Postby Lapino » Tue Mar 19, 2013 8:09 am

But that's what he wanted didn't he? He didn't manage to send nothing in case of signal loss...
Lapino
 
Posts: 84
Joined: Tue Aug 16, 2011 10:01 am

Re: Failsafe methods

Postby ardufriki » Tue Mar 19, 2013 8:51 am

Hi, I soldered a wire from 9x8c Turnigy rx, near to the internal LED, and now I have an ON/OFF Failsafe feature. I have it attached to A6 input and then modified the code as previous post. It works fine.

This is not a real RSSI signal, but at least I have something. The stock Turnigy 9x doesnt have failsafe.
ardufriki
 
Posts: 88
Joined: Thu Dec 13, 2012 4:47 pm

Re: Failsafe methods

Postby ardufriki » Wed Mar 27, 2013 12:41 pm

ardufriki
 
Posts: 88
Joined: Thu Dec 13, 2012 4:47 pm


Return to ESCs, propellers , servos and radios

Who is online

Users browsing this forum: No registered users and 3 guests

cron