Failsafe methods

Post Reply
User avatar
djrm
Posts: 40
Joined: Wed Feb 15, 2012 11:32 pm
Location: North Yorkshire, UK

Failsafe methods

Post by djrm »

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.

copterrichie
Posts: 2261
Joined: Sat Feb 19, 2011 8:30 pm

Re: Failsafe methods

Post by copterrichie »

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.

User avatar
Hamburger
Posts: 2557
Joined: Tue Mar 01, 2011 2:14 pm
Location: air
Contact:

Re: Failsafe methods

Post by Hamburger »

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
djrm
Posts: 40
Joined: Wed Feb 15, 2012 11:32 pm
Location: North Yorkshire, UK

Re: Failsafe methods

Post by djrm »

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

Post by djrm »

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.

copterrichie
Posts: 2261
Joined: Sat Feb 19, 2011 8:30 pm

Re: Failsafe methods

Post by copterrichie »

This is excellent!

User avatar
Hamburger
Posts: 2557
Joined: Tue Mar 01, 2011 2:14 pm
Location: air
Contact:

Re: Failsafe methods

Post by Hamburger »

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?

ajazz76
Posts: 2
Joined: Wed Aug 01, 2012 5:41 pm

Re: Failsafe methods

Post by ajazz76 »

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...

mahomedia
Posts: 12
Joined: Tue Feb 05, 2013 10:59 pm

Re: Failsafe methods

Post by mahomedia »

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.

Andy7
Posts: 129
Joined: Fri Dec 28, 2012 5:09 pm
Location: Oxford, UK
Contact:

Re: Failsafe methods

Post by Andy7 »

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.

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

Re: Failsafe methods

Post by Goetz »

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

Post by Goetz »


Lapino
Posts: 84
Joined: Tue Aug 16, 2011 10:01 am

AW: Failsafe methods

Post by Lapino »

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

scrat
Posts: 925
Joined: Mon Oct 15, 2012 9:47 am
Location: Slovenia

Re: AW: Failsafe methods

Post by scrat »

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.

Lapino
Posts: 84
Joined: Tue Aug 16, 2011 10:01 am

AW: Failsafe methods

Post by Lapino »

But that's what he wanted didn't he? He didn't manage to send nothing in case of signal loss...

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

Re: Failsafe methods

Post by ardufriki »

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

Post by ardufriki »


Post Reply