|
|
|
|
|
Spockie-Tech
Site Admin
Joined: 31 May 2004
Posts: 3160
Location: Melbourne, Australia
|
If you are using servo motors on a non-PCM receiver, then you need 1 failsafe per receiver channel that you want to auto return to off.
So if you are using Microswitches in the usual H-Bridge configuration, you will need 2. If your switches are setup in the drive/steer configuration (not a great idea, since you cant turn on the spot), then only the drive one needs a failsafe.
If you have an active weapon being switched on and off, then you would need an extra one for that too. If you need all 3 of them, it would almost be worth spending the extra money and either building a simple pic-axe relay controller, or going for something like Electronize's or an IBC, since you'd be looking at over $100 worth of failsafes. _________________ Great minds discuss ideas. Average minds discuss events. Small minds discuss people
|
Wed Dec 01, 2004 8:09 am |
|
|
|
|
|
|
Spockie-Tech
Site Admin
Joined: 31 May 2004
Posts: 3160
Location: Melbourne, Australia
|
It depends on the failsafe..
Most speed controllers have one built into their microprocessor that simply monitors the servo-drive pulse for out-of-spec invalid servo signals. If they receive an invalid servo pulse, they shut the motor drive and auxillary ouputs down until they have received a number of valid pulses in a row, when they start up again.
PCM Radio receivers monitor the receiver voltage as well as the digital error-checked signal from the transmitter and if either go out of spec, then they set the servo ouputs to a pre-set position, or hold the last position as programmed.
Add-on Failsafes usually check the incoming servo signal and if it goes invalid, then they set the output to a preset position (usually adjusted with a trimpot screw on the failsafe). I dont know if the aftermarket ones monitor receiver voltage as well.. they could do, since the servo power and receiver power are the same voltage.
Spring return systems are fine, as long as they reliably shut things down when you turn off the radio.
Failsafing the main power might work, although it would require a big high-current servo-actuated main power switch, and obviously couldnt include the receiver power, or once you switched off, you would stay off until manually reset, which might be annoying in a match
You would need a spring return on your main power actuater servo as welll.
Apart from the safety issues, one of the main uses of Failsafes is reassuring Insurance Companies, Venue Owners, and Legal Beagles that these destructive machines are completely under our control (hah)..
"Yessir, All I have to do is flip this radio off, and that there machine wont do a thing".. _________________ Great minds discuss ideas. Average minds discuss events. Small minds discuss people
|
Wed Dec 01, 2004 12:12 pm |
|
|
|
|
Spockie-Tech
Site Admin
Joined: 31 May 2004
Posts: 3160
Location: Melbourne, Australia
|
quote:
ive had 3 runaways with the IBC because of the aerial dangling down and touching the metal frame, twice it planted itself into my side wall and another it took a mad dash for freedom up the road
I've seen that behaviour on rare occasion as well.. but unless there is some obscure timing bug in the IBC/OSMC code, I suspect its more likely to do with the receiver putting out a valid, but not correct (if you follow what I mean) servo signal.
Remember, all that ESC's failsafes can do is look to see if the servo drive signal is in the valid 1ms-2ms range. If the receiver puts out a 1.7ms pulse, the ESC will treat it as valid, even if the radio is actually off, or the antenna is grounded or whatever.
I have a PCM radio now, so I'll see if I ever observe that behaviour on it.. If you know a way of *making* it do that by grounding your aqntenna or whatever, please hook up a servo motor and see what it does in those circumstances.. that would help define whether its a Code bug or a receiver quirk. _________________ Great minds discuss ideas. Average minds discuss events. Small minds discuss people
|
Wed Dec 01, 2004 10:02 pm |
|
|
|
|
|