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Old 05-09-2012, 06:43 PM
JensR JensR is offline
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Join Date: May 2011
Location: Bath, UK
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Default Re: how to change controls on Spektrum DX6i?

Hi Footprint!

Good to read from you!
I haven't managed more with my Arduino radio than before.
http://www.youtube.com/watch?v=_Cm3TxekJO4
It works quite wonderfully, but the idea of writing my own menu system is a bit intimidating...
Maybe I'll do everything in Arduino code, but this less flexible in the testing phase.
It seems that you do this? Are you happy with it?
Plus I need to get the machine running - the current control is nice enough, so the new one is not my priority.
I have not yet learned to work with electronic _components_ like you have. :-/
Hence I wiggle my way around that gap

Regarding your servo mount: because the axes are not parallel, you get a kinematic error and possibly binding in the servohorn.
/Captain Hindsight over


Anyway, for the SPDT, you could use something like:
http://defconbots.org/defcon14/design_gun.php
http://www.ntxbg.org/pgOnTheWays/pgRadioBasics.htm
(two SPST non-latching switches)

You could use a multi-pole rotary switch:
http://www.crashed.net/~nebulous/keg/index.html

Rotating the switch?
http://www.vac-u-boat.com/FireBoat.htm

Wicked way to use a stripboard for the switch
http://www.rcgroups.com/forums/attac...mentid=3955114

If one switch isn't enough:
http://www.rcgroups.com/forums/attac...mentid=3954038

Taken from here:
http://www.rcgroups.com/forums/showthread.php?t=1426075

Another way of using two SPST:
http://www.wopba.com/controls.htm
Interesting here the warning:
""""
Do Not mount a switch to a servo
Done it and fried the servo.
When contact is made it sends a pulse that will knock out the electronics in the servo.
"""
What do we make of this?
I can't imagine this being a problem - I have plugged in servos while the receiver was powered up, without a problem.

While I find the above pretty simple, your solution would probably be my preference.
If I understood it
Whereto is RCa connected?
TP102 is a transistor?
NPN?
Should that be TIP102?
Does this work with ~1A current draw per servo?
I guess it does:
http://www.futurlec.com/Transistors/TIP102.shtml
8A?

Would using a transistor create a problem because the switching and switched circuit are then not galvanically isolated?

7404 is an inverter?
555 a timer (I knew that one!)
7408 are AND gates (I remember the shape)

So, the RCa somehow sets a value for the value that the upper AND gate compares to the receiver signal? But these can only compare 1s and 0s? So it must be a pulse-width thing? Based on the 20ms pulse of radios, and the ~1500µs servo neutral?

The inverter means that the lower AND gate will always have the other value than the upper? That ensures that only one of the transistors will be active at any moment in time. (Neglecting switching speed?)
I think some distance between switching points is needed.
You cannot have 1501µs mean channel A and 1500µs mean channel B.
Does your circuit do that? If so, how?

I guess you see why _I_ think the switch is easier

Cheers
Jens
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