Servo return to center on start up
Lew
Posts: 5
Hello all. I am brand new (obsessing on What's a M. manual for two days now!), hate to ask for help, but I haven't found this yet and thought I'd ask anyway.
On page 133, the exercise is to rotate the servo left and right using buttons:
This does what I want it to do ... EXCEPT, when powered down then restarted, it goes back to center because of the "duration = 750". I am controling a lever that I need it to start where I left it when I powered down, NOT at center.
I thought maybe I could take the last position (DEBUG DEC4 duration) and write that to an EEPROM address, then read that into "duration = ___" somehow on start up? But I can't seem to find out how to do that automatically. My eyes are starting to cross trying to absorb so much so fast ... DATA? READ/WRITE? DEBUGIN? Other chips have "scratch pad memory"?
I am using a BS2 Rev F, with a Board of Education Rev. B, a 4.5 v. power adapter, and a USB adapter.
My "heat oppressed brain" would appreciate any pointing in the right direction and I'm all about learning, so please feel free to educate!
Later, - Lew
On page 133, the exercise is to rotate the servo left and right using buttons:
' {$STAMP BS2}
' {$PBASIC 2.5}
duration VAR Word
duration = 750
PAUSE 1000
DO
IF IN3 = 1 THEN
IF duration > 500 THEN
duration = duration - 25
ENDIF
ENDIF
IF IN4 = 1 THEN
IF duration < 1000 THEN
duration = duration + 25
ENDIF
ENDIF
PULSOUT 14, duration
PAUSE 10
DEBUG HOME, DEC4 duration, " = duration"
LOOP' {$PBASIC 2.5}
duration VAR Word
duration = 750
PAUSE 1000
DO
IF IN3 = 1 THEN
IF duration > 500 THEN
duration = duration - 25
ENDIF
ENDIF
IF IN4 = 1 THEN
IF duration < 1000 THEN
duration = duration + 25
ENDIF
ENDIF
PULSOUT 14, duration
PAUSE 10
DEBUG HOME, DEC4 duration, " = duration"
This does what I want it to do ... EXCEPT, when powered down then restarted, it goes back to center because of the "duration = 750". I am controling a lever that I need it to start where I left it when I powered down, NOT at center.
I thought maybe I could take the last position (DEBUG DEC4 duration) and write that to an EEPROM address, then read that into "duration = ___" somehow on start up? But I can't seem to find out how to do that automatically. My eyes are starting to cross trying to absorb so much so fast ... DATA? READ/WRITE? DEBUGIN? Other chips have "scratch pad memory"?
I am using a BS2 Rev F, with a Board of Education Rev. B, a 4.5 v. power adapter, and a USB adapter.
My "heat oppressed brain" would appreciate any pointing in the right direction and I'm all about learning, so please feel free to educate!
Later, - Lew
Comments
10,000,000 writes / address, but all things must pass.
Check out WRITE and READ in PBASIC Help.
Are you going to write/record that position everytime it changes or only
when you want to, based on some "orderly shutdown" cue? Things to
think about.
I don't see how you could do that without knowing the initial position of the servo.
Rich H
Why do you need to know the current position if your just going to move the servos to a known starting position?
OK, here's the deal. I'm dreaming of using this as trim control for rudder and aileron on real (not model) planes. The ones that are used now are big, heavy, expensive, etc. and just use switch and relays to control a servo motor (which controls a small flap on the rudder or aileron) -- which stays put after the power is off. Once the trim is set for a particular passenger load, to compensate for a "heavy wing", etc. it usually doesn't need to be set again from flight to flight, or only minorly. This pulse control servo will do the trick, but as is, it will have to be reset every time the plane is powered up. I don't want to have to read a pulse duration at shut down (position of trim) and re-enter it by hand every time -- I want it to do it automatically based on the processor reading it's last pulse duration and entering that on start up ... if it can be done.
Keep it coming! - Lew
You don't need to know the current position to move to a starting position, but to move it slowly to a starting position, I think you do.
Rich H
My 2 cents...
Options one: Use a DC motor with SCREW gear, so pressure, when flying, won't move it. And it does not need a pulse, simple switches for TRIM.
Options two: Although it will center the servo at the beginning, it will re-position it-self. Good way to PRE-FLIGHT CHECK LIST functionnality. Use the servo approach, and just use a button to : Once happy with the TRIM, by pushing the button, it will store the value in memory. Upon Startup, the trim will NEUTRAL itself, read value in memory and re-position according to it. So the 10,000,000 of write limits will seem to be "UNLIMITED".
Just a thought!
CHeers
Yoshi... FLying a Spitfire (RC) from Parkzone.
Option one: Yup, old tried and trued, clunky technology -- I just like the challenge of improving on it, and these are very small trim tabs (not much pressure).
Option two: My thought too ... now, how do I get that duration variable that I want, stored as a value into memory "by pushing the button"? Surely there's somebody out there that has wired up this magic button! The simplest low tech solution is to fly it with a laptop attatched to the BS2, get the number that's close to most applications, then make that "duration = __" instead of neutral.
But where's the challenge? I just want to know how to translate the variable that's being sent to "DEBUG HOME, DEC4 duration" into a value that can be saved (written) then retrieved (read) upon startup, without the computer attached to BS2.
I still think there must be a way (as in a spread sheet -- read calculated value of cell (x,y) , copy to cell (a,b) , then insert value of cell (a,b) into a formula in another cell.
Then today, the pilot I'm working with says he kind of LIKES the idea of the tabs resetting to neutral and setting them every flight .... SHEESH!
Later, - Lew
The BS2 has an area where you can store some value. So no need for an external PC to read and write from every time.
I'm no expert in BS2 ... kind of given up on it.
So... In general. Upon start-up, with the BS2, you can intialize everything you need, then with a read command go fetch in memory the value, then apply the value for the servo. In flight, you noticed an adjustement for the TRIM, once happy and perfect , the pushbutton execute a routine to take that value and store it to replace the old one.
Will need the big guns here, to help with the read and write commands. I've tried before, and never worked. all garble stuff. Gave up on this.
I had my own project running a display on PC with a BS2, but that required a laptop to be hooked up.
Yosh
This is such a rush! BTW, I'm 66, be gentle!
Later, - Lew
' {$STAMP BS2}
' {$PBASIC 2.5}
duration VAR Word 'defines pulse variable
saved VAR Word 'defines saved pulse variable
READ 0, Word saved 'reads number saved in EEPROM at 0 into "saved"
duration = saved 'sets position at last saved number
DO
IF IN3 = 1 THEN 'if switch on input 3 is 1
'and duration is greater than the
IF duration > 450 THEN 'lower limit of the servo,then reduce the
duration = duration - 15 'pulse by 15, each cycle
ENDIF
ENDIF
IF IN4 = 1 THEN 'if switch on input 4 ... etc.
IF duration < 1050 THEN
duration = duration + 15
ENDIF
ENDIF
PULSOUT 14, duration
PAUSE 10
DEBUG HOME, DEC4 duration, " = duration" 'display duration
'LOOP
IF IN1 = 1 THEN 'defines button which when pushed, writes
WRITE 0, Word duration 'current position to EEPROM position 0
READ 0, saved 'reads position 0 into "saved" variable
saved = duration 'so that when pushed, displayes saved position
DEBUG HOME,CR, DEC4 duration, " = saved"
ENDIF
LOOP
OOPS! Guess I should have attached a file -- the spacing is all off.
(I wouldn't say that if you were jacking hardware,
but I don't grind anyone for his programming as such.)
Here's the file (I think).
Later, - Lew
the output of a comparator, other like signs & wonders.
That's the classic way to increase a comparator's resolution. Proof: that's exactly why they make an LM339 quad comparator AND an ADC0834 quad ADC! Now you can have 4 times 8 bit =32 bit resolution reading a pot or a photoresistor, using just 2 "chips"!
What's the purpose in "measuring" the output of a comparator?
A comparator's output is binary, it has two states: HI or LO, on or off, true or false.
There's no middle ground.