Building a circuit with servo and timer.

[ezy172]

its a 555 timer chip and i want to connect a servo to it.

555 timer chip :http://www.solarbotics.com/assets/images/lm555/lm555_pl.jpg

servo: http://www.redrc.net/wp-content/uploads/2007/08/ttacercds0606servo.jpg

Would anyone have a schematic diagram to show how to connect these in a circuit? What resistors or any other components do i need. i am running the circuit off 4 nicads (4.8v).

thanks
lukus

[Chippie]

Lukus,

Have a read here:
http://www.rcgroups.com/forums/showthread.php?t=959976

[slipstick]

See
http://www.uoguelph.ca/~antoon/gadgets/servo3.htm
http://www.uoguelph.ca/~antoon/gadgets/servo4.htm

Steve

[ezy172]

slipstick looks like exactly what i want, 2nd link. They are talking about a normal model plane servo? also what is the signal that goes into 3?

[Tomapowa]

3 is the signal (output) which connects to the servo signal wire which controls the position of the servo.
http://www.uoguelph.ca/~antoon/gadgets/servo4.gif

[ezy172]

I want the circuit to have a switch so that once it is switched on the servo moves position after 4 seconds and stays there until it is switched off where it goes back up. how could i do this with the circuit?

[Tomapowa]

I want the circuit to have a switch so that once it is switched on the servo moves position after 4 seconds and stays there until it is switched off where it goes back up. how could i do this with the circuit?

This circuit probably could be mod'd to do what you'd like (i.e. add another timer for 4sec control of servo swing, etc...) but best bet is to do this with a PIC and a few lines of code. If you are not a programmer or do not have a PIC programmer handy, simple projects like this lend themselves to prototyping using a Picaxe microcontroller (www.picaxe.com). These are pre-programmed PICs (bootloader/interpreter) that are easily programmable using free software they provide, a serial (9-pin) port on your PC (or a USB-to-Serial converter) and a little "basic" logic programming on your part. The Picaxe has a cool built-in "servo" function that allows you (via one line of code) to easily ouput a continuous (20ms) servo pulse stream from a PIC output pin. You can probably perform the functionality you want with as simple as a few lines of code/logic such as:

-Define pin for switch input
-Define pin for servo pulse train output

LOOP
-Check switch pin and if 0 (open), then output a servo pulse of 2ms
-Check switch pin and if 1 (closed), then pause 4 seconds, then output a servo pulse of 1ms
GOTO LOOP (repeat indefinitely)

Additionally, if you wanted to very the speed of the servo when it goes from one position to the other, you could put in a loop/delay that varies the changing of the servo pulse from 1ms-2ms... something like :

LOOP
-If switch pin = 0 (open) then
---for i = 1000 to 2000
-----Set servo pulse to i
-----delay a little... (the larger delay, the slower the speed)
---next i
End If
-Check switch pin and if 1 (closed), then pause 4 seconds, then output a servo pulse of 1ms
GOTO LOOP (repeat indefinitely)

Note: The servo function of the picaxe accepts pulse values between 75 and 225. 75 is actually .75ms and 225 is actually 2.25 ms (i.e. 10us increments). For example, to output a servo signal from the picaxe pin #3 (output#4), such to center most servo (1.5ms), the Picaxe command would be:

servo 3, 150

[Acetronics]

Hi, Ezy

I think you could use a "Failsafe" device for one servo ( commercially existing )... like this one : http://www.futaba-rc.com/radioaccys/futm0992.html

just place your switch in the signal input wire (or use the 555 to tie signal to ground after the 4 sec ! ) ... :

signal enabled - the servo will follow the position given by a channel switch or pot of your Tx

signal cut - the servo will reach the PROGRAMMABLE fail safe position ...

Isn't it marvellous ???

Alain

[Tomapowa]

Hi, Ezy

I think you could use a "Failsafe" device for one servo ( commercially existing )... like this one : http://www.futaba-rc.com/radioaccys/futm0992.html

just place your switch in the signal input wire (or use the 555 to tie signal to ground after the 4 sec ! ) ... :

signal enabled - the servo will follow the position given by a channel switch or pot of your Tx

signal cut - the servo will reach the PROGRAMMABLE fail safe position ...

Isn't it marvellous ???

Alain

But what controls the 4 second delay he requires?

I know as a fact they some (maybe just DIY) servo fail-safes allow you to not only adjust the fail-safe servo position, but they also allow the user to adjust the fail-safe delay time (the time it waits to kick into fail-safe upon receiving no servo signal). The Futaba model mentioned above unfort. does not include such adjustment.

[Acetronics]

But what controls the 4 second delay he requires?

The Futaba model mentioned above unfort. does not include such adjustment.

Hi Tomapowa,



or use the 555 to tie signal to ground after the 4 sec !



Might I provide you the 555 ( in timer design ...) - plus a diode and a resistor , scheme for your site ???

no processor required here ... Deluxe design could also use a 4011 as timer + signal gating. just another idea.

Alain :D

[Tomapowa]

Hi Tomapowa,



Might I provide you the 555 ( in timer design ...) - plus a diode and a resistor , scheme for your site ???

no processor required here ... Deluxe design could also use a 4011 as timer + signal gating. just another idea.

Alain :D

Sure Alain,
I full working schematic is what ezy172 is looking for from what it sounds... feel free to post a copy.

I still think the most elegant solution (i.e. smallest and least components) is one programmed PIC and maybe a couple resistors at best, although discrete component circuit are fun too!

[Acetronics]

I still think the most elegant solution (i.e. smallest and least components) is one programmed PIC and maybe a couple resistors at best,!

Hi,

I do agree ... but something tells me our friend is not a rugged µp programmer ... nor user. :D




Alain