Hi,

So I need to control a 30kgcm hobby-type servo with a momentary push button. Basically every time I press the button, the servo actuates for as long as I hold down the button, and then stops actuating when I release the button.

I've found the Kitronik servo controller but I don't think its current rating of 500mA is enough for a 30kgcm servo. Aside from designing an entire pcb and having it fabricated, does anyone know how I could do this? ideally off the shelf components/controllers without an arduino (space constraints )...

 

So I need to control a 30kgcm hobby-type servo with a momentary push button. Basically every time I press the button, the servo actuates for as long as I hold down the button, and then stops actuating when I release the button.

Servo motors don't quite work that way.

A typical hobby servo motor is controlled by a
50 Hz frequency (20 ms period) and a pulse width that varies from approximately 1.0 mSec to 2.0 mSec 1.5 mSec pulse width being center.

What exactly are you trying to do? You make no mention of servo position? Normally a servo motor has 3 leads (connections). We have power + and - and a control line. I suggest you read up a little on servo motors, applications and control.

Ron

 

the servo actuates

What does 'actuate' mean here? Move from extreme left to extreme right, rotate continuously anti-clockwise, .....?
Welcome to AAC!

 

What does 'actuate' mean here? Move from extreme left to extreme right, rotate continuously anti-clockwise, .....?
Welcome to AAC!

It means moving a setup like this: https://uk.robotshop.com/products/k...servo-kit?qd=87c23a944141d6b65f6abf11157ca7a0

Basically it starts at the right hand side, I push the button and the motor moves pushing the rod to the right. Hope this makes it clearer what I'm on about.

And thanks for the warm welcome!

 

OK, you push a button, I would suggest using a uC (Micro-Controller) and the servo travels to a fixed point depending on how you drive it. Then what? Do you have a uC? How do you plan to drive the servo?

Ron

 

I agree with @Reloadron. An MCU, like the 8-pin chip ATTiny85, and pair of limit switches would work great. You might need more pins for I/O but you can stay in the same Atmel family and use a 16-pin chip. A minimal configuration would require only a capacitor in addition to the MCU (for the MCU portion).

 

Hi,

So I need to control a 30kgcm hobby-type servo with a momentary push button. Basically every time I press the button, the servo actuates for as long as I hold down the button, and then stops actuating when I release the button.

I've found the Kitronik servo controller but I don't think its current rating of 500mA is enough for a 30kgcm servo. Aside from designing an entire pcb and having it fabricated, does anyone know how I could do this? ideally off the shelf components/controllers without an arduino (space constraints )...

The Kitronic servo controller does exactly what you want. Even small R/C servos can draw more than an amp when they actuate, so you will have to provide a suitable power source.

 

no need for micro controller... timer can do it nicely.
https://www.555-timer-circuits.com/servo-tester.html

all you need is button press to produce one setting (actuate) and release to create another setting (retract).

Modification like this would do, just note that button need to be normally closed. That way when button is released, 10k will let the servo move back (R1). if you want both positions adjustable, put pair of 100k trimmers in place of R1,R2.

 

The specification doesn't make what "actuates" means clear.

Does it mean moves fully to the end of travel when the button is pressed then returns to the inactive position when released, or doesn it mean moves towards the end of travel for as long as the button is pressed, then stops when released, then moves more when pressed again?

Also, the limit switches I mentioned are important. If you make an open loop system that depends solely on timing, or on the alignment of the servo's position sensing potentiometer, there is a real danger of overrunning the maximum travel. Limit switches provide absolute positioning in a. closed loop.

 

The servo kit shown in the link apparently has a standard 9g micro-servo driving a rack. So the servo would need to be energised with a (selectable) pulse width as per post #2. Simply pushing and releasing a momentary button would not allow any control of the direction of travel of the rack, nor accurate movement to a selected position. If you want proportional movement of the rack in either direction then a potentiometer in the drive circuit could be used.