Automatically actuated grill block - Mk3

[RoadCyclist]

I love it when a plan comes together... That looks great!

[gumby79]

You will have to program the idle time off (no power) . The servo uses power to hold position.
--- for shutdown
Add a capacitor the power the unit after shutdown. program when the unit sees the engine shutdown to close the flap

[Daox]

Thanks RoadCyclist.

I got the rest of the bits all printed up last night. They all go together pretty well. The blade doesn't fit up perfectly. I'll get that sorted out though.




Next up I'll get the servo hooked up.

[Daox]

Originally Posted by gumby79

You will have to program the idle time off (no power) . The servo uses power to hold position.
--- for shutdown
Add a capacitor the power the unit after shutdown. program when the unit sees the engine shutdown to close the flap

Does the servo use power to hold position, or only when it gets pushed out of position? I'll have to hook up an ammeter and see how its been programmed.

[LittleBlackDuck]

Originally Posted by Daox

Does the servo use power to hold position, or only when it gets pushed out of position? I'll have to hook up an ammeter and see how its been programmed.

Most servos have plain spur gears but the ratio is quite high, resulting in a significant torque required to move them without power. There is no power used by the servo motor when in position, but the electronics uses a small amount. The pulse position tells the servo the desired position, which is compared to the internal position and the potor actuated till they match. If it is moved out of position it will resist and try to move back.

For closing after ignition off you will need a really big capacitor to provide enough power to close the grille, probably in excess of 100,000uF. You can use a resistive divider and an analog input to monitor the input voltage before the regulator to detect power off.

Simon

[gumby79]

The load will be speed based bell curve accentuated by the off center pen .
Anxious to see the results of your testing. It will answer some of the questions I've had in my idea .http://ecomodder.com/forum/showthrea...all-33611.html

[Daox]

I got it fully assembled and tested out, and shot a quick video. Its running a slightly modified version of the 'sweep' program that is an example of how to use the servo library. Obviously, this program just sweeps the servo back and forth.

I did hook an ammeter up to the servo while it was in use. Sitting idle it used 10mA. While it was moving it used 60-70mA. However, the program it was running does not actuate the servo at full speed (which would be fine for this application). I imagine full speed would draw a lot more power.

https://www.youtube.com/watch?v=uQS91D-95Po

[gone-ot]

Have you tried "cycling" it under a wind load, such as a hair-drier or desk fan?

[Daox]

Nope, I have not tried that. I'll fire it back up today and see what I can do. I don't think I have a blow drier though... I know I have a fan but that is going to be a fairly low wind speed. Good idea though. Perhaps I'll just try to hold it with my hand and see how much oomph it has. I'm pretty confident that it'll be okay. There is a bit of travel that I didn't use in the servo. It has 180 degrees of rotation and I think I'm using about 110 degrees of that. If worst comes to worst, I can use more of that throw that for a bit more mechanical advantage. Also, as you can see in the video, I stop the servo actuator arm parallel to the push rod. This gives me tons of mechanical advantage since the push rod is pushing straight into the servo pivot point vs trying to rotate the arm.

[RoadCyclist]

It doesn't look from the video like it is closing all the way. If true, you could lengthen the wire arm some.

Speaking of the wire arm, I'm not sure it would stay straight trying to hold a flap closed in high speed conditions.

(My 2 cents)