servo "bounce" issues

Robotics
1

Good evening (or morning in Amman),

I have incorporated a servo into a project for my 1959 Impala and am getting some “bounce” at the end of each cycle. The idea is to press a (locking) button which will activate a set of relays and a geared motor (with position sensor) and a servo. The geared motor will rotate the license plate down to expose a rear view camera and the servo motor will rotate the (former) ashtray to expose the display to view what the camera is “seeing”. There is also a separate button to activate the license plate to expose the gas tank filler (no issues with this circuit). However, when I activate the “camera” button, both mechanisms activate but the servo bounces at then end of the cycle and basically opens and closes a few times before finally opening. The same happens when closing. I have diodes everywhere but that does not seem to help. I put the SparkFun servo trigger on it’s own power supply and that seemed to do the trick but that is not a real world solution (as everything will be on the 12vdc car power).

I am using this for the geared motor:

https://www.amazon.com/gp/product/B07GD … UTF8&psc=1

(I wold be happy to use a servo but am not sure there is one available to handle the required torque to rotate the license plate AND can be controlled by the SparkFun servo trigger). I will look into using a servo for this once I finish the fabrication but living in Amman, Jordan I do not have access to the machines I would in the US.

For the ashtray, I have a SparkFun generic high torque servo and a SparkFun servo trigger.

I have attached the TinyCAD circuit I designed using relays. I would attach a video but am not sure what file types are allowed.

So my questions are:

What is causing the bounce and how do I get rid of it?

Could I do all of this with an Arduino logic circuit? I am a mechanical engineer and NOT a programmer so the coding will take me some time to learn.

Thanks!

tinyCAD v6.jpg
tinyCAD v6.jpg3840×2160 519 KB

2

Hello burrism.

This sounds like a very cool project!

Does the ServoTrigger work correctly when you use a separate 5 volt power supply and use a toggle switch on the IN and GND terminals?

If it works there, but not connected to the rest of your circuit, there could be some noise on the power supply that’s causing the ‘bouncing.’ You might try a noise filter like the ones used on a car stereo to clean up the power source for the ServoTrigger and you might also try using a DC to DC converter that isolates the GND pin on it’s input and output to see if that helps.

3

So I tried that earlier and it worked. My only conclusion is that the geared motor is sending some funky signals as it is getting feedback to the shaft position. What I was able to do was try the the high torque servo in place of the geared motor and it seemed to work. Regarding your DC to DC converter, I am using one to convert the 12vdc source to 5 vdc for the servo trigger. I was getting the same (negative) results.

I uploaded the bounce video here: https://youtu.be/huQK1yPhiz4

and here is the servo replacing the geared motor: https://youtu.be/EJ_hPvBoBCc

It appears that the problem has been solved. I now need to order another servo trigger board and servo to put it all together.

I will update this post when I get it all together.